阅读说明：本技术 一种氨基酸改性负载型杂多酸盐催化剂及其制备方法 (Amino acid modified supported heteropolyacid salt catalyst and preparation method thereof ) 是由 李彦君 房德仁 任万忠 于 2020-07-09 设计创作，主要内容包括：本发明属于催化剂技术领域,尤其涉及一种氨基酸改性负载型杂多酸盐催化剂及其制备方法。本发明制备的催化剂活性组分分布均匀,热稳定性高,可有效抑制催化剂的分解失活,极大地延长催化剂的使用寿命；将载体改性和杂多酸负载两步过程合二为一,简化了催化剂的制备流程,降低了过程能耗,制备的催化剂对烯丙基醛选择氧化为烯丙基酸表现出优异的催化性能；原料价格便宜,催化剂成本低,适合工业化生产。(The invention belongs to the technical field of catalysts, and particularly relates to an amino acid modified supported heteropolyacid salt catalyst and a preparation method thereof. The catalyst prepared by the method has the advantages of uniform distribution of active components and high thermal stability, can effectively inhibit the decomposition and inactivation of the catalyst, and greatly prolongs the service life of the catalyst; the two-step process of carrier modification and heteropoly acid loading is combined into one, the preparation process of the catalyst is simplified, the energy consumption of the process is reduced, and the prepared catalyst shows excellent catalytic performance for selectively oxidizing allyl aldehyde into allyl acid; the raw materials are cheap, the catalyst is low in cost, and the method is suitable for industrial production.)

1. An amino acid modified supported heteropolyacid salt catalyst is characterized in that the catalyst has the following general formula: a. the_xB_yC_zD_mP_nMo₁₁VO_f/E；

Wherein A is one or more than two of alkali metal elements of Na, K, Rb or Cs; b is one or more than two of Mg, Ba, Be, Ca, Sb or Si; c is one or more than two of Cu, Co, Cd, Fe, Zn or Mn; d is one or more than two of Ga, Ge, As, Ag, Ni or Ti; e is a carrier which is porous silicon dioxide, an MCM-41 molecular sieve, an MCM-48 molecular sieve, a ZMS-5 molecular sieve or an SBA-15 molecular sieve;

x, y, z, m and n respectively represent the molar ratio of each element in the catalyst; wherein x is 0.01-3; y is 0.1-2; z is 0.1-3; m is 0.01-3; n is 0.1-5; f is an atomic ratio of oxygen required to satisfy the valence of each element.

2. A method for preparing the amino acid modified supported heteropolyacid salt catalyst according to claim 1, characterized by comprising the steps of:

(1) adding the carrier into deionized water, adjusting the pH value of the solution, adding an amino acid-containing aqueous solution under the conditions of heating and stirring, and continuing stirring;

(2) dissolving phosphomolybdovanadophosphoric acid in deionized water, and adding the solution prepared in the step (1) under the conditions of heating and stirring to obtain a mixed solution;

(3) dripping a mixture of compounds containing A, B, C, D elements into the mixed solution obtained in the step (2), stirring and drying under a heating condition to obtain catalyst precursor powder;

(4) and (4) roasting the catalyst precursor powder obtained in the step (3) under the condition of air circulation to obtain the catalyst.

3. The method according to claim 2, wherein in the step (1), the amino acid is one or more of glycine, serine, threonine, cysteine, tyrosine, asparagine, glutamine, aspartic acid and glutamic acid.

4. The method according to claim 2, wherein in the step (1), the pH is adjusted to 2 to 5, and the pH adjusting agent is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, oxalic acid or citric acid.

5. The method according to claim 2, wherein in the step (1), the heating temperature is 20 to 90 ℃ and the stirring is carried out for 0.5 to 5 hours.

6. The method according to claim 2, wherein in the step (2), the heating temperature is 40 to 80 ℃ and the stirring is carried out for 1 to 12 hours.

7. The method according to claim 2, wherein in the step (3), the A, B, C, D element-containing compound is a nitrate, a carbonate, an acetate, an oxalate, a chloride, a hydroxide or an oxide of the corresponding element.

8. The preparation method according to claim 2, wherein in the step (3), the heating temperature is 40-80 ℃, and the stirring is carried out for 4-24 h; the drying is normal pressure evaporation drying, vacuum evaporation drying or spray drying.

9. The method as claimed in claim 2, wherein the calcination temperature in step (4) is 300-500 ℃ and the calcination time is 4-24 h.

10. The use of the amino acid-modified supported heteropolyacid salt catalyst according to claim 1 in the field of catalyzing the oxidation of propenyl aldehyde to acrylic acid.

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to an amino acid modified supported heteropolyacid salt catalyst and a preparation method thereof.

Background

Methyl Methacrylate (MMA) is an important organic chemical product, is mainly used for producing organic glass, can be used for manufacturing polyvinyl chloride auxiliaries ACR and MBS after being copolymerized with other vinyl compounds, and can be used as a second monomer for producing acrylic fibers. The mainstream process for producing MMA at present is the traditional acetone cyanohydrin method, but the process flow relates to the treatment of a large amount of highly toxic and highly corrosive concentrated acid and solid waste products, and the environmental bearing pressure is extremely high, so that the development of an advanced clean MMA production process is imperative. The isobutene oxidation route starting from isobutene, which is a petrochemical byproduct, as a raw material has the advantages of environmental friendliness, low operation cost and the like, and is the best choice for replacing the traditional process at present. The selective oxidation of Methacrolein (MAL) to methacrylic acid (MAA) is the core reaction of the process, and heteropoly acid shows better catalytic performance for the reaction, but the catalyst has the problems of short service life, low mechanical strength, poor MAA selectivity and the like. For this reason, some patents (US4803302A, CN1647854A, CN10481342A, ZL95407159.9) improve the reaction performance of the catalyst by modulating the composition, preparation method and operation conditions of the heteropoly acid compound, however, the MAL conversion rate and MAA selectivity still need to be further improved.

The oxidation reaction of MAL on the heteropolyacid salt catalyst is a surface reaction, and the surface area of the catalyst is closely related to the catalytic performance. The heteropolyacid salt is an ionic crystal, the smaller specific surface area of the heteropolyacid salt limits further improvement of the catalyst performance, the use efficiency of the catalyst can be improved in a loading mode, continuous aggregation of a heat effect can be greatly reduced by means of the better heat transfer performance of the porous carrier, and decomposition of the catalyst caused by reaction temperature runaway is avoided. Chinese patents ZL200480004485.6 and CN102203040 report a method of coating a catalyst active component on an inert carrier, in which the content of a catalyst constituent element is adjusted to improve the catalytic performance, but during the calcination process, the carrier reacts with the catalyst active component, so that the catalytic activity is reduced. The patent CN107042121 prepares a vanadium-modified three-dimensional macroporous silica carrier, and after heteropoly acid salts are loaded, the selectivity of MAA can be improved, but the conversion rate of MAL is low, the preparation process is complex, and the cost is high. Patent CN105363491A discloses a method for loading heteropoly acid catalyst after roasting polymerization by using amino compound coated carrier to obtain high performance catalyst. However, the selectivity of the catalyst is still low, and the amino compound modified carrier needs to be calcined at a high temperature (500-700 ℃) for one time in the preparation process, and the calcination damages the amino structure of the amino compound, which is not beneficial to the loading of the heteropoly acid and increases the energy consumption in the preparation process of the catalyst. Therefore, there is still a need to develop a new technology for preparing or modifying a carrier in the reaction of preparing MAA by selective oxidation of MAL, so as to improve the reaction performance of the catalyst and prolong the service life of the catalyst.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides an amino acid modified supported heteropolyacid salt catalyst and a preparation method thereof.

The technical scheme for solving the technical problems is as follows: an amino acid modified supported heteropolyacid salt catalyst, which has the following general formula: a. the_xB_yC_zD_mP_nMo₁₁VO_f/E；

Wherein A is one or more than two of alkali metal elements of Na, K, Rb or Cs; b is one or more than two of Mg, Ba, Be, Ca, Sb or Si; c is one or more than two of Cu, Co, Cd, Fe, Zn or Mn; d is one or more than two of Ga, Ge, As, Ag, Ni or Ti; e is a carrier which is porous silicon dioxide, an MCM-41 molecular sieve, an MCM-48 molecular sieve, a ZMS-5 molecular sieve or an SBA-15 molecular sieve;

x, y, z, m and n respectively represent the molar ratio of each element in the catalyst; wherein x is 0.01-3; y is 0.1-2; z is 0.1-3; m is 0.01-3; n is 0.1-5; f is an atomic ratio of oxygen required to satisfy the valence of each element.

The second purpose of the invention is to provide a preparation method of the amino acid modified supported heteropolyacid salt catalyst, which comprises the following steps:

(1) adding the carrier into deionized water, adjusting the pH value of the solution, adding an amino acid-containing aqueous solution under the conditions of heating and stirring, and continuing stirring;

(2) dissolving phosphomolybdovanadophosphoric acid in deionized water, and adding the solution prepared in the step (1) under the conditions of heating and stirring to obtain a mixed solution;

(3) dripping a mixture of compounds containing A, B, C, D elements into the mixed solution obtained in the step (2), stirring and drying under a heating condition to obtain catalyst precursor powder;

(4) and (4) roasting the catalyst precursor powder obtained in the step (3) under the condition of air circulation to obtain the catalyst.

Further, in the step (1), the amino acid is one or more than two of glycine, serine, threonine, cysteine, tyrosine, asparagine, glutamine, aspartic acid and glutamic acid; aspartic acid and glutamic acid are preferred.

Further, in the step (1), the pH is adjusted to 2-5, preferably 3-4; the pH regulator is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, oxalic acid or citric acid, preferably oxalic acid.

Further, in the step (1), the heating temperature is 20-90 ℃, and the stirring is carried out for 0.5-5 h.

Further, in the step (2), the heating temperature is 40-80 ℃, and the stirring is carried out for 1-12 h;

the weight ratio of the phosphomolybdovanadophosphoric acid to the carrier in the step (1) is (5-50):100, namely the loading amount of the phosphomolybdovanadophosphoric acid is 5-50%.

Further, in the step (3), the A, B, C, D element-containing compound is a nitrate, a carbonate, an acetate, an oxalate, a chloride, a hydroxide or an oxide of the corresponding element.

Further, in the step (3), the heating temperature is 40-80 ℃, and the stirring is carried out for 4-24 h; the drying is normal pressure evaporation drying, vacuum evaporation drying or spray drying.

Further, in the step (4), the roasting temperature is 300-.

The third purpose of the invention is to provide the application of the amino acid modified supported heteropolyacid salt catalyst in the field of catalyzing the oxidation of propenyl aldehyde into acrylic acid.

The invention has the characteristics and beneficial effects that:

1. the invention can effectively carry the amino acid by utilizing the reaction of carboxyl in the amino acid and hydroxyl on the porous oxide carrier under the acidic condition, and then the heteropolyacid is carried on the carrier by utilizing the chemical bonding of amino in the amino acid and the heteropolyacid, and the chemical bonding can prevent the active component in the catalyst from losing and being inactivated due to the loss caused by infirm carrying in the reaction. In addition, the preparation process of the catalyst can be simplified by utilizing the characteristics of the bifunctional chemical groups of the amino acid, the energy consumption loss caused by independently roasting the modified carrier is avoided, and the (1) isolation of the carrier and the heteropoly acid catalyst and the (2) formation of the crystal form structure of the heteropoly acid catalyst can be realized simultaneously by one-step roasting.

2. The catalyst prepared by the method has the advantages of uniform distribution of active components and high thermal stability, can effectively inhibit the decomposition and inactivation of the catalyst, and greatly prolongs the service life of the catalyst; the two-step process of carrier modification and heteropoly acid loading is combined into one, the preparation process of the catalyst is simplified, the energy consumption of the process is reduced, and the prepared catalyst shows excellent catalytic performance for selectively oxidizing allyl aldehyde into allyl acid; the raw materials are cheap, the catalyst is low in cost, and the method is suitable for industrial production.

Detailed Description

The principles and features of this invention are described below in conjunction with examples, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

The preparation process of the phosphomolybdovanadophosphoric acid used in the embodiment of the invention is as follows:

(1) 195g of ammonium molybdate is dissolved in 500mL of deionized water, and colorless transparent solution is obtained under the condition of room temperature stirring;

(2) adding 11.7g of ammonium metavanadate into 300mL of deionized water, heating to 90 ℃, and stirring for dissolving; then 14.2g of Na₂HPO₄Adding into the hot solution, and stirring for 10 min; adding 10mL of concentrated sulfuric acid into the mixed solution to obtain a red mixed solution;

(3) adding the red mixed solution obtained in the step (2) into the solution containing ammonium molybdate obtained in the step (1) under the conditions of 50 ℃ and strong stirring, slowly adding concentrated sulfuric acid, and adjusting the pH value to 2.2; cooling the solution, extracting with diethyl ether for several times, and removing diethyl ether under ventilation condition to obtain red crystal;

(4) and (4) dissolving the red crystal obtained in the step (3) in 500mL of deionized water, and recrystallizing under vacuum drying to obtain an orange crystal, namely the phosphomolybdovanadophosphoric acid.

The molecular formula of the phosphomolybdovanadophosphoric acid is H by analysis₄PMo₁₁VO₄₀˙14H₂O, relative molecular weight 2032.81.