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

Abstract

The application discloses a fluidized bed activated carbon catalyst in a vinyl acetate synthesis reaction and a preparation method thereof, and belongs to the technical field of activated carbon. The prepared activated carbon catalyst has the advantages of high catalytic efficiency, long service life, and the like, can operate under high pressure, and has the advantages of high vinyl acetate yield, few by-products, and the like, and can significantly reduce the content of benzene in the vinyl acetate product.

Description

TECHNICAL FIELD

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

[0002] Vinyl acetate, also known as VAc, is an important organic chemical raw material. Its monomer can be copolymerized to produce various adhesives. It can also be copolymerized with chloroethylene, acrylonitrile, butenoic acid, acrylic acid and ethylene monomer to produce high molecular synthetic materials with different properties, and has a wide range of applications.

[0003] Currently, the main methods for producing vinyl acetate are ethylene method and acetylene method. In 1922, the German Wacker Company discovered the acetylene method production process and used zinc acetate / activated carbon catalyst. After improvement, it was put into industrial production of vinyl acetate. The active component and carrier have been used until now. The carrier and active component of the zinc acetate / activated carbon catalyst are widely available, have good catalytic activity, high selectivity and other advantages. However, it also has some disadvantages, such as low reaction activity, many by-products, easy shedding of active components, short service life, high replacement cycle and the like.

[0004] Chinese patent document CN105457683A discloses a vinyl acetate catalyst, which mainly solves the problems of low catalyst activity and low acetylene single-pass conversion rate in the prior art. The catalyst includes an active component, a catalyst promoter and a carrier. The active component is zinc acetate, the catalyst promoter is potassium acetate, and the carrier is activated carbon modified by TiO2. The technical solution can be used in the industrial production of vinyl acetate prepared by the acetylene method. However, the vinyl acetate product contains a small amount of benzene, which is generally difficult to remove by reaction, limiting the popularization and application of the catalyst. SUMMARY

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

[0006] To achieve the above purpose, the present application provides a preparation method of a fluidized bed activated carbon catalyst in vinyl acetate synthesis reaction, which comprises the following steps: dissolving an active component and an additive in water to obtain a mixed solution, then dipping modified activated carbon in the mixed solution, filtering after the dipping is completed, collecting solid substances, and drying the solid substances to obtain the fluidized bed activated carbon catalyst in the vinyl acetate synthesis reaction.

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

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

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

[0010] After drying and crushing the biomass raw material, the biomass raw material is impregnated in a sodium hydroxide aqueous solution, and after impregnation, the solid is filtered and collected, and the solid is washed and dried to obtain pretreated biomass; the pretreated biomass, sodium carboxymethyl cellulose, ammonium molybdate, sodium sulfate and water are ultrasonically dispersed, and then subjected to a hydrothermal reaction, and after the reaction, the solid is filtered, washed, dried and calcined to obtain porous carbon; the porous carbon is dispersed in an ethanol aqueous solution, and gamma-glycidoxypropyltrimethoxysilane is added and heated to react, and the solid is collected by filtration; the solid is dispersed in N,N-dimethylformamide, and 4-amino-phthalhydrazide is added and heated to react, and the solid is collected by filtration, washed and dried to obtain the modified activated carbon.

[0011] Preferably, the biomass raw material is at least one of peanut shell, rice husk, corn straw, coconut shell, animal excrement and tree branches.

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

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

[0014] The modified activated carbon has good mechanical strength and is not easy to break, the loading of the active component is improved, the service life of the catalyst is improved, the catalytic activity of the catalyst is improved, the space-time yield of vinyl acetate is improved, and trace benzene in the product can be well removed.

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

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

[0017] The application also discloses a synthesis method of vinyl acetate, which comprises the following steps: taking acetic acid and acetylene as raw material gas, and reacting to obtain vinyl acetate in the presence of a fluidized bed activated carbon catalyst in the synthesis reaction of the vinyl acetate.

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

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

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] (1) The fluidized bed activated carbon catalyst used in the synthesis reaction of the vinyl acetate prepared by the application has high catalytic efficiency, can be operated under high pressure and for a long time, has a long service life, and the prepared vinyl acetate has high yield, few by-products and low benzene content;

[0022] (2) The preparation of the modified activated carbon in the application firstly comprises the following steps: pretreating 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 destroy the hydrogen bonds between the cellulose molecules in the biomass, so that the distance between the molecules is increased and the cellulose is loose, which is beneficial to the subsequent steps; then, the sodium carboxymethyl cellulose, ammonium molybdate and sodium sulfate are subjected to a hydrothermal reaction to generate MoS2 in situ on the porous carbon, MoS2 can improve the thermal stability of the porous carbon, avoid coking of the porous carbon during the high-temperature reaction of the acetic acid and the acetylene, and thus avoid the pore blockage and the influence on the catalytic activity of the catalyst, and can also improve the mechanical strength of the porous carbon, so that the porous carbon is not easy to be broken and can better load the active components, which is beneficial to the improvement of the service life of the catalyst; then, the epoxy group is introduced on the surface of the porous carbon, which is beneficial to the grafting reaction with 4-amino phthalhydrazide, and 4-amino phthalhydrazide can form a conjugate with the by-product benzene in the vinyl acetate product, so that the by-product benzene can be adsorbed and removed, and the purity of the vinyl acetate product is improved. DETAILED DESCRIPTION

[0023] For the sake of brevity, the articles used in the following examples are all commercially available products if no special instructions are given, and the methods used are all conventional methods if no special instructions are given.

[0024] Example 1

[0025] A method for preparing a fluidized bed activated carbon catalyst for vinyl acetate synthesis includes the following steps: dissolving 15g of zinc acetate and 8g of cobalt nitrate in 150mL of water to obtain a mixed solution, then impregnating 35g of modified activated carbon in the mixed solution at 80℃ for 5h, cooling and filtering after impregnation, collecting the solid, and drying the solid to obtain the fluidized bed activated carbon catalyst for vinyl acetate synthesis.

[0026] The modified activated carbon is prepared as follows:

[0027] 100g of biomass raw material (a mixture of rice husks and corn stalks in a mass ratio of 1:4) was dried, pulverized through an 80-mesh sieve, and then soaked in a 1mol / L sodium hydroxide aqueous solution for 2 hours. After soaking, the mixture was filtered and the solids were collected. The solids were washed and dried to obtain pretreated biomass. 80g of pretreated biomass, 12.5g of sodium carboxymethyl cellulose, 35g of ammonium molybdate, 28g of sodium sulfate, and 200mL of water were ultrasonically dispersed and subjected to a hydrothermal reaction at 230℃ for 30 hours. After cooling, the mixture was filtered, washed, and dried, and then calcined at 650℃ for 3 hours to obtain porous carbon. 68g of porous carbon was dispersed in 200mL of 50wt% ethanol aqueous solution, and 10g of γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was heated at 50℃ for 3 hours, and the solids were collected after cooling and filtration. The solids were dispersed in 200mL of N,N-dimethylformamide, and 17g of... 4-Aminophthalic acid hydrazide was heated at 60°C for 2 hours. After the reaction was completed, the mixture was cooled, filtered, and the solid was collected, washed, and dried to obtain modified activated carbon.

[0028] Catalyst performance evaluation

[0029] The experiment was evaluated using a fixed-bed reactor under the following conditions: catalyst loading volume: 40 ml; reactant composition (molar ratio): acetylene:acetic acid = 10:1; reactant volume hourly space velocity: 300 h⁻¹ -1 Reaction pressure: 0.3 atm; Reaction temperature: 180℃; 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 content of benzene in the reaction product was analyzed by GC-MS.

[0030] Example 2

[0031] A method for preparing a fluidized bed activated carbon catalyst for vinyl acetate synthesis includes the following steps: dissolving 10g of zinc acetate and 5g of ammonium molybdate in 150mL of water to obtain a mixed solution, then impregnating 30g of modified activated carbon in the mixed solution at 60℃ for 8h, cooling and filtering after impregnation, collecting the solid, and drying the solid to obtain the fluidized bed activated carbon catalyst for vinyl acetate synthesis.

[0032] The modified activated carbon is prepared as follows:

[0033] 100g of biomass raw material (a mixture of peanut shells and corn stalks in a mass ratio of 3:2) was dried, pulverized through an 80-mesh sieve, and then soaked in a 1mol / L sodium hydroxide aqueous solution for 2 hours. After soaking, the mixture was filtered and the solids were collected. The solids were washed and dried to obtain pretreated biomass. 50g of pretreated biomass, 10.5g of sodium carboxymethyl cellulose, 30g of ammonium molybdate, 25g of sodium sulfate, and 200mL of water were ultrasonically dispersed and subjected to a hydrothermal reaction at 170℃ for 40 hours. After cooling, the mixture was filtered, washed, and dried, and then calcined at 500℃ for 4 hours to obtain porous carbon. 45g of porous carbon was dispersed in 200mL of 50wt% ethanol aqueous solution, and 6g of γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was heated at 50℃ for 3 hours, and the solids were collected after cooling and filtration. The solids were dispersed in 200mL of N,N-dimethylformamide, and 9g of... 4-Aminophthalic acid hydrazide was heated at 60°C for 2 hours. After the reaction was completed, the mixture was cooled, filtered, and the solid was collected, washed, and dried to obtain modified activated carbon.

[0034] Catalyst performance evaluation

[0035] The experiment was evaluated using a fixed-bed reactor under the following conditions: catalyst loading volume: 40 ml; reactant composition (molar ratio): acetylene:acetic acid = 5:1; reactant volume hourly space velocity: 350 h⁻¹. -1 Reaction pressure: 0.1 atm; Reaction temperature: 200℃; 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 content of benzene in the reaction product was analyzed by GC-MS.

[0036] Example 3

[0037] A method for preparing a fluidized bed activated carbon catalyst for vinyl acetate synthesis includes the following steps: dissolving 20g of zinc acetate and 10g of ammonium molybdate in 150mL of water to obtain a mixed solution, then impregnating 40g of modified activated carbon in the mixed solution at 100℃ for 3h, cooling and filtering after impregnation, collecting the solid, and drying the solid to obtain the fluidized bed activated carbon catalyst for vinyl acetate synthesis.

[0038] The modified activated carbon is prepared as follows:

[0039] 100g of biomass raw material (a mixture of peanut shells and coconut shells in a mass ratio of 3:2) was dried, pulverized through an 80-mesh sieve, and then soaked in a 1mol / L sodium hydroxide aqueous solution for 2 hours. After soaking, the mixture was filtered and the solids were collected. The solids were washed and dried to obtain pretreated biomass. 70g of pretreated biomass, 14g of sodium carboxymethyl cellulose, 35g of ammonium molybdate, 35g of sodium sulfate, and 200mL of water were ultrasonically dispersed and subjected to a hydrothermal reaction at 250℃ for 10 hours. After cooling, the mixture was filtered, washed, and dried, and then calcined at 700℃ for 2 hours to obtain porous carbon. 60g of porous carbon was dispersed in 200mL of 50wt% ethanol aqueous solution, and 9g of γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was heated at 50℃ for 3 hours, and the solids were collected after cooling and filtration. The solids were dispersed in 200mL of N,N-dimethylformamide, and 15g of... 4-Aminophthalic acid hydrazide was heated at 60°C for 2 hours. After the reaction was completed, the mixture was cooled, filtered, and the solid was collected, washed, and dried to obtain modified activated carbon.

[0040] Catalyst performance evaluation

[0041] The experiment was evaluated using a fixed-bed reactor under the following conditions: catalyst loading volume: 40 ml; reactant composition (molar ratio): acetylene:acetic acid = 12:1; reactant volume hourly space velocity: 250 h⁻¹. -1 Reaction pressure: 0.5 atm; Reaction temperature: 160℃; 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 content of benzene in the reaction product was analyzed by GC-MS.

[0042] Comparative Example 1

[0043] A method for preparing a fluidized bed activated carbon catalyst for the vinyl acetate synthesis reaction is similar to that in Example 1, except that the modified activated carbon is porous carbon. The method includes the following steps: dissolving 15g of zinc acetate and 8g of cobalt nitrate in 150mL of water to obtain a mixed solution, then immersing 35g of modified activated carbon in the mixed solution at 80°C for 5h. After immersion, cooling and filtering are performed, the solid is collected, and the solid is dried to obtain the fluidized bed activated carbon catalyst for the vinyl acetate synthesis reaction.

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

[0045] 100g of biomass raw material (a mixture of rice husks and corn stalks in a mass ratio of 1:4) was dried, pulverized through an 80-mesh sieve, and then added to a 1mol / L sodium hydroxide aqueous solution for soaking for 2 hours. After soaking, the mixture was filtered and the solids were collected. The solids were washed and dried to obtain pretreated biomass. 80g of pretreated biomass, 12.5g of sodium carboxymethyl cellulose, 35g of ammonium molybdate, 28g of sodium sulfate, and 200mL of water were ultrasonically dispersed and subjected to a hydrothermal reaction at 230℃. After reacting for 30 hours, the mixture was cooled, filtered, washed, and dried, and then calcined at 650℃ for 3 hours to obtain porous carbon.

[0046] Catalyst performance evaluation

[0047] The experiment was evaluated using a fixed-bed reactor under the following conditions: catalyst loading volume: 40 ml; reactant composition (molar ratio): acetylene:acetic acid = 10:1; reactant volume hourly space velocity: 300 h⁻¹ -1 Reaction pressure: 0.3 atm; Reaction temperature: 180℃; 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 content of benzene in the reaction product was analyzed by GC-MS.

[0048] Comparative Example 2

[0049] A method for preparing a fluidized bed activated carbon catalyst for the vinyl acetate synthesis reaction is similar to that in Example 1, except that ammonium molybdate and sodium sulfate are not added to the modified activated carbon. Specifically, the method includes the following steps: dissolving 15g of zinc acetate and 8g of cobalt nitrate in 150mL of water to obtain a mixed solution, then immersing 35g of modified activated carbon in the mixed solution at 80°C for 5 hours. After immersion, the solution is cooled and filtered, the solid is collected, and the solid is dried to obtain the fluidized bed activated carbon catalyst for the vinyl acetate synthesis reaction.

[0050] The modified activated carbon is prepared as follows:

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

[0052] Catalyst performance evaluation

[0053] The experiment was evaluated using a fixed-bed reactor under the following conditions: catalyst loading volume: 40 ml; reactant composition (molar ratio): acetylene:acetic acid = 10:1; reactant volume hourly space velocity: 300 h⁻¹ -1 Reaction pressure: 0.3 atm; Reaction temperature: 180℃; 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 content of benzene in the reaction product was analyzed by GC-MS.

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

[0055] Table 1 Catalyst Evaluation Results

[0056] Space-time 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 Comparative Example 3 43.2 657

[0057] Compressive strength test: The length of the dried modified activated carbon particles in Example 1 and Comparative Example 2 was measured using vernier calipers. The modified activated carbon was then placed in a particle strength tester, pressure was applied, and the instantaneous pressure value at which the modified activated carbon was crushed was recorded. The average force per unit length of a specified quantity of modified activated carbon 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] From the experimental results in Table 1 and Table 2, it can be seen that the modified activated carbon prepared by the present application has good mechanical strength, the catalyst of the present application 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 merely describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the patent protection scope of the present application.

Claims

1. A method for preparing a fluidized bed activated carbon catalyst for use in the synthesis of vinyl acetate, characterized in that, The method comprises the following steps: dissolving an active component and an auxiliary agent in water to obtain a mixed solution, then dipping modified activated carbon in the mixed solution, filtering after the dipping is completed, collecting solid substances, and drying the solid substances to obtain the fluidized bed activated carbon catalyst for vinyl acetate synthesis reaction. The active component is a zinc precursor; and the zinc precursor is zinc acetate. The auxiliary agent is one of a cobalt precursor and a molybdenum precursor; the cobalt precursor is cobalt nitrate and / or cobalt chloride; and the molybdenum precursor is at least one of sodium molybdate, ammonium molybdate and potassium molybdate. The method for preparing the modified activated carbon comprises the following steps: After the biomass raw material is dried and crushed, the biomass raw material is dipped in a sodium hydroxide aqueous solution, then the dipping is completed, the solid substances are collected after filtering, and the solid substances are washed and dried to obtain pretreated biomass. After the pretreated biomass, sodium carboxymethyl cellulose, ammonium molybdate, sodium sulfate and water are ultrasonically dispersed, a hydrothermal reaction is performed, the reaction is completed, the solid substances are collected after filtering and washing, and the solid substances are dried and calcined to obtain porous carbon; the porous carbon is dispersed in an ethanol aqueous solution, gamma-glycidoxypropyltrimethoxysilane is added, a heating reaction is performed, the solid substances are collected after filtering, the solid substances are dispersed in N,N-dimethylformamide, 4-amino phthalhydrazide is added, a heating reaction is performed, the solid substances are collected after filtering, washing and drying to obtain the modified activated carbon.

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

3. The method of claim 1, wherein: The biomass raw material is at least one of peanut shells, rice husks, corn stalks, coconut shells, animal excrement and tree branches.

4. The method of claim 1, wherein: The mass ratio of the pretreated biomass, sodium carboxymethyl cellulose, ammonium molybdate and sodium sulfate is 5-10:1-2:3-5:2.5-5.

5. The method of claim 1, wherein: The hydrothermal reaction temperature is 170-250 DEG C, and the hydrothermal reaction time is 10-50 h.

6. The method of claim 1, wherein: The mass ratio of the porous carbon, gamma-glycidoxypropyltrimethoxysilane and 4-amino phthalhydrazide is 15-20:2-3:3-5.

7. A fluidized bed activated carbon catalyst for use in the synthesis of vinyl acetate, characterized in that: The modified activated carbon is prepared by the method in any one of claims 1-6.

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