Preparation method of catalyst for preparing maleic anhydride through butane oxidation

Abstract

The invention provides a preparation method of a catalyst for preparing maleic anhydride through butane oxidation, and belongs to the technical field of molecular sieve catalysts. According to the method, a methanol and formaldehyde (or paraformaldehyde) pretreatment step is added after an isobutanol and benzyl alcohol reduction step, and the reduction degree of non-valent vanadium can be improved through pretreatment of a methanol and formaldehyde mixed system, so that the catalytic activity of the finally obtained catalyst is improved. In addition, the molybdenum element is added into the vanadium-phosphorus catalytic system, so that the selectivity and the yield of maleic anhydride can be further improved.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve catalysts, and in particular to a method for preparing a catalyst for preparing maleic anhydride by oxidation of butane. Background Art

[0002] Maleic anhydride, also known as maleic anhydride, is the third largest anhydride in the world after phthalic anhydride and acetic anhydride. Maleic anhydride is widely used in fiberglass, coatings, lubricant additives, pesticides, pharmaceuticals and other industries because of its high activity and the ability to undergo chemical reactions such as amidation, addition, polymerization, esterification and alkylation. According to the "Research Report on the Supply and Demand Status and Market Trends of Maleic Anhydride (Maleic Anhydride) Industry in China", in recent years, the production capacity of maleic anhydride in my country has basically remained at around 1.9 million tons. The production of maleic anhydride by n-butane oxidation and the production of maleic anhydride by benzene oxidation are the two mainstream processes for preparing maleic anhydride. Among them, the benzene oxidation process has high costs, high toxicity and high prices of raw material benzene, and environmental pollution, which puts it under pressure to be eliminated. Compared with the benzene oxidation process, the n-butane oxidation process has the advantages of a wide range of raw material sources, low costs, high atomic utilization and low environmental pollution. It has broad development prospects and will gradually replace the benzene oxidation process in the future.

[0003] For the production of maleic anhydride by n-butane oxidation, the catalyst plays a key role and affects the yield and selectivity of the entire reaction. Vanadium phosphorus oxide (VPO) catalyst is the most efficient catalyst reported for butane oxidation, but the catalyst has a problem of low catalyst activity due to insufficient reduction during the preparation process, which in turn affects the product yield and selectivity. Summary of the invention

[0004] In order to solve the problem of low vanadium reduction degree and low catalyst activity in the pretreatment step of butane oxidation to maleic anhydride catalyst, the present invention provides a method for preparing a butane oxidation to maleic anhydride catalyst.

[0005] The technical solution of the present invention is a method for preparing a catalyst for preparing maleic anhydride by oxidation of butane, which comprises the following steps: S1: reacting a phosphorus source and a vanadium source or a phosphorus source and a vanadium source and an auxiliary agent for preparing a catalyst for butane oxidation to maleic anhydride in an organic mixed phase, and filtering to obtain a catalyst precursor.

[0006] S2: pretreating the catalyst precursor obtained in step S1 in a pretreatment agent at 80-120° C. for 1-20 h, filtering, washing, drying, and calcining to obtain the catalyst.

[0007] The organic mixed phase is a mixture of benzyl alcohol and isobutyl alcohol.

[0008] The pretreatment agent is a mixture of benzyl alcohol, methanol, formaldehyde or paraformaldehyde, the amount of formaldehyde or paraformaldehyde added is 0.1-5% of the mass of vanadium pentoxide, and the mass ratio of formaldehyde or paraformaldehyde to methanol is not less than 1:9 and not more than 3:7.

[0009] The auxiliary agent is at least one of ammonium molybdate, ammonium heptamolybdate and ammonium dimolybdate, the vanadium source is vanadium pentoxide, the phosphorus source is phosphoric acid or polyphosphoric acid, molybdenum accounts for 0.05-2% of the catalyst mass in terms of molybdenum oxide, and the atomic ratio of phosphorus to vanadium in the phosphorus source and the vanadium source is 0.5-2.

[0010] In some specific preparation methods of catalysts for the oxidation of butane to maleic anhydride, molybdenum, calculated as molybdenum oxide, accounts for 0.5-0.7% of the mass of the catalyst.

[0011] The atomic ratio of phosphorus to vanadium in the phosphorus source and the vanadium source is 1 to 1.7.

[0012] In some specific methods for preparing catalysts for preparing maleic anhydride by oxidation of butane, the amount of the organic mixed phase used is 5 to 10 times the mass of the vanadium source, and the mass ratio of isobutanol to benzyl alcohol in step S1 is 6 to 9:1.

[0013] In some specific methods for preparing catalysts for preparing maleic anhydride by oxidation of butane, the mass of benzyl alcohol in step S2 is 5 to 10 times that of vanadium pentoxide.

[0014] Some specific methods for preparing catalysts for preparing maleic anhydride by oxidation of butane are characterized in that, in step S1, vanadium pentoxide or vanadium pentoxide and an auxiliary agent are added to an organic mixed phase, the temperature is raised to 80-120° C., phosphoric acid or polyphosphoric acid is added to the reaction system to react for 10-20 h, and the catalyst precursor is obtained by filtering.

[0015] Some specific methods for preparing catalysts for preparing maleic anhydride by oxidation of butane are characterized in that the reaction temperature in step S1 is 100-110° C. and the reaction time is 10-20 h.

[0016] In some specific preparation methods, the reaction temperature of step S2 is 90-110° C., and the reaction time is 3-15 h.

[0017] Some specific preparation methods, the reaction temperature of step S1 is 102~105℃, and the reaction time is 13~18 h; the reaction temperature of step S2 is 90~105℃, and the reaction time is 5~10 h.

[0018] In some specific preparation methods, the amount of formaldehyde added is 1-3% of the mass of vanadium pentoxide.

[0019] In some specific preparation methods, the mass ratio of formaldehyde or paraformaldehyde to methanol is not less than 1:4 and not more than 3:7.

[0020] The catalyst prepared by the above-mentioned preparation method has a bulk density of 0.7 g / cm 3 , with a specific surface area of ​​40-50m 2 / g.

[0021] The catalyst is used in catalyzing the reaction of preparing maleic anhydride by oxidizing butane.

[0022] The application is to load the catalyst into a fixed bed reactor, with a butane flow rate of 17-31 ml / min, an inlet butane concentration of 1.5-1.8%, and react at 350-450°C.

[0023] Beneficial effects of the present invention: The present invention provides a method for preparing a catalyst for preparing maleic anhydride by oxidation of butane, wherein the method adds a methanol and formaldehyde (or polyformaldehyde) pretreatment step after the isobutyl alcohol and benzyl alcohol reduction step, and the reduction degree of the priceless vanadium can be increased by the pretreatment of the methanol and formaldehyde mixed system, thereby increasing the catalytic activity of the catalyst finally obtained. In addition, the present invention can further improve the selectivity and yield of maleic anhydride by adding molybdenum element to the vanadium-phosphorus catalyst system. DETAILED DESCRIPTION Example 1

[0024] S1: Add 50 g (0.275 mol) of vanadium pentoxide to a mixture of 400 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 7:1, heat to 100 °C, add 97 g of 80% phosphoric acid, stir and react for 15 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 300 g benzyl alcohol, 1.15 g formaldehyde and 2.69 g methanol, and the mixture was pretreated at 100 °C for 5 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst. Example 2

[0025] S1: Add 50 g (0.275 mol) of vanadium pentoxide to a mixture of 250 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 6:1, heat to 100 °C, add 97 g of 80% phosphoric acid, stir and react for 10 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 300 g benzyl alcohol, 1 g formaldehyde and 2.84 g methanol, and the mixture was pretreated at 100 °C for 5 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst. Example 3

[0026] S1: Add 50 g (0.275 mol) of vanadium pentoxide to a mixture of 500 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 9:1, heat to 110 °C, add 97 g of 80% phosphoric acid, stir and react for 15 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 250 g benzyl alcohol, 0.77 g formaldehyde and 3.07 g methanol, and the mixture was pretreated at 110 °C for 8 h, filtered, washed, dried at 85 °C for 12 h, and calcined at 550 °C for 5 h to obtain the target catalyst. Example 4

[0027] S1: Add 50 g (0.275 mol) of vanadium pentoxide to a mixture of 300 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 7:1, heat to 90 °C, add 102 g of 105% polyphosphoric acid, stir and react for 10 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 300 g benzyl alcohol, 0.768 g formaldehyde and 1.792 g methanol, and the mixture was pretreated at 95 °C for 10 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst. Example 5

[0028] S1: Add 50 g (0.275 mol) of vanadium pentoxide to a mixture of 350 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 7:1, heat to 100 °C, add 55 g of 98% phosphoric acid, stir and react for 15 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 300 g benzyl alcohol, 1.15 g formaldehyde and 2.69 g methanol, and the mixture was pretreated at 105 °C for 5 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst. Example 6

[0029] S1: Add 50 g (0.275 mol) of vanadium pentoxide to a mixture of 400 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 7:1, heat to 100 °C, add 107 g of 80% phosphoric acid, stir and react for 15 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 250 g benzyl alcohol, 0.384 g formaldehyde and 0.896 g methanol, and the mixture was pretreated at 105 °C for 15 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst. Example 7

[0030] S1: Add 50 g (0.275 mol) of vanadium pentoxide and 0.9 g of ammonium dimolybdate to a mixture of 400 g of isobutyl alcohol and benzyl alcohol in a mass ratio of 7:1, heat to 100 °C, add 97 g of 80% phosphoric acid, stir and react for 15 h, and filter to obtain a catalyst precursor; S2: The catalyst precursor obtained in step S1 was added to a mixture of 300 g benzyl alcohol, 1.15 g formaldehyde and 2.69 g methanol, and the mixture was pretreated at 100 °C for 5 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst.

[0031] Comparative Example 1: 50 g (0.275 mol) of vanadium pentoxide was added to a mixture of 400 g of isobutanol and benzyl alcohol in a mass ratio of 7:1, the temperature was raised to 100 °C, 97 g of 80% phosphoric acid was added and stirred for 15 h, filtered, washed, dried at 80 °C for 12 h, and calcined at 500 °C for 5 h to obtain the target catalyst.

[0032] Comparative Example 2: 50 g (0.275 mol) of vanadium pentoxide and 0.9 g of ammonium dimolybdate were added to a mixture of 400 g of isobutanol and benzyl alcohol in a mass ratio of 7:1, the temperature was raised to 100 °C, 97 g of 80% phosphoric acid was added and stirred for 15 h, the target catalyst was obtained by filtering, washing, drying at 80 °C for 12 h, and calcining at 500 °C for 5 h.

[0033] Test Example: The catalysts prepared in Examples 1-7 and Comparative Examples 1-2 were used to catalyze the oxidation of n-butane to produce maleic anhydride, and the catalytic performance of the catalysts was evaluated. The catalyst was loaded in a fixed bed, the air flow rate was 2 L / min, the butane flow rate was 30.5 ml / min, the inlet flow rate of butane was 1.6 ml / min, and the reaction was carried out at 400 °C. After online gas chromatography analysis, the specific data are shown in Table 1.

[0034] Table 1 Catalytic effect data of examples and comparative examples catalyst Maleic Anhydride Selectivity Maleic anhydride molar yield Example 1 77% 62% Example 2 75% 61% Example 3 75% 61.5% Example 4 76% 62% Example 5 74% 59% Example 6 73% 57% Example 7 80% 67% Comparative Example 1 65% 50% Comparative Example 2 72% 55% It can be seen from the data in Table 1 that, compared with the conventional method, the catalyst prepared by the present invention can significantly improve the selectivity and conversion rate of maleic anhydride.

Claims

1. A method for preparing a catalyst for preparing maleic anhydride by oxidation of butane, characterized in that: Use the following steps: S1: reacting a phosphorus source, a vanadium source or a phosphorus source, a vanadium source and an additive for preparing a catalyst for butane oxidation to maleic anhydride in an organic mixed phase, and filtering to obtain a catalyst precursor; S2: pretreating the catalyst precursor obtained in step S1 in a pretreatment agent at 80-120° C. for 1-20 h, filtering, washing, drying, and calcining to obtain the catalyst; The organic mixed phase is a mixture of benzyl alcohol and isobutyl alcohol; The pretreatment agent is a mixture of benzyl alcohol, methanol, formaldehyde or paraformaldehyde, the amount of formaldehyde added is 0.1-5% of the mass of vanadium pentoxide, and the mass ratio of formaldehyde or paraformaldehyde to methanol is not less than 1:9 and not more than 3:7; The auxiliary agent is at least one of ammonium molybdate, ammonium heptamolybdate and ammonium dimolybdate, the vanadium source is vanadium pentoxide, the phosphorus source is phosphoric acid or polyphosphoric acid, molybdenum accounts for 0.05-2% of the catalyst mass in terms of molybdenum oxide, and the atomic ratio of phosphorus to vanadium in the phosphorus source and the vanadium source is 0.5-2.

2. The method for preparing a catalyst for preparing maleic anhydride by oxidation of butane according to claim 1, characterized in that: Molybdenum accounts for 0.5-0.7% of the catalyst mass as molybdenum oxide; The atomic ratio of phosphorus to vanadium in the phosphorus source and the vanadium source is 1 to 1.

7.

3. The method for preparing a catalyst for preparing maleic anhydride by oxidation of butane according to claim 2, characterized in that: The amount of the organic mixed phase is 5 to 10 times the mass of the vanadium source, and the mass ratio of isobutanol to benzyl alcohol in step S1 is 6 to 9:1; The mass of benzyl alcohol in step S2 is 5 to 10 times that of vanadium pentoxide.

4. The method for preparing a catalyst for preparing maleic anhydride by oxidation of butane according to claim 3, characterized in that: In step S1, vanadium pentoxide or vanadium pentoxide and an auxiliary agent are added to an organic mixed phase, the temperature is raised to 80-120° C., phosphoric acid or polyphosphoric acid is added to the reaction system to react for 10-20 hours, and the catalyst precursor is obtained by filtering.

5. The method for preparing a catalyst for preparing maleic anhydride by oxidation of butane according to claim 4, characterized in that: The reaction temperature of step S1 is 100-110°C, and the reaction time is 10-20 h; The reaction temperature of step S2 is 90-110° C., and the reaction time is 3-15 h.

6. The method for preparing a catalyst for preparing maleic anhydride by oxidation of butane according to claim 5, characterized in that: The reaction temperature of step S1 is 102-105°C, and the reaction time is 13-18 h; The reaction temperature of step S2 is 90-105°C, and the reaction time is 5-10 h.

7. The method for preparing a catalyst for preparing maleic anhydride by oxidation of butane according to claim 6, characterized in that: The formaldehyde or paraformaldehyde is 1-3% of the mass of vanadium pentoxide; the mass ratio of formaldehyde or paraformaldehyde to methanol is not less than 1:4 and not more than 3:

7.

8. A catalyst prepared by the preparation method according to any one of claims 1 to 7, wherein the bulk density of the catalyst is 0.7 g / cm 3 , with a specific surface area of ​​40-50 m 2 / g.

9. Use of the catalyst according to claim 8 in catalyzing the oxidation of butane to prepare maleic anhydride.

10. The use according to claim 9, characterized in that: The catalyst is loaded into a fixed bed reactor, the butane flow rate is 17-30 ml / min, the inlet concentration of butane is 1.5-1.8%, and the reaction is carried out at 350-450°C.