Catalyst for methacrylic acid production, method for producing same, and method for producing methacrylic acid and methacrylic acid ester

文档序号：554869 发布日期：2021-05-14 浏览：14次中文

阅读说明：本技术 甲基丙烯酸制造用催化剂及其制造方法、以及甲基丙烯酸和甲基丙烯酸酯的制造方法 (Catalyst for methacrylic acid production, method for producing same, and method for producing methacrylic acid and methacrylic acid ester ) 是由平田纯菅野充二宫航上田涉石川理史于 2019-09-17 设计创作，主要内容包括：本发明提供用于以比以往更高的收率制造甲基丙烯酸的Mo－V系氧化物催化剂。一种甲基丙烯酸制造用催化剂,其特征在于,是在通过甲基丙烯醛的氧化而制造甲基丙烯酸时使用的催化剂,上述催化剂包含含有钼的金属氧化物,上述金属氧化物具有满足下述条件(a)和(b)的环状结构。(a)满足下述式(I)的环状结构。(Mo、V和X的摩尔数的合计)：(O的摩尔数)：O＝7：35(I)(式(I)中,Mo、V和O分别表示钼、钒和氧。X表示选自钨、铁、铜、铋等中的至少1种元素)(b)7个金属－氧八面体(八面结构体)各自共有邻接的顶点的氧键合而成的环状结构。(The present invention provides a Mo-V oxide catalyst for producing methacrylic acid at a higher yield than conventional catalysts. A catalyst for methacrylic acid production, which is used for producing methacrylic acid by oxidation of methacrolein, wherein the catalyst contains a metal oxide containing molybdenum, and the metal oxide has a cyclic structure satisfying the following conditions (a) and (b). (a) A cyclic structure satisfying the following formula (I). (total of the number of moles of Mo, V and X): (number of moles of O): o is 7: 35(I) (in the formula (I), Mo, V and O respectively represent molybdenum, vanadium and oxygen, X represents at least 1 element selected from tungsten, iron, copper, bismuth and the like), and (b)7 metal-oxygen octahedrons (octahedral structures) each having an oxygen bond with an adjacent vertex.)

1. A catalyst for methacrylic acid production, which is used for producing methacrylic acid by oxidation of methacrolein, and which comprises a metal oxide containing molybdenum, said metal oxide having a cyclic structure satisfying the following conditions (a) and (b),

(a) a cyclic structure satisfying the following formula (I),

(total of the number of moles of Mo, V and X): (number of moles of O) 7: 35(I)

In the formula (I), Mo, V and O respectively represent molybdenum, vanadium and oxygen, X represents at least 1 element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium,

(b)7 metal-oxygen octahedrons are ring structures formed by bonding oxygen at the vertices of the octahedral structures which are adjacent to each other.

2. The catalyst for methacrylic acid production according to claim 1, wherein the metal oxide satisfies the following condition (c),

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

in the formula (II), Mo, V, NH₄And O represents molybdenum, vanadium, ammonium and oxygen, respectively, X represents at least 1 element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium, Z represents at least 1 element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium, c to g represent the molar ratio of each component, c is 0. ltoreq. c < 0.5, d is 0. ltoreq. d < 0.5, e is 0. ltoreq. e.ltoreq.0.1, f is 0. ltoreq. f.ltoreq.0.1, and g is the molar ratio of oxygen required to satisfy the valency of each component.

3. The catalyst for producing methacrylic acid according to claim 2, wherein 0 < c < 0.5 in the formula (II).

4. The catalyst for methacrylic acid production according to any one of claims 1 to 3, wherein the metal oxide satisfies the following condition (d),

(d) a metal oxide satisfying the following formula (III) when the mass of the metal oxide is M1 and the mass of an inactive component contained in the metal oxide is M2,

0≤M2/M1＜0.05 (III)。

5. the catalyst for methacrylic acid production according to any one of claims 1 to 4, wherein the metal oxide satisfies the following condition (e),

(e) the difference spectrum between the infrared absorption spectrum of the metal oxide measured by FT-IR and the infrared absorption spectrum of the metal oxide measured by FT-IR after the metal oxide is kept in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes is 1557 + -10 cm^-1、1456±10cm^-1And 1374 + -10 cm^-1A metal oxide having an absorption peak.

6. The catalyst for methacrylic acid production according to any one of claims 1 to 5, wherein the metal oxide satisfies the following condition (f),

(f) a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60m²(ii) metal oxide per gram.

7. The catalyst for methacrylic acid production according to any one of claims 1 to 6, wherein the metal oxide satisfies the following condition (g),

(g) a metal oxide which shows diffraction peaks at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern using Cu — K α rays.

8. The catalyst for producing methacrylic acid according to claim 7, wherein the metal oxide satisfies the following condition (g1),

(g1) a metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° 2 θ in an X-ray diffraction pattern using Cu — K α rays.

9. The catalyst for methacrylic acid production according to claim 7, wherein in condition (g), further diffraction peaks are shown at 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °.

10. The catalyst for methacrylic acid production according to claim 7, wherein in condition (g), further diffraction peaks are displayed at 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °.

11. A method for producing the catalyst for methacrylic acid production according to any one of claims 1 to 10, comprising the steps of:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component, and

(2) and a step of calcining the solid component to obtain a metal oxide.

12. A method for producing the catalyst for methacrylic acid production according to claim 9 or 10, comprising the steps of:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component,

(1b) a step of dispersing the solid component in an aqueous oxalic acid solution, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid component, and

(2b) and (3) calcining the solid component obtained in (1b) to obtain a metal oxide.

13. The method for producing a catalyst for methacrylic acid production according to claim 11 or 12, wherein the solid component satisfies the following conditions (h) and (i),

(h) a solid component having an average length of 2 to 50 μm of the crystal observed by an electron microscope,

(i) a solid component having an average aspect ratio of 2 to 30 in a crystal observed with an electron microscope,

wherein the average aspect ratio is (average length of crystal)/(average diameter of crystal).

14. A process for producing methacrylic acid by oxidizing methacrolein using the catalyst for methacrylic acid production according to any one of claims 1 to 10.

15. A process for producing methacrylic acid by the process according to any one of claims 11 to 13, wherein a catalyst for methacrylic acid production is produced, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for methacrylic acid production.

16. The method for producing methacrylic acid according to claim 14 or 15, wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas,

methacrolein: oxygen: water vapor: a ═ k: l: m: n (IV)

In the formula (IV), A represents nitrogen or helium, k to n represent the molar ratio of each gas, and when k + l + m + n is 100, k is 0.5 < 8.0, l is 2.0 < 20.0, and m is 0. ltoreq.m < 45.

17. The method for producing methacrylic acid according to any one of claims 14 to 16, wherein the reaction temperature is 180 to 500 ℃, the raw material gas containing methacrolein is supplied so as to satisfy the following formula (V),

15＜W/F＜550 (V)

in the formula (V), W represents the mass of the metal oxide packed in the reactor, F represents the amount of methacrolein supplied per unit time, the unit of the mass is g, and the unit of the supplied amount is mol/h.

18. The method for producing methacrylic acid according to any one of claims 14 to 17, wherein the reaction temperature is 180 to 500 ℃, the raw material gas containing methacrolein is supplied so as to satisfy the following formula (VI),

0.00002＜F/(S×W)＜0.008 (VI)

in the formula (VI), S represents the BET specific surface area of the metal oxide calculated by nitrogen adsorption, W represents the mass of the metal oxide packed in the reactor, and F represents methylpropane per unit timeThe feed amount of the enal, the unit of the BET specific surface area is m²The unit of the mass is g, and the unit of the supply amount is mol/h.

19. A method for producing a methacrylic acid ester, comprising esterifying methacrylic acid produced by the method according to any one of claims 14 to 18.

20. A method for producing a methacrylic acid ester, comprising producing methacrylic acid by the method according to any one of claims 14 to 18 and esterifying the methacrylic acid.

21. A catalyst for methacrylic acid production, which is used for producing methacrylic acid by oxidation of methacrolein, and which is characterized by containing a metal oxide satisfying the following conditions (b') and (c),

(b') a metal oxide having a cyclic structure in which 7 metal-oxygen octahedra, i.e., octahedral structures are bonded to each other,

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

22. The catalyst for producing methacrylic acid according to claim 21, wherein 0 < c < 0.5 in the formula (II).

23. The catalyst for producing methacrylic acid according to claim 21 or 22, wherein the metal oxide satisfies the following condition (d),

(d) a metal oxide satisfying the following formula (III) when the mass of the metal oxide is M1 and the mass of an inactive component contained in the metal oxide is M2,

0≤M2/M1＜0.05 (III)。

24. the catalyst for producing methacrylic acid according to any one of claims 21 to 23, wherein the metal oxide satisfies the following condition (e),

25. The catalyst for producing methacrylic acid according to any one of claims 21 to 24, wherein the metal oxide satisfies the following condition (f),

(f) a BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60m²(ii) metal oxide per gram.

26. The catalyst for producing methacrylic acid according to any one of claims 21 to 25, wherein the metal oxide satisfies the following condition (g),

(g) a metal oxide which shows diffraction peaks at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern using Cu — K α rays.

27. The catalyst for producing methacrylic acid according to claim 26, wherein the metal oxide satisfies the following condition (g1),

(g1) a metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° 2 θ in an X-ray diffraction pattern using Cu — K α rays.

28. The catalyst for methacrylic acid production according to claim 26, wherein in the condition (g), diffraction peaks are further displayed at 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °.

29. The catalyst for methacrylic acid production according to claim 26, wherein in the condition (g), diffraction peaks are further displayed at 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °.

30. A catalyst for methacrylic acid production, which is a catalyst used in the production of methacrylic acid by oxidation of methacrolein, comprising a metal oxide satisfying the following conditions (c) and (g1),

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

in the formula (II), Mo, V, NH₄And O represents molybdenum, vanadium, ammonium and oxygen, respectively, X represents at least 1 element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium, Z represents at least 1 element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium, c to g represent the molar ratio of each component, c is 0. ltoreq. c.ltoreq.0.5, d is 0. ltoreq. d.ltoreq.0.5, e is 0. ltoreq. e.ltoreq.0.1, f is 0. ltoreq. f.ltoreq.0.1, g is the molar ratio of oxygen required to satisfy the valency of each component,

(g1) a metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° 2 θ in an X-ray diffraction pattern using Cu — K α rays.

31. A method for producing the catalyst for methacrylic acid production according to any one of claims 21 to 30, comprising the steps of:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component, and

(2) and a step of calcining the solid component to obtain a metal oxide.

32. A method for producing the catalyst for methacrylic acid production according to claim 28 or 29, comprising the steps of:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component,

(1b) a step of dispersing the solid component in an aqueous oxalic acid solution, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid component, and

(2b) and (3) calcining the solid component obtained in (1b) to obtain a metal oxide.

33. The method for producing a catalyst for methacrylic acid production according to claim 31 or 32, wherein the solid component satisfies the following conditions (h) and (i),

(h) a solid component having an average length of 2 to 50 μm of the crystal observed by an electron microscope,

(i) a solid component having an average aspect ratio of 2 to 30 in a crystal observed with an electron microscope,

wherein the average aspect ratio is (average length of crystal)/(average diameter of crystal).

34. A process for producing methacrylic acid by oxidizing methacrolein using the catalyst for methacrylic acid production according to any one of claims 21 to 30.

35. A process for producing methacrylic acid by the method according to any one of claims 31 to 33, wherein a catalyst for methacrylic acid production is produced, and methacrylic acid is produced by oxidation of methacrolein using the catalyst for methacrylic acid production.

36. The method for producing methacrylic acid according to claim 34 or 35, wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas,

methacrolein: oxygen: water vapor: a ═ k: l: m: n (IV)

In the formula (IV), A represents nitrogen or helium, k to n represent the molar ratio of each gas, and when k + l + m + n is 100, k is 0.5 < 8.0, l is 2.0 < 20.0, and m is 0. ltoreq.m < 45.

37. The method for producing methacrylic acid according to any one of claims 34 to 36, wherein the reaction temperature is 180 to 500 ℃, the raw material gas containing methacrolein is supplied so as to satisfy the following formula (V),

15＜W/F＜550 (V)

38. The method for producing methacrylic acid according to any one of claims 34 to 37, wherein the reaction temperature is 180 to 500 ℃, the raw material gas containing methacrolein is supplied so as to satisfy the following formula (VI),

0.00002＜F/(S×W)＜0.008 (VI)

in the formula (VI), S represents the BET specific surface area of the metal oxide calculated by nitrogen adsorption, W represents the mass of the metal oxide filled in the reactor, F represents the amount of methacrolein supplied per unit time, and the unit of the BET specific surface area is m²The unit of the mass is g, and the unit of the supply amount is mol/h.

39. A method for producing a methacrylic acid ester, comprising esterifying methacrylic acid produced by the method according to any one of claims 34 to 38.

40. A method for producing a methacrylic acid ester, comprising producing methacrylic acid by the method according to any one of claims 34 to 38, and esterifying the methacrylic acid.

Technical Field

The present invention relates to a catalyst for methacrylic acid production, a method for producing the same, and a method for producing methacrylic acid and methacrylic acid ester.

Background

Metal oxide catalysts are being put to practical use in oxidation reactions of oxygen-containing organic substances such as hydrocarbons, carbonyl compounds, and alcohols, ammoxidation, oxidative dehydration, hydrogenation of CO and unsaturated compounds, dehydrogenation catalysts, solid acid and base catalysts, and the like (non-patent document 1).

As a metal oxide catalyst, an oxide catalyst containing molybdenum and vanadium (hereinafter, also referred to as "Mo — V-based oxide catalyst") is known. Mo — V-based oxide catalysts are being commercialized as catalysts used for selective oxidation and ammoxidation of lower alkanes such as ethane and propane, and catalysts for producing acrylic acid by selective oxidation of acrolein. The Mo — V oxide catalyst is excellent in heat resistance compared to a molybdenum-containing heteropolyacid catalyst, and therefore a long catalyst life can be expected.

Examples of applying the Mo — V-based oxide catalyst to selective oxidation of unsaturated aldehydes include the following. The results of applying the Mo — V-based oxide catalyst to selective oxidation of acrolein and methacrolein show "acrolein conversion rate 100%, acrylic acid selectivity 97%", and "methacrolein conversion rate 57%, methacrylic acid selectivity 19%" (non-patent document 2). The results of applying a Mo — V-based oxide catalyst containing tungsten to selective oxidation of acrolein and methacrolein show "acrolein conversion 95%, acrylic acid selectivity 90%", methacrolein conversion 40%, methacrylic acid selectivity 35% "(non-patent document 3). Thus, the Mo-V based oxide is suitable for selective oxidation of acrolein, and is not suitable for selective oxidation of methacrolein.

Documents of the prior art

Non-patent document

Non-patent document 1: beanliang-like tablets, "catalyst", volume 26, No. 2, p.76 in 1984

Non-patent document 2: makoto Misono, "Applied Catalysis", 1990, Vol.64, p.1-30

Non-patent document 3: drocher, d.ohlig, s.knoche, n.gora, m.heid, n.menning, t.petiold, h.vogel, "Topics in Catalysis", 2016, volume 59, p.1518-1532

Disclosure of Invention

As described above, the Mo — V oxide catalyst is superior in heat resistance to the molybdenum-containing heteropoly acid catalyst, but the methacrylic acid yield is insufficient.

The purpose of the present invention is to provide a molybdenum-containing oxide catalyst for producing methacrylic acid in a higher yield than conventional ones, a method for producing the same, a method for producing methacrylic acid using the catalyst, and a method for producing methacrylic acid esters.

The present inventors have intensively studied a molybdenum-containing oxide catalyst which can be suitably used for the oxidation of methacrolein in view of the above-mentioned problems, and as a result, have found that methacrylic acid can be produced at a higher yield than ever by using a catalyst containing a metal oxide having a specific cyclic structure, and have completed the present invention.

That is, the present invention is [1] to [40] and [1 '] to [ 21' ].

[1] A catalyst for methacrylic acid production, which is used for producing methacrylic acid by oxidation of methacrolein, wherein the catalyst contains a metal oxide containing molybdenum, and the metal oxide has a cyclic structure satisfying the following conditions (a) and (b).

(a) A cyclic structure satisfying the following formula (I).

(total of the number of moles of Mo, V and X): (number of moles of O) 7: 35(I)

(in the formula (I), Mo, V and O respectively represent molybdenum, vanadium and oxygen. X represents at least 1 element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium)

(b)7 metal-oxygen octahedrons (octahedral structures) each share a cyclic structure in which oxygen atoms at adjacent vertices are bonded.

[2] The catalyst for methacrylic acid production according to [1], wherein the metal oxide satisfies the following condition (c).

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

(in the formula (II), Mo, V, NH₄And O represents molybdenum, vanadium, ammonium and oxygen, respectively. X represents at least 1 element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium. Z represents at least 1 element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium. c to g represent the molar ratio of each component, 0. ltoreq. c.ltoreq.0.5, 0. ltoreq. d.ltoreq.0.5, 0. ltoreq. e.ltoreq.0.1, 0. ltoreq. f.ltoreq.0.1, and g is the molar ratio of oxygen necessary for satisfying the valence of each component mentioned above)

[3] The catalyst for methacrylic acid production according to [2], wherein 0 < c < 0.5 in the formula (II).

[4] The catalyst for methacrylic acid production according to any one of [1] to [3], wherein the metal oxide satisfies the following condition (d).

(d) And (b) a metal oxide satisfying the following formula (III) when the mass of the metal oxide is M1 and the mass of an inactive component contained in the metal oxide is M2.

0≤M2/M1＜0.05 (III)

[5] The catalyst for methacrylic acid production according to any one of [1] to [4], wherein the metal oxide satisfies the following condition (e).

(e) The difference spectrum between the infrared absorption spectrum of the metal oxide obtained by FT-IR measurement and the infrared absorption spectrum of the metal oxide obtained by FT-IR measurement after maintaining the metal oxide in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes was 1557. + -.10 cm^-1、1456±10cm^-1And 1374 + -10 cm^-1A metal oxide having an absorption peak.

[6] The catalyst for methacrylic acid production according to any one of [1] to [5], wherein the metal oxide satisfies the following condition (f).

(f) A BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60m²(ii) metal oxide per gram.

[7] The catalyst for methacrylic acid production according to any one of [1] to [6], wherein the metal oxide satisfies the following condition (g).

(g) A metal oxide which shows diffraction peaks at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

[8] The catalyst for methacrylic acid production according to [7], wherein the metal oxide satisfies the following condition (g 1).

(g1) A metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

[9] The catalyst for methacrylic acid production according to [7], wherein, in the above condition (g), diffraction peaks are further displayed at 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °.

[10] The catalyst for methacrylic acid production according to [7], wherein, in the above condition (g), diffraction peaks are further displayed at 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °.

[11] A method for producing a catalyst for methacrylic acid production according to any one of [1] to [10], comprising:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component, and

(2) and a step of calcining the solid component to obtain a metal oxide.

[12] A method for producing a catalyst for methacrylic acid production according to [9] or [10], comprising the steps of:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component,

(1b) a step of dispersing the solid component in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid component, and

(2b) calcining the solid component obtained in (1b) to obtain a metal oxide;

the solid component is a substance dispersed in an aqueous oxalic acid solution, hydrochloric acid, ethylene glycol or hydrogen peroxide solution.

[13] The method for producing a catalyst for methacrylic acid production according to [11] or [12], wherein the solid component satisfies the following conditions (h) and (i).

(h) A solid content having an average length of 2 to 50 μm as observed by an electron microscope.

(i) And a solid component having an average aspect ratio of 2 to 30 in the crystal observed by an electron microscope.

(wherein, the average aspect ratio is (average length of crystal)/(average diameter of crystal))

[14] A process for producing methacrylic acid by oxidizing methacrolein using the catalyst for methacrylic acid production according to any one of [1] to [10 ].

[15] A process for producing methacrylic acid by the process according to any one of [11] to [13], wherein methacrylic acid is produced by oxidizing methacrolein using the catalyst for producing methacrylic acid.

[16] The method for producing methacrylic acid according to [14] or [15], wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas.

Methacrolein: oxygen: water vapor: a ═ k: l: m: n (IV)

(in the formula (IV), A represents nitrogen or helium, k to n represent the molar ratio of each gas, and when k + l + m + n is 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0. ltoreq. m < 45.)

[17] The method for producing methacrylic acid according to any one of [14] to [16], wherein the reaction temperature is 180 to 500 ℃ and the raw material gas containing methacrolein is supplied so as to satisfy the following formula (V).

15＜W/F＜550 (V)

(in the formula (V), W represents the mass (g) of the metal oxide packed in the reactor, and F represents the amount (mol/h) of methacrolein supplied per unit time.)

[18] The method for producing methacrylic acid according to any one of [14] to [17], wherein the reaction temperature is 180 to 500 ℃ and the raw material gas containing methacrolein is supplied so as to satisfy the following formula (VI).

0.00002＜F/(S×W)＜0.008 (VI)

(in the formula (VI), S represents the BET specific surface area (m) of the metal oxide calculated by nitrogen adsorption²(g)), W represents the mass (g) of the metal oxide packed in the reactor, F represents the amount of methacrolein supplied per unit time (mol/h))

[19] A method for producing a methacrylic acid ester, comprising esterifying methacrylic acid produced by the method according to any one of [14] to [18 ].

[20] A method for producing a methacrylic acid ester, wherein methacrylic acid is produced by the method according to any one of [14] to [18], and the methacrylic acid is esterified.

[21] A catalyst for methacrylic acid production, which is used for producing methacrylic acid by oxidation of methacrolein, and which contains a metal oxide satisfying the following conditions (b') and (c).

(b') a metal oxide having a cyclic structure in which 7 metal-oxygen octahedra (octahedral structures) are bonded to each other.

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

(in the formula (II), Mo, V, NH₄And O represents molybdenum, vanadium, ammonium and oxygen, respectively. X represents at least 1 element selected from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, copper, cobalt, rhodium, nickel, palladium, platinum, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium. Z represents at least 1 element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and calcium. c to g represent eachThe molar ratio of the components, c is 0. ltoreq. c < 0.5, d is 0. ltoreq. d < 0.5, e is 0. ltoreq. e.ltoreq.0.1, f is 0. ltoreq. f.ltoreq.0.1, and g is the molar ratio of oxygen necessary to satisfy the valences of the above components)

[22] The catalyst for producing methacrylic acid according to [21], wherein 0 < c < 0.5 in the formula (II).

[23] The catalyst for producing methacrylic acid according to [21] or [22], wherein the metal oxide satisfies the following condition (d).

(d) And (b) a metal oxide satisfying the following formula (III) when the mass of the metal oxide is M1 and the mass of an inactive component contained in the metal oxide is M2.

0≤M2/M1＜0.05 (III)

[24] The catalyst for producing methacrylic acid according to any one of [21] to [23], wherein the metal oxide satisfies the following condition (e).

[25] The catalyst for producing methacrylic acid according to any one of [21] to [24], wherein the metal oxide satisfies the following condition (f).

(f) A BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60m²(ii) metal oxide per gram.

[26] The catalyst for producing methacrylic acid according to any one of [21] to [25], wherein the metal oxide satisfies the following condition (g).

(g) A metal oxide which shows diffraction peaks at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

[27] The catalyst for methacrylic acid production according to [26], wherein the metal oxide satisfies the following condition (g 1).

(g1) A metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

[28] The catalyst for methacrylic acid production according to [26], wherein, in the above condition (g), diffraction peaks are further displayed at 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °.

[29] The catalyst for methacrylic acid production according to [26], wherein, in the above condition (g), diffraction peaks are further displayed at 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °.

[30] A catalyst for methacrylic acid production, which is used in the production of methacrylic acid by oxidation of methacrolein, and which contains a metal oxide satisfying the following conditions (c) and (g 1).

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

(g1) A metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

[31] A method for producing a catalyst for methacrylic acid production according to any one of [21] to [30], comprising:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component, and

(2) and a step of calcining the solid component to obtain a metal oxide.

[32] A method for producing a catalyst for methacrylic acid production according to [28] or [29], which comprises the steps of:

(1) heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component,

(1b) a step of dispersing the solid component in an aqueous solution of oxalic acid, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid component, and

(2b) and (3) calcining the solid component obtained in (1b) to obtain a metal oxide.

[33] The method for producing a catalyst for methacrylic acid production according to [31] or [32], wherein the solid component satisfies the following conditions (h) and (i).

(h) A solid content having an average length of 2 to 50 μm as observed by an electron microscope.

(i) And a solid component having an average aspect ratio of 2 to 30 in the crystal observed by an electron microscope.

(wherein, the average aspect ratio is (average length of crystal)/(average diameter of crystal))

[34] A method for producing methacrylic acid by oxidizing methacrolein using the catalyst for producing methacrylic acid according to any one of [21] to [30 ].

[35] A method for producing methacrylic acid by the method according to any one of [31] to [33], wherein methacrylic acid is produced by oxidizing methacrolein using the catalyst for producing methacrylic acid.

[36] The method for producing methacrylic acid according to [34] or [35], wherein a gas having a composition represented by the following formula (IV) is supplied as a raw material gas.

Methacrolein: oxygen: water vapor: a ═ k: l: m: n (IV)

(in the formula (IV), A represents nitrogen or helium, k to n represent the molar ratio of each gas, and when k + l + m + n is 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0. ltoreq. m < 45.)

[37] The method for producing methacrylic acid according to any one of [34] to [36], wherein the reaction temperature is 180 to 500 ℃ and the raw material gas containing methacrolein is supplied so as to satisfy the following formula (V).

15＜W/F＜550 (V)

(in the formula (V), W represents the mass (g) of the metal oxide packed in the reactor, and F represents the amount (mol/h) of methacrolein supplied per unit time.)

[38] The method for producing methacrylic acid according to any one of [34] to [37], wherein the reaction temperature is 180 to 500 ℃ and the raw material gas containing methacrolein is supplied so as to satisfy the following formula (VI).

0.00002＜F/(S×W)＜0.008 (VI)

[39] A method for producing a methacrylic acid ester, comprising esterifying methacrylic acid produced by the method according to any one of [34] to [38 ].

[40] A method for producing methacrylic acid esters, which comprises producing methacrylic acid by the method described in [34] to [38] and esterifying the methacrylic acid.

[1 '] A catalyst for methacrylic acid production, which is a catalyst used in the production of methacrylic acid by the gas-phase catalytic oxidation reaction of methacrolein, and which contains a metal oxide satisfying the following condition (a').

(a') a cyclic structure having a molar ratio represented by the following formula (I) and comprising at least molybdenum and having a metal-oxygen octahedron (octahedral structure) having a metal coordination number of 6 bonded in a cyclic manner.

(total of the number of moles of Mo, V and X): (number of moles of O) 7: 35(I)

[2 '] the catalyst for methacrylic acid production according to [ 1' ], wherein the metal oxide satisfies the following condition (c).

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

[3 '] the catalyst for methacrylic acid production according to [ 2' ], wherein 0 < c < 0.5 in the formula (II).

[4 ' ] the catalyst for methacrylic acid production according to any one of [1 ' ] to [3 ' ], wherein the metal oxide satisfies the following condition (d).

(d) And (b) a metal oxide satisfying the following formula (III) when the mass of the metal oxide is M1 and the mass of an inactive component contained in the metal oxide is M2.

0≤M2/M1＜0.05 (III)

[5 ' ] the catalyst for methacrylic acid production according to any one of [1 ' ] to [4 ' ], wherein the metal oxide satisfies the following condition (e).

[6 ' ] the catalyst for methacrylic acid production according to any one of [1 ' ] to [5 ' ], wherein the metal oxide satisfies the following condition (f).

(f) A BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60m²(ii) metal oxide per gram.

[7 ' ] the catalyst for methacrylic acid production according to any one of [1 ' ] to [6 ' ], wherein the metal oxide satisfies the following condition (g).

(g) A metal oxide which shows diffraction peaks at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

[8 '] the catalyst for methacrylic acid production according to [ 7' ], wherein, in the above condition (g), diffraction peaks are shown only at 2 θ ═ 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 °.

[9 '] the catalyst for methacrylic acid production according to [ 7' ], wherein, in the above condition (g), diffraction peaks are further shown at 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °.

[10 '] the catalyst for methacrylic acid production according to [ 7' ], wherein, in the above condition (g), diffraction peaks are further shown at 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °.

[11 ' ] A method for producing a catalyst for methacrylic acid production, which is any one of [1 ' ] to [7 ' ], [9 ' ] and [10 ' ], comprising the following steps (1) and (2).

(1) Heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to obtain a solid component.

(2) And a step of calcining the solid component to obtain a metal oxide.

[12 '] A method for producing a catalyst for methacrylic acid production [ 8' ] comprising the following steps (1) and (2).

(1) Heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to obtain a solid component.

(2) And a step of calcining the solid component to obtain a metal oxide.

[13 '] the method for producing a catalyst for methacrylic acid production according to [ 11' ], comprising a dispersion treatment step of: dispersing the solid component in an aqueous oxalic acid solution, hydrochloric acid, ethylene glycol or hydrogen peroxide water until the solid component is calcined in the step (2) after the solid component is obtained in the step (1).

[14 ' ] the method for producing a catalyst for methacrylic acid production according to any one of [11 ' ] to [13 ' ], wherein in the step (2), the solid component or the solid component after the dispersion treatment obtained in the dispersion treatment step satisfies the following conditions (h) and (i).

(h) A solid content having an average length of 2 to 50 μm as observed by an electron microscope.

(i) And a solid component having an average aspect ratio of 2 to 30 in the crystal observed by an electron microscope.

(wherein, the average aspect ratio is (average length of crystal)/(average diameter of crystal))

[15 ' ] A method for producing methacrylic acid by a gas-phase contact oxidation reaction of methacrolein using the catalyst for producing methacrylic acid according to any one of [1 ' ] to [10 ' ].

[16 ' ] A method for producing methacrylic acid, wherein a catalyst for producing methacrylic acid is produced by the method according to any one of [11 ' ] to [14 ' ], and methacrylic acid is produced by a gas-phase contact oxidation reaction of methacrolein using the catalyst for producing methacrylic acid.

[17 ' ] the method for producing methacrylic acid according to [15 ' ] or [16 ' ], wherein the reaction temperature is 180 to 500 ℃ and the raw material gas containing methacrolein is supplied so as to satisfy the following formula (V).

15＜W/F＜550 (V)

(in the formula (V), W represents the mass (g) of the metal oxide packed in the reactor, and F represents the amount (mol/h) of methacrolein supplied per unit time.)

[18 ' ] the method for producing methacrylic acid according to any one of [15 ' ] to [17 ' ], wherein the reaction temperature is 180 to 500 ℃, and the raw material gas containing methacrolein is supplied so as to satisfy the following formula (VI).

0.00002＜F/(S×W)＜0.008 (VI)

[19 '] the method for producing methacrylic acid according to any one of [ 15' ] to [18 '], wherein a gas having a composition represented by the following formula (IV') is supplied as a raw material gas.

Methacrolein: oxygen: water vapor: a ═ k: l: m: n (IV')

(in the formula (IV'), A represents nitrogen or helium, k to n represent the molar ratio of each gas, and when k + l + m + n is 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 4.5 < m < 45.)

[20 ' ] A method for producing a methacrylic acid ester, wherein methacrylic acid produced by any one of the methods [15 ' ] to [19 ' ] is esterified.

[21 ' ] A method for producing a methacrylic acid ester, wherein methacrylic acid is produced by any one of the methods [15 ' ] to [19 ' ] and esterified.

According to the present invention, a molybdenum-containing oxide catalyst having a high methacrylic acid yield, which is used for the oxidation of methacrolein, a method for producing the same, a method for producing methacrylic acid using the catalyst, and a method for producing methacrylic acid ester can be provided.

Drawings

Fig. 1 is a diagram showing the molecular structure of a metal-oxygen octahedron (octahedral structure).

Fig. 2 is a diagram showing a molecular structure in the case where 7 octahedral structures share oxygen at adjacent vertices to form a cyclic structure.

Fig. 3 is a view showing an example of the molecular structure of the ab-face of the metal oxide when the face where the octahedral structures are bonded in a ring form is taken as the ab-face.

Detailed Description

The present invention will be described in detail below.

[ catalyst for methacrylic acid production ]

One embodiment of the catalyst for methacrylic acid production of the present invention includes a metal oxide containing molybdenum, and the metal oxide has a cyclic structure satisfying the following conditions (a) and (b).

(a) A cyclic structure satisfying the following formula (I).

(total of the number of moles of Mo, V and X): (number of moles of O) 7: 35(I)

(b)7 metal-oxygen octahedrons (octahedral structures) each share a cyclic structure in which oxygen atoms at adjacent vertices are bonded.

Another embodiment of the catalyst for methacrylic acid production of the present invention contains a metal oxide satisfying the following conditions (b') and (c).

(b') a metal oxide having a cyclic structure in which 7 metal-oxygen octahedrons (octahedral structures) are bonded to each other (7 octahedral structures are a ring structure in which the octahedral structures are bonded to each other).

Mo₁V_cX_dZ_e(NH₄)_fO_g (II)

In another embodiment of the catalyst for methacrylic acid production of the present invention, the catalyst contains a metal oxide satisfying the above condition (c) and the following condition (g 1).

(g1) A metal oxide which shows diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

The details of each condition will be described below.

< Condition (a) >

The metal oxide having a cyclic structure satisfying the condition (a) can be confirmed, for example, by high-angle annular dark field (HAADF) measurement using a Scanning Transmission Electron Microscope (STEM) (hereinafter also referred to as "HAADF-STEM measurement") and the type of element contained in the metal oxide.

The presence of the cyclic structure can be confirmed as an image by observing the metal oxide powder using HAADF-STEM measurement.

The kind of the metal element contained in the metal oxide can be determined by, for example, dissolving the metal oxide in an aqueous solution of ammonia or hydrofluoric acid and analyzing the solution by ICP emission spectrometry.

The cyclic structure confirmed by the HAADF-STEM image satisfies the formula (I) described above, and can be confirmed by determining the elements displayed in the HAADF-STEM image from the contrast of the HAADF-STEM image and the types of metal elements contained in the metal oxide, and determining the ratio of each metal element in the cyclic structure.

When the metal oxide is composed of only the components contained in the formula (I), if the presence of a cyclic structure is confirmed, it can be judged that the cyclic structure satisfies the formula (I). In this case, the presence of the cyclic structure can be confirmed by the molecular probe method in the gas adsorption method, in addition to the HAADF-STEM measurement of the metal oxide as described above.

In the molecular probe method of the gas adsorption method, the metal oxide is filled in a closed vacuum system, and after pretreatment at 200 to 400 ℃, several gas molecules having different molecular diameters are introduced into the vacuum system as probes to create an adsorption isotherm, and the pore diameter (m.m. dubinin, v.a. astakhov, "Advances in Chemistry", 1971, volume 102, p.69) is calculated by the DA method. If the calculated pore diameter is 0.35 to 0.5nm, it can be judged that a cyclic structure exists.

In the formula (I), X is preferably at least 1 element selected from the group consisting of niobium, tantalum, tungsten, manganese, iron, copper, cobalt, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium and cerium, and more preferably at least 1 element selected from the group consisting of tungsten, iron, copper, antimony and bismuth, from the viewpoint of methacrylic acid selectivity.

In the above formula (I), Mo, V and X preferably have a molar ratio represented by the following formula (I') from the viewpoint of methacrylic acid yield.

(number of moles of Mo): (number of moles of V): (number of moles of X) ═ 7-a-b: a: b (I')

(in the formula (I'), a and b are integers each representing the molar ratio of vanadium to X, and a is 0 to 3, more preferably 1 to 3, and b is 0 to 3)

The values of a and b can be determined by Rietvelt analysis of an X-ray diffraction pattern of the metal oxide measured by X-ray structural analysis, for example.

< conditions (b) and (b') >)

The molecular structure of the metal-oxygen octahedron (octahedral structure) is shown in fig. 1. In FIG. 1, a metal element (Mo, V or X) having a coordination number of 6 is located at the center of an octahedral structure, and oxygen is located at all vertices of the octahedral structure. Fig. 2 shows a molecular structure in the case where 7 octahedral structures shown in fig. 1 share oxygen at adjacent vertices and are bonded to form a ring structure.

In the oxidation of methacrolein, the cyclic structure shown in fig. 2 has high catalyst activity. This is presumably because, due to the presence of the cyclic structure, adsorption sites capable of producing methacrylic acid from methacrolein with high selectivity are formed. In addition, by controlling the kind, combination, and amount of the metal element contained in the cyclic structure, the catalyst performance can be controlled. In addition, a structure containing Mo, V, or X may be disposed in the pore formed by the above-described annular structure.

The ring structure shown in fig. 2 corresponds to a part of the structure of the metal oxide. Fig. 3 shows an example of the molecular structure of the metal oxide on the ab-plane, where the plane where the octahedral structures are bonded in a ring shape is the ab-plane in fig. 2. In FIG. 3, the above-mentioned ring structure shown in FIG. 2 is bonded to other ring structures with oxygen at the apex in common. The octahedral structures are arranged such that the cyclic structure in which the octahedral structures are bonded in a cyclic manner shares one octahedral structure with another adjacent cyclic structure. The metal oxide may have a cyclic structure in which 6 or less octahedral structures share oxygen at adjacent vertices and are bonded together.

The metal oxide having a cyclic structure satisfying the condition (b) can be confirmed by, for example, a molecular probe method in HAADF-STEM measurement or a gas adsorption method.

When the measurement is performed using HAADF-STEM, the presence of the cyclic structure satisfying the condition (b) can be confirmed in the form of an image by observing the metal oxide powder.

In the case of using the molecular probe method among the gas adsorption methods, the metal oxide may be filled in a closed vacuum system, pretreated at 200 to 400 ℃, and then adsorbed at a diameter of 0.40 to 0.Probe with pore of 43nm, i.e. CO₂、CH₄Or C₂H₆An adsorption isotherm was prepared by introducing the mixture into a vacuum system, and the pore diameter (m.m. dubin, v.a. Astakhov, "Advances in Chemistry", 1971, vol.102, p.69) was calculated by the DA (Dubinin-Astakhov) method. If the calculated pore diameter is 0.40 to 0.43nm, it is judged that a cyclic structure satisfying the above condition (b) exists.

In addition, the metal oxide having a cyclic structure satisfying the condition (b) means that the metal oxide satisfies the condition (b').

< Condition (c) >)

The molar ratio of each element in the metal oxide can be calculated by completely dissolving the metal oxide in ammonia water, nitric acid, hydrochloric acid, sulfuric acid, aqua regia, or hydrofluoric acid, and analyzing the solution by ICP emission analysis.

The molar ratio of ammonium groups can be calculated by analyzing the metal oxide by kjeldahl method. In the present invention, "ammonium group" means that it can be converted into ammonium ion (NH)₄ ⁺) Ammonia (NH)₃) And ammonium contained in an ammonium-containing compound such as an ammonium salt.

In the above formula (II), the molar ratio of vanadium is preferably 0 < c < 0.5 from the viewpoint of methacrylic acid selectivity.

In the formula (II), from the viewpoint of methacrylic acid selectivity, X is preferably at least 1 element selected from the group consisting of niobium, tantalum, tungsten, manganese, iron, copper, cobalt, phosphorus, arsenic, antimony, tellurium, bismuth, boron, indium, zinc, magnesium, and cerium, and more preferably at least 1 element selected from the group consisting of tungsten, iron, copper, antimony, and bismuth.

In addition, when the metal oxide has a cyclic structure satisfying the conditions (a) and (b), and when the metal oxide satisfies the conditions (b') and (c), the metal oxide preferably further satisfies the condition (g).

(g) A metal oxide which shows diffraction peaks at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

< Condition (g) and (g1) >)

In an X-ray diffraction pattern (using Cu — K α rays), a diffraction peak appearing at 2 θ ═ 22.1 ° ± 0.3 ° is from the (001) plane of the crystal structure of the metal oxide, and a diffraction peak appearing at 2 θ ═ 45.2 ° ± 0.3 ° is from the (002) plane. When an axis perpendicular to the ab-plane is defined as a c-axis, the presence of these diffraction peaks indicates that the metal oxide has a structure in which the metal oxide is regularly stacked in the c-axis direction. When the metal oxide satisfies the condition (g), the ab-plane of the metal oxide is layered at an interval of 0.396 to 0.410 nm. The diffraction peak is a peak having a height of 5/100 or more with respect to a peak having a maximum intensity appearing in a range of 2 θ to 60 °.

In the condition (g), when the following condition (g1) is further satisfied, it can be determined that the metal oxide has an amorphous structure.

(g1) A metal compound showing diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern (using Cu — K α rays).

In addition, in the condition (g), in addition to 2 θ being 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 °, when diffraction peaks are further displayed at 2 θ being 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 °, it can be determined that the above-mentioned metal oxide has an orthorhombic crystal structure. In addition, in addition to 2 θ of 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 °, when diffraction peaks are further displayed at 2 θ of 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 °, it can be determined that the above-mentioned metal oxide has a crystal structure of a trigonal crystal. From the viewpoint of methacrylic acid yield, the metal oxide preferably has an amorphous structure, an orthorhombic crystal structure, or a trigonal crystal structure.

From the viewpoint of methacrylic acid yield, the metal oxide preferably further satisfies at least one selected from the following conditions (d) to (f), and more preferably satisfies all of the following conditions (d) to (f).

(d) And (b) a metal oxide satisfying the following formula (III) when the mass of the metal oxide is M1 and the mass of an inactive component contained in the metal oxide is M2.

0≤M2/M1＜0.05 (III)

(f) A BET specific surface area S calculated by nitrogen adsorption of 1.5 to 60m²(ii) metal oxide per gram.

The following describes the details of the respective conditions.

< Condition (d) >)

In the formula (III), M2/M1 represents the mass ratio of the inactive component contained in the metal oxide. The inactive component is a compound which shows no or very low catalytic activity when methacrolein is oxidized at a reaction temperature of 180 to 500 ℃. As the inactive component, Al is exemplified₂O₃、SiO₂、TiO₂Zeolites and other catalyst support compounds.

When M2/M1 satisfies the formula (III), since the ratio of the active ingredient per unit volume in the metal oxide is sufficiently high, it is easy to achieve a desired methacrolein conversion rate and continuous operation time in the production of methacrylic acid.

< Condition (e) >

The device used for FT-IR measurement is not particularly limited as long as it can measure at least 1200 to 2000cm^-1The above range may be used. The measurement method may be either a transmission method or a diffuse reflection method, or the measurement may be performed by diluting the metal oxide with a diluent. As the diluent, at least 1200 to 2000cm can be used^-1The range of (a) does not show infrared absorbing substances. As the diluent, KBr can be mentioned, for example. The FT-IR measurement of the above metal oxide is carried out by disposing the above metal oxide in an apparatus,the pretreatment is carried out at 300 ℃ or higher for 10 minutes or longer under nitrogen or helium flow, and then the measurement is carried out by cooling to the measurement temperature. Then, the metal oxide is maintained in a steam atmosphere of 15 to 25% by volume for 5 to 60 seconds, and further maintained in a methacrolein atmosphere of 2.0% by volume or more for 60 minutes, and then subjected to FT-IR measurement, and a differential spectrum is obtained from the difference between the two. In the differential spectrum, at 1557 + -10 cm^-1、1456±10cm^-1And 1374 + -10 cm^-1When the side chain has an absorption peak, methacrylic acid can be produced with a higher methacrylic acid selectivity. The absorption peak is a peak whose peak area has a value of 0.1 or more when the horizontal axis is a wavelength and the vertical axis is an absorbance detected by FT-IR measurement.

< Condition (f) >)

The BET specific surface area S can be calculated by nitrogen adsorption measurement using nitrogen as a probe in a gas adsorption method. Nitrogen adsorption measurement the metal oxide was filled in a closed vacuum system, pretreated at 200 to 400 ℃, nitrogen was adsorbed on the metal oxide at a liquid nitrogen temperature, an adsorption isotherm was drawn, and the specific surface area was calculated by the BET method. The BET specific surface area S by the above metal oxide was 1.5m²(ii) a ratio of methacrolein to methacrolein is higher than that of the above-mentioned (g). Further, the BET specific surface area S was 60m²The amount of heat generation during the production of methacrylic acid can be suppressed to a value of/g or less, and stable continuous operation can be achieved.

[ method for producing catalyst for methacrylic acid production ]

One embodiment of the method for producing a catalyst for methacrylic acid production of the present invention includes the following steps (1) and (2).

(1) Heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component.

(2) And a step of calcining the solid component to obtain a metal oxide.

Another embodiment of the method for producing a catalyst for methacrylic acid production according to the present invention includes the following steps (1), (1b), and (2 b).

(1) Heating an aqueous solution or slurry containing at least molybdenum at 80 to 300 ℃ for 3 to 200 hours to form a solid component.

(1b) And a step of dispersing the solid component in an aqueous oxalic acid solution, hydrochloric acid, ethylene glycol or hydrogen peroxide to obtain a solid component after the dispersion treatment.

(2b) And a step of calcining the solid component after the dispersion treatment to obtain a metal oxide.

The details of each step will be described below.

(step (1))

In the step (1), a part or the whole of a catalyst raw material containing at least molybdenum is mixed with a solvent to prepare a solution or slurry, and the solution or slurry is heated at 80 to 300 ℃ for 3 to 200 hours to form a solid component. When the above-mentioned solution or slurry is prepared by mixing a part of the catalyst raw materials into a solvent, the remaining catalyst raw materials may be mixed after the preparation of the above-mentioned solution or slurry.

< catalyst raw Material >

The catalyst raw material is not particularly limited, and nitrates, carbonates, acetates, ammonium salts, oxides, halides, and the like of the respective elements contained in the composition of the target metal oxide may be used in combination.

Examples of the molybdenum raw material include ammonium heptamolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, and the like, and molybdenum polyoxometallate and the like can be used. As the molybdenum-based polyoxometallate, heteropoly acids, isopoly acids, raw materials obtained by modifying heteropoly acids and isopoly acids with alkylammonium ions, and the like can be used. As a raw material obtained by modifying an isopoly acid with an alkylammonium ion, (CH) can be used₃NH₃)₆Mo₇O₂₄、(C₂H₅NH₃)Mo₃O₁₀And the like.

The catalyst raw material preferably contains vanadium, and examples of the vanadium raw material include vanadyl sulfate, vanadium pentoxide, ammonium metavanadate, vanadium chloride, and the like. In addition, a surfactant may be added as a catalyst raw material. The surfactant includes an anionic surfactant and a cationic surfactant, and the cationic surfactant includes sodium lauryl sulfate and the like.

< solvent >

As the solvent, water or an organic solvent can be used, and water is preferably used from the viewpoint of ease of handling and safety. The solvent is preferably used in an amount of 500 to 5000 parts by mass based on 100 parts by mass of the total amount of the catalyst raw materials used for the preparation of the solution or slurry.

< preparation of solution or slurry >

The above solution or slurry is prepared by mixing the above catalyst raw materials into the above solvent. The mixing method is not particularly limited, and a method of adding the catalyst raw material to the solvent and mixing the mixture with stirring is preferred. The order of addition is not particularly limited and may be set as appropriate.

The solution or slurry is preferably prepared using the components contained in the formula (I) from the viewpoint of forming a metal oxide having a cyclic structure satisfying the condition (a) in the step (2) described later.

In addition, a trace amount of a metal oxide having a composition represented by the above formula (II) may be added to the above solution or slurry. By adding the metal oxide in advance, the methacrylic acid yield of the finally obtained catalyst is improved.

In order to form a metal oxide having a cyclic structure satisfying the condition (b) in the step (2) described later, it is preferable to bubble hydrogen or helium with the solution or slurry having a pH of 1.7 to 3.5. The pH of the above solution or slurry can be adjusted by using, for example, ammonia water or sulfuric acid as a catalyst raw material. The pH of the solution or slurry can be measured by a portable pH meter D-72 (product name) manufactured by HORIBA.

< formation of solid component >

Next, the solution or slurry is heated to generate a solid component. The heating temperature of the solution or slurry is preferably 80 to 300 ℃. When the heating temperature is 80 ℃ or higher, a metal oxide having a cyclic structure satisfying the above condition (b) can be advantageously formed in the step (2) described later. Further, when the heating temperature is 300 ℃ or lower, the methacrylic acid yield of the finally obtained catalyst is improved. The lower limit of the heating temperature is more preferably 120 ℃ or higher, and still more preferably 175 ℃ or higher. The upper limit of the heating temperature is more preferably 260 ℃ or less, and still more preferably 230 ℃ or less.

The heating time of the solution or slurry is preferably 3 to 200 hours from the viewpoint of methacrylic acid yield. The lower limit of the heating time is more preferably 10 hours or more and the upper limit is preferably 72 hours or less.

A sheet or a glass plate made of teflon (registered trademark) may be added in advance to the solution or the slurry. Since orthorhombic and trigonal structures have properties of being easily formed on the surface of teflon, the formation of these crystal structures can be promoted by adding a sheet or a glass plate made of teflon.

Production of solid component by hydrothermal method

From the viewpoint of the methacrylic acid yield of the obtained catalyst, it is preferable to use a hydrothermal method capable of suppressing evaporation of water to produce a solid component. The hydrothermal method is a method in which a compound is synthesized or the like in the presence of hot water at high temperature and high pressure, and a reaction is performed by heating and pressurizing a raw material and water in a closed vessel called an autoclave. The hydrothermal method may use a pressure vessel such as an autoclave. The container may be left standing or rotated, or the electromagnetic wave may be irradiated from the outside of the container.

When the hydrothermal method is used, the structure of the solid component to be produced can be controlled by the concentration of the molybdenum raw material to be used and the pH of the solution or slurry. For example, when ammonium heptamolybdate molybdenum is used as a raw material, the concentration of ammonium heptamolybdate is set to 0.02 to 0.04mol/L relative to the solvent, the pH of the solution or slurry is set to 2.3 to 3.5, which tends to promote the formation of an orthorhombic structure, and the pH is set to 1.7 to 2.3, which tends to promote the formation of a trigonal structure. Further, the concentration of ammonium heptamolybdate is 0.05 to 0.30mol/L relative to the solvent, and the pH of the solution or slurry is 1.7 to 3.5, so that the formation of an amorphous structure tends to be promoted.

< drying of the solution or slurry >

After the solid content is produced, the solution or slurry may be dried by suction filtration, centrifugal separation, a drum dryer, a spray dryer, or the like to obtain a solid content. When suction filtration or centrifugal separation is used, it is preferable to further remove water at 20 to 150 ℃ to obtain a solid component.

(step (1b))

In the method for producing a catalyst for methacrylic acid production according to the present invention, when the metal oxide has an orthorhombic or trigonal crystal structure, the method may further include a step (1b) of dispersing the solid component produced in the step (1) in an oxalic acid aqueous solution, hydrochloric acid, ethylene glycol or hydrogen peroxide water. When the solid component contains a component having a hexagonal structure or a pseudo-hexagonal structure, the yield may be lowered in the production of methacrylic acid. By dispersing the solid component in an oxalic acid aqueous solution, hydrochloric acid, ethylene glycol, or hydrogen peroxide water, a component having a hexagonal structure or a pseudo-hexagonal structure is eluted, and these components can be separated from the solid component.

On the other hand, since the component having an amorphous structure is also eluted in the step (1b), when the metal oxide has an amorphous structure, it is preferable to produce the catalyst for methacrylic acid production without performing the step (1 b).

The solid component produced in the step (1) or the solid component after the dispersion treatment obtained in the step (1b) (hereinafter, collectively referred to as "solid component") preferably satisfies the following conditions (h) and (i).

(h) A solid content having an average length of 2 to 50 μm as observed by an electron microscope.

(i) And a solid component having an average aspect ratio of 2 to 30 in the crystal observed by an electron microscope.

(wherein, the average aspect ratio is (average length of crystal)/(average diameter of crystal))

< Condition (h) and Condition (i) >

The electron microscope used for observing the average length and average aspect ratio of the crystal is not limited, and the length may be measured as long as the electron microscope can recognize 0.1 to 50 μm, and at least 2 to 50 μm. For example, the solid component can be observed by fixing it on a carbon ribbon, a grid (grid) for an electron microscope, or a mesh (mesh) using a Scanning Electron Microscope (SEM), a Transmission Electron Microscope (TEM), a Scanning Transmission Electron Microscope (STEM), or the like.

In the conditions (h) and (i), the average length of the crystals represents an average of the lengths in the major axis direction of the observed crystals, and the average diameter of the crystals represents an average of the lengths in the minor axis direction of the observed crystals. The lengths of the long axis direction and the short axis direction of the crystal may be obtained by manually measuring the lengths in consideration of a scale (scale) or by performing length measurement through image analysis. In either case of manual and image analysis, at least 500 different crystals capable of identifying the crystal length are extracted, and the lengths in the major axis direction and the minor axis direction measured for all the extracted crystals are obtained. The average length of the crystals is calculated by averaging the lengths in the major axis direction, and the average diameter of the crystals is calculated by averaging the lengths in the minor axis direction. When the cross section of the crystal in the short axis direction is not a perfect circle, the length in the short axis direction is calculated from the cross section in the short axis direction using the following formula.

The average diameter of the crystals and the average aspect ratio of the crystals can be controlled by adding a surfactant as a catalyst raw material in the step (1). When the amount of the surfactant added is increased, the average diameter of the crystals of the solid component becomes large and the average aspect ratio becomes small. The average length of the crystals and the average aspect ratio of the crystals can be controlled by pulverizing the solid component. If the pulverization time is long, the crystals are physically broken, the average length of the crystals becomes small, and the average aspect ratio becomes small. Examples of the pulverization include a method using a mortar, a ball mill, a high-speed rotary mill, a jet mill, a kneader, or the like.

From the viewpoint of stably maintaining the above-mentioned cyclic structure, the average length of the crystals is preferably 0.1 μm or more, more preferably 0.2 μm or more, further preferably 1 μm or more, and particularly preferably satisfies the condition (h) (2 μm or more).

In the condition (h), when the average length of the crystals is 2 μm or more, the cyclic structure satisfying the conditions (a) and (b) can stably maintain the structure, and the continuous operation time in the production of methacrylic acid can be increased by a simple method. Further, when the average length of the crystals is 50 μm or less, the cross section of the crystals in the short axis direction can be effectively used in the production of methacrylic acid, and the yield of methacrylic acid can be improved. From these viewpoints, the average length of the crystals is more preferably 3 μm or more, further preferably 5 μm or more, and further preferably 40 μm or less, and more preferably 30 μm or less.

In the condition (i), if the average aspect ratio of the crystal is 2 to 30, collapse of the cyclic structure satisfying the conditions (a) and (b) is easily suppressed, and the cyclic structure effectively contributes to the reaction in the production of methacrylic acid, so that the yield of methacrylic acid is improved.

(Molding Process)

The method for producing a catalyst for methacrylic acid production of the present invention may include a molding step of molding the solid component before the step (2) or the step (2b) described later. By molding the solid component, the pressure loss in the reactor is reduced in the production of methacrylic acid, and the influence of the diffusion of the raw material gas can be suppressed, thereby improving the selectivity of methacrylic acid.

The molding method is not particularly limited, and a known dry or wet molding method can be used. Examples of the molding method include tablet molding, extrusion molding, press molding, and rotary granulation. The shape of the solid component after molding is not particularly limited, and examples thereof include any shape such as spherical particles, annular, cylindrical particles, star-shaped particles, and particles obtained by pulverizing and classifying after molding. The size of the solid component after molding is preferably 0.1 to 10mm in diameter. When the diameter is 0.1mm or more, the pressure loss in the reactor can be sufficiently reduced in the production of methacrylic acid. Further, the conversion rate of methacrolein is improved by having a diameter of 10mm or less. More preferably, the lower limit of the diameter is 3mm or more and the upper limit thereof is 8mm or less.

(step (2) and step (2b))

In the step (2) and the step (2b), the solid component or the molded solid component obtained in the molding step is calcined to obtain a metal oxide. By calcining the solid component or the molded solid component obtained in the molding step, the conversion rate of methacrolein in the production of methacrylic acid can be improved. The step (2) represents a case where the solid component is the solid component produced in the step (1), and the step (2b) represents a case where the solid component is the solid component after the dispersion treatment obtained in the step (1 b).

The calcination method is not particularly limited, and an appropriate method can be appropriately selected from static calcination, fluidized calcination, and the like. Examples of the static calcination include calcination using a box-type electric furnace, a ring calciner, or the like. The fluidized calcination includes, for example, a method of calcination using a fluidized calciner, a rotary kiln, or the like. The calcination gas is, for example, an atmosphere containing an oxygen-containing gas such as air or an inert gas. The "inert gas" means a gas that does not lower the catalyst activity in the production of methacrylic acid, and examples thereof include nitrogen, carbon dioxide gas, helium, argon, and the like. These may be used in a mixture of 1 or more than 2. The atmosphere of the calcination may be a flow of the calcination gas or a non-flow of the calcination gas, as long as the atmosphere can maintain a desired calcination gas atmosphere. From the viewpoint of forming a metal oxide having a cyclic structure satisfying the above conditions (a) and (b), the calcination temperature is preferably 200 to 500 ℃. The lower limit of the calcination temperature is more preferably 300 ℃ or more and the upper limit thereof is more preferably 470 ℃ or less. The calcination time is preferably 1 to 40 hours.

[ method for producing methacrylic acid ]

The method for producing methacrylic acid of the present invention is a method for producing methacrylic acid by oxidizing methacrolein using the catalyst for producing methacrylic acid of the present invention. The method for producing methacrylic acid of the present invention is a method for producing methacrylic acid by producing a catalyst for methacrylic acid production by the method of the present invention, and producing methacrylic acid by oxidizing methacrolein using the catalyst for methacrylic acid production. The oxidation may be carried out by filling a reactor with a catalyst for methacrylic acid production containing the metal oxide, and supplying a raw material gas containing methacrolein to the reactor.

< filling of catalyst >

The catalyst for methacrylic acid production may contain a known oxidation catalyst such as polyoxometallate in addition to the metal oxide, but from the viewpoint of the continuous operating time in methacrylic acid production, the metal oxide is preferably contained in an amount of 80% by mass or more, and more preferably 90% or more. The catalyst layer may be 1 layer, or a plurality of catalysts having different activities may be packed in a plurality of layers. For heat removal, it is preferable to use the mixture in admixture with an inert diluent such as sea sand or silicon carbide.

< supply of raw gas >

The raw material gas may be a gas obtained by diluting methacrolein and molecular oxygen with an inert gas such as nitrogen or carbon dioxide gas. Further, water vapor may be added to the raw material gas.

As the raw material gas, a gas having a composition represented by the following formula (IV) is preferably supplied.

Methacrolein: oxygen: water vapor: a ═ k: l: m: n (IV)

(in the formula (IV), A represents nitrogen or helium, k to n represent the molar ratio of each gas, and when k + l + m + n is 100, 0.5 < k < 8.0, 2.0 < l < 20.0, 0. ltoreq. m < 45.)

In the formula (IV), from the viewpoint of methacrylic acid selectivity, k to m are preferably 2.0 < k < 4.0, 5.0 < l < 12.0, and 0. ltoreq. m < 25.

From the viewpoint of utility cost, the upper limit of m is preferably 10 or less. This reduces the raw material cost in the production of methacrylic acid. Further, the amount of wastewater is reduced, and therefore the cost required for wastewater treatment is cut. The upper limit of m is more preferably 5 or less, and still more preferably m is 0.

Further, the raw material gas containing methacrolein is preferably supplied so as to satisfy at least one selected from the following formulae (V) and (VI), and more preferably supplied so as to satisfy the following formulae (V) and (VI).

15＜W/F＜550 (V)

(in the formula (V), W represents the mass (g) of the metal oxide packed in the reactor, and F represents the amount (mol/h) of methacrolein supplied per unit time.)

0.00002＜F/(S×W)＜0.008 (VI)

In the formula (V), W/F represents the contact time between the catalyst packed in the reactor and methacrolein. When W/F is more than 15, excessive heat generation of the catalyst in the production of methacrylic acid can be suppressed. Further, when W/F is less than 550, the catalyst cost can be suppressed. The lower limit of W/F is more preferably 20 or more, still more preferably 40 or more, particularly preferably 50 or more, and most preferably 80 or more. The upper limit of W/F is more preferably 500 or less, still more preferably 400 or less, and particularly preferably 270 or less.

In the formula (VI), F/(sxw) represents the supply amount of methacrolein per specific surface area of the catalyst. If F/(sxw) is greater than 0.00002, the size of the reactor required to ensure the desired production amount of methacrylic acid can be suppressed. When F/(sxw) is less than 0.008, the catalyst cost can be suppressed. The lower limit of F/(sxw) is more preferably 0.00007 or more. The upper limit of F/(sxw) is more preferably 0.005 or less, still more preferably 0.001 or less, and particularly preferably 0.0008 or less.

< reaction temperature and pressure >

The reaction temperature is preferably 180 to 500 ℃, more preferably, the lower limit is 200 ℃ or more, and the upper limit is 400 ℃ or less. The reaction pressure is preferably 0.1 to 1MPa (G). Wherein (G) is gauge pressure.

[ method for producing methacrylic acid ester ]

The method for producing methacrylic acid esters of the present invention is a method for esterifying methacrylic acid produced by the method of the present invention. The method for producing methacrylic acid esters of the present invention is a method for producing methacrylic acid by the method of the present invention and esterifying the methacrylic acid. According to these methods, methacrylic acid ester can be obtained by using methacrylic acid obtained by oxidation of methacrolein. The alcohol to be reacted with methacrylic acid is not particularly limited, and examples thereof include methanol, ethanol, isopropanol, n-butanol, and isobutanol. Examples of the obtained methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and the like. The reaction may be carried out in the presence of an acidic catalyst such as a sulfonic acid type cation exchange resin. The reaction temperature is preferably 50-200 ℃.

Examples

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

(measurement of average Length and average aspect ratio of Crystal)

The average length and average aspect ratio of the crystals in the solid content were calculated by manually measuring the lengths in the major axis direction and the minor axis direction of at least 500 crystals by SEM (product name: JSM-7400F, manufactured by JEOL) and obtaining the average value.

(measurement of pore diameter by molecular Probe method)

The pore diameter of the metal oxide is determined by pretreating the metal oxide at 300 deg.C and then by using CO₂、CH₄Or C₂H₆The adsorption isotherm (product name: BELSORP-MAX, manufactured by Microtrac Bel) was prepared by the molecular probe method of (1) and calculated by the DA method.

(measurement of X-ray diffraction Pattern)

The X-ray diffraction pattern of the metal oxide was measured by an X-ray structure analyzer (product name: RINT Ultima)⁺Rigaku system, tube voltage 40kV, tube current 20mA), and measured using Cu-K.alpha.rayIn (1). With respect to the obtained X-ray diffraction pattern, only cases where diffraction peaks were shown at 2 θ of 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° were determined to have an amorphous structure. In addition, in addition to 2 θ of 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 °, cases where diffraction peaks are further displayed at 2 θ of 6.6 ° ± 0.3 °, 7.9 ° ± 0.3 °, 9.0 ° ± 0.3 °, 26.4 ° ± 0.3 °, 26.9 ° ± 0.3 °, 27.2 ° ± 0.3 ° and 27.4 ° ± 0.3 ° were determined as a crystal structure having an orthorhombic crystal. In addition, in addition to 2 θ of 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 °, cases where diffraction peaks are further displayed at 2 θ of 4.7 ° ± 0.3 °, 8.3 ° ± 0.3 °, 25.3 ° ± 0.3 °, 25.7 ° ± 0.3 °, 27.0 ° ± 0.3 °, 27.9 ° ± 0.3 ° and 28.3 ° ± 0.3 ° are determined as a crystal structure having a trigonal crystal. For structures other than the amorphous structure, the orthorhombic crystal structure, and the trigonal crystal structure, the crystal structure was determined by performing the already reported XRD pattern and Search-Match analysis. Search-Match analysis was performed using analysis software JADE9.8 and using the already reported XRD pattern data recorded in ICDD 2017.

(calculation of molar ratio)

The molar ratio of each element in the metal oxide is calculated by dissolving the metal oxide component in an aqueous solution of ammonia or hydrofluoric acid and analyzing the solution by ICP emission analysis. The molar ratio of ammonium groups is a value obtained by analyzing the metal oxide by kjeldahl method. When the solid component is recovered by suction filtration, a part of the metal component is eluted to the filtrate side, and therefore the molar ratio calculated from the charge ratio of the raw materials does not necessarily coincide with the molar ratio calculated by the above analysis of the obtained metal oxide.

(calculation of differential spectra by FT-IR measurement)

FT-IR measurement of the metal oxide (product name: FT/IR-6100, manufactured by Nissan Spectroscopy) was carried out by the transmission method. Firstly, 40-50 mg of metal oxide is made into particles with the diameter of 20mm, then the particles are arranged in a device, the temperature is raised to 400 ℃ at the speed of 10 ℃/min under the flow of helium, and the pretreatment is carried out for 10 min. Thereafter, the metal oxide was cooled to 100 ℃ and the infrared absorption spectrum was measured (FT-IR measurement 1). Next, the metal oxide was kept in a water vapor atmosphere of 20% by volume for 10 seconds, methacrolein was introduced so as to be in a methacrolein atmosphere of 2.0% by volume or more, the gas flow was switched to oxygen and kept for 60 minutes, and then the infrared absorption spectrum was measured (FT-IR measurement 2). The infrared absorption spectrum obtained by FT-IR measurement 1 was subtracted from the infrared absorption spectrum obtained by FT-IR measurement 2, thereby calculating a differential spectrum.

(measurement of BET specific surface area)

The BET specific surface area S of the metal oxide was calculated by a BET method using a nitrogen adsorption isotherm (product name: BELSORP-MAX, manufactured by MicrotracBEL) prepared by pretreating the metal oxide at 300 ℃.

(analysis of raw gas and product)

The raw material gas and the product were analyzed by gas chromatography (apparatus: GC-14B manufactured by Shimadzu corporation, column: Porapak-QS). From the results of the gas chromatography, the conversion of methacrolein, the selectivity for methacrylic acid produced, and the yield of methacrylic acid were determined by the following formulae.

Methacrolein conversion (%) (. beta./. alpha.). times.100

Methacrylic acid selectivity (%) (γ/β) × 100

Methacrylic acid yield (%) - (γ/α) × 100

In the above formula, α represents the number of moles of methacrolein supplied, β represents the number of moles of methacrolein reacted, and γ represents the number of moles of methacrylic acid formed.

Production example 1

To a solution obtained by adding 8.83g of ammonium heptamolybdate tetrahydrate to 120g of pure water and stirring at room temperature, 3.29g of vanadyl sulfate was added to 120g of pure water and stirred at room temperature, and stirred for 10 minutes. The pH at this point was 3.19. The mixed solution thus obtained was transferred into a Teflon autoclave previously charged with a Teflon sheet, and bubbled with nitrogen at a flow rate of 50L/min for 10 minutes. Thereafter, the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 48 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid content was mixed with 1.26g of oxalic acid dihydrate and 25g of pure water based on 1.0g of the solid content, and dispersed and mixed at 60 ℃ for 30 minutes. Thereafter, the solid content was recovered by suction filtration while thoroughly washing with 500g of pure water, and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar. The average length and average aspect ratio of the crystals were measured for the obtained solid content after the pulverization treatment. The results are shown in Table 1.

Then, the solid component after the pulverization treatment was calcined at 400 ℃ for 2 hours under a nitrogen flow of 50mL/min to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II). The metal oxide was measured by FT-IR measurement, and the mass ratio M2/M1 of the inactive component, the differential spectrum obtained by FT-IR measurement, and the BET specific surface area S are shown in Table 1.

Production example 2

The solid content after the dispersion treatment was obtained by the same method as in production example 1. The solid content after the dispersion treatment was not subjected to pulverization treatment, and the average length and average aspect ratio of the crystals were measured. The results are shown in Table 1.

Next, the solid component after the dispersion treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

Production example 3

To a solution obtained by adding 8.83g of ammonium heptamolybdate tetrahydrate to 120g of pure water and stirring at room temperature, 3.29g of vanadyl sulfate was added to 120g of pure water and stirred at room temperature, and stirred for 10 minutes. Next, 2M sulfuric acid was added to adjust the pH to 2.30. The mixed solution thus obtained was transferred into a Teflon autoclave previously charged with a Teflon sheet, and bubbled with nitrogen at a flow rate of 50L/min for 10 minutes. Thereafter, purification of the solid content by hydrothermal method was carried out in an oven at 175 ℃ for 20 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

Production example 4

To a solution obtained by adding 17.7g of ammonium heptamolybdate tetrahydrate to 120g of pure water and stirring at room temperature, 6.58g of vanadyl sulfate was added to 120g of pure water and stirred at room temperature, and stirred for 10 minutes. The pH at this point was 3.26. The resulting mixed solution was transferred into an autoclave made of Teflon, and nitrogen was bubbled at a flow rate of 50L/min for 10 minutes. Thereafter, the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 48 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid content was pulverized with an agate mortar for 5 minutes.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II), and has an amorphous structure showing diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern. The metal oxide was measured by FT-IR measurement, and the mass ratio M2/M1 of the inactive component, the differential spectrum obtained by FT-IR measurement, and the BET specific surface area S are shown in Table 1.

Production example 5

(C) was obtained by adding 21.594g of molybdenum trioxide to a solution prepared by adding 28.04g of pure water to 28.04mL of a 70% ethylamine solution, completely dissolving the molybdenum trioxide in the solution, and then evaporating the solution₂H₅NH₃)Mo₃O₁₀. 1.799g of (C) to be obtained₂H₅NH₃)Mo₃O₁₀The resulting solution was dissolved in 20g of pure water, and 0.658g of vanadyl sulfate was added to 20g of pure water and stirred at room temperature for 10 minutes. Then, 0.327g of bismuth oxychloride was added and stirred for a further 10 minutes, and 2M sulfuric acid was added to adjust the pH to 2.0. The mixed solution thus obtained was transferred into a Teflon autoclave previously charged with a Teflon sheet, and bubbled with nitrogen at a flow rate of 50L/min for 10 minutes. Thereafter, the autoclave was rotated at 1rpm, and the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 48 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid component was mixed with 20mL of 1.2M hydrochloric acid per 1.0g of the solid component, and dispersed and mixed at room temperature for 30 minutes. Thereafter, while thoroughly washing with 1000g of pure water, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II). The metal oxide was measured by FT-IR measurement, and the mass ratio M2/M1 of the inactive component, the molar ratio of oxygen-free component, the differential spectrum obtained by FT-IR measurement, and the BET specific surface area S are shown in Table 1.

Production example 6

21.594g of molybdenum trioxide was added to 33.2mL of a 40% methylamine solution, and after completely dissolving the molybdenum trioxide, the mixture was evaporated to obtain (CH)₃NH₃)₆Mo₇O₂₄. 1.780g of (CH) will be obtained₃NH₃)₆Mo₇O₂₄The resulting solution was dissolved in 20g of pure water, and 0.658g of vanadyl sulfate was added to 20g of pure water and stirred at room temperature for 10 minutes. Then, 0.156g of copper sulfate pentahydrate was added thereto and further stirred for 10 minutes. The pH at this point was 3.2. The mixed solution thus obtained was transferred into a Teflon autoclave previously charged with a Teflon sheet, and bubbled with nitrogen at a flow rate of 50L/min for 10 minutes. Thereafter, the autoclave was rotated at 1rpm, and the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 20 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

Production example 7

(C) was obtained by adding 21.594g of molybdenum trioxide to a solution prepared by adding 28.04g of distilled water to 28.04mL of a 70% ethylamine solution, completely dissolving the molybdenum trioxide in the solution, and then evaporating the solution₂H₅NH₃)Mo₃O₁₀. 1.799g of (C) to be obtained₂H₅NH₃)Mo₃O₁₀The resulting solution was dissolved in 20g of pure water, and 0.658g of vanadyl sulfate was added to 20g of pure water and stirred at room temperature for 10 minutes. Subsequently, 0.161g of ammonium metatungstate was added and further stirred for 10 minutes. The pH at this point was 2.4. The mixed solution thus obtained was transferred into a Teflon autoclave previously charged with a Teflon sheet, and bubbled with nitrogen at a flow rate of 50L/min for 10 minutes. Thereafter, the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 48 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

Production example 8

1.780g of (CH) was obtained in the same manner as in production example 6₃NH₃)₆Mo₇O₂₄The resulting solution was dissolved in 20g of pure water, and 0.642g of vanadyl sulfate was added to 20g of pure water and stirred at room temperature for 10 minutes. Then, 0.176g of iron sulfate heptahydrate was added and further stirred for 10 minutes. The pH at this point was 2.84. The resulting mixed solution was transferred into an autoclave made of Teflon, and nitrogen was bubbled at a flow rate of 50L/min for 10 minutes. Thereafter, the autoclave was rotated at 1rpm, and the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 20 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained solid content after the dispersion treatment was pulverized for 5 minutes using an agate mortar.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II). The mass ratio of the inactive ingredients M2/M1 and the differential spectrum obtained by FT-IR measurement of the metal oxide are shown in Table 1.

Production example 9

The solid content after the pulverization treatment obtained in the same manner as in production example 1 was calcined at 400 ℃ for 2 hours under an air flow of 50mL/min, and then calcined at 550 ℃ for 2 hours under a nitrogen flow of 50mL/min, to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide did not have a cyclic structure in which 7 metal-oxygen octahedrons (octahedral structures) share oxygen at adjacent vertices and are bonded together. In addition, the mass ratio of the inactive component M2/M1, the molar ratio of not containing oxygen, the differential spectrum obtained by FT-IR measurement, and the BET specific surface area S of the metal oxide are shown in table 1.

Production example 10

A solution obtained by adding 0.658g of vanadyl sulfate to 20g of purified water and stirring at room temperature was mixed with a solution obtained by adding 1.766g of ammonium heptamolybdate tetrahydrate to 120g of purified water and stirring at room temperature, and stirred for 10 minutes. Subsequently, 2M sulfuric acid was added to adjust the pH to 1.20. The resulting mixed solution was transferred into an autoclave made of Teflon, and nitrogen was bubbled at a flow rate of 50L/min for 10 minutes. Thereafter, the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 20 hours. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid content was pulverized with an agate mortar for 5 minutes.

Then, the solid component after the pulverization treatment was calcined at 400 ℃ for 2 hours under a nitrogen flow of 50mL/min to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified from the obtained X-ray diffraction pattern by performing X-ray diffraction measurement. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide did not have a cyclic structure in which 7 metal-oxygen octahedrons (octahedral structures) share oxygen at adjacent vertices and are bonded together. In addition, the mass ratio of the inactive ingredients M2/M1, the molar ratio of the inactive ingredients not containing oxygen, and the differential spectrum obtained by FT-IR measurement are shown in table 1.

Production example 11

A solution obtained by adding 0.159g of ammonium metavanadate to 20g of pure water and stirring the mixture at room temperature was mixed with a solution obtained by adding 1.766g of ammonium heptamolybdate tetrahydrate to 20g of pure water and stirring the mixture at room temperature, and the mixture was stirred for 10 minutes. The pH of the resulting solution was 2.21. The solid obtained by evaporating the mixed solution was recovered and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid content was pulverized with an agate mortar for 5 minutes.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide did not have a cyclic structure in which 7 metal-oxygen octahedrons (octahedral structures) share oxygen at adjacent vertices and are bonded together. Further, the crystal structure was analyzed from the obtained X-ray diffraction pattern by X-ray diffraction measurement, and the obtained metal oxide was found to contain MoO₃、(V_0.12Mo_0.88)O_2.94、V_0.95Mo_0.97O₅A mixture of these at least 3 compounds. The mass ratio of the inactive component M2/M1, the molar ratio of oxygen-free component, and the differential spectrum obtained by FT-IR measurement are shown in table 1.

Production example 12

To a solution prepared by adding 5.30g of ammonium heptamolybdate tetrahydrate in 30g of pure water and stirring at room temperature was added 1.40g of antimony sulfate and the mixture was stirred for 15 minutes. Subsequently, a solution obtained by adding 2.35g of vanadyl sulfate to 20g of pure water and stirring at room temperature was mixed and stirred for 5 minutes. The pH at this time was 1.80. The mixed solution thus obtained was transferred to an autoclave made of Teflon, and the formation of a solid content by a hydrothermal method was carried out in an oven at 175 ℃ for 24 hours while rotating the autoclave at 1 rpm. Thereafter, the solid content was recovered by suction filtration and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid content was pulverized with an agate mortar for 5 minutes. The average length and average aspect ratio of the crystals were measured for the obtained solid content after the pulverization treatment. The results are shown in Table 1.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

Production example 13

The dried solid content obtained by the same method as in production example 1 was pulverized with an agate mortar for 5 minutes. The average length and average aspect ratio of the crystals were measured for the obtained solid content after the pulverization treatment. The results are shown in Table 1.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II). The mass ratio of the inactive ingredients M2/M1 and the differential spectrum obtained by FT-IR measurement of the metal oxide are shown in Table 1.

Production example 14

The dried solid content obtained by the same method as in production example 1 was calcined by the same method as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II). The mass ratio of the inactive ingredients M2/M1 and the differential spectrum obtained by FT-IR measurement of the metal oxide are shown in Table 1.

Production example 15

To a solution obtained by adding 1.766g of ammonium heptamolybdate tetrahydrate to 20g of pure water and stirring at room temperature was mixed a solution obtained by adding 0.642g of vanadyl sulfate to 20g of pure water and stirring at room temperature, and stirred for 10 minutes. The pH at this time was 3.16. The obtained mixed solution was evaporated to obtain a solid, which was recovered and dried in an oven at 80 ℃ to remove water.

Subsequently, the obtained dried solid content was pulverized with an agate mortar for 5 minutes.

Next, the solid component after the pulverization treatment was calcined in the same manner as in production example 1 to obtain a metal oxide.

The pore diameter of the obtained metal oxide was measured by a molecular probe method. Further, the crystal structure was specified by X-ray diffraction measurement, and the molar ratio of each element was calculated by ICP emission analysis. The results are shown in Table 1. From these measurement results, it was confirmed that the obtained metal oxide had a cyclic structure satisfying the formula (I) and 7 metal-oxygen octahedrons (octahedral structures) were bonded to each other while sharing oxygen at adjacent vertices. In addition, it was confirmed that the metal oxide satisfies the above formula (II), and has an amorphous structure showing diffraction peaks only at 22.1 ° ± 0.3 ° and 45.2 ° ± 0.3 ° in an X-ray diffraction pattern. The mass ratio of the inactive component M2/M1, the molar ratio of oxygen-free component, and the differential spectrum obtained by FT-IR measurement are shown in table 1.

[ examples 1 to 6]

The metal oxide obtained in production example 1 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 2.

[ examples 7 to 14]

The metal oxide obtained in production example 1 was used as a catalyst, and 4.5g of sea sand was mixed with 0.1g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 2.

[ examples 15 to 17]

The metal oxide obtained in production example 2 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 2.

[ examples 18 to 20]

The metal oxide obtained in production example 3 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 2.

[ examples 21 to 23]

The metal oxide obtained in production example 4 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 2.

[ examples 24 to 28]

The metal oxide obtained in production example 5 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ examples 29 to 32]

The metal oxide obtained in production example 6 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ examples 33 to 37]

The metal oxide obtained in production example 7 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ examples 38 to 40]

The metal oxide obtained in production example 8 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ comparative examples 1 to 3]

The metal oxide obtained in production example 9 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ comparative examples 4 to 6]

The metal oxide obtained in production example 10 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is supplied to the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ comparative examples 7 to 8]

The metal oxide obtained in production example 11 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 3.

[ examples 41 to 45]

The metal oxide obtained in production example 12 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

[ examples 46 to 50]

The metal oxide obtained in production example 13 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

[ examples 51 to 54]

The metal oxide obtained in production example 14 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

[ examples 55 and 56]

The metal oxide obtained in production example 15 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

[ example 57]

The metal oxide obtained in production example 1 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

[ example 58]

The metal oxide obtained in production example 1 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, and nitrogen is passed through the reactor to perform a reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

Examples 59 to 60

The metal oxide obtained in production example 2 was used as a catalyst, and 4.5g of sea sand was mixed with 0.5g of the catalyst and charged into a reactor. Subsequently, a raw material gas composed of methacrolein, oxygen, water vapor and nitrogen is passed through the reaction vessel to carry out the reaction. The composition of the raw material gas, the supply conditions, the reaction temperature and the reaction results are shown in table 4.

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

As shown in tables 1 to 4, in examples 1 to 60 using a metal oxide containing at least molybdenum, having a specific composition ratio, and containing a specific cyclic structure as a catalyst, methacrylic acid was obtained at a high yield. Further, it was confirmed from the X-ray diffraction peaks that the metal oxides obtained in production examples 1, 2, 5, 6, 8 and 12 to 14 were orthorhombic, the metal oxides obtained in production examples 3 and 7 were trigonal, and the metal oxides obtained in production examples 4 and 15 were amorphous.

On the other hand, in comparative examples 1 to 8 in which the metal oxide not containing the cyclic structure was used as a catalyst, the methacrylic acid yield was lower than in the examples.

In production example 2, the dried solid content having an average crystal length of 7.9 μm was not subjected to pulverization treatment to obtain a metal oxide. That is, a metal oxide can be obtained by a simpler method as compared with production example 1, and when such a metal oxide is further used as a catalyst, the effect of improving the continuous operation time in the production of methacrylic acid as described above can be expected. This point can also be estimated from examples 1 to 4 and 57 and examples 59 and 60 in which the metal oxides obtained in production examples 1 and 2 were used as catalysts and the reaction was carried out with the same W/F and raw material gas composition. From examples 1 to 4 and 57 in which the metal oxide obtained in production example 1 was used as a catalyst, it was found that: when the reaction temperature was increased to a high temperature, the yield of methacrylic acid was greatly decreased, and the yield of methacrylic acid was decreased to 18.8% in example 57 in which the reaction temperature was 317.0 ℃. In contrast, from examples 59 and 60 in which the metal oxide obtained in production example 2 was used as a catalyst: the decrease in the methacrylic acid yield at a high reaction temperature was suppressed, and the methacrylic acid yield as high as 29.8% was maintained in example 59 at a reaction temperature of 318.0 ℃. From this fact, it can be said that when the average crystal length of the solid component is within a specific range, a specific cyclic structure can be stably maintained even at a high reaction temperature, and a catalyst advantageous in continuous operation for a long time can be obtained by a simple method.

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Catalyst for methacrylic acid production, method for producing same, and method for producing methacrylic acid and methacrylic acid ester

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