A vanadium-based catalyst, a preparation method thereof, and its application in the preparation of homoanhydrides

Abstract

The present invention belongs to the field of catalyst technology and provides a vanadium-based catalyst, a preparation method thereof, and its application in the preparation of homogenized anhydrides. The method comprises the following steps: mixing vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid, and water to obtain an active component slurry A; mixing titanyl sulfate, lanthanum nitrate, rubidium nitrate, ammonia water, and water, and calcining to obtain a composite oxide; mixing ammonium metavanadate, ammonium heptamolybdate, the composite oxide, oxalic acid, and water to obtain an active component slurry B; spraying the active component slurries A and B onto a support in sequence and calcining to obtain a vanadium-based catalyst. By selecting specific types and contents of active components, arranging the active components in a double layer, and preparing the composite oxide as a support within the outer layer of the active components, the activity and stability of the catalyst are improved, thereby increasing the yield of homogenized anhydrides. When the vanadium-based catalyst prepared by the present invention is applied to the preparation of homogenized anhydrides, the homogenized anhydride yield reaches as high as 112.7 wt%.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a vanadium-based catalyst, a preparation method thereof, and application thereof in the preparation of homoanhydrides. Background Art

[0002] Pyromellitic dianhydride (pyromellitic dianhydride) is a widely used, high-value-added fine chemical product, used in the synthesis of polyimides, matting agents for powder coatings, and epoxy resin curing agents. Polyimides, among other specialty materials with excellent overall performance, are used in defense and aerospace applications, as components for electronic devices, and in flexible solar cell substrates. The main methods for producing pyromellitic dianhydride include liquid-phase oxidation of durenyl and vapor-phase oxidation of durenyl. The vapor-phase oxidation of durenyl has gained widespread attention due to its short process flow and simple production equipment. However, it should be noted that the production of pyromellitic dianhydride by vapor-phase oxidation of durenyl involves a complex catalytic selective oxidation of hydrocarbons, making the catalyst crucial for this process. Currently, the catalysts used to prepare pyromellitic dianhydride by vapor-phase oxidation primarily use vanadium as the active component, supplemented with a small amount of metal elements. According to the chemical reaction equation, the theoretical yield of pyromellitic dianhydride should reach 163%. However, the catalyst activity obtained by traditional preparation methods is relatively low, and the actual yield of pyromellitic dianhydride reaches only 56% of the theoretical yield at best. Therefore, it is of great significance to provide a method for preparing a catalyst with high activity and high average anhydride yield. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art and to provide a vanadium-based catalyst and a preparation method thereof and application thereof in the preparation of homoanhydrides.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing a vanadium-based catalyst, comprising the following steps:

[0006] (1) mixing vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water to obtain active component slurry A;

[0007] (2) mixing titanyl sulfate, lanthanum nitrate, rubidium nitrate, ammonia water and water, and calcining to obtain a composite oxide;

[0008] (3) mixing ammonium metavanadate, ammonium heptamolybdate, composite oxide, oxalic acid and water to obtain active component slurry B;

[0009] (4) The active component slurry A and the active component slurry B are sequentially sprayed onto the carrier and calcined to obtain the vanadium-based catalyst.

[0010] Preferably, the mass ratio of vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water in step (1) is 20-30:0.4-0.8:0.45-0.6:80-120:300-400.

[0011] Preferably, the mixing temperature in step (1) is 75-85° C., and the mixing time is 1-5 h.

[0012] Preferably, the molar volume ratio of titanyl sulfate, lanthanum nitrate, rubidium nitrate and water in step (2) is 1-2 mol: 0.25-0.35 mol: 0.05-0.2 mol: 1-2 L;

[0013] The pH value of the mixed solution is 8.5-10.5.

[0014] Preferably, the calcination temperature in step (2) is 450-650° C., and the calcination time is 1.5-5.5 h.

[0015] Preferably, the mass ratio of the ammonium metavanadate, ammonium heptamolybdate, composite oxide, oxalic acid and water in step (3) is 35-45:5.5-6.5:80-100:100-120:400-600.

[0016] Preferably, the mixing temperature in step (3) is 75-85° C., and the mixing time is 1.5-5 h.

[0017] Preferably, the carrier in step (4) is one or more of α-Al2O3, silicon carbide, and a ceramic ring; the mass ratio of the active component slurry A, the active component slurry B, and the carrier is 0.5-2:1-3:95-105;

[0018] The calcination temperature is 400-600° C., and the calcination time is 2-8 hours.

[0019] The present invention also provides a vanadium-based catalyst obtained by the preparation method.

[0020] The present invention also provides application of the vanadium-based catalyst in the reaction of oxidizing durene to prepare homoanhydride.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention provides a vanadium-based catalyst, wherein the active components include a certain amount of vanadium, phosphorus, rubidium, titanium, lanthanum and molybdenum. The present invention improves the activity and stability of the catalyst by selecting specific types and contents of active components, thereby improving the yield of homoanhydrides.

[0023] (2) The active components in the present invention are distributed in an inner and outer double layer on the catalyst surface. The outer layer active components have a stronger oxidizing ability and can ensure the complete conversion of tetramethylbenzene to anhydride. The inner layer active components have a weaker oxidizing ability and can prevent the tetramethylbenzene that diffuses into the inner layer from undergoing excessive oxidation reaction. It can also replenish the vanadium and rubidium lost in the outer layer. The setting of the inner and outer double layers of active components further improves the catalytic performance of the catalyst.

[0024] (3) The present invention further improves the reactivity of the active components in the outer layer by doping lanthanum and rubidium elements into titanium oxide to form a composite oxide, and then uses the composite oxide as a carrier for other active components in the outer layer, thereby ensuring the complete conversion of tetramethylbenzene to anhydride, thereby greatly improving the reaction efficiency of the catalyst.

[0025] (4) The present invention provides a method for preparing a vanadium-based catalyst, comprising the following steps: mixing vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water to obtain an active component slurry A; mixing titanyl sulfate, lanthanum nitrate, rubidium nitrate, ammonia water and water, and calcining to obtain a composite oxide; mixing ammonium metavanadate, ammonium heptamolybdate, the composite oxide, oxalic acid and water to obtain an active component slurry B; spraying the active component slurry A and the active component slurry B onto a carrier in sequence, and calcining to obtain a vanadium-based catalyst; the preparation process provided by the present invention is simple and highly practical; the vanadium-based catalyst prepared by the present invention is applied to the oxidation of durene to prepare anhydride, and the anhydride yield is as high as 112.7 wt%. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a vanadium-based catalyst, comprising the following steps:

[0027] (1) mixing vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water to obtain active component slurry A;

[0028] (2) mixing titanyl sulfate, lanthanum nitrate, rubidium nitrate, ammonia water and water, and calcining to obtain a composite oxide;

[0029] (3) mixing ammonium metavanadate, ammonium heptamolybdate, composite oxide, oxalic acid and water to obtain active component slurry B;

[0030] (4) The active component slurry A and the active component slurry B are sequentially sprayed onto the carrier and calcined to obtain the vanadium-based catalyst.

[0031] In the present invention, the mass ratio of vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water in step (1) is preferably 20-30: 0.4-0.8: 0.45-0.6: 80-120: 300-400, more preferably 22-28: 0.5-0.7: 0.47-0.58: 85-115: 320-380, and more preferably 24-26: 0.55-0.65: 0.50-0.55: 90-110: 340-360.

[0032] In the present invention, in step (1), oxalic acid and water are first mixed, and then the remaining materials are added to carry out the mixing of step (1).

[0033] In the present invention, the temperature of the first mixing is preferably 75-85°C, more preferably 77-83°C, more preferably 79-81°C; the time of the first mixing is preferably 0.2-1.5h, more preferably 0.5-1.3h, more preferably 0.7-1.1h; the temperature of the mixing in step (1) is preferably 75-85°C, more preferably 77-83°C, more preferably 79-81°C; the time of the mixing is preferably 1-5h, more preferably 2-4h, more preferably 2.5-3.5h.

[0034] In the present invention, the molar volume ratio of titanyl sulfate, lanthanum nitrate, rubidium nitrate and water in step (2) is preferably 1-2 mol: 0.25-0.35 mol: 0.05-0.2 mol: 1-2 L, more preferably 1.2-1.8 mol: 0.27-0.33 mol: 0.1-0.15 mol: 1.2-1.8 L, more preferably 1.3-1.7 mol: 0.29-0.31 mol: 0.12-0.13 mol: 1.3-1.7 L;

[0035] The pH value of the mixed solution is preferably 8.5 to 10.5, more preferably 9 to 10, and even more preferably 9.2 to 9.8.

[0036] In the present invention, the mass fraction of the ammonia water in step (2) is preferably 20-30%, more preferably 22-28%, and even more preferably 23-27%.

[0037] In the present invention, in step (2), titanyl sulfate and water are preliminarily mixed, and then lanthanum nitrate and rubidium nitrate are added and mixed for a second time, and finally ammonia water is added and mixed.

[0038] In the present invention, the temperature of the preliminary mixing is preferably 20-30°C, more preferably 22-28°C, more preferably 24-26°C, and the time of the preliminary mixing is preferably 0.2-1.5h, more preferably 0.5-1.3h, more preferably 0.7-1.1h; the temperature of the secondary mixing is preferably 20-30°C, more preferably 22-28°C, more preferably 24-26°C, and the time of the secondary mixing is preferably 0.2-1.5h, more preferably 0.5-1.3h, more preferably 0.7-1.1h; the temperature of the mixing in step (2) is preferably 35-55°C, more preferably 40-50°C, more preferably 44-46°C; the mixing time is preferably 0.5-5h, more preferably 1.5-4h, more preferably 2.5-3h.

[0039] In the present invention, the calcination temperature in step (2) is preferably 450-650°C, more preferably 500-600°C, and more preferably 520-580°C; the calcination time is preferably 1.5-5.5h, more preferably 2-5h, and more preferably 3-4h.

[0040] In the present invention, the mass ratio of the ammonium metavanadate, ammonium heptamolybdate, composite oxide, oxalic acid and water in step (3) is preferably 35-45: 5.5-6.5: 80-100: 100-120: 400-600, more preferably 37-43: 5.7-6.3: 85-95: 105-115: 450-550, and more preferably 39-41: 5.9-6.1: 87-93: 107-113: 470-530.

[0041] In the present invention, in step (3), oxalic acid and water are first mixed, and then the remaining materials are added to carry out the mixing of step (3).

[0042] In the present invention, the temperature of the first mixing is preferably 75-85°C, more preferably 77-83°C, more preferably 79-81°C; the time of the first mixing is preferably 0.2-1.5h, more preferably 0.5-1.3h, more preferably 0.7-1.1h; the temperature of the mixing in step (3) is preferably 75-85°C, more preferably 77-83°C, more preferably 79-81°C; the time of the mixing is preferably 1.5-5h, more preferably 2-4.5h, more preferably 3-3.5h.

[0043] In the present invention, the carrier in step (4) is preferably one or more of α-Al2O3, silicon carbide, and a porcelain ring; the mass ratio of the active component slurry A, the active component slurry B, and the carrier is preferably 0.5-2:1-3:95-105, further preferably 0.7-1.8:1.5-2.5:97-103, and more preferably 0.9-1.6:1.7-2.3:99-101.

[0044] In the present invention, the spraying temperature is preferably 50-180°C, more preferably 60-170°C, and more preferably 70-160°C; after the active component slurry A is sprayed, it is dried, and then the active component B is sprayed, followed by secondary drying, and then roasting is performed after the end; the drying and secondary drying are not limited to specific conditions and can be completed by conventional technical means in the field.

[0045] In the present invention, the calcination temperature is preferably 400-600°C, more preferably 450-550°C, and more preferably 470-530°C; the calcination time is preferably 2-8h, more preferably 3-7h, and more preferably 4-6h.

[0046] The present invention also provides a vanadium-based catalyst obtained by the preparation method.

[0047] The present invention also provides application of the vanadium-based catalyst in the reaction of oxidizing durene to prepare homoanhydride.

[0048] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] Example 1

[0050] 100g oxalic acid and 350g water were mixed at 80℃ for 0.6h, then 25g vanadium pentoxide, 0.6g phosphoric acid and 0.52g rubidium nitrate were added, and then mixed at 80℃ for 2h to obtain active component slurry A; 1.5mol titanyl sulfate and 1.5L water were preliminarily mixed at 25℃ for 0.5h, then 0.3mol lanthanum nitrate and 0.12mol rubidium nitrate were added, and mixed at 25℃ for 0.5h, and finally 25% ammonia water was added and mixed at 50℃ for 3h, wherein the pH value of the mixed solution was 9.5. After mixing, it was calcined at 500℃ for 3.5h to obtain to the composite oxide; weigh 90g of the composite oxide for use, mix 110g of oxalic acid and 500g of water at 80°C for 0.6h, then add 40g of ammonium metavanadate, 6g of ammonium heptamolybdate and 90g of the composite oxide, and mix at 80°C for 2h to obtain active component slurry B; at 100°C, spray 1.5g of active component slurry A onto 100g of α-Al2O3, and then dry, and then at 100°C, spray 2g of active component slurry B onto the α-Al2O3 containing the active component slurry A and dry it. After drying, calcine at 500°C for 5h to obtain a vanadium-based catalyst.

[0051] 50 mL of the catalyst was placed in a reaction tube with an inner diameter of 25 mm and the reaction gas was introduced to start the reaction. The reaction conditions were: reaction temperature 395 ° C, durene concentration 22 g / m 3 , the reaction space velocity is 5100h -1 After the reaction was completed, the mass yield of the anhydride was measured to be 112.7 wt%.

[0052] Example 2

[0053] 105g oxalic acid and 370g water were mixed at 82°C for 0.9h, and then 26.5g vanadium pentoxide, 0.68g phosphoric acid and 0.55g rubidium nitrate were added, and then mixed at 82°C for 3.2h to obtain active component slurry A; 1.7mol titanyl sulfate and 1.6L water were preliminarily mixed at 27°C for 1h, and then 0.33mol lanthanum nitrate and 0.15mol rubidium nitrate were added, and mixed at 27°C for 0.8h, and finally 28% ammonia water was added, and mixed at 52°C for 3.5h, wherein the pH value of the mixed solution was 10. After mixing, it was calcined at 600°C for 4h to obtain a composite composite oxide; weigh 92g of composite oxide for use, mix 115g of oxalic acid and 520g of water at 82°C for 1.2h, then add 42g of ammonium metavanadate, 6.3g of ammonium heptamolybdate and 92g of composite oxide, and mix at 82°C for 3.5h to obtain active component slurry B; at 120°C, spray 1.7g of active component slurry A onto 100g of α-Al2O3, and then dry, and then at 120°C, spray 2.5g of active component slurry B onto the α-Al2O3 containing active component slurry A and dry. After drying, calcine at 550°C for 7h to obtain a vanadium-based catalyst.

[0054] 50 mL of the catalyst was placed in a reaction tube with an inner diameter of 25 mm and the reaction gas was introduced to start the reaction. The reaction conditions were: reaction temperature 395 ° C, durene concentration 22 g / m 3 , the reaction space velocity is 5100h -1 After the reaction was completed, the mass yield of the anhydride was measured to be 111.4 wt%.

[0055] Example 3

[0056] 95g of oxalic acid and 320g of water were mixed at 75°C for 0.5h, and then 23g of vanadium pentoxide, 0.45g of phosphoric acid and 0.45g of rubidium nitrate were added, and then mixed at 75°C for 1.7h to obtain active component slurry A; 1mol of titanium oxysulfate and 1.3L of water were preliminarily mixed at 22°C for 0.5h, and then 0.26mol of lanthanum nitrate and 0.08mol of rubidium nitrate were added, and mixed at 22°C for 0.3h, and finally 22% ammonia water was added, and mixed at 45°C for 2.5h, wherein the pH value of the mixed solution was 9.2. After mixing, it was roasted at 470°C for 2.6h to obtain to the composite oxide; weigh 85g of the composite oxide for use, mix 100g of oxalic acid and 450g of water at 77°C for 0.5h, then add 36g of ammonium metavanadate, 5.5g of ammonium heptamolybdate and 85g of the composite oxide, and mix at 77°C for 2h to obtain active component slurry B; at 80°C, spray 0.75g of active component slurry A onto 95g of α-Al2O3, and then dry, and then at 80°C, spray 1.2g of active component slurry B onto the α-Al2O3 containing the active component slurry A and dry it. After drying, calcine at 470°C for 4h to obtain a vanadium-based catalyst.

[0057] 50 mL of the catalyst was placed in a reaction tube with an inner diameter of 25 mm and the reaction gas was introduced to start the reaction. The reaction conditions were: reaction temperature 395 ° C, durene concentration 22 g / m 3 , the reaction space velocity is 5100h -1 After the reaction was completed, the mass yield of the anhydride was measured to be 110.9 wt%.

[0058] As can be seen from the above examples, the present invention provides a vanadium-based catalyst, the active components of which contain a certain amount of vanadium, phosphorus, rubidium, titanium, lanthanum and molybdenum; the present invention improves the activity and stability of the catalyst by selecting specific types and contents of active components, thereby improving the yield of homoanhydrides. In the present invention, the active components are distributed in an inner and outer double layer on the surface of the catalyst. The outer layer active components have a strong oxidizing ability and can ensure the complete conversion of tetramethylbenzene to homoanhydrides; the inner layer active components have a weak oxidizing ability and can prevent the tetramethylbenzene diffused into the inner layer from undergoing excessive oxidation reaction, and can also replenish the vanadium and rubidium lost in the outer layer; the setting of the inner and outer double layers of active components further improves the catalytic performance of the catalyst. The present invention further improves the reaction activity of the outer layer active components by doping lanthanum and rubidium into titanium oxide to form a composite oxide, and then using the composite oxide as a carrier for other active components in the outer layer, thereby ensuring the complete conversion of tetramethylbenzene to homoanhydrides, and greatly improving the reaction efficiency of the catalyst. The preparation process of the invention is simple and practical; when the vanadium-based catalyst prepared by the invention is applied to the reaction of oxidizing durene to prepare homoanhydride, the homoanhydride yield is as high as 112.7 wt%.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a vanadium-based catalyst, characterized in that: It includes the following steps: (1) mixing vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water to obtain active component slurry A; The mass ratio of vanadium pentoxide, phosphoric acid, rubidium nitrate, oxalic acid and water in step (1) is 20-30:0.4-0.8:0.45-0.6:80-120:300-400; (2) mixing titanyl sulfate, lanthanum nitrate, rubidium nitrate, ammonia water and water, and calcining to obtain a composite oxide; The molar volume ratio of titanyl sulfate, lanthanum nitrate, rubidium nitrate and water in step (2) is 1-2 mol: 0.25-0.35 mol: 0.05-0.2 mol: 1-2 L; The calcination temperature in step (2) is 470-500° C., and the calcination time is 1.5-3.5 hours; The pH value of the mixed solution in step (2) is 8.5 to 10.5; (3) mixing ammonium metavanadate, ammonium heptamolybdate, composite oxide, oxalic acid and water to obtain active component slurry B; In step (3), the mass ratio of ammonium metavanadate, ammonium heptamolybdate, composite oxide, oxalic acid and water is 35-45:5.5-6.5:80-100:100-120:400-600; (4) The active component slurry A and the active component slurry B are sequentially sprayed onto the carrier and calcined to obtain the vanadium-based catalyst.

2. The preparation method according to claim 1, wherein The mixing temperature in step (1) is 75-85° C., and the mixing time is 1-5 hours.

3. The preparation method according to claim 1, wherein The mixing temperature in step (3) is 75-85° C., and the mixing time is 1.5-5 h.

4. The preparation method according to claim 1, wherein In step (4), the carrier is one or more of α-Al2O3, silicon carbide, and a ceramic ring; the mass ratio of the active component slurry A, the active component slurry B, and the carrier is 0.5-2:1-3:95-105; The calcination temperature is 400-600° C., and the calcination time is 2-8 hours.

5. The vanadium-based catalyst obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the vanadium-based catalyst according to claim 5 in the oxidation of durene to produce homoanhydride.