Catalyst for synthesis of vinyl acetate by ethylene method, preparation method and application thereof, and method for synthesis of vinyl acetate

Abstract

The present application relates to the field of catalyst, in particular to a kind of catalyst for ethylene method synthesis vinyl acetate and its preparation method and application and the method of vinyl acetate synthesis, the optimum reaction temperature point of the catalyst in temperature programmed surface reaction process TPSR is 125~135 ℃;The catalyst contains Pd, Au and alkali metal acetate.The present application adopts the optimum reaction temperature point of temperature programmed surface reaction process TPSR for ethylene method synthesis vinyl acetate catalyst, and the problem of low selectivity of existing ethylene method vinyl acetate catalyst can be better solved.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a catalyst for the synthesis of vinyl acetate via the ethylene process, its preparation method and application, and a method for the synthesis of vinyl acetate. Background Technology

[0002] Vinyl acetate (VAc), as an important organic monomer, is a crucial raw material for the synthesis of chemical products such as polyvinyl alcohol (PVA), polyvinyl acetate (PVA), ethylene-vinyl acetate copolymer (EVA), vinyl acetate-vinyl chloride copolymer (EVC), and polypropylene comonomers. It has wide applications in synthetic fibers, leather processing, films, vinylon, adhesives, and coatings. Among these, the ethylene gas-phase method is currently one of the most important industrial methods for producing VAc, offering advantages such as high energy efficiency and low environmental impact. Especially in recent years, with the development of biomass-to-ethanol and further dehydration technologies to produce ethylene, the ethylene gas-phase synthesis of VAc has received increasing attention.

[0003] Currently, the industrial gas-phase synthesis of vinyl acetate (VAc) from ethylene mainly uses palladium-gold / potassium acetate / silica as a catalyst, with palladium sites on the catalyst surface being the primary active sites. In the reaction, ethylene, oxygen, and acetic acid are used as raw materials, and the product is vinyl acetate, water, and carbon dioxide as a byproduct, produced through a gas-phase catalytic reaction. The reactor shell temperature can be approximately 100–180°C, the reaction pressure approximately 0.5–1.0 MPa, and the gas hourly space velocity (GHSV) approximately 500–3000 hr. -1 .

[0004] Currently, the optimal reaction temperature for the TPSR in the industrial synthesis of vinyl acetate via the ethylene process is 145℃±5℃, and the catalyst selectivity is not high. Therefore, to address these issues, we have developed a new catalyst that can lower the optimal reaction temperature for TPSR and effectively solve the problem of low catalyst selectivity. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of low selectivity of existing ethylene-based vinyl acetate catalysts, and to provide a catalyst for the synthesis of vinyl acetate by the ethylene process, its preparation method and application, as well as a method for the synthesis of vinyl acetate. This catalyst for the synthesis of vinyl acetate by the ethylene process has the characteristic of high selectivity.

[0006] To achieve the above objectives, the first aspect of the present invention provides a catalyst for the synthesis of vinyl acetate by the ethylene process, wherein the optimal reaction temperature in the temperature programmed surface reaction (TPSR) of the catalyst is 125–135 °C.

[0007] A second aspect of the present invention provides a method for preparing the catalyst described above, the method comprising:

[0008] (a) The catalyst support was impregnated with N,N-methylenebisacrylamide solution to prepare catalyst precursor I;

[0009] (b) Catalyst precursor I is impregnated in a solution containing noble metal ions, preferably a solution of palladium and gold ions, to prepare catalyst precursor II;

[0010] (c) Catalyst precursor II is treated with a solution of an alkaline compound to convert noble metal ions into precipitates, thereby preparing catalyst precursor III.

[0011] (d) The noble metal ions in catalyst precursor III were reduced to zero valence, and then washed and dried to prepare catalyst precursor IV.

[0012] (e) Impregnate catalyst precursor IV with alkali metal acetate, dry, and obtain the finished catalyst.

[0013] A third aspect of the present invention provides the application of the catalyst described herein in the synthesis of vinyl acetate.

[0014] A fourth aspect of the present invention provides a method for synthesizing vinyl acetate, the method comprising: contacting ethylene with acetic acid in the presence of the catalyst described in the present invention.

[0015] Through the above technical solution, the present invention has the following beneficial effects:

[0016] This invention employs a catalyst for the synthesis of vinyl acetate via the ethylene process, with the optimal reaction temperature in the programmed temperature rise surface reaction (TPSR) being 125–135 °C. This effectively addresses the problem of low selectivity in existing ethylene-based vinyl acetate catalysts. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] This invention provides a catalyst for the synthesis of vinyl acetate by the ethylene process, wherein the optimal reaction temperature in the temperature programmed surface reaction (TPSR) of the catalyst is 125–135 °C.

[0019] This invention employs a catalyst for the synthesis of vinyl acetate via the ethylene process, with the optimal reaction temperature in the programmed temperature rise surface reaction (TPSR) being 125–135 °C. This effectively addresses the problem of low selectivity in existing ethylene-based vinyl acetate catalysts.

[0020] According to a preferred embodiment of the present invention, the catalyst contains noble metal and alkali metal acetate, preferably Pd, Au and alkali metal acetate. By adopting the aforementioned preferred embodiment, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0021] In this invention, as long as the objective of the invention can be achieved, there are no particular limitations on the content of Pd, Au, and alkali metal acetate in the catalyst. According to a preferred embodiment of the invention, the content of Pd in ​​the catalyst is 1-12 g / L, the amount of Au is 0.1-10 g / L, and the content of alkali metal acetate is 10-100 g / L. By adopting the aforementioned preferred embodiment, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0022] In this invention, the alkali metal acetate can be a conventional choice in the art. According to a preferred embodiment of the invention, the alkali metal acetate is potassium acetate and / or sodium acetate. By adopting the aforementioned preferred embodiment, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0023] This invention provides a method for preparing the catalyst described above, the method comprising:

[0024] (a) The catalyst support was impregnated with N,N-methylenebisacrylamide solution to prepare catalyst precursor I;

[0025] (b) Catalyst precursor I is impregnated in a solution containing noble metal ions, preferably a solution containing palladium and gold ions, to prepare catalyst precursor II;

[0026] (c) Catalyst precursor II is treated with a solution of an alkaline compound to convert noble metal ions into precipitates, thereby preparing catalyst precursor III.

[0027] (d) The noble metal ions in catalyst precursor III were reduced to zero valence, and then washed and dried to prepare catalyst precursor IV.

[0028] (e) Impregnate catalyst precursor IV with alkali metal acetate, dry, and obtain the finished catalyst.

[0029] The catalyst prepared by the aforementioned method can further improve the selectivity of vinyl acetate catalysts in the ethylene process.

[0030] In this invention, the carrier can be a conventional choice in the art. According to a preferred embodiment of the invention, the carrier is selected from one or two of silicon dioxide and alumina.

[0031] In this invention, as long as the objective of the invention can be achieved, there is no particular limitation on the concentration of the N,N-methylenebisacrylamide solution in step (a). According to a preferred embodiment of the invention, the concentration of the N,N-methylenebisacrylamide solution in step (a) is 0.1–1.0 g / L. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0032] In this invention, the solvent for the N,N-methylenebisacrylamide solution in step (a) can be a conventional choice in the art. According to a preferred embodiment of this invention, in step (a), the solvent for the N,N-methylenebisacrylamide solution is one or both of water and ethanol. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0033] In this invention, the impregnation conditions in step (a) can be conventionally chosen in the art. According to a preferred embodiment of the invention, the impregnation conditions in step (a) include: the volume ratio of the N,N-methylenebisacrylamide solution to the support volume is 1-1.5:1. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0034] In this invention, the impregnation conditions in step (b) can be conventionally chosen in the art. According to a preferred embodiment of the invention, the impregnation conditions in step (b) include: the palladium ion content in the solution containing noble metal ions is 1-12 g / L, and the gold ion content is 0.1-10 g / L. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0035] According to a preferred embodiment of the present invention, in step (b), the palladium ions are sourced from an acidic solution containing palladium, and the gold ions are sourced from an acidic solution containing gold.

[0036] According to a preferred embodiment of the present invention, in step (b), the impregnation conditions include: the volume ratio of the solution containing noble metal ions to the volume of catalyst precursor I is 1.0-1.5. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0037] According to a preferred embodiment of the present invention, in step (b), the impregnation conditions include an impregnation time of 0.5-3 hours. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0038] According to a preferred embodiment of the present invention, in step (c), the conditions for treatment with a solution of an alkaline compound include standing and drying.

[0039] In this invention, the alkaline compound can be a conventional choice in the art. According to a preferred embodiment of the invention, in step (c), the alkaline compound is selected from sodium silicate and / or potassium silicate. By employing the aforementioned preferred embodiment, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0040] In this invention, the concentration of the alkaline compound solution is not particularly limited as long as the objective of the invention can be achieved. According to a preferred embodiment of the invention, the concentration of the alkaline compound solution is 1-1000 mmol / L. By adopting the aforementioned preferred embodiment, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0041] According to a preferred embodiment of the present invention, the settling time is 0.5-3 hours, the drying time is 0.5-1 hour, and the drying temperature is 50-100°C. By adopting the aforementioned preferred embodiment, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0042] In this invention, the reduction conditions in step (d) can be conventionally chosen in the art. According to a preferred embodiment of the invention, the reduction conditions in step (d) include: the reducing agent is selected from hydrazine hydrate, the reducing agent concentration is 5wt%-85wt%, the addition amount is 1-10ml, and the reduction time is 1-5 hours. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0043] According to a preferred embodiment of the present invention, in step (d), the drying conditions include: a drying time of 1-10 hours and a drying temperature of 50-100°C. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0044] In this invention, the impregnation conditions in step (e) can be conventionally chosen in the art. According to a preferred embodiment of the invention, the impregnation conditions in step (e) include: a volume ratio of alkali metal acetate to catalyst precursor IV of 1-1.5:1, where the alkali metal acetate is one or both of potassium acetate and sodium acetate; and drying conditions including: a drying time of 1-5 hours and a drying temperature of 50-100°C. By adopting the aforementioned preferred scheme, the selectivity of the vinyl acetate catalyst in the ethylene process can be further improved.

[0045] This invention provides an application of the catalyst described above in the synthesis of vinyl acetate.

[0046] Using the catalyst of this invention in the synthesis of vinyl acetate can greatly improve the selectivity of vinyl acetate.

[0047] This invention provides a method for synthesizing vinyl acetate, the method comprising: contacting ethylene with acetic acid in the presence of the catalyst, wherein the contact conditions include:

[0048] The reaction raw materials are in the following molar ratio: oxygen: ethylene: nitrogen: acetic acid = 1:6-7:7-8:1-2.

[0049] According to a preferred embodiment of the present invention, the contact conditions include: reactant feed volume hourly space velocity: 1500-2000 hr -1 .

[0050] According to a preferred embodiment of the present invention, the contact conditions include: reaction pressure: 0.5-1.0 MPa; reaction temperature: 120-140°C; reaction time: 80-100 hr.

[0051] By employing the method for synthesizing vinyl acetate of the present invention, the selectivity of vinyl acetate can be greatly improved.

[0052] The present invention will be described in detail below through embodiments.

[0053] Example 1

[0054] 1. Catalyst Preparation

[0055] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0056] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid for 2 hours (wherein, the palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L; the ratio of the volume of the immersion liquid to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0057] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0058] (d) Add 10 ml of 85%wt hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100℃ for 6 hours to obtain catalyst precursor IV.

[0059] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0060] The preparation conditions are listed in Table 1.

[0061] 2. Catalyst Evaluation

[0062] The evaluation was conducted using a fixed-bed reactor, under the following conditions:

[0063] Catalyst loading volume: 40 ml;

[0064] Composition of reaction raw materials (in molar ratio): Oxygen: Ethylene: Nitrogen: Acetic acid = 1:6.8:7.2:1.7;

[0065] Reactant feed volume hourly space velocity: 2000 hr -1 ;

[0066] Reaction pressure: 0.7 MPa;

[0067] Reaction temperature: 135℃;

[0068] Reaction time: 100 hours;

[0069] The content of each component in the reaction product was analyzed by gas chromatography, and then the space-time yield and selectivity of the catalyst to ethylene were calculated. The experimental results are listed in Table 2.

[0070] Example 2

[0071] 1. Catalyst Preparation

[0072] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 The catalyst precursor I was prepared by impregnating a sample (g) in an ethanol solution of N,N-methylenebisacrylamide (wherein the concentration of N,N-methylenebisacrylamide was 0.1 g / L and the ratio of impregnation volume to support volume was 1.5) for half an hour and then drying the surface of the support.

[0073] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L; the ratio of the volume of the immersion liquid to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0074] (c) Add 100 ml of potassium silicate aqueous solution (27.5 g K2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0075] (d) Add 10 ml of 85%wt hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100℃ for 6 hours to obtain catalyst precursor IV.

[0076] (e) The catalyst precursor IV was impregnated with an aqueous sodium acetate solution (the ratio of the impregnation liquid volume to the support volume was 1:1) and dried at 80°C for 2 hours to obtain the finished catalyst, so that the sodium acetate content in the catalyst was 30 g / L.

[0077] The preparation conditions are listed in Table 1.

[0078] 2. Catalyst Evaluation

[0079] The catalyst evaluation method is the same as in Example 1.

[0080] The experimental results are listed in Table 2.

[0081] Example 3

[0082] 1. Catalyst Preparation

[0083] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 1.0 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0084] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L; the ratio of the volume of the immersion liquid to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0085] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0086] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0087] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0088] The preparation conditions are listed in Table 1.

[0089] 2. Catalyst Evaluation

[0090] The catalyst evaluation method is the same as in Example 1.

[0091] The experimental results are listed in Table 2.

[0092] Example 4

[0093] 1. Catalyst Preparation

[0094] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0095] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 1.0 g / L and the gold content is 0.625 g / L; the ratio of the volume of the immersion solution to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0096] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0097] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0098] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0099] The preparation conditions are listed in Table 1.

[0100] 2. Catalyst Evaluation

[0101] The catalyst evaluation method is the same as in Example 1.

[0102] The experimental results are listed in Table 2.

[0103] Example 5

[0104] 1. Catalyst Preparation

[0105] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0106] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 6.0 g / L and the gold content is 0.625 g / L; the ratio of the volume of the immersion solution to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0107] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0108] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0109] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0110] The preparation conditions are listed in Table 1.

[0111] 2. Catalyst Evaluation

[0112] The catalyst evaluation method is the same as in Example 1.

[0113] The experimental results are listed in Table 2.

[0114] Example 6

[0115] 1. Catalyst Preparation

[0116] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0117] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 12.0 g / L and the gold content is 0.625 g / L; the ratio of the volume of the immersion solution to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0118] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0119] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0120] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0121] The preparation conditions are listed in Table 1.

[0122] 2. Catalyst Evaluation

[0123] The catalyst evaluation method is the same as in Example 1.

[0124] The experimental results are listed in Table 2.

[0125] Example 7

[0126] 1. Catalyst Preparation

[0127] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0128] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 2.75 g / L and the gold content is 0.1 g / L; the ratio of the volume of the immersion solution to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0129] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0130] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0131] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0132] The preparation conditions are listed in Table 1.

[0133] 2. Catalyst Evaluation

[0134] The catalyst evaluation method is the same as in Example 1.

[0135] The experimental results are listed in Table 2.

[0136] Example 8

[0137] 1. Catalyst Preparation

[0138] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0139] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 2.75 g / L and the gold content is 5.0 g / L; the ratio of the volume of the immersion solution to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0140] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0141] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0142] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0143] The preparation conditions are listed in Table 1.

[0144] 2. Catalyst Evaluation

[0145] The catalyst evaluation method is the same as in Example 1.

[0146] The experimental results are listed in Table 2.

[0147] Example 9

[0148] 1. Catalyst Preparation

[0149] (a) Spherical silica carrier (5 mm in diameter, 175 μm of specific surface area) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of the impregnation liquid volume to the support volume was 1.5), and after impregnation for half an hour, the surface of the support was dried to obtain catalyst precursor I;

[0150] (b) Take 1000 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid (wherein, the palladium content in the solution is 2.75 g / L and the gold content is 10.0 g / L; the ratio of the volume of the immersion liquid to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II;

[0151] (c) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor III;

[0152] (d) Add 10 ml of 85 wt% hydrazine hydrate for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100°C for 6 hours to obtain catalyst precursor IV.

[0153] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0154] The preparation conditions are listed in Table 1.

[0155] 2. Catalyst Evaluation

[0156] The catalyst evaluation method is the same as in Example 1.

[0157] The experimental results are listed in Table 2.

[0158] Example 10

[0159] Same as Example 1, except that step (b) is as follows: 1000 ml of catalyst precursor I is immersed in a mixed aqueous solution of chloropalladic acid and chloroauric acid for 2 hours (wherein, the palladium content in the solution is 15 g / L and the gold content is 0.0625 g / L; the ratio of the volume of the immersion liquid to the volume of catalyst precursor I is 1.2) to prepare catalyst precursor II.

[0160] Example 11

[0161] Same as Example 1, except that step (a) is: a spherical silica carrier (5 mm in diameter, 175 μm specific surface area) is used. 2 / g, pore volume 0.8cm 3 The catalyst precursor I was prepared by impregnating a sample (g) in an aqueous solution of N,N-methylenebisacrylamide (wherein the concentration of N,N-methylenebisacrylamide was 1.6 g / L and the ratio of the impregnation volume to the support volume was 1.5) for half an hour and then drying the surface of the support.

[0162] Comparative Example 1

[0163] 1. Catalyst Preparation

[0164] (a) Take 1000 ml of spherical silica carrier (5 mm in diameter, with a specific surface area of ​​175 μm). 2 / g, pore volume 0.8cm 3 / g) was impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid, and the solid-liquid volume ratio was calculated to be 1:1.2. The palladium content in the solution used was 2.75 g / L and the gold content was 0.625 g / L, to prepare catalyst precursor I;

[0165] (b) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), mix well and let stand for 24 hours, then dry at 80 °C for 8 hours to obtain catalyst precursor II;

[0166] (c) Add 60g of hydrazine hydrate with a concentration of 85%wt for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100℃ for 6 hours to obtain catalyst precursor III.

[0167] (d) The catalyst precursor III was impregnated with an aqueous solution of potassium acetate (the ratio of the volume of the impregnation solution to the volume of the support was 1:1), and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0168] The preparation conditions are listed in Table 1.

[0169] 2. Catalyst Evaluation

[0170] The catalyst evaluation method was the same as in Example 1, and the experimental results are listed in Table 2.

[0171] Table 1

[0172]

[0173]

[0174] Table 2

[0175]

[0176] If the data in the table differs from the description in the embodiments, the description in the embodiments shall prevail.

[0177] In summary, this invention effectively solves the problem of low selectivity of existing vinyl acetate catalysts in the ethylene process by achieving the optimal reaction temperature during the programmed temperature rise surface reaction of the catalyst.

[0178] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for the synthesis of vinyl acetate via the ethylene process, characterized in that, The catalyst contains Pd, Au, and alkali metal acetate. The optimal reaction temperature for the temperature-programmed surface reaction (TPSR) of the catalyst is 125-135℃. The catalyst contains 1-12 g / L of Pd, 0.1-10 g / L of Au, and 10-100 g / L of alkali metal acetate.

2. The catalyst according to claim 1, wherein, The alkali metal acetate is potassium acetate and / or sodium acetate.

3. The method for preparing the catalyst according to any one of claims 1-2, characterized in that, The method includes: (a) The catalyst support was impregnated with N,N-methylenebisacrylamide solution to prepare catalyst precursor I; (b) Catalyst precursor I was impregnated in a solution containing noble metal ions, wherein the solution contained palladium and gold ions, to prepare catalyst precursor II; (c) Catalyst precursor II is treated with a solution of an alkaline compound to convert noble metal ions into precipitates, thereby preparing catalyst precursor III; (d) The noble metal ions in catalyst precursor III were reduced to zero valence, washed and dried to prepare catalyst precursor IV; (e) Impregnate catalyst precursor IV with alkali metal acetate, dry, and obtain the finished catalyst; The concentration of the N,N-methylenebisacrylamide solution is 0.1 ~ 1.0 g / L; The solvent for the N,N-methylenebisacrylamide solution is one or both of water and ethanol; The palladium ion content in the solution containing noble metal ions is 1-12 g / L, and the gold ion content is 0.1-10 g / L.

4. The method for preparing the catalyst according to claim 3, wherein, In step (a), The impregnation conditions include a volume ratio of the N,N-methylenebisacrylamide solution to the carrier volume of 1-1.5:

1.

5. The method for preparing the catalyst according to claim 3 or 4, wherein, In step (b), the impregnation conditions include: The volume ratio of the solution containing noble metal ions to the volume of catalyst precursor I is 1.0-1.

5.

6. The method for preparing the catalyst according to claim 3 or 4, wherein, In step (c), the conditions for treatment with a solution of an alkaline compound include standing and drying, wherein... The alkaline compound is selected from sodium silicate and / or potassium silicate; and / or The concentration of the alkaline compound in the solution is 1-1000 mmol / L; and / or The settling time is 0.5-30 hours, the drying time is 0.5-10 hours, and the drying temperature is 50-100℃.

7. The method for preparing the catalyst according to claim 3 or 4, wherein, In step (d), the reduction conditions include: the reducing agent is selected from hydrazine hydrate, the reducing agent concentration is 5wt%-85wt%, the amount of reducing agent added is 1-10 ml, and the reduction time is 1-5 hours; and / or In step (d), the drying conditions include: a drying time of 1-10 hours and a drying temperature of 50-100℃; and / or In step (e), the impregnation conditions include: the volume ratio of alkali metal acetate to catalyst precursor IV is 1-1.5:1, and the alkali metal acetate is one or both of potassium acetate and sodium acetate; the drying conditions include: drying time of 1-5 hours and drying temperature of 50-100℃.

8. The application of the catalyst according to claim 1 or 2 in the synthesis of vinyl acetate.

9. A method for synthesizing vinyl acetate, characterized in that, The method comprises: contacting ethylene with acetic acid in the presence of the catalyst as described in claim 1 or 2, wherein the contact conditions include: In molar ratio, the reactants are: oxygen: ethylene: nitrogen: acetic acid = 1:6~7:7~8:1~2; and / or Reactant feed volume hourly space velocity: 1500~2000hr -1 ; and / or Reaction pressure: 0.5~1.0MPa; Reaction temperature: 120~140℃; Reaction time: 80~100hr.

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