Process for the preparation of a catalyst for the oxidation of alcohols to aldehydes and its use

Abstract

The present application relates to a kind of catalyst for preparing aldehyde by oxidation method and its application, the catalyst is prepared by coprecipitation method, add trimethylol ethane and macromolecular polymer polyphenyl diamide during preparation process and modify, improve catalyst structure, enhance the binding force between components, so as to improve the stability and selectivity of catalyst.The catalyst prepared by the method can be applied to alcohol oxidation to prepare aldehyde industrial device, such as methanol oxidation to prepare formaldehyde, etc.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst preparation, in particular to a preparation method of a catalyst for preparing aldehyde by oxidation method and application thereof. BACKGROUND

[0002] Formaldehyde is an important basic organic chemical raw material, and plays a decisive role in the adjustment of future energy structure and the development of chemical industry. Since Germany first realized formaldehyde industrial production in 1888, the production methods of formaldehyde have appeared the following types according to different raw materials: non-catalytic oxidation method with liquefied petroleum gas as raw material, dimethyl ether oxidation method, methane oxidation method, and methanol air oxidation method. At present, methanol oxidation method is mainly used in industry. China's formaldehyde industry started in 1956, and has a history of more than 50 years. With the continuous development of China's economy, China's formaldehyde industry is growing.

[0003] There are many patents for preparing formaldehyde by iron-molybdenum catalyst, such as patent US4420421 which describes the use of different raw materials of sodium molybdate, so that the conversion rate of methanol is 93%~95%, and the selectivity is increased to 92%. Patent CN103933998 A discloses a catalyst for preparing formaldehyde by methanol oxidation. According to the catalyst of the embodiment, the catalyst contains MoaNibFecBidPreCofCegVhCriAjOk as an active component, which is a multi-component combined catalyst. Patent CN105457648A discloses an iron-molybdenum formaldehyde catalyst which is modified by adding nickel metal. Patent CN108097259A discloses the use of a macromolecular heterocyclic compound as a raw material to synthesize catalysts with different grain sizes and morphologies, which can realize the regulation of the distance, proportion and distribution of iron-molybdenum binary active centers. Patent CN109012682A discloses a modification method of a catalyst for preparing formaldehyde by methanol oxidation, which relates to a modified catalyst prepared by a mechanical chemical method. Patent CN109806881A discloses an iron-molybdenum catalyst which adds rare earth elements as additives and organic matter as dispersants during synthesis to optimize the catalyst.

[0004] However, most of the existing patents of iron-molybdenum catalysts add other heteroatoms and other precipitation processes to improve the activity and selectivity of the catalyst, and the influence of the physical structure of the catalyst itself on the activity and selectivity is less discussed. SUMMARY

[0005] The present application provides a preparation method of a catalyst for preparing aldehyde by oxidation method and application thereof. The catalyst prepared by the method of the present application can improve the strength of the catalyst after reaction, improve the binding force between the active components, and prolong the service life of the catalyst.

[0006] The present application adopts the following technical solutions:

[0007] A method for preparing a catalyst for preparing aldehyde by oxidation method, comprising the following steps:

[0008] a) adding a water solution containing molybdenum salt and a water solution containing iron salt into a kettle containing trimethylol ethane in parallel flow for co-precipitation, and the pH value is controlled at 1.0-3.0, preferably 1.5-2.5 during co-precipitation, and the temperature of the reaction kettle is 50-100℃;

[0009] b) aging at 50-100℃ after co-precipitation, and the aging time is preferably 24-48h, then filtering and washing to obtain a filter cake;

[0010] c) drying the filter cake, and preferably, drying the filter cake at 50-100℃ for 10-20h, and then drying at 100-150℃ for 10-20h;

[0011] d) calcining the catalyst obtained after drying at 400-560℃, and the preferred calcining time is 5-20h, and then crushing to obtain a catalyst powder.

[0012] e) mixing the catalyst powder and polyphenylene diamide, and then shaping to obtain a catalyst.

[0013] Preferably, the molybdenum salt and the iron salt are added in a molar ratio of Mo / Fe of 2.0-2.5:1. Preferably, in the step a), the mass concentration of the molybdenum salt in the water solution containing the molybdenum salt is 10wt%-30wt%.

[0014] Preferably, in the step a), the mass concentration of the iron salt in the water solution containing the iron salt is 10wt%-30wt%.

[0015] The molybdenum salt in the present application includes one or more of ammonium polymolybdate, molybdenum trioxide, molybdic acid and molybdenum disulfide, and preferably, the water-soluble molybdenum salt ammonium polymolybdate.

[0016] The iron salt in the present application includes one or more of ferric chloride, ferric nitrate, iron oxide and iron powder, and preferably, ferric chloride and / or ferric nitrate.

[0017] In the present application, trimethylol ethane is added in the preparation process, and this organic compound can improve the binding force between the active components and reduce the loss of the active components in the reaction process, and the addition amount is 1-5% of the total mass of the generated metal oxide.

[0018] In the present application, the addition amount of polyphenylene diamide is 1-5% of the total mass of the generated metal oxide, and if the addition amount is too small, the catalyst strength cannot be improved, and the formation of the catalyst micro-pore structure is not conducive, and if the addition amount is too large, the catalyst activity is easily reduced.

[0019] The molding method in step e) of this invention includes, but is not limited to, extrusion, tableting, etc., such as adding a pore-forming agent, binder, and / or lubricant to a mixture of catalyst powder and polyphthalamide for molding. The resulting molded catalyst can be in the shape of, but is not limited to, strips, cylinders, hollow cylinders, spherical particles, etc.

[0020] A suitable extrusion molding method includes the following steps: adding a pore-forming agent and a binder to the catalyst powder and then extruding it to obtain strip-shaped particles.

[0021] A suitable tableting method includes the following steps: adding a pore-forming agent and a lubricant to a mixture of catalyst powder and polyphthalamide and then pressing the mixture into tablets to obtain cylindrical or hollow cylindrical particles.

[0022] In the molding method of this invention, the pore-forming agent used is one or more of guar gum powder, cellulose, polyvinyl alcohol, polyvinylpyrrolidone, starch, and pullulan, preferably one or more of guar gum powder, polyvinylpyrrolidone, and starch. The amount of the pore-forming agent is 1% to 5% of the mass of the catalyst powder. The binder used is one or more of water, ethanol, ethylene glycol, and glycerol, preferably one or more of water, ethanol, and glycerol, and the amount of the binder is 5% to 25% of the catalyst powder.

[0023] The present invention also provides the application of the catalyst, which is used for the oxidation of alcohols and oxygen to prepare aldehydes in the presence of the catalyst.

[0024] The catalyst described in this invention undergoes pretreatment before use, the pretreatment comprising the following steps: the catalyst is subjected to a volume hourly space velocity (VHSV) of 7000–12000 h⁻¹. -1 In an air or O2 atmosphere, the temperature is raised to 200-400°C at a heating rate of 1-20°C / min and held for 1-180 min, preferably 30-150 min.

[0025] In this invention, the reaction temperature for preparing aldehydes via alcohol oxidation is 300–360°C, preferably 310–350°C; the reaction pressure is 0.01–0.2 MPa absolute, preferably 0.02–0.1 MPa; and the gaseous feedstock volume hourly space velocity is 7000–12000 h⁻¹. -1 Preferred operating time: 8000-11000h -1 .

[0026] In this invention, the gaseous raw materials include methanol, dilution gas, and O2, wherein the molar ratio of methanol to dilution gas is 1:7 to 12, preferably 1:7.5 to 11; the molar ratio of methanol to O2 is 1:0.8 to 4, preferably 1:1 to 3.5; and the dilution gas is a reactive inert gas, preferably N2.

[0027] The suitable bulk density of the catalyst in this invention is 0.8-1.2 g / cm³. 3 .

[0028] The present invention has the following technical effects:

[0029] Adding trimethylolethane during catalyst preparation enhances the binding force between active components, reduces the loss of active components, and extends the catalyst's lifespan.

[0030] Introducing a waterproofing agent during catalyst preparation improves the catalyst's water resistance, preventing deactivation due to water during operation and thus extending its lifespan. Furthermore, the waterproofing agent helps maintain good catalyst strength during use, superior to conventional catalysts.

[0031] Introducing polyphthalamide, a high molecular weight polymer, into the catalyst molding process creates a three-dimensional framework that constrains the material space, forming a microreactor. This effectively controls the catalyst structure, improving its activity and selectivity. Furthermore, due to its inherent physicochemical properties, polyphthalamide can enhance the catalyst's thermal stability, toughness, and other properties, extending its service life. Detailed Implementation

[0032] The method of the present invention will be described in detail below with reference to embodiments, but is not limited to the embodiments.

[0033] Unless otherwise specified, all reagents used below are of analytical grade.

[0034] The strength test was conducted using the DL3 intelligent particle strength tester.

[0035] Example 1

[0036] 1320g of ammonium heptamolybdate (chemical formula (NH4)6Mo7O) was added. 24 Solution A was obtained by dissolving 1360g of ferric nitrate nonahydrate (chemical formula Fe(NO3)3·9H2O) in 6kg of pure water. Solution B was obtained by dissolving 1000g of deionized water and 26.92g of trimethylolethane in the bottom solution. The solution temperature in the reactor was maintained at 70℃. While stirring, solutions B and A were added to the reactor simultaneously. Ammonia was added to adjust the pH to 2.0 for co-precipitation. After precipitation, the solution was aged at 70℃ with stirring for 28 hours.

[0037] The slurry was filtered and washed to obtain a filter cake. The filter cake was dried at 90℃ for 10 hours and then dried at 120℃ for 10 hours before being crushed. Finally, it was calcined at 450℃ for 8 hours to obtain catalyst powder.

[0038] Take 100g of catalyst powder, add 2.5g of pore-forming agent guar gum powder, 2g of lubricant microcrystalline cellulose and 5g of polyphthalamide, mix evenly, and use a tablet press to form cylindrical particles to obtain catalyst A with a molybdenum-iron atomic ratio of 2.22.

[0039] Evaluation of oxidation experiments

[0040] 20 ml of catalyst with a particle size of 4-8 mesh was loaded into a 50 cm long reactor, with the reaction tube being a Ф20 mm stainless steel tube. The catalyst pretreatment process was as follows: air was first introduced at a volume hourly space velocity (VHSV) of 8000 h⁻¹. -1 The reaction tube temperature was increased from room temperature to 250°C at a rate of 5°C / min and held for 120 min. After catalyst pretreatment, the mixture was prepared with a methanol:oxygen:nitrogen:water ratio of 1:1.3:10:0.13 (molar ratio) and a feed gas volume hourly space velocity of 10000 h⁻¹. -1 The oxidation reaction was carried out under standard conditions, at a temperature of 340°C and at normal pressure.

[0041] Example 2

[0042] The catalyst preparation process is the same as in Example 1, except that the amount of trimethylolethane added is 67.3g and the amount of polyphthalamide added is 1g.

[0043] Example 3

[0044] The catalyst preparation process is the same as in Example 1, except that the amount of trimethylolethane added is 13.46 g and the amount of polyphthalamide added is 2.5 g.

[0045] Comparative Example 1

[0046] The catalyst preparation process is the same as in Example 1, except that trimethylolethane is not added.

[0047] Comparative Example 2

[0048] The catalyst preparation process is the same as in Example 1, except that the amount of trimethylolethane added is 137.49.

[0049] Comparative Example 3

[0050] The catalyst preparation process is the same as in Example 1, except that polyphenylene oxide is not added.

[0051] Comparative Example 4

[0052] The catalyst preparation process is the same as in Example 1, except that the amount of polyphenylene oxide added is 10g.

[0053] Comparative Example 5

[0054] The catalyst preparation process is the same as in Example 1, except that polyphenylene oxide and trimethylolpropane are not added.

[0055] The results of the sample analysis after 1000 hours of catalyst operation are shown in the table below:

[0056] Methanol conversion % Formaldehyde selectivity % Example 1 96.2 89.2 Example 2 96.6 89.3 Example 3 96.1 89.3 Comparative Example 1 94.1 87.2 Comparative Example 2 93.5 87.6 Comparative Example 3 95.1 87.0 Comparative Example 4 92.1 85.9 Comparative Example 5 91.8 84.2

[0057] The data in the table show that the modified catalyst has higher activity and selectivity.

Claims

1. A process for the preparation of a catalyst for the oxidation process for the preparation of aldehydes, characterized in that, The method comprises the following steps: a) adding a water solution containing a molybdenum salt and a water solution containing an iron salt into a kettle containing trimethylol ethane in parallel flow for co-precipitation, the pH value is controlled at 1.0-3.0 during the co-precipitation, and the temperature of the reaction kettle is 50-100℃; b) aging at 50-100℃ after the co-precipitation, then filtering and washing to obtain a filter cake; c) drying the filter cake, d) calcining the catalyst obtained after drying at 400-560℃, then crushing to obtain a catalyst powder; e) mixing the catalyst powder and polyphenylene diamine, then shaping to obtain a catalyst; The addition amount of trimethylol ethane is 1-5% of the total mass of the generated metal oxide; The addition amount of polyphenylene diamine is 1-5% of the total mass of the generated metal oxide.

2. The production method according to claim 1, characterized by, The addition amount of the molybdenum salt and the iron salt is according to the molar ratio of element Mo / Fe of 2.0-2.5:

1.

3. The preparation method according to claim 1, characterized in that, In the step a), the mass concentration of the molybdenum salt in the water solution containing the molybdenum salt is 10wt%-30wt%.

4. The method of claim 1, wherein, In the step a), the mass concentration of the iron salt in the water solution containing the iron salt is 10wt%-30wt%.

5. The preparation method according to claim 1, characterized in that, In the step a), the pH value is controlled at 1.5-2.

5.

6. The method of claim 1, wherein, In the step b), the aging time is 24-48h.

7. The preparation method according to claim 1, characterized in that, In the step c), the filter cake is dried at 50-100℃ for 10-20h, and then dried at 100-150℃ for 10-20h.

8. The method of claim 1, wherein, In the step d), the calcination time is 5-20h.

9. The method of claim 1, wherein, The mixture of the catalyst powder and polyphenylene diamine is added with a pore-forming agent, a binder and / or a lubricant for shaping.

10. The method of claim 1, wherein, The pore-forming agent used is one or more of sesbania powder, cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, starch and pullulan, and the amount of the pore-forming agent is 1%-5% of the mass of the catalyst powder.

11. The method of claim 10, wherein, The pore-forming agent used is one or more of sesbania powder, polyvinyl pyrrolidone and starch.

12. The method of claim 9, wherein, The binder used is one or more of water, ethanol, ethylene glycol and glycerol, and the amount of the binder is 5%-25% of the mass of the catalyst powder.

13. The method of claim 12, wherein, The binder used is one or more of water, ethanol and glycerol.

14. Use of the catalyst prepared by the preparation method of any one of claims 1-13 for preparing an aldehyde by oxidizing an alcohol and oxygen under the action of the catalyst.

15. Use according to claim 14, characterized in that, The catalyst is pretreated before use, which includes the following steps: the catalyst is heated to 200-400°C at a temperature increasing rate of 1-20°C / min in air or O2 atmosphere at a volume space velocity of 7000-12000h -1 -1-180 min.

16. The use according to claim 14, characterized in that, The reaction temperature for preparing aldehyde by alcohol oxidation is 300-360℃; the reaction pressure is 0.01-0.2 MPa in absolute pressure; the gas raw material volume space velocity is 7000-12000h -1 .

17. Use according to claim 16, characterized in that, The reaction temperature for preparing aldehyde by alcohol oxidation is 310-350℃; the reaction pressure is 0.02-0.1 MPa in absolute pressure; the gas raw material volume space velocity is 8000-11000h -1 .

18. The use according to claim 14, characterized in that, The gas raw material comprises methanol, a dilution gas and O2, wherein the molar ratio of methanol to the dilution gas is 1:7-12, and the molar ratio of methanol to O2 is 1:0.8-4, and the dilution gas is a reaction inert gas.

19. Use according to claim 18, characterized in that, The gas raw material comprises methanol, a dilution gas and O2, wherein the molar ratio of methanol to the dilution gas is 1:7.5-11, and the molar ratio of methanol to O2 is 1:1-3.5, and the dilution gas is N2.

20. The use according to claim 14, characterized in that, The bulk density of the catalyst is 0.8-1.2 g / cm 3 .