阅读说明：本技术 一种氧化催化剂及其制备方法与应用 (Oxidation catalyst and preparation method and application thereof ) 是由 师慧敏 张东顺 袁滨 冯晔 张作峰 于 2020-06-28 设计创作，主要内容包括：本发明公开了一种氧化催化剂及其制备方法与应用,所述氧化催化剂包括第一钒钼催化剂和/或第二钒钼催化剂,在所述第一钒钼催化剂和/或第二钒钼催化剂中各自独立地含有钒、钼、镍和助剂,其中,第一钒钼催化剂中钒的平均氧化态低于第二钒钼催化剂中钒的平均氧化态。本发明在制备催化活性物质前体的过程中,利用氧化还原反应对活性物质前体中主要金属钒氧化态进行调变,并将其与不同种类的金属助剂耦合。利用所述催化剂应用于氧化合成顺酐的反应中,在苯浓度40-65g/Nm～(3)条件下,苯转化率达>98％,顺酐的重量收率达到94-99％。在同样的操作条件下,苯的转化率最高可提高3.6％,顺酐的重量收率最高可提高4.4％。(The invention discloses an oxidation catalyst and a preparation method and application thereof, wherein the oxidation catalyst comprises a first vanadium-molybdenum catalyst and/or a second vanadium-molybdenum catalyst, the first vanadium-molybdenum catalyst and/or the second vanadium-molybdenum catalyst respectively and independently contain vanadium, molybdenum, nickel and an auxiliary agent, and the average oxidation state of vanadium in the first vanadium-molybdenum catalyst is lower than that of vanadium in the second vanadium-molybdenum catalyst. In the process of preparing the catalytic active substance precursor, the oxidation-reduction reaction is utilized to modulate the oxidation state of main metal vanadium in the active substance precursor, and the main metal vanadium is coupled with different types of metal additives. The catalyst is applied to the reaction of synthesizing maleic anhydride by oxidation, and the benzene concentration is 40-65g/Nm 3 Under the condition, the conversion rate of benzene is up to>98 percent and the weight yield of the maleic anhydride reaches 94 to 99 percent. Under the same operation conditions, the conversion rate of benzene can be improved by 3.6 percent at most, and the weight yield of maleic anhydride can be improved by 4.4 percent at most.)

1. An oxidation catalyst comprising a first vanadium molybdenum catalyst and/or a second vanadium molybdenum catalyst in which vanadium, molybdenum, nickel and a promoter are each independently contained, wherein the average oxidation state of vanadium in the first vanadium molybdenum catalyst is lower than the average oxidation state of vanadium in the second vanadium molybdenum catalyst.

2. An oxidation catalyst according to claim 1, comprising an active component of formula (I) in each of the first and second vanadium molybdenum catalysts independently:

VMo_aNi_bA_cB_dC_eD_fO_xformula (I);

in formula (I), A, B, C, D represents the auxiliary agent, a, b, c, d, e, f and x respectively represent the atomic ratio of the corresponding elements; preferably, element a is selected from at least one of group IA elements; and/or the element B is selected from boron and/or phosphorus; and/or the element C is selected from at least one of iron, magnesium, cobalt, copper, zinc and silver; and/or the element D is at least one of bismuth, niobium, indium, antimony, thallium, tellurium and germanium.

3. The oxidation catalyst according to claim 2, wherein in the formula (I), a is 0.1 to 0.8, b is 0.001 to 0.05, c is 0.001 to 0.05, d is 0.002 to 0.1, e is 0.001 to 0.05, f is 0.001 to 0.05, and x is the number of oxygen required to satisfy the balance of valence states of other non-oxygen elements in the composite oxide forming the catalytically active substance.

4. An oxidation catalyst according to claim 1, wherein in the first and second vanadium molybdenum catalysts, the average oxidation state of the vanadium element is each independently in the range of from 4.50 to 4.95, and the average oxidation state of the vanadium in the first vanadium molybdenum catalyst is lower than the average oxidation state of the vanadium in the second vanadium molybdenum catalyst;

preferably, the average oxidation state of vanadium in the first vanadium molybdenum catalyst is 4.50-4.80, the average oxidation state of vanadium in the second vanadium molybdenum catalyst is 4.60-4.95, and the average oxidation state of vanadium in the first vanadium molybdenum catalyst is lower than the average oxidation state of vanadium in the second vanadium molybdenum catalyst.

5. The oxidation catalyst according to claim 1, further comprising a support in the first vanadium-molybdenum catalyst and/or the second vanadium-molybdenum catalyst, each independently, preferably wherein the support is an inert non-porous material, more preferably wherein the support is selected from at least one of alumina, silicon carbide, magnesium silicate, aluminum silicate, quartz, ceramic, and magnesium oxide.

6. The oxidation catalyst according to any one of claims 1 to 5,

in the first vanadium-molybdenum catalyst, the content of the active component shown in the formula (I) is 13-20 wt%, preferably 15-18 wt%; and/or

In the second vanadium-molybdenum catalyst, the content of the active component shown in the formula (I) is 13-20 wt%, preferably 15-18 wt%.

7. An oxidation catalyst according to claim 6, wherein when the oxidation catalyst comprises both the first vanadium-molybdenum catalyst and the second vanadium-molybdenum catalyst, the volume content of the first vanadium-molybdenum catalyst is (20-80)%, preferably (30-70)%; the volume content of the second vanadium-molybdenum catalyst is (80-20)%, preferably (70-30)%.

8. A method for preparing the oxidation catalyst according to any one of claims 1 to 7, comprising preparing the first vanadium molybdenum catalyst and/or the second vanadium molybdenum catalyst respectively, wherein the first vanadium molybdenum catalyst and/or the second vanadium molybdenum catalyst are obtained by the following steps independently:

step 1, mixing a vanadium-containing compound with oxalic acid to obtain a solution;

step 2, adding a molybdenum-containing compound, a nickel-containing compound, a compound containing A, a compound containing B, a compound containing C and a compound containing D into the dispersion liquid to obtain a dispersion liquid, and mixing the dispersion liquid with the solution obtained in the step 1 to obtain a dispersion system;

step 3, mixing the dispersion system with an organic solvent and a binder, and emulsifying to obtain a suspension;

and 4, spraying the obtained suspension on the surface of a carrier to obtain a catalyst precursor, and roasting to obtain the first vanadium-molybdenum catalyst or the second vanadium-molybdenum catalyst.

9. The method according to claim 8,

the vanadium-containing compound is at least one of metavanadate, orthovanadate, vanadium pentoxide, vanadium trichloride, vanadium dioxide and vanadium tetraoxide, and is preferably metavanadate; and/or

The molybdenum-containing compound is at least one of molybdate and molybdenum trioxide, and is preferably molybdate; and/or

The A-containing compound, the C-containing compound and the D-containing compound are respectively and independently selected from at least one of A-containing, C-containing and D-containing oxides, ammonium salts, nitrates, carbonates, bicarbonates, sulfates, halides, oxalates, phosphates, hydrogenphosphates and complexes; and/or

The B-containing compound is at least one selected from phosphorus pentoxide, phosphoric acid, hydrogen phosphate, dihydrogen phosphate, boric acid, metaboric acid, borate and metaborate.

10. The method according to claim 8, wherein in step 1, the molar ratio of oxalic acid to vanadium-containing compound is 1: (1.6-2.3), preferably,

in step 1 of preparing the first vanadium molybdenum catalyst, the molar ratio of oxalic acid to vanadium-containing compound is 1: (2 to 2.3), preferably 1: (2-2.28); and/or

In step 1 of preparing the second vanadium molybdenum catalyst, the molar ratio of oxalic acid to vanadium-containing compound is 1: (1.6-1.99), preferably 1: (1.7-1.96).

11. The production method according to claim 8, wherein, in step 2,

the dispersion is selected from acid solution and/or water; preferably, the acid solution is at least one selected from dilute nitric acid, dilute hydrochloric acid, dilute oxalic acid, dilute acetic acid and dilute sulfuric acid solution, and the weight concentration of the acid solution is preferably less than 15 wt%, and preferably 2-10 wt%; and/or

The weight ratio of the total amount of the molybdenum-containing compound, the nickel-containing compound, the A-containing compound, the B-containing compound, the C-containing compound and the D-containing compound to the dispersion is 1: (5-25), preferably 1: (8-20).

12. The production method according to claim 8, wherein, in step 3,

the organic solvent is a hydrophilic organic solvent, preferably at least one of monohydric alcohol, polyhydric alcohol, water-soluble ether and water-soluble amide, and more preferably at least one of methanol, ethanol, tetrahydrofuran, ethylene glycol dimethyl ether, formamide, N-dimethylformamide, pyrrolidone and N-methylpyrrolidone; and/or

The weight ratio of the organic solvent to the water in the suspension is (0-0.15): 1, preferably (0.05-0.15): 1; and/or

The binder is selected from cellulose and derivatives thereof and/or copolymer vinyl acetate; preferably, the cellulose and the derivatives thereof are selected from at least one of cellulose ether, anionic cellulose derivatives and nonionic cellulose derivatives, preferably at least one of methylcellulose, ethylcellulose, sodium carboxymethylcellulose, cellulose acetate, hydroxyethyl cellulose, hydroxypropyl cellulose and hypromellose; the copolymerization type vinyl acetate is selected from at least one of vinyl acetate-vinyl laurate, vinyl acetate-acrylic ester, vinyl acetate-ethylene and vinyl acetate-styrene; and/or

The binder is added in the form of a binder-containing dispersion, preferably, the binder is contained in the binder-containing dispersion in an amount of 5 to 30 wt%, preferably 5 to 20 wt%; and/or

The viscosity of the suspension obtained in the step 3 is 5-30 mPas.

13. The method for preparing according to claim 8, wherein step 2 comprises the substeps of:

step 2.1, adding a molybdenum-containing compound into the dispersion to obtain a first dispersion;

step 2.2, adding a nickel-containing compound, a compound containing A, a compound containing B and a compound containing C into the dispersion liquid to obtain a second dispersion liquid;

step 2.3, adding the compound containing D into the dispersion liquid to obtain a third dispersion liquid;

step 2.4, mixing the obtained solution, the first dispersion liquid, the second dispersion liquid and the third dispersion liquid to obtain a fourth dispersion liquid;

preferably, step 2.4 and step 3 are carried out in a back-mixed reactor, and more preferably, step 3 is emulsified for 0.1 to 2 hours under an inert atmosphere.

14. The method according to any one of claims 8 to 13, wherein in step 4, the carrier is subjected to a heat treatment, preferably at 250 to 300 ℃;

preferably, in step 4, the spraying is carried out in a coating machine as follows:

(1) putting the carrier into a rotary drum of a coating machine, and heating to 250-300 ℃;

(2) and (4) atomizing the suspension liquid obtained in the step (3), spraying the suspension liquid onto a carrier in a rotary drum, and controlling the temperature of the carrier to be 250-300 ℃.

15. The method of claim 14, wherein step 4 is optionally followed by step 5:

step 5, activating the first vanadium-molybdenum catalyst or the second vanadium-molybdenum catalyst obtained in the step 4;

preferably, the activation is carried out as follows:

(1) raising the temperature of the first vanadium-molybdenum catalyst or the second vanadium-molybdenum catalyst to 150 ℃ at a heating rate of 70-100 ℃/h, and preserving the temperature for 5-30 minutes;

(2) raising the temperature to 380 ℃ at a heating rate of 100-150 ℃/h, and preserving the heat for 20-60 minutes;

(3) heating to 420-480 ℃ at a heating rate of 20-60 ℃/h, preserving heat for 5-10 hours, and cooling to room temperature.

16. An oxidation catalyst obtained by the production method according to any one of claims 8 to 15.

17. A catalyst bed packed with the oxidation catalyst according to any one of claims 1 to 7 or the oxidation catalyst obtained by the production method according to any one of claims 8 to 15; preferably, the catalyst bed layer comprises an inlet section catalyst bed layer and an outlet section catalyst bed layer, the first vanadium-molybdenum catalyst is filled in the inlet section catalyst bed layer, and the second vanadium-molybdenum catalyst is filled in the outlet section catalyst bed layer.

18. Use of the oxidation catalyst according to any one of claims 1 to 7 or obtained by the production method according to any one of claims 8 to 15 for producing an acid anhydride by oxidation of benzene;

preferably, the benzene oxidation preparation anhydride is prepared in a reactor, the first vanadium-molybdenum catalyst is filled in an inlet section of the reactor, and the second vanadium-molybdenum catalyst is filled in an outlet section of the reactor;

more preferably, the loading volume of the first vanadium molybdenum catalyst is (20-80)% of the total catalyst loading volume; the loading volume of the second vanadium molybdenum catalyst is (80-20)% of the total catalyst loading volume.

Technical Field

The invention belongs to the field of catalysts, and particularly relates to an oxidation catalyst, a preparation method and application thereof, in particular to a catalyst for preparing maleic anhydride (maleic anhydride for short) by selective oxidation.

Background

Maleic anhydride (maleic anhydride) is mainly used for producing unsaturated polyester resin, in particular glass fiber reinforced unsaturated polyester resin, and is used as a raw material for manufacturing parts of vehicles (ships, automobiles and the like), corrosion-resistant chemical devices, decorative daily necessities and the like. In addition, the maleic anhydride can also be used for preparing nearly hundreds of downstream fine chemical organic intermediates and special chemicals such as coatings, lubricating oil additives, agricultural chemicals, papermaking chemicals and the like.

The maleic anhydride production in the world mainly takes n-butane and benzene as main raw materials. Although the production capacity of maleic anhydride from n-butane is expanding in recent years, the production method of benzene still accounts for 40% of the total production capacity in China, especially when the benzene resource is rich or C₄In areas with relatively insufficient resources, the benzene process has a larger living space. Technological advances in the process have been shown in recent years primarily in process improvements and catalyst improvements in existing units. Wherein the improvement of the catalyst performance is the technical key of the production. At present, maleic anhydride catalyst manufacturers in China all adopt a high-temperature spraying method to prepare catalysts suitable for benzene oxidation. The catalytically active mass of the catalyst is usually represented by V₂O₅-MoO₃Mainly, a small amount of phosphate, sodium salt, potassium salt, nickel salt and the like are added as promoters, and the carrier is generally alpha-Al with low surface area₂O₃SiC or TiO₂。

The surface property, the auxiliary agent composition, the spraying method, the activating method, the filling mode and the like of the catalyst all have obvious influence on the performance of the catalyst. Patents CN1026557C, CN107999107A, CN1106714A, CN104525231A, CN1106714A and CN103816931 mention the effect of modulating the composition of the surface active substance of the catalyst on the catalytic performance. For the selective oxidation catalyst, the modulation of the metal species composition on the surface of the catalyst can influence the efficiency of adsorbing reaction molecule (raw material hydrocarbon) centers on the catalyst and receiving electrons released from adjacent adsorption centers to form lattice oxygen oxidation centers, thereby playing the role of improving the activity and selectivity of the catalyst.

For the catalyst forming mode, the benzene method catalyst is mostly prepared by a spraying method. This method was adopted in patent CN1060042A, patent CN107999107A, patent CN1106714A, CN104525231A, CN1106714A, and patent CN 1031120964A. The load structure formed by spraying can greatly improve the utilization rate of the active component, and can also utilize the dilution effect and the heat conduction capability of the inert carrier to remove heat in time, thereby improving the selectivity of the catalyst and being beneficial to improving the stability of the catalyst in the strong heat release effect generated by the selective oxidation of the hydrocarbons. However, because the spraying process mostly adopts high-temperature spraying, the problem that active substances are greatly taken away along with the evaporation of a solvent exists; in addition, in the use of the catalyst, enterprises find that the problem of weak adhesion between the active substance attached to the carrier in a solid form and the carrier causes certain powder or piece shedding of the catalyst in the carrying, filling or using processes, so that the actual effect and long-term service life of the catalyst are influenced. Patent CN103120964A mentions a method of adding one or more of polyacrylic resin, poly-phenolic resin, polyvinyl alcohol glue and polyvinyl acetate into the spraying mother liquor as a binder to improve the loading effect of the catalytic active substance. The catalyst is activated (without material activation) before the reactor is filled, so that the balance and stabilization time of the maleic anhydride catalyst in the reactor in practical application can be greatly shortened, and the consumption of raw materials and energy is reduced.

In the aspect of catalyst activation, the chinese patent CN2643995Y puts the catalyst into a micro solid phase reactor, and then puts the reactor into an activation furnace to introduce ammonia gas with certain reducibility for high temperature roasting reduction. After the catalyst is activated, the weight yield of maleic anhydride can quickly reach 98-102% when the catalyst is used in the device. The patent CN102371187A discloses that the maleic anhydride catalyst is put in an activation device to carry out temperature control operation. Evaluation shows that the catalyst activated by the method can achieve higher weight yield of maleic anhydride. The process takes ammonia generated by the self-heating decomposition of the catalyst as a reducing agent during activation, does not need to introduce ammonia again, and has simple operation process. Based on the technology, the patent CN102371188A discloses a special ex-situ activator. The equipment can activate a large amount of catalyst, and the catalyst has uniform activation effect and convenient loading and unloading. Meanwhile, in the aspect of improving the performance of the catalyst, the multi-section bed catalyst filling technology is considered to be a method which can relatively effectively avoid the overhigh temperature of a hot spot of a catalyst bed layer and further ensure the high conversion rate of the benzene raw material and the yield of the maleic anhydride when the treatment load of the raw material is high.

In order to make the process for preparing maleic anhydride by benzene oxidation have larger competitiveness, the performance of V-Mo series catalyst for oxidation reaction needs to be improved, namely the catalyst needs to be on the basis of ensuring higher benzene conversion rate (generally>98 percent) to further improve the selectivity of the catalyst for generating the maleic anhydride and reduce CO and CO₂To increase the weight yield of maleic anhydride. And meanwhile, the service performance of the catalyst is further improved, and higher catalytic performance and more stable service life are ensured.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides an oxidation catalyst for preparing maleic anhydride by benzene oxidation, which comprises a first vanadium-molybdenum catalyst and/or a second vanadium-molybdenum catalyst, wherein the first vanadium-molybdenum catalyst and the second vanadium-molybdenum catalyst are obtained by coupling different types of metal auxiliary agents and modulating the oxidation state of main metal vanadium in an oxide by using an oxidation-reduction reaction generated in the mother liquor preparation process, and raw material gas contacts with the first vanadium-molybdenum catalyst and then contacts with the second vanadium-molybdenum catalyst for reaction in the reaction process.

One of the objects of the present invention is to provide an oxidation catalyst comprising a first vanadium molybdenum catalyst and/or a second vanadium molybdenum catalyst, each of which independently contains vanadium, molybdenum, nickel and a promoter, wherein the average oxidation state of vanadium in the first vanadium molybdenum catalyst is lower than the average oxidation state of vanadium in the second vanadium molybdenum catalyst.

In a preferred embodiment, the first vanadium molybdenum catalyst and the second vanadium molybdenum catalyst each independently comprise an active component represented by formula (I):

VMo_aNi_bA_cB_dC_eD_fO_xformula (I);

in formula (I), A, B, C, D represents the assistant, and a, b, c, d, e, f, g, h and x respectively represent the atomic ratio of the corresponding elements.

In a further preferred embodiment, the element a is selected from at least one of group IA elements, preferably at least one of potassium, rubidium, cesium; and/or the element B is selected from boron and/or phosphorus; and/or the element C is selected from at least one of iron, magnesium, cobalt, copper, zinc and silver; and/or the element D is at least one of bismuth, niobium, indium, antimony, thallium, tellurium and germanium.

In a preferred embodiment, in formula (I), a is 0.1 to 0.8, b is 0.001 to 0.05, c is 0.001 to 0.05, d is 0.002 to 0.1, e is 0.001 to 0.05, f is 0.001 to 0.05, and x is the number of oxygen required to satisfy the valence equilibrium of other non-oxygen elements in the composite oxide forming the catalytically active material.

In a further preferred embodiment, in formula (I), a is 0.2 to 0.5, b is 0.002 to 0.01, c is 0.002 to 0.02, d is 0.005 to 0.05, e is 0.001 to 0.01, f is 0.001 to 0.01, and x is the number of oxygen required to satisfy the valence equilibrium of other non-oxygen elements in the composite oxide forming the catalytically active material.

All of the above values are the calcination state of the composite formed of the catalytically active component, and may be, for example, a state formed after calcining the catalyst at 400-500 ℃ for 6 hours. Preferably, the molar ratio of the vanadium element to the molybdenum element is 1 (0.2-0.5), and may be, for example, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, and any value therebetween; more preferably 1 (0.2-0.4).

In a preferred embodiment, the average oxidation state of the vanadium element in the first vanadium molybdenum catalyst and the second vanadium molybdenum catalyst is each independently from 4.50 to 4.95, preferably from 4.60 to 4.90, more preferably from 4.60 to 4.85, and the average oxidation state of the vanadium in the first vanadium molybdenum catalyst is lower than the average oxidation state of the vanadium in the second vanadium molybdenum catalyst.

In a further preferred embodiment, the average oxidation state of the vanadium in the first vanadium molybdenum catalyst is from 4.50 to 4.80, preferably from 4.60 to 4.75, the average oxidation state of the vanadium in the second vanadium molybdenum catalyst is from 4.60 to 4.95, preferably from 4.75 to 4.90, and the average oxidation state of the vanadium in the first vanadium molybdenum catalyst is lower than the average oxidation state of the vanadium in the second vanadium molybdenum catalyst.

The average oxidation state of the vanadium in the first vanadium molybdenum catalyst is from 4.50 to 4.80, and can be, for example, 4.50, 4.55, 4.60, 4.65, 4.70, 4.75, 4.80 and any value therebetween, and the average oxidation state of the vanadium in the second vanadium molybdenum catalyst is from 4.60 to 4.95, and can be, for example, 4.60, 4.65, 4.70, 4.75, 4.80, 4.85, 4.90, 4.95 and any value therebetween. Among them, the valence of the V metal center has a significant influence on the whole catalyst. For example, in the conversion of benzene to maleic anhydride, the catalytic activity of the catalyst is selected based on the characteristics of the oxygen-selective oxidation lattice catalystAnd V₂MoO₈Mutual synergy between the phases, V⁵⁺Is reduced to V⁴⁺In the process, lattice oxygen is simultaneously released to activate benzene molecules to be oxidized into maleic anhydride, V⁴⁺Reoxidation of adsorbed gas phase oxygen to V⁵⁺. Containing a certain number of V⁴⁺Is very important for obtaining better maleic anhydride selectivity. V⁴⁺Phase sum V⁵⁺The different proportions of the phases cause the V in the catalyst to assume different valences.

In a preferred embodiment, the active component represented by the formula (I) is contained in the first vanadium-molybdenum catalyst in an amount of 13 to 20 wt%, preferably 15 to 18 wt%.

In a further preferred embodiment, the second vanadium-molybdenum catalyst contains the active component represented by the formula (I) in an amount of 13 to 20 wt%, preferably 15 to 18 wt%.

In a preferred embodiment, the first vanadium molybdenum catalyst and/or the second vanadium molybdenum catalyst further each independently comprises a support.

In a further preferred embodiment, the support is an inert, non-porous material.

The inert non-porous material has good heat-conducting property, and an inorganic material with a heat-conducting coefficient of 10-100W/(m.K) is generally preferred.

In a still further preferred embodiment, the support is selected from at least one of alumina, silicon carbide, magnesium silicate (sintered talc), aluminum silicate, quartz, ceramics, magnesium oxide.

In a preferred embodiment, the support is hollow cylindrical, spherical, pellet, helical or toothed spherical.

In a further preferred embodiment, the carrier is a hollow cylinder, and has an outer diameter of 3 to 8mm, a length of 3 to 8mm, and a wall thickness of 1 to 2 mm.

In a preferred embodiment, when the oxidation catalyst comprises both the first vanadium-molybdenum catalyst and the second vanadium-molybdenum catalyst, the volume content of the first vanadium-molybdenum catalyst is (20 to 80)%, and the volume content of the second vanadium-molybdenum catalyst is (80 to 20)%.

In a further preferred embodiment, when the oxidation catalyst comprises both the first vanadium-molybdenum catalyst and the second vanadium-molybdenum catalyst, the volume content of the first vanadium-molybdenum catalyst is (30 to 70)%, and the volume content of the second vanadium-molybdenum catalyst is (70 to 30)%.

The catalyst comprises a first vanadium-molybdenum catalyst and a second vanadium-molybdenum catalyst, wherein the first vanadium-molybdenum catalyst and the second vanadium-molybdenum catalyst are vanadium-molybdenum catalysts with different surface compositions obtained by coupling different types of metal additives and modulating the oxidation state of main metal vanadium in oxides by using an oxidation-reduction reaction generated in the mother liquor preparation process, and a benzene-containing feed gas is firstly contacted with the first vanadium-molybdenum catalyst and then contacted with the second vanadium-molybdenum catalyst in the reaction process to react to generate maleic anhydride.

The second purpose of the present invention is to provide a method for preparing the oxidation catalyst of the first purpose of the present invention, comprising preparing the first vanadium molybdenum catalyst and/or the second vanadium molybdenum catalyst respectively, wherein the first vanadium molybdenum catalyst and/or the second vanadium molybdenum catalyst are obtained by the following steps independently:

step 1, mixing a vanadium-containing compound with oxalic acid to obtain a solution;

step 2, adding a molybdenum-containing compound, a nickel-containing compound, a compound containing A, a compound containing B, a compound containing C and a compound containing D into the dispersion liquid to obtain a dispersion liquid, and mixing the dispersion liquid with the solution obtained in the step 1 to obtain a dispersion system;

step 3, mixing the dispersion system with an organic solvent and a binder, and emulsifying to obtain a suspension;

and 4, spraying the obtained suspension on the surface of a carrier to obtain a catalyst precursor, and roasting to obtain the first vanadium-molybdenum catalyst or the second vanadium-molybdenum catalyst.

The method is characterized In that salts or oxides containing V, Mo, Ni, K, Rb, Cs, In, Tl, W, Co, Sb, Mg and Nb and acids or salts containing B, P are added In the preparation process of the catalyst to form a uniform dispersion system, and the dispersion system and/or a certain amount of hydrophilic organic solvent and a certain amount of aqueous dispersion containing an organic binder are subjected to high-speed dispersion and emulsification, so that soluble and/or insoluble species, the binder and the solvent In a mother solution form a uniform and stable suspension system, the stability of the catalyst In the processes of spraying, forming and using is improved, and the usability of the catalyst is improved.

In a preferred embodiment, the vanadium-containing compound is any one of vanadium-containing compounds conventionally used in the art, preferably but not limited to at least one selected from the group consisting of metavanadate, orthovanadate, vanadium pentoxide, vanadium trichloride, vanadium dioxide, vanadium tetraoxide, preferably metavanadate.

Preferably, the metavanadate is selected from at least one of sodium metavanadate, potassium metavanadate and ammonium metavanadate, and the orthovanadate is selected from at least one of sodium orthovanadate, potassium orthovanadate and ammonium orthovanadate.

In a preferred embodiment, the molybdenum-containing compound is any of various molybdenum-containing compounds conventionally used in the art, preferably but not limited to at least one selected from molybdates, molybdenum trioxide, preferably molybdates (e.g., ammonium molybdate and/or sodium molybdate).

In a preferred embodiment, the a-containing compound, the C-containing compound, and the D-containing compound are each independently selected from at least one of a-containing, C-containing, and D-containing oxide, ammonium salt, nitrate, carbonate, bicarbonate, sulfate, halide, oxalate, phosphate, hydrogen phosphate, complex.

Wherein the complex may be an acetylacetone complex.

In a preferred embodiment, the B-containing compound is at least one selected from the group consisting of phosphorus pentoxide, phosphoric acid, hydrogen phosphate, dihydrogen phosphate, boric acid, metaboric acid, borate, and metaborate.

Wherein the phosphorus element is at least one of phosphorus pentoxide, phosphoric acid (85-105%), hydrogen phosphate, dihydrogen phosphate and phosphate; the boron element is derived from at least one of boric acid, borate and metaborate.

In a preferred embodiment, in step 1, oxalic acid and the vanadium-containing compound are used in a molar ratio of 1: (1.6-2.3).

In a further preferred embodiment, in the step 1 of preparing the first vanadium molybdenum catalyst, the molar ratio of oxalic acid to the vanadium-containing compound is 1 (2-2.3), preferably 1 (2-2.28).

In a further preferred embodiment, in the step 1 of preparing the second vanadium molybdenum catalyst, the molar ratio of oxalic acid to the vanadium-containing compound is 1 (1.6-1.99), preferably 1 (1.7-1.96).

In a preferred embodiment, in step 1, stirring is continued for 0-2 hours after the vanadium-containing compound and oxalic acid are completely dissolved.

In a preferred embodiment, in step 2, the dispersion is selected from an acid solution and/or water.

In a further preferred embodiment, the acid solution is at least one selected from the group consisting of dilute nitric acid, dilute hydrochloric acid, dilute oxalic acid, dilute acetic acid and dilute sulfuric acid solution, and preferably has a weight concentration (weight concentration of acid in the dispersion) of 15 wt% or less, and preferably 2 to 10 wt%.

In a preferred embodiment, in step 2, the total amount of the molybdenum-containing compound, the nickel-containing compound, the a-containing compound, the B-containing compound, the C-containing compound, and the D-containing compound is used in a ratio of 1: (5-25), preferably 1 (8-20).

In a preferred embodiment, in step 3, the organic solvent is a hydrophilic organic solvent, preferably at least one selected from monohydric alcohols, polyhydric alcohols, water-soluble ethers, and water-soluble amides.

In a further preferred embodiment, in step 3, the organic solvent is at least one selected from the group consisting of methanol, ethanol, tetrahydrofuran, ethylene glycol dimethyl ether, formamide, N-dimethylformamide, pyrrolidone, N-methylpyrrolidone.

In a further preferred embodiment, in step 3, the weight ratio of the organic solvent to water in the suspension is (0-0.15): 1, preferably (0.05-0.15): 1.

Wherein the water in the suspension mainly comes from the water and the dilute acid solution in the step 1-2 and the aqueous dispersion containing the binding agent in the step 3.

In a preferred embodiment, in step 3, the binder is selected from cellulose and its derivatives and/or co-polymeric vinyl acetate.

In a further preferred embodiment, the cellulose and its derivatives are selected from at least one of cellulose ethers, anionic cellulose derivatives, non-ionic cellulose derivatives, preferably at least one of methylcellulose, ethylcellulose, sodium carboxymethylcellulose, cellulose acetate, hydroxyethylcellulose, hydroxypropylcellulose, hypromellose.

In a still further preferred embodiment, the copolymerized vinyl acetate is selected from at least one of vinyl acetate-vinyl laurate, vinyl acetate-acrylate, vinyl acetate-ethylene, vinyl acetate-styrene.

According to the invention, the binder is added in the step 3, so that the active substances of the catalyst on the surface of the carrier are not easy to fall off, and the service performance of the catalyst is effectively improved.

In a preferred embodiment, the binder is added in the form of a dispersion containing the binder.

In a further preferred embodiment, the binder content by weight in the binder-containing dispersion is 5 to 30 wt.%, preferably 5 to 20 wt.%.

In a preferred embodiment, in the suspension described in step 3, the weight ratio of binder to catalyst precursor is (0.01-0.15):1, preferably (0.01-0.1): 1.

The catalyst precursor refers to various components added for forming a catalyst active substance, and comprises a vanadium-containing compound, a molybdenum-containing compound, a nickel-containing compound, an A-containing compound, a B-containing compound, a C-containing compound and a D-containing compound.

In a preferred embodiment, the suspension obtained in step 3 has a viscosity of 5 to 30 mPas.

In a preferred embodiment, step 2 comprises the following sub-steps:

step 2.1, adding a molybdenum-containing compound into the dispersion to obtain a first dispersion;

step 2.2, adding a nickel-containing compound, a compound containing A, a compound containing B and a compound containing C into the dispersion liquid to obtain a second dispersion liquid;

step 2.3, adding the compound containing D into the dispersion liquid to obtain a third dispersion liquid;

and 2.4, mixing the obtained solution, the first dispersion liquid, the second dispersion liquid and the third dispersion liquid to obtain a fourth dispersion liquid.

Wherein the respective preparation of the respective active compounds as a dispersion promotes good dispersion or dissolution of the respective active compounds, wherein: (1) the molybdenum-containing compound is dispersed separately in order to promote complete dissolution in the dispersion to obtain a solution; (2) the reason why the D-containing compound is dispersed alone is that the inventors found in experiments that if the D compound is dispersed together with the nickel-containing compound, the a-containing compound, the B-containing compound and the C-containing compound, serious dispersion unevenness such as precipitation or generation of flocs may be caused.

In a preferred embodiment, step 2.4 and step 3 are carried out in a back-mixed reactor.

The back mixing reactor is an instrument capable of mixing and back mixing the dispersion system at a high speed, and particularly preferably adopts a series of colloid mill instruments commonly used in the market.

In a further preferred embodiment, the step 3 is emulsified in the back-mixing reactor for 0.1 to 2 hours to break up the aggregates of suspended solids to obtain a solution or suspension of the slurry of the catalytically active material in a uniform suspension.

In a more preferred embodiment, step 3 is performed under an inert atmosphere, which may be a closed inert atmosphere or a flowing inert atmosphere, and the gas flow rate is preferably 0 to 0.2 SLPM.

And 3, emulsifying for 0.1-2 hours in an inert atmosphere.

In a preferred embodiment, in step 4, the carrier is first heated, preferably at 250 to 300 ℃, more preferably at 250 to 280 ℃.

In a preferred embodiment, in step 4, the spraying is carried out in a coating machine as follows:

(1) putting the carrier into a rotary drum of a coating machine, and heating to 250-300 ℃, preferably 250-280 ℃;

(2) and (3) atomizing the suspension liquid in the step (3), spraying the suspension liquid on a carrier in a rotary drum, and simultaneously controlling the temperature of the carrier to be 250-300 ℃, preferably 250-280 ℃.

Wherein, after the dispersant is quickly evaporated and extracted, the catalytic active substance slurry sprayed on the surface of the carrier is quickly dried to form the catalyst precursor. And during spraying, controlling until the mass percent of the catalytic active substance coating reaches 13-20% of the total mass of the catalyst, and stopping spraying.

In a preferred embodiment, step 4 is optionally followed by step 5:

and 5, activating the first vanadium-molybdenum catalyst or the second vanadium-molybdenum catalyst obtained in the step 4.

In a further preferred embodiment, the activation is carried out as follows:

(1) raising the temperature of the first vanadium-molybdenum catalyst or the second vanadium-molybdenum catalyst to 150 ℃ at a heating rate of 70-100 ℃/h, and preserving the temperature for 5-30 minutes;

(2) raising the temperature to 380 ℃ at a heating rate of 100-150 ℃/h, and preserving the heat for 20-60 minutes;

(3) heating to 420-480 ℃ at a heating rate of 20-60 ℃/h, preserving heat for 5-10 hours, and cooling to room temperature.

Wherein, before activation, a certain amount of inert gas can be used for replacing the gas in the closed reactor. The inert gas used may be a dry nitrogen atmosphere, a dry helium atmosphere, or a mixture of both.

The third object of the present invention is to provide an oxidation catalyst obtained by the preparation method described above for the second object of the present invention.

The fourth object of the present invention is to provide a catalyst bed packed with the oxidation catalyst according to the first object of the present invention or the oxidation catalyst obtained by the preparation method according to the second object of the present invention, preferably, the catalyst bed comprises an inlet section catalyst bed packed with the first vanadium-molybdenum catalyst and an outlet section catalyst bed packed with the second vanadium-molybdenum catalyst.

In the process of preparing the catalytic active substance precursor, the oxidation-reduction reaction is utilized to modulate the oxidation state of main metal vanadium in the active substance precursor, the active substance precursor is coupled with different types of metal additives, meanwhile, a hydrophilic organic solvent and an organic binder are added into a dispersion system to improve the stability of components contained in the dispersion system, a solution or a suspension with a high dispersion state is formed by high-speed back mixing to strengthen the dispersion and emulsification, and the catalyst with a load structure of different oxidation states and compositions of metal elements is prepared by spraying, so that the catalyst with a double-stage bed with different bed layer filling ratios is further obtained. The supported catalyst greatly improves the bonding strength of a catalytic active substance on the surface of a carrier, improves the utilization rate of a metal oxide active component catalyst on the carrier, and achieves the purposes of improving the catalytic performance and the service performance of the catalyst.

The fourth purpose of the invention is to provide the application of the oxidation catalyst of the first purpose of the invention or the oxidation catalyst obtained by the preparation method of the second purpose of the invention in preparing acid anhydride by benzene oxidation.

In a preferred embodiment, the benzene is oxidized to produce the anhydride in a reactor, the first vanadium molybdenum catalyst is loaded in the inlet section of the reactor, and the second vanadium molybdenum catalyst is loaded in the outlet section of the reactor.

In a further preferred embodiment, the loading volume of the first vanadium molybdenum catalyst is (20-80)% of the total catalyst loading volume and the loading volume of the second vanadium molybdenum catalyst is (80-20)% of the total catalyst loading volume.

In a still further preferred embodiment, the loading volume of the first vanadium molybdenum catalyst is (30-70)% of the total catalyst loading volume and the loading volume of the second vanadium molybdenum catalyst is (70-30)% of the total catalyst loading volume.

In a preferred embodiment, the contact temperature of the gas raw material and the first vanadium molybdenum catalyst and the second vanadium molybdenum catalyst bed layer is 300-500 ℃, and the preferred contact temperature is 320-500 ℃.

Wherein, the contact temperature of the raw material and the catalyst bed layer is controlled to obtain higher benzene conversion rate and maleic anhydride yield.

In a further preferred embodiment, the gaseous feed comprises benzene and an oxidizing gas (e.g. oxygen and/or air), the concentration of benzene in the gaseous feed being in the range of 40-65g/Nm³。

Wherein, controlling the benzene concentration in the gas raw material can prevent the explosion caused by the over-high benzene concentration of the gas phase. In the present invention, unless otherwise specified, the volume of gas is the volume of gas in a standard state.

In a preferred embodimentIn the embodiment, the total space velocity of the gas raw material is 1800-3000 h^-1Preferably 2000 to 2500h^-1。

The apparatus for producing maleic anhydride of the present invention is not particularly operated under increased pressure or reduced pressure, and usually the apparatus is operated under normal pressure, and the pressure in the apparatus (i.e., the pressure at which benzene is contacted with the catalyst) may be 0.01 to 0.2 MPa.

Compared with the prior art, the invention has the following beneficial effects: the catalyst provided by the invention is used for catalyzing the reaction of synthesizing maleic anhydride by gas phase selective catalytic oxidation in a fixed bed reactor, and the concentration of benzene is 40-65g/Nm³Under the condition, the conversion rate of benzene is up to>98 percent and the weight yield of the maleic anhydride reaches 94 to 99 percent. Under the same operation conditions, the conversion rate of benzene can be improved by 3.6 percent at most, and the weight yield of maleic anhydride can be improved by 4.4 percent at most.

Detailed Description

The following specific examples are provided to illustrate the preparation of high performance catalysts and the performance of the catalysts in catalyzing the selective oxidation of benzene to maleic anhydride, and it is to be understood that the following examples are included to further illustrate the present invention and are not to be construed as limiting the scope of the invention.

If not specifically stated, the chemical reagents used in the present invention are all commercially available products and are not further processed.

The oxidation state of vanadium of the catalyst is determined and analyzed by a potassium permanganate-ammonium ferrous sulfate method, the bulk density of the catalyst is determined by a tap density meter, the strength of the catalyst is determined by a strength tester, and the viscosity of the spraying liquid is determined by a viscometer. The content of each element in the catalyst is detected by adopting an ICP-MASS method.

In the following examples and comparative examples, a fixed bed reactor was used, in which the inner diameter was 21mm, the effective length of the reaction tube was 3600mm, a temperature jacket tube having an outer diameter of 6mm was inserted, a thermocouple was inserted into the jacket tube, the actual catalyst loading in the reaction tube was 1200mL, and a small amount of inert carrier was loaded on the upper and lower sections of the catalyst bed layer to facilitate gas distribution and support of the catalyst; the highest point in the catalyst bed during the reaction, referred to as the catalyst hot spot temperature, was measured using a thermocouple. The following operating conditions include the volumetric space velocity of the mixed gas containing benzene and an oxidizing gas (here, air) into the fixed bed reactor, the concentration of benzene in the mixed gas, and the salt bath temperature.

In the following examples and comparative examples, benzene was selectively oxidized under the following conditions: the temperature is 345-365 ℃, and preferably 350-360 ℃; the pressure is 0.01-0.2 MPa; the total airspeed of the reaction raw material mixed gas is 2000-2500 h^-1。

[ example 1 ]

Weighing 173.4g of oxalic acid (90.0g/mol) at room temperature, dissolving in 600mL of deionized water, and stirring until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 51.0g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 0.56g of nickel nitrate (290.7g/mol), 3.89g of ferric nitrate (404.0g/mol), 0.29g of rubidium nitrate (147.7g/mol), 2.37g of trisodium phosphate (164.3g/mol) and 0.89g of boric acid (61.8g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 1.97g of indium acetate (292.0g/mol), adding the indium acetate into 100mL of dilute acetic acid solution with the mass fraction of 5%, and stirring to obtain a dispersion system 4; after the solution 1 reacts for 0.5 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 100mL of ethanol and 300g of an aqueous dispersion with 5% of solid content of sodium carboxymethyl cellulose into a colloid mill, mixing and emulsifying the mixture into a uniform suspension under high-speed shearing and back mixing conditions, wherein the back mixing time is 0.2 hour, and the viscosity of the suspension is controlled to be 10-20 mPa & S.

The spraying and activation operations were the same as in example 1 except that 581g of the supported catalyst was obtained after spraying, and the weight of the active material was 13.9% of the weight of the carrier, to obtain an activated catalyst A-1. The valence state of V was determined to be 4.74 by redox titration. The composition of the catalyst is shown in table 1.

The obtained catalyst A-1 was individually loaded in a single-tube reactor and loadedThen carrying out the reaction for preparing maleic anhydride by benzene oxidation, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out the reaction for preparing maleic anhydride by benzene oxidation. The benzene selective oxidation reaction conditions are as follows: the temperature is 350 ℃, the pressure is 0.08MPa, and the benzene concentration is 50g/m³The airspeed of the reaction raw material mixed gas is 2200h^-1. The catalyst performance is shown in table 2.

[ example 2 ]

177.7g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water at room temperature, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 34.0g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 1.79g of boric acid (61.8g/mol), 1.40g of nickel nitrate (290.7g/mol), 3.75g of cesium nitrate (194.9g/mol), 1.40g of cobalt nitrate (291.1g/mol) and 0.41g of phosphorus pentoxide (141.9g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 1.41g of indium acetate (292.0g/mol), adding the indium acetate into 100mL of deionized water, and stirring to obtain a dispersion system 4; after the solution 1 reacts for 0.5 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4 and a mixed system of 100mL formamide, 200g of an aqueous dispersion with 10% vinyl acetate-ethylene content and 100g of an aqueous dispersion with 5% sodium carboxymethyl cellulose into a colloid mill, mixing and emulsifying under high-speed shearing and back-mixing states to form a uniform suspension, wherein the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 20-30 mPa & S.

The spraying and activation operations were the same as in example 1 except that 579g of supported catalyst was obtained after spraying, and the weight of active material was 13.6% of the weight of the carrier. Thus obtaining the activated catalyst A-2. The valence state of V was determined to be 4.72 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst A-2 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. Benzene selectionThe oxidation reaction conditions are as follows: the temperature is 355 ℃, the pressure is 0.06MPa, and the benzene concentration is 55g/m³The space velocity of the reaction raw material mixed gas is 2000h^-1. The catalyst performance is shown in table 2.

[ example 3 ]

At room temperature, 182.0g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 37.4g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 2.80g of nickel nitrate (290.7g/mol), 1.73g of magnesium nitrate (256.4g/mol), 0.78g of potassium nitrate (101.1g/mol), 1.58g of trisodium phosphate (164.3g/mol) and 1.96g of cobalt nitrate (291.1g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; 0.78g of antimony pentoxide (323.5g/mol) is weighed and added into 100mL of dilute nitric acid solution with the mass fraction of 10%, and a dispersion system 4 is obtained by stirring; after the solution 1 reacts for 0.5 hour, the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 100mL of pyrrolidone and 100g of vinyl acetate-ethylene aqueous dispersion with the solid content of 15% are poured into a colloid mill at the same time, mixed and emulsified into uniform suspension under the high-speed shearing and back-mixing state, the back-mixing time is 0.2 hour, and the viscosity of the suspension is controlled to be 15-25 mPa & S.

The spraying procedure was as in example 1 except that the supported catalyst obtained after spraying was 575g, and the weight of the active material was 13.0% of the weight of the carrier.

The catalyst is put in a closed container for activation. 200g of the catalyst precursor was placed in an activator, and helium as an inert shielding gas was introduced into the activation furnace at a space velocity of 0.1 SLPM. Heating from room temperature to 100 ℃ at a heating rate of 100 ℃/h, keeping the temperature for 5 minutes, then continuously heating to 380 ℃ at a heating rate of 120 ℃/h, keeping the temperature for 30 minutes, then continuously heating to 450 ℃ at a heating rate of 30 ℃/h, keeping the temperature for 5 hours, and then naturally cooling to room temperature to obtain the activated catalyst A-3. The valence state of V was determined to be 4.69 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst A-3 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 360 ℃, the pressure is 0.07MPa, and the benzene concentration is 60g/m³The space velocity of the reaction raw material mixed gas is 2000h^-1. The catalyst performance is shown in table 2.

[ example 4 ]

At room temperature, 186.4g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 42.5g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 2.98g of boric acid (61.8g/mol), 2.24g of nickel nitrate (290.7g/mol), 3.89g of ferric nitrate (404.0g/mol), 2.85g of rubidium nitrate (147.7g/mol) and 0.58g of sodium dihydrogen phosphate (120.0g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; 0.62g of antimony pentoxide (323.5g/mol) is weighed and added into 80mL of dilute nitric acid solution with the mass fraction of 10%, and a dispersion system 4 is obtained by stirring; after the solution 1 reacts for 0.8 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 80mL of glycol dimethyl ether and 200g of aqueous dispersion with 5% of solid content of sodium carboxymethyl cellulose into a colloid mill, mixing and emulsifying under high-speed shearing and back-mixing conditions to obtain uniform suspension, wherein the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 15-25 mPa & S.

The spraying and activation procedure was as in example 9 except that 587g of supported catalyst was obtained after spraying, the weight of active material was 14.8% of the weight of the support. Thus obtaining the activated catalyst A-4. The valence state of V was determined to be 4.66 by redox titration. The composition of the catalyst is shown in table 1.

The obtained catalyst A-4 is separately filled in a single-tube reactor and then is subjected to benzene oxidation reaction to prepare maleic anhydride, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactorAnd performing benzene oxidation to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 355 ℃, the pressure is 0.09MPa, and the benzene concentration is 55g/m³The airspeed of the reaction raw material mixed gas is 2200h^-1. The catalyst performance is shown in table 2.

[ example 5 ]

Weighing 190.7g of oxalic acid (90.0g/mol) at room temperature, dissolving in 600mL of deionized water, and stirring until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 47.6g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.87g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 0.60g of boric acid (61.8g/mol), 2.52g of nickel nitrate (290.7g/mol), 1.12g of cobalt nitrate (291.1g/mol), 2.28g of rubidium nitrate (147.7g/mol) and 0.68g of phosphorus pentoxide (141.9g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 1.69g of indium acetate (292.0g/mol) and adding the indium acetate into 100mL of deionized water, and stirring to obtain a dispersion system 4; after the solution 1 reacts for 1.0 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 100mL of tetrahydrofuran and 300g of aqueous dispersion with 5% of solid content of sodium carboxymethyl cellulose into a colloid mill, mixing and emulsifying under high-speed shearing and back-mixing conditions to obtain uniform suspension, wherein the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 10-20 mPa & S.

The spraying procedure was as in example 1 except that 597g of the supported catalyst was obtained after spraying, and the weight of the active material was 16.2% of the weight of the support.

The catalyst is put in a closed container for activation. 200g of the catalyst precursor was placed in an activator, and helium as an inert shielding gas was introduced into the activation furnace at a space velocity of 0.2 SLPM. Heating from room temperature to 100 ℃ at a heating rate of 100 ℃/h, keeping the temperature for 30 minutes, then continuously heating to 350 ℃ at a heating rate of 140 ℃/h, keeping the temperature for 40 minutes, then continuously heating to 450 ℃ at a heating rate of 60 ℃/h, keeping the temperature for 6 hours, and then naturally cooling to room temperature to obtain the activated catalyst A-5. The valence state of V was determined to be 4.60 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst A-5 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 360 ℃, the pressure is 0.07MPa, and the benzene concentration is 60g/m³The space velocity of the reaction raw material mixed gas is 2000h^-1. The catalyst performance is shown in table 2.

[ example 6 ]

Weighing 195.0g of oxalic acid (90.0g/mol) at room temperature, dissolving in 600mL of deionized water, and stirring until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 50.1g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 0.46g of sodium borate (381.37g/mol), 1.68g of nickel nitrate (290.7g/mol), 3.38g of cesium nitrate (194.9g/mol), 2.80g of cobalt nitrate (291.1g/mol) and 2.31g of sodium dihydrogen phosphate (120.0g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 1.56g of antimony pentoxide (323.5g/mol) and 2.53g of indium acetate (292.0g/mol), adding into 200mL of dilute nitric acid solution with the mass fraction of 10%, and stirring to obtain a dispersion system 4; after the solution 1 reacts for 1.5 hours, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 60mL of N, N-dimethylformamide and 100g of vinyl acetate-styrene aqueous dispersion with the solid content of 15 percent into a colloid mill, mixing and emulsifying into uniform suspension under the high-speed shearing and back-mixing state, wherein the back-mixing time is 1 hour, and the viscosity of the suspension is controlled to be 20-30 mPa & S.

The spraying and activation were carried out as in example 11, except that 607g of supported catalyst were obtained after spraying, and the weight of active material was 17.6% of the total weight. The activated catalyst A-6 is prepared. The valence state of V was determined to be 4.55 by redox titration. The composition of the catalyst is shown in table 1.

The obtained catalyst A-6 is separately filled in a single-tube reactor and then is subjected to benzene oxidation to prepare maleic anhydride, wherein the reactionThe reaction gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out the reaction of benzene oxidation for preparing maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 360 ℃, the pressure is 0.09MPa, and the benzene concentration is 60g/m³The airspeed of the reaction raw material mixed gas is 2200h^-1. The catalyst performance is shown in table 2.

[ example 7 ]

At room temperature, 162g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 51g of ammonium molybdate ((NH) was weighed₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 7.07g of trisodium phosphate (164.3g/mol), 2.38g of nickel nitrate (290.7g/mol), 25.9g of niobium oxalate (538.0g/mol), 0.90g of cobalt nitrate (291.1g/mol) and 0.99g of rubidium nitrate (147.7g/mol) are weighed and gradually added into 150ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 22.2g of bismuth nitrate (485.0g/mol), adding into 50mL of dilute nitric acid with the mass fraction of 15%, and stirring to dissolve the bismuth nitrate to obtain a dispersion system 4; after the solution 1 reacts for half an hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 100mL of formamide and 100g of an aqueous dispersion with 5% of the solid content of sodium carboxymethylcellulose into a colloid mill, mixing and emulsifying under high-speed shearing and back-mixing conditions to obtain a uniform suspension, wherein the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 5-15 mPa.

The prepared suspension is moved into a feeding tank of a feeding system of the spraying equipment for stirring. 500g of a silicon carbide hollow cylindrical support having an outer diameter of 5mm, a length of 3mm and a wall thickness of 1.5mm was placed in a rotatable and heatable stainless steel drum at a speed of 10 to 20 revolutions per minute. When the surface temperature of the carrier reaches 280 ℃, spraying the suspension liquid on the surface of the carrier in a stirring state by a pump, controlling the spraying speed to be 20mL/min, and drying until the quality is constant after the spraying is finished. Weighing gave 598g of supported catalyst. The weight of the active material was 16.4% of the total weight.

The catalyst is put in a closed container for activation. 200g of catalyst precursor is placed in an activator, the temperature is raised from room temperature to 100 ℃ at the heating rate of 100 ℃/h, the temperature is kept for 30 minutes, then the temperature is raised to 380 ℃ at the heating rate of 150 ℃/h, the temperature is kept for 30 minutes, then the temperature is raised to 450 ℃ at the heating rate of 20 ℃/h, the temperature is kept for 5 hours, and then the temperature is naturally reduced to the room temperature, so that the activated catalyst B-1 is obtained. The valence state of V was determined to be 4.78 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst B-1 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 350 ℃, the pressure is 0.08MPa, and the benzene concentration is 50g/m³The airspeed of the reaction raw material mixed gas is 2200h^-1. The catalyst performance is shown in table 2.

[ example 8 ]

At room temperature, 156g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring; to obtain solution 1, 59.5g of ammonium molybdate ((NH) was weighed₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 120mL of 50 ℃ deionized water to give solution 2; 11.6g of trisodium phosphate (164.3g/mol), 1.40g of nickel nitrate (290.7g/mol), 5.54g of ferric nitrate (404.0g/mol) and 1.13g of cesium nitrate (194.9g/mol) are weighed and gradually added into 150ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 4.01g of indium acetate (292.0g/mol), adding the indium acetate into 50mL of dilute nitric acid with the mass fraction of 15%, and stirring to dissolve the indium acetate to obtain a dispersion system 4; after the solution 1 reacts for 1 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4 and 100mL of 200g of aqueous dispersion with the solid content of 10% of formamide and vinyl acetate-vinyl laurate into a colloid mill, mixing and emulsifying the aqueous dispersion into uniform suspension under the high-speed shearing and back-mixing state, wherein the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 10-20 mPa & S.

The spraying and activation procedure was as in example 1 except that 589g of supported catalyst was obtained after spraying, and the weight of active material was 15.1% of the weight of the support. The activated catalyst B-2 is prepared. The valence state of V was determined to be 4.80 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst B-2 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 350 ℃, the pressure is 0.12MPa, and the benzene concentration is 50g/m³The airspeed of the reaction raw material mixed gas is 2500h^-1. The catalyst performance is shown in table 2.

[ example 9 ]

Weighing 147.4g of oxalic acid (90.0g/mol) at room temperature, dissolving in 600mL of deionized water, and stirring until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 67.9g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 150mL of 50 ℃ deionized water to give solution 2; 31.6g of trisodium phosphate (164.3g/mol), 4.56g of nickel nitrate (290.7g/mol), 2.51g of magnesium nitrate (256.4g/mol) and 0.39g of potassium nitrate (101.0g/mol) were weighed out and gradually added to 150ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 2.10g of niobium oxalate (538.0g/mol), adding into 50mL of dilute oxalic acid solution with the mass fraction of 10%, and stirring to dissolve the solution to obtain a dispersion system 4; after the solution 1 reacts for 2 hours, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4 and 100mL of 200g of aqueous dispersion system containing 5% of formamide and methyl cellulose into a colloid mill, mixing and emulsifying under high-speed shearing and back-mixing conditions to obtain a uniform suspension, wherein the back-mixing time is 0.2 hour, and the viscosity of the suspension is controlled to be 10-20 mPa & S.

The spraying procedure was as in example 1 except that the amount of the supported catalyst obtained after spraying was 594g, and the weight of the active material was 15.8% of the weight of the carrier.

The catalyst is put in a closed container for activation. 200g of the catalyst precursor was placed in an activator, and an inert blanket gas of nitrogen was introduced into the activation furnace at a space velocity of 0.1 SLPM. Heating from room temperature to 120 ℃ at a heating rate of 80 ℃/h, keeping the temperature for 20 minutes, then continuously heating to 380 ℃ at a heating rate of 150 ℃/h, keeping the temperature for 40 minutes, then continuously heating to 450 ℃ at a heating rate of 20 ℃/h, keeping the temperature for 5 hours, and then naturally cooling to room temperature to obtain the activated catalyst B-3. The valence state of V was determined to be 4.89 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst B-3 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 355 ℃, the pressure is 0.07MPa, and the benzene concentration is 55g/m³The space velocity of the reaction raw material mixed gas is 2000h^-1. The catalyst performance is shown in table 2.

[ example 10 ]

151.7g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water at room temperature, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 85.1g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 200mL of 50 ℃ deionized water to give solution 2; 2.98g of boric acid (61.8g/mol), 2.79g of nickel nitrate (290.7g/mol), 0.28g of cobalt nitrate (291.1g/mol) and 3.76g of cesium nitrate (194.9g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; 0.78g of antimony pentoxide (323.5g/mol) is weighed and added into 80mL of dilute hydrochloric acid solution with the mass fraction of 10%, and a dispersion system 4 is obtained by stirring; after the solution 1 reacts for 0.5 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4 and 100mL of 100g of aqueous dispersion with 20% of formamide and vinyl acetate-ethylene content into a colloid mill, mixing and emulsifying under high-speed shearing and back mixing conditions to form uniform suspension, wherein the back mixing time is 1 hour, and the viscosity of the suspension is controlled to be 15-25 mPa & S.

The spraying and activation procedure was as in example 3 except that 582g of the supported catalyst was obtained after spraying, and the weight of the active material was 14.1% of the weight of the support. The activated catalyst B-4 is prepared. The valence state of V is 4.85 as determined by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst B-4 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 355 ℃, the pressure is 0.09MPa, and the benzene concentration is 55g/m³The airspeed of the reaction raw material mixed gas is 2200h^-1. The catalyst performance is shown in table 2.

[ example 11 ]

At room temperature, 160.3g of oxalic acid (90.0g/mol) is weighed and dissolved in 600mL of deionized water, and stirred until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 42.5g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 100mL of 50 ℃ deionized water to give solution 2; 0.21g of metaboric acid (43.8g/mol), 0.56g of nickel nitrate (290.7g/mol), 3.88g of ferric nitrate (404.0g/mol), 1.95g of potassium nitrate (101.1g/mol) and 1.67g of 85% phosphoric acid (98.0g/mol) were weighed out and gradually added to 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 1.56g of antimony pentoxide (323.5g/mol), adding into 100mL of dilute hydrochloric acid solution with the mass fraction of 10%, and stirring to obtain a dispersion system 4; after the solution 1 reacts for 0.5 hour, quickly pouring the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 120mL of formamide and 200g of an aqueous dispersion with the vinyl acetate-acrylate solid content of 10% into a colloid mill, mixing and emulsifying under high-speed shearing and back-mixing conditions to obtain a uniform suspension, wherein the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 15-25 mPa & S.

The spraying procedure was as in example 1 except that the amount of the supported catalyst obtained after spraying was 577g, and the weight of the active material was 13.3% of the weight of the carrier.

The catalyst is put in a closed container for activation. 200g of the catalyst precursor was placed in an activator, and an inert blanket gas of nitrogen was introduced into the activation furnace at a space velocity of 0.2 SLPM. Raising the temperature from room temperature to 150 ℃ at a heating rate of 80 ℃/h, keeping the temperature for 40 minutes, then continuing to raise the temperature to 350 ℃ at a heating rate of 130 ℃/h, keeping the temperature for 30 minutes, then continuing to raise the temperature to 450 ℃ at a heating rate of 40 ℃/h, keeping the temperature for 5 hours, and then naturally cooling to room temperature to obtain the activated catalyst B-5. The valence state of V was determined to be 4.77 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst B-5 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 360 ℃, the pressure is 0.07MPa, and the benzene concentration is 60g/m³The space velocity of the reaction raw material mixed gas is 2000h^-1. The catalyst performance is shown in table 2.

[ example 12 ]

Weighing 169.0g of oxalic acid (90.0g/mol) at room temperature, dissolving in 600mL of deionized water, and stirring until the oxalic acid is dissolved; 112.7g of ammonium metavanadate (117.0g/mol) was added thereto under stirring to obtain a solution 1; 76.4g of ammonium molybdate ((NH) was weighed out₄)₆Mo₇O₂₄1235.9g/mol) was dissolved in 160mL of 50 ℃ deionized water to give solution 2; 1.79g of boric acid (61.8g/mol), 1.40g of nickel nitrate (290.7g/mol), 0.25g of magnesium nitrate (256.4g/mol), 1.42g of rubidium nitrate (147.7g/mol) and 2.32g of sodium dihydrogen phosphate (120.0g/mol) are weighed and gradually added into 100ml of deionized water at 50 ℃ to obtain a dispersion system 3; weighing 1.87g of bismuth nitrate (485.0g/mol), adding into 100mL of dilute nitric acid solution with the mass fraction of 10%, and stirring to obtain a dispersion system 4; after the solution 1 reacts for 0.5 hour, the solution 1, the solution 2, the dispersion system 3, the dispersion system 4, 80mL of formamide and 300g of an aqueous dispersion with 5% of sodium carboxymethylcellulose solid content are poured into a colloid mill at the same time, mixed and emulsified into a uniform suspension under high-speed shearing and back-mixing conditions, the back-mixing time is 0.5 hour, and the viscosity of the suspension is controlled to be 15-25 mPa · S.

The spraying and activation operations were the same as in example 5 except that the amount of the supported catalyst obtained after spraying was 592g and the weight of the active material was 15.5% of the weight of the support. The activated catalyst B-6 is prepared. The valence state of V was determined to be 4.75 by redox titration. The composition of the catalyst is shown in table 1.

And independently filling the obtained catalyst B-6 into a single-tube reactor, and performing benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to perform benzene oxidation reaction to prepare maleic anhydride. The benzene selective oxidation reaction conditions are as follows: the temperature is 360 ℃, the pressure is 0.09MPa, and the benzene concentration is 60g/m³The airspeed of the reaction raw material mixed gas is 2200h^-1. The catalyst performance is shown in table 2.

[ example 13 ]

Filling the catalyst A-1 in the upper part of the single-tube reactor, wherein the filling height is 60% of the total bed height, filling the catalyst B-1 in the lower part of the single-tube reactor, the filling height is 40% of the total bed height, and the filling height is marked as T1; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

[ example 14 ]

Filling the catalyst A-2 in the upper part of the single-tube reactor, wherein the filling height is 40% of the total bed height, filling the catalyst B-2 in the lower part of the single-tube reactor, the filling height is 60% of the total bed height, and the mark is T2; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

[ example 15 ]

Filling the catalyst A-3 into the upper part of the single-tube reactor, wherein the filling height is 50% of the total bed height, filling the catalyst B-3 into the lower part of the single-tube reactor, the filling height is 50% of the total bed height, and the mark is T3; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

[ example 16 ]

Filling the catalyst A-4 into the upper part of the single-tube reactor, wherein the filling height is 30% of the total bed height, filling the catalyst B-4 into the lower part of the single-tube reactor, the filling height is 70% of the total bed height, and the mark is T4; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

[ example 17 ]

Filling the catalyst A-5 into the upper part of the single-tube reactor, wherein the filling height is 20% of the total bed height, filling the catalyst B-5 into the lower part of the single-tube reactor, the filling height is 80% of the total bed height, and the mark is T5; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

[ example 18 ]

Filling the catalyst A-6 in the upper part of the single-tube reactor, wherein the filling height is 70% of the total bed height, filling the catalyst B-6 in the lower part of the single-tube reactor, the filling height is 30% of the total bed height, and the filling height is marked as T6; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

Comparative example 1

Changing the filling sequence of different catalyst combinations, filling the catalyst B-1 at the upper part of the single-tube reactor with the filling height of 60% of the total bed height, filling the catalyst A-1 at the lower part of the single-tube reactor with the filling height of 40% of the total bed height, and marking as T7; and (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

Comparative example 2

Changing the filling sequence of different catalyst combinations, filling the catalyst B-2 at the upper part of the single-tube reactor with the filling height of 40% of the total bed height, filling the catalyst A-2 at the lower part of the single-tube reactor with the filling height of 60% of the total bed height, and marking as T8; the reaction gas mixture still enters from the upper part of the reactor and is discharged from the lower part of the reactor. And (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

Comparative example 3

Changing the filling sequence of different catalyst combinations, filling the catalyst B-3 at the upper part of the single-tube reactor with the filling height of 50% of the total bed height, filling the catalyst A-3 at the lower part of the single-tube reactor with the filling height of 50% of the total bed height, and marking as T9; the reaction gas mixture still enters from the upper part of the reactor and is discharged from the lower part of the reactor. And (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

Comparative example 4

Changing the filling sequence of different catalyst combinations, filling the catalyst B-4 at the upper part of the single-tube reactor with the filling height of 25% of the total bed height, filling the catalyst A-4 at the lower part of the single-tube reactor with the filling height of 75% of the total bed height, and marking as T10; the reaction gas mixture still enters from the upper part of the reactor and is discharged from the lower part of the reactor. And (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

Comparative example 5

Changing the filling sequence of different catalyst combinations, filling the catalyst B-5 at the upper part of the single-tube reactor with the filling height of 20% of the total bed height, filling the catalyst A-5 at the lower part of the single-tube reactor with the filling height of 80% of the total bed height, and marking as T11; the reaction gas mixture still enters from the upper part of the reactor and is discharged from the lower part of the reactor. And (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

Comparative example 6

Changing the filling sequence of different catalyst combinations, filling the catalyst B-6 at the upper part of the single-tube reactor with the filling height of 70% of the total bed height, filling the catalyst A-6 at the lower part of the single-tube reactor with the filling height of 30% of the total bed height, and marking as T12; the reaction gas mixture still enters from the upper part of the reactor and is discharged from the lower part of the reactor. And (3) carrying out benzene oxidation reaction to prepare maleic anhydride after filling, wherein reaction mixed gas enters from the upper part of the reactor and is discharged from the lower part of the reactor to carry out benzene oxidation reaction to prepare maleic anhydride, and the performance of the catalyst is shown in Table 3.

TABLE 1 composition of active materials in vanadium molybdenum catalysts

	Catalyst and process for preparing same	Active material composition in catalyst
			Example 1	A-1	V1Mo0.30Ni0.002Rb0.002B0.015P0.015Fe0.01In0.007Ox
Example 2	A-2	V1Mo0.20Ni0.005Cs0.02P0.006Co0.005In0.005Ox
			Example 3	A-3	V1Mo0.22Ni0.01K0.008P0.01Mg0.007Co0.007Ox
Example 4	A-4	V1Mo0.25Ni0.008Rb0.02B0.05P0.005Fe0.01Sb0.004Ox
			Example 5	A-5	V1Mo0.28Ni0.009Rb0.016B0.01P0.01Co0.004In0.006Ox
Example 6	A-6	V1Mo0.30Ni0.006Cs0.018B0.005P0.02Co0.01Sb0.001In0.009Ox
			Example 7	B-1	V1Mo0.30Ni0.009Rb0.007P0.017Co0.003Nb0.05Ox
Example 8	B-2	V1Mo0.35Ni0.005Cs0.006P0.03Fe0.007In0.007Ox
			Example 9	B-3	V1Mo0.40Ni0.008K0.002P0.04Mg0.005Nb0.002Ox
Example 10	B-4	V1Mo0.50Ni0.01Cs0.02B0.05Co0.001Sb0.005Ox
			Example 11	B-5	V1Mo0.25Ni0.002K0.02B0.005P0.015Fe0.01Sb0.01Ox
Example 12	B-6	V1Mo0.45Ni0.005Rb0.01P0.02Mg0.001Bi0.004Ox

TABLE 2 reaction results of preparing maleic anhydride by selective oxidation of benzene with vanadium-molybdenum catalyst

Table 3 results of the reaction of preparing maleic anhydride by selective oxidation of benzene with vanadium-molybdenum catalyst

It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.