Fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction and preparation method

Abstract

The invention discloses a fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction and a preparation method thereof, and belongs to the technical field of activated carbon. The active carbon catalyst prepared by the method has the advantages of high catalytic efficiency, long service life and the like, can be operated under relatively high pressure, the prepared vinyl acetate is high in yield and few in by-products, and the content of benzene in the vinyl acetate product can be remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of activated carbon, and particularly relates to a fluidized bed activated carbon catalyst and a preparation method thereof in the synthesis reaction of vinyl acetate. Background Art

[0002] Vinyl acetate, abbreviated as vinyl acetate (VAc), is an important organic chemical raw material. Its monomers can be copolymerized to produce various adhesives; it can also be copolymerized, grafted, and block-copolymerized with vinyl chloride, acrylonitrile, crotonic acid, acrylic acid, and ethylene monomers to make polymer synthetic materials with different properties, and has a wide range of application fields.

[0003] At present, the main methods for producing vinyl acetate are the ethylene method and the acetylene method. Among them, in 1922, the German company Wacker discovered the acetylene production process and used a zinc acetate / activated carbon catalyst. After improvement, it was put into industrial production of vinyl acetate, and its active components and carriers have been used until now. The carriers and active components in the zinc acetate / activated carbon catalyst are widely sourced, and have advantages such as good catalytic activity and high selectivity; however, there are also some disadvantages, such as low reaction activity, many by-products, easy shedding of active components, short service life, and high replacement cycle.

[0004] Chinese Patent Document CN105457683A discloses a vinyl acetate catalyst, which mainly solves the problems of low catalyst activity and low single-pass conversion of acetylene in the prior art. The invention adopts a vinyl acetate catalyst, the catalyst comprising an active component, a promoter, and a carrier, the active component being zinc acetate, the promoter being potassium acetate, and the carrier being activated carbon modified with TiO2, which preferably solves the problem and can be used in the industrial production of vinyl acetate by the acetylene method. However, the problem of trace benzene in the vinyl acetate product is generally difficult to remove through the reaction, which limits the popularization and application of this catalyst. Summary of the Invention

[0005] The main object of the present invention is to provide a fluidized bed activated carbon catalyst and a preparation method thereof in the synthesis reaction of vinyl acetate. The activated carbon catalyst has the advantages of high catalytic efficiency, can operate at a higher pressure, has a long service life, etc., and the obtained vinyl acetate has a high yield, few by-products, and can significantly reduce the benzene content in the vinyl acetate product.

[0006] To achieve the above object, the present invention provides a preparation method of a fluidized bed activated carbon catalyst in the synthesis reaction of vinyl acetate, comprising the following steps: dissolving the active component and the additive in water to obtain a mixed solution, then impregnating the modified activated carbon in the mixed solution, after impregnation, filtering, collecting the solid matter, and drying the solid matter to obtain the fluidized bed activated carbon catalyst in the synthesis reaction of vinyl acetate.

[0007] Preferably, the mass ratio of the modified activated carbon, the active component, and the promoter is 3 - 4:1 - 2:0.5 - 1.

[0008] Preferably, the impregnation temperature is 60 - 100 °C, and the impregnation time is 3 - 8 h.

[0009] Preferably, the preparation method of the modified activated carbon includes the following steps:

[0010] Dry and crush the biomass raw material, then add it to an aqueous sodium hydroxide solution for impregnation. After impregnation, filter and collect the solid matter. Wash and dry the solid matter to obtain the pretreated biomass. Ultrasonically disperse the pretreated biomass, sodium carboxymethylcellulose, ammonium molybdate, sodium sulfate, and water, and then carry out a hydrothermal reaction. After the reaction is completed, filter, wash, dry, and calcine to obtain porous carbon. Disperse the porous carbon in an aqueous ethanol solution, add γ - glycidoxypropyltrimethoxysilane, and heat for reaction. Filter and collect the solid matter. Disperse the solid matter in N,N - dimethylformamide, add 4 - aminophthalhydrazide, heat for reaction, filter and collect the solid matter, wash and dry to obtain the modified activated carbon.

[0011] Preferably, the biochar raw material is at least one of peanut shells, rice husks, corn straws, coconut shells, animal excreta, and tree branches.

[0012] Preferably, the mass ratio of the pretreated biomass, sodium carboxymethylcellulose, sodium molybdate, and sodium sulfate is 5 - 10:1 - 2:3 - 5:2.5 - 5; the hydrothermal reaction temperature is 170 - 250 °C, and the hydrothermal reaction time is 10 - 50 h; the calcination temperature is 500 - 700 °C, and the calcination time is 2 - 4 h.

[0013] Preferably, the mass ratio of the porous carbon, γ - glycidoxypropyltrimethoxysilane, and 4 - aminophthalhydrazide is 15 - 20:2 - 3:3 - 5.

[0014] In the present invention, by modifying the activated carbon, the modified activated carbon has good mechanical strength, is not easily broken, improves the loading of the active component, is beneficial to improving the service life of the catalyst, improves the catalytic activity of the catalyst, and further improves the space - time yield of vinyl acetate, and can well remove trace benzene in the product.

[0015] Preferably, the active component is a zinc precursor; the zinc precursor is zinc acetate.

[0016] Preferably, the promoter is one of a cobalt precursor and a molybdenum precursor; the cobalt precursor is cobalt nitrate and / or cobalt chloride; the molybdenum precursor is at least one of sodium molybdate, ammonium molybdate, and potassium molybdate.

[0017] The present invention also discloses a method for synthesizing vinyl acetate. Specifically, acetic acid and acetylene are used as raw material gases, and vinyl acetate is obtained through reaction in the presence of a fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction.

[0018] Preferably, the molar ratio of acetic acid to acetylene is 1:5 - 12.

[0019] Preferably, the reaction conditions are as follows: the reaction pressure is 0.1 - 0.5 atm, the reaction temperature is 160 - 200 °C, and the space velocity of the raw material gas is 250 - 350 h -1 .

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) The fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction prepared by the present invention has high catalytic efficiency, can operate under higher pressure and temperature, has the advantages of long service life, etc., and the prepared vinyl acetate has high yield, few by-products, and can significantly reduce the benzene content in the vinyl acetate product;

[0022] (2) The preparation of the modified activated carbon of the present invention is first to pretreat the biomass raw material with sodium hydroxide to remove a large amount of impurities on the surface of the biomass raw material, expose more active groups, and at the same time break the hydrogen bonds between cellulose molecules inside the biomass, increase the distance between molecules, make the cellulose become loose, and is beneficial to the progress of subsequent steps; then carry out a hydrothermal reaction with sodium carboxymethylcellulose, ammonium molybdate, and sodium sulfate to in-situ generate MoS2 on the porous carbon. On the one hand, MoS2 can improve the thermal stability of the porous carbon, avoid coking of the porous carbon during the high-temperature reaction of acetic acid and acetylene, which may lead to blockage of the pores and affect the catalytic activity of the catalyst. On the other hand, it can also improve the mechanical strength of the porous carbon, is not easy to break, can better load the active components, and is beneficial to improving the service life of the catalyst; then introduce epoxy groups on the surface of the porous carbon, which is beneficial to the grafting reaction with 4-aminophthalhydrazide. 4-aminophthalhydrazide can form a conjugate with the by-product benzene in the vinyl acetate product, thereby realizing the adsorption and removal of the by-product benzene and improving the purity of the vinyl acetate product. Specific Embodiments

[0023] To avoid repetition, the items used in the following examples are all commercially available products without special instructions, and the methods used are all conventional methods without special instructions.

[0024] Example 1

[0025] A preparation method of a fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction, comprising the following steps: Dissolve 15 g of zinc acetate and 8 g of cobalt nitrate in 150 mL of water to obtain a mixed solution, then immerse 35 g of modified activated carbon in the mixed solution, immerse at 80 °C for 5 h, after the immersion is completed, cool and filter, collect the solid, and dry the solid to obtain the fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction.

[0026] The preparation method of the modified activated carbon is as follows:

[0027] Dry 100 g of biomass raw materials (a mixture of rice husk and corn straw with a mass ratio of 1:4), crush and pass through an 80-mesh sieve, then add them to 1 mol / L sodium hydroxide aqueous solution and immerse for 2 h. After the immersion is completed, filter and collect the solid. The solid is washed and dried to obtain pretreated biomass; Ultrasonically disperse 80 g of pretreated biomass, 12.5 g of sodium carboxymethylcellulose, 35 g of ammonium molybdate, 28 g of sodium sulfate, and 200 mL of water, and carry out hydrothermal reaction at 230 °C. After reacting for 30 h, cool, filter, wash, and dry, and calcine at 650 °C for 3 h to obtain porous carbon; Disperse 68 g of porous carbon in 200 mL of 50 wt% ethanol aqueous solution, add 10 g of γ-glycidyletheroxypropyltrimethoxysilane, heat and react at 50 °C for 3 h, cool and filter to collect the solid; Disperse the solid in 200 mL of N,N-dimethylformamide, add 17 g of 4-aminophthalhydrazide, heat and react at 60 °C for 2 h. After the reaction is completed, cool, filter, collect the solid, wash and dry to obtain the modified activated carbon.

[0028] Catalyst performance evaluation

[0029] Evaluate with a fixed-bed reactor, and the specific conditions are: Catalyst loading volume: 40 ml; Reaction raw material composition (in molar ratio): acetylene:acetic acid = 10:1; Reaction raw material volume space velocity: 300 h -1 ; Reaction pressure: 0.3 atm; Reaction temperature: 180 °C; Reaction time: 100 h; Analyze the content of vinyl acetate in the reaction product by gas chromatography, and calculate the space-time yield of the catalyst; Analyze the benzene content in the reaction product by GC-MS method.

[0030] Example 2

[0031] A preparation method of a fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction, comprising the following steps: Dissolve 10 g of zinc acetate and 5 g of ammonium molybdate in 150 mL of water to obtain a mixed solution, then immerse 30 g of modified activated carbon in the mixed solution, immerse at 60 °C for 8 h, after the immersion is completed, cool and filter, collect the solid, and dry the solid to obtain the fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction.

[0032] The preparation method of the modified activated carbon is as follows:

[0033] 100 g of biomass raw materials (a mixture of peanut shells and corn straw with a mass ratio of 3:2) are dried, crushed through an 80-mesh sieve, and then added to a 1 mol / L sodium hydroxide aqueous solution for impregnation for 2 h. After impregnation, the solid matter is filtered and collected. The solid matter is washed and dried to obtain pretreated biomass. 50 g of pretreated biomass, 10.5 g of sodium carboxymethylcellulose, 30 g of ammonium molybdate, 25 g of sodium sulfate, and 200 mL of water are ultrasonically dispersed and then subjected to hydrothermal reaction at 170 °C for 40 h. After the reaction, it is cooled, filtered, washed, and dried, and calcined at 500 °C for 4 h to obtain porous carbon. 45 g of porous carbon is dispersed in 200 mL of 50 wt% ethanol aqueous solution, 6 g of γ-glycidoxypropyltrimethoxysilane is added, and the mixture is heated and reacted at 50 °C for 3 h. After cooling, the solid matter is filtered and collected. The solid matter is dispersed in 200 mL of N,N-dimethylformamide, 9 g of 4-aminophthalhydrazide is added, and the mixture is heated and reacted at 60 °C for 2 h. After the reaction is completed, it is cooled, filtered, the solid matter is collected, washed, and dried to obtain the modified activated carbon.

[0034] Catalyst performance evaluation

[0035] Evaluated using a fixed-bed reactor, and the specific conditions are as follows: catalyst loading volume: 40 ml; reaction raw material composition (in terms of molar ratio): acetylene: acetic acid = 5:1; reaction raw material volume space velocity: 350 h -1 ; reaction pressure: 0.1 atm; reaction temperature: 200 °C; reaction time: 100 h; analyze the content of vinyl acetate in the reaction product by gas chromatography and calculate the space-time yield of the catalyst; analyze the benzene content in the reaction product by GC-MS method.

[0036] Example 3

[0037] A preparation method of a fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction includes the following steps: Dissolve 20 g of zinc acetate and 10 g of ammonium molybdate in 150 mL of water to obtain a mixed solution, and then immerse 40 g of modified activated carbon in the mixed solution and impregnate it at 100 °C for 3 h. After impregnation, it is cooled and filtered to collect the solid matter, and the solid matter is dried to obtain the fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction.

[0038] The preparation method of the modified activated carbon is as follows:

[0039] 100 g of biomass raw materials (a mixture of peanut shells and coconut shells with a mass ratio of 3:2) were dried, crushed, and sieved through a 80-mesh sieve, and then added to a 1 mol / L sodium hydroxide aqueous solution for impregnation for 2 h. After impregnation, the solid was filtered and collected, and the solid was washed and dried to obtain pretreated biomass. 70 g of the pretreated biomass, 14 g of sodium carboxymethylcellulose, 35 g of ammonium molybdate, 35 g of sodium sulfate, and 200 mL of water were ultrasonically dispersed and then subjected to a hydrothermal reaction at 250 °C for 10 h. After the reaction, it was cooled, filtered, washed, and dried, and then calcined at 700 °C for 2 h to obtain porous carbon. 60 g of the porous carbon was dispersed in 200 mL of a 50 wt% ethanol aqueous solution, 9 g of γ-glycidoxypropyltrimethoxysilane was added, and the mixture was heated and reacted at 50 °C for 3 h. After cooling, the solid was filtered and collected. The solid was dispersed in 200 mL of N,N-dimethylformamide, 15 g of 4-aminophthalhydrazide was added, and the mixture was heated and reacted at 60 °C for 2 h. After the reaction was completed, it was cooled, filtered, the solid was collected, washed, and dried to obtain modified activated carbon.

[0040] Catalyst performance evaluation

[0041] It was evaluated using a fixed-bed reactor. The specific conditions were as follows: catalyst loading volume: 40 ml; reaction raw material composition (in terms of molar ratio): acetylene: acetic acid = 12:1; reaction raw material volume space velocity: 250 h -1 ; reaction pressure: 0.5 atm; reaction temperature: 160 °C; reaction time: 100 h; the content of vinyl acetate in the reaction product was analyzed by gas chromatography, and the space-time yield of the catalyst was calculated; the benzene content in the reaction product was analyzed by GC-MS.

[0042] Comparative Example 1

[0043] A preparation method of a fluidized bed activated carbon catalyst in the synthesis reaction of vinyl acetate was similar to Example 1, except that the modified activated carbon was porous carbon. The specific steps were as follows: 15 g of zinc acetate and 8 g of cobalt nitrate were dissolved in 150 mL of water to obtain a mixed solution, and then 35 g of the modified activated carbon was impregnated in the mixed solution and impregnated at 80 °C for 5 h. After impregnation, it was cooled, filtered, and the solid was collected. The solid was dried to obtain the fluidized bed activated carbon catalyst in the synthesis reaction of vinyl acetate.

[0044] The modified activated carbon was porous carbon, and its preparation method was as follows:

[0045] 100 g of biomass raw materials (a mixture of rice husk and corn straw with a mass ratio of 1:4) were dried, crushed, and passed through an 80-mesh sieve, and then added to a 1 mol / L aqueous sodium hydroxide solution for impregnation for 2 h. After impregnation, the solid was filtered and collected, and the solid was washed and dried to obtain pretreated biomass; 80 g of pretreated biomass, 12.5 g of sodium carboxymethylcellulose, 35 g of ammonium molybdate, 28 g of sodium sulfate, and 200 mL of water were ultrasonically dispersed and then subjected to a hydrothermal reaction at 230 °C. After reacting for 30 h, it was cooled, filtered, washed, and dried, and calcined at 650 °C for 3 h to obtain porous carbon.

[0046] Catalyst performance evaluation

[0047] It was evaluated using a fixed-bed reactor. The specific conditions were as follows: catalyst loading volume: 40 ml; reaction raw material composition (in terms of molar ratio): acetylene:acetic acid = 10:1; reaction raw material volume space velocity: 300 h -1 ; reaction pressure: 0.3 atm; reaction temperature: 180 °C; reaction time: 100 h; the content of vinyl acetate in the reaction product was analyzed by gas chromatography, and the space-time yield of the catalyst was calculated; the benzene content in the reaction product was analyzed by GC-MS.

[0048] Comparative Example 2

[0049] A preparation method of a fluidized-bed activated carbon catalyst for vinyl acetate synthesis reaction is similar to Example 1, except that ammonium molybdate and sodium sulfate were not added to the modified activated carbon. The specific steps are as follows: 15 g of zinc acetate and 8 g of cobalt nitrate were dissolved in 150 mL of water to obtain a mixed solution, and then 35 g of modified activated carbon was impregnated in the mixed solution and impregnated at 80 °C for 5 h. After impregnation, it was cooled and filtered, and the solid was collected. The solid was dried to obtain the fluidized-bed activated carbon catalyst for vinyl acetate synthesis reaction.

[0050] The preparation method of the modified activated carbon is as follows:

[0051] 100 g of biomass raw materials (a mixture of rice husk and corn straw with a mass ratio of 1:4) were dried, pulverized, passed through an 80-mesh sieve, and then added to a 1 mol / L aqueous sodium hydroxide solution for impregnation for 2 h. After impregnation, the solid was filtered and collected. The solid was washed and dried to obtain pretreated biomass. 80 g of the pretreated biomass, 12.5 g of sodium carboxymethyl cellulose, and 200 mL of water were ultrasonically dispersed and then subjected to a hydrothermal reaction at 230 °C for 30 h. After the reaction, it was cooled, filtered, washed, and dried, and then calcined at 650 °C for 3 h to obtain porous carbon. 68 g of the porous carbon was dispersed in 200 mL of a 50 wt% ethanol aqueous solution, 10 g of γ-glycidoxypropyltrimethoxysilane was added, and the mixture was heated and reacted at 50 °C for 3 h. After cooling, the solid was filtered and collected. The solid was dispersed in 200 mL of N,N-dimethylformamide, 17 g of 4-aminophthalhydrazide was added, and the mixture was heated and reacted at 60 °C for 2 h. After the reaction was completed, the solid was cooled, filtered, collected, washed, and dried to obtain modified activated carbon.

[0052] Catalyst performance evaluation

[0053] It was evaluated using a fixed-bed reactor. The specific conditions were as follows: catalyst loading volume: 40 ml; reaction raw material composition (in terms of molar ratio): acetylene:acetic acid = 10:1; reaction raw material volume space velocity: 300 h -1 ; reaction pressure: 0.3 atm; reaction temperature: 180 °C; reaction time: 100 h; the content of vinyl acetate in the reaction product was analyzed by gas chromatography, and the space-time yield of the catalyst was calculated; the benzene content in the reaction product was analyzed by GC-MS.

[0054] The test results of the catalyst performance evaluation are shown in Table 1

[0055] Table 1 Catalyst evaluation results

[0056] <![CDATA[Spatial-temporal yield (g AVM / l catal ·h)]]> Benzene content (ppb) Example 1 51.2 385 Example 2 49.3 406 Example 3 52.1 362 Comparative Example 1 46.5 854 Comparative Example 2 43.2 657

[0057] Compressive strength test: The length of the modified activated carbon particles after drying in Example 1 and Comparative Example 2 was measured with a vernier caliper. Then, the modified activated carbon was placed in a particle strength tester, pressure was applied, and the instantaneous pressure value when the modified activated carbon was crushed was recorded. The average force value per unit length of a specified number of modified activated carbons was calculated as the strength value. The test results are shown in Table 2:

[0058] Table 2 Compressive strength test results of modified activated carbon

[0059]

[0060]

[0061] As can be seen from the experimental results in Table 1 and Table 2, the modified activated carbon prepared by the present invention has good mechanical strength. The catalyst of the present invention can well catalyze the reaction of acetic acid and acetylene, improve the space-time yield of vinyl acetate, and significantly reduce the content of impurity benzene in the vinyl acetate product.

[0062] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the patent protection scope of the present invention.

Claims

1. A preparation method of a fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction, characterized in that, It includes the following steps: dissolving the active component and the promoter in water to obtain a mixed solution, then impregnating the modified activated carbon into the mixed solution, after the impregnation is completed, filtering, collecting the solid, and drying the solid to obtain the fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction.

2. The preparation method according to claim 1, wherein: The mass ratio of the modified activated carbon, the active component, and the promoter is 3 - 4:1 - 2:0.5 - 1.

3. The preparation method according to claim 2, characterized in that, The preparation method of the modified activated carbon includes the following steps: Drying and crushing the biomass raw material, then adding it to an aqueous sodium hydroxide solution for impregnation, after the impregnation is completed, filtering and collecting the solid, and washing and drying the solid to obtain the pretreated biomass; Ultrasonically dispersing the pretreated biomass, sodium carboxymethylcellulose, ammonium molybdate, sodium sulfate, and water, then carrying out a hydrothermal reaction, after the reaction is completed, filtering, washing, drying, and calcining to obtain porous carbon; dispersing the porous carbon in an ethanol aqueous solution, adding γ - glycidoxypropyltrimethoxysilane, heating and reacting, filtering and collecting the solid; dispersing the solid in N,N - dimethylformamide, adding 4 - aminophthalhydrazide, heating and reacting, filtering and collecting the solid, washing and drying to obtain the modified activated carbon.

4. The preparation method according to claim 3, characterized in that: The biomass raw material is at least one of peanut shells, rice husks, corn straws, coconut shells, animal excreta, and tree branches.

5. The preparation method according to claim 3, characterized in that: The mass ratio of the pretreated biomass, sodium carboxymethylcellulose, sodium molybdate, and sodium sulfate is 5 - 10:1 - 2:3 - 5:2.5 - 5.

6. The preparation method according to claim 3, wherein: The hydrothermal reaction temperature is 170 - 250 °C, and the hydrothermal reaction time is 10 - 50 h.

7. The preparation method according to claim 3, characterized in that: The mass ratio of the porous carbon, γ - glycidoxypropyltrimethoxysilane, and 4 - aminophthalhydrazide is 15 - 20:2 - 3:3 - 5.

8. The preparation method according to claim 1, wherein: The active component is a zinc precursor; the zinc precursor is zinc acetate.

9. The preparation method according to claim 1, characterized in that, The promoter is one of a cobalt precursor and a molybdenum precursor; the cobalt precursor is cobalt nitrate and / or cobalt chloride; the molybdenum precursor is at least one of sodium molybdate, ammonium molybdate, and potassium molybdate.

10. A fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction, characterized in that: Prepared by the preparation method according to any one of claims 1 - 9.

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