Synthesis methods of vinyl acetate, its synthesis catalysts and preparation methods

Abstract

This invention provides a method for synthesizing vinyl acetate and a catalyst for the ethylene-based synthesis of vinyl acetate, as well as a method for preparing the catalyst; the catalyst includes a support and Pd, Group IB metal, and alkali metal acetates supported on the support, wherein the X-ray photoelectron spectroscopy (XPS) of the catalyst shows Pd... 2+ The content of the Pd element in the catalyst is 10% to 45% of the total Pd element content, preferably 15% to 42%; the optimal reaction temperature in the temperature-programmed surface reaction (TPSR) of the catalyst is 125 to 135°C. The vinyl acetate catalyst of this invention mainly solves the problems of ethylene diacetate as a byproduct and high reaction temperature in the gas-phase synthesis of vinyl acetate from ethylene.

Description

Technical Field

[0001] This invention relates to catalysts for the synthesis of vinyl acetate via the ethylene process, methods for their preparation, and methods for synthesizing vinyl acetate. Background Technology

[0002] Currently, the main method for producing vinyl acetate is to use ethylene, oxygen, and acetic acid as raw materials, and palladium-gold-potassium acetate / silica as a catalyst, through a gas-phase catalytic reaction to produce vinyl acetate, water, and carbon dioxide as a byproduct. Trace amounts of ethyl acetate, acetaldehyde, and other acetoxylated products are also generated.

[0003] Vinyl acetate, also known as vinyl acetate ester, is a colorless, sweet-smelling, and highly flammable liquid. It is soluble in alcohols, benzene, ethers, and acetone, and slightly soluble in water. Vinyl acetate is a precursor to polyvinyl acetate and ethylene-vinyl acetate copolymers, and is an important industrial polymer. It can be used as an adhesive, as a raw material for synthesizing vinylon (for white glue), and in the production of coatings, demonstrating broad application prospects in the chemical field.

[0004] US3743607 discloses a catalyst containing palladium, gold, and alkali metal acetates. This catalyst is prepared by the following steps: impregnating a support, such as silica, alumina, silicate, or aluminum phosphate, with an aqueous solution of palladium and gold salts; and evaporating the resulting mixture to dryness. This method results in a high impurity content. Summary of the Invention

[0005] The purpose of this invention is to provide a vinyl acetate catalyst that can significantly reduce the impurity content of ethylene diacetate in the product and lower the reaction temperature.

[0006] In this invention, Pd 2+ / (Pd 0 +Pd 2+ The method for calculating the mass ratio is to use the peak area of ​​XPS to calculate Pd separately. 0 With Pd 2+ The amount.

[0007] In this invention, the composition of each substance in the catalyst is obtained by calculation based on the amount of feed.

[0008] This invention provides a catalyst for the synthesis of vinyl acetate via the ethylene process, comprising a support and Pd, Group IB metal, and alkali metal acetates supported on the support, wherein the X-ray photoelectron spectroscopy (XPS) of the catalyst shows Pd... 2+ The content of the catalyst in the TPSR (Temperature-Programmed Surface Reaction) state accounts for 10% to 45% of the total Pd element content, preferably 15% to 42%; the optimal reaction temperature in the TPSR is 125 to 135°C. The Pd of this invention... 2+ / (Pd 0+Pd 2+ The catalyst with the mass ratio characteristic can significantly reduce the impurity content of ethylene diacetate in the product.

[0009] In this invention, the Group IB metals in the catalyst mainly exist in elemental form.

[0010] In this invention, Pd exists in both elemental and oxide forms.

[0011] According to a preferred embodiment of the present invention, the total Pd content in the catalyst, calculated by element, is 1-12 g / L, preferably 2-5 g / L, for example, 2.1 g / L, 2.2 g / L, 2.3 g / L, 2.4 g / L, 2.5 g / L, 2.6 g / L, 2.7 g / L, 2.8 g / L, 2.9 g / L, 3 g / L, 3.1 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.7 g / L, 3.8 g / L, 3.9 g / L, 4 g / L, 4.1 g / L, 4.2 g / L, 4.3 g / L, 4.4 g / L, 4.5 g / L, 4.6 g / L, 4.7 g / L, 4.8 g / L, 4.9 g / L, or 5 g / L. This can significantly reduce the impurity content of ethylene diacetate in the product.

[0012] According to a preferred embodiment of the present invention, the catalyst contains, by elemental calculation, 0.1–10 g / L of Group IB metals, preferably 0.4–0.8 g / L, for example 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, or 0.8 g / L. This significantly reduces the impurity content of ethylene diacetate in the product.

[0013] According to a preferred embodiment of the present invention, the content of alkali metal acetate is 10-100 g / L, preferably 20-40 g / L, for example 20 g / L, 30 g / L, or 40 g / L. This significantly reduces the impurity content of ethylene diacetate in the product.

[0014] According to a preferred embodiment of the present invention, any Group IB metal can be used. For the present invention, the preferred Group IB metals are Au and / or Cu, with Au being the most preferred. This significantly reduces the impurity content of ethylene diacetate in the product.

[0015] According to a preferred embodiment of the present invention, the alkali metal element is selected from one or more of Li, Na, K, Rb, Cs, and Fr, preferably one or more of Na and K; preferably, the alkali metal acetate is potassium acetate; thereby, the impurity content of ethylene diacetate in the product can be significantly reduced.

[0016] In this invention, there are no special requirements for the carrier; any carrier commonly used in the field can achieve the purpose of this invention. According to a preferred embodiment of the invention, the carrier is selected from one or more of silicon oxide and aluminum oxide. According to a preferred embodiment of the invention, preferably, the carrier is selected from spherical silicon dioxide, preferably with a diameter of 2-8 mm and a specific surface area of ​​150-200 m². 2 / g, pore volume 0.6-1cm 3 / g. This invention uses spherical silica with a diameter of 5mm and a specific surface area of ​​175m². 2 / g, pore volume 0.8cm 3 / g is used as an example to illustrate the advantages of the invention, but the invention is not limited thereto.

[0017] Catalysts possessing the aforementioned features of this invention can achieve the objectives of this invention, and there are no special requirements for their preparation methods. In view of this invention, a method for preparing a catalyst for the synthesis of vinyl acetate by the ethylene method is provided. The method includes: (a) impregnating a catalyst support source in an N,N-methylenebisacrylamide solution and drying it to obtain precursor I'; then impregnating it in a solution containing a Pd source and a Group IB metal source and drying it to obtain precursor I;

[0018] (b) Precursor I is mixed and contacted with a solution of an alkaline compound, and then dried to obtain precursor II;

[0019] (c) Reduce precursor II with a reducing agent, wash with water and dry to prepare precursor III;

[0020] (d) Precursor III was immersed in a solution containing a Pd source and dried to prepare precursor IV;

[0021] (e) Impregnate precursor IV with alkali metal acetate, dry, and obtain the finished catalyst.

[0022] According to a preferred embodiment of the present invention, the optimal reaction temperature in the temperature-programmed surface reaction (TPSR) process of the prepared catalyst is 125–135 °C.

[0023] According to a preferred embodiment of the present invention, the X-ray photoelectron spectroscopy (XPS) of the prepared catalyst shows Pd 2+ The content of this state accounts for 10% to 45% of the total Pd element content, preferably 15% to 42%; this can significantly reduce the impurity content of ethylene diacetate in the product.

[0024] According to a preferred embodiment of the present invention, the total Pd content in the prepared catalyst is 1-12 g / L, preferably 2-5 g / L, based on elemental composition; thereby significantly reducing the impurity content of ethylene diacetate in the product.

[0025] According to a preferred embodiment of the present invention, the catalyst prepared contains, by element, 0.1 to 10 g / L of Group IB metals, preferably 0.4 to 0.8 g / L; thereby significantly reducing the impurity content of ethylene diacetate in the product.

[0026] According to a preferred embodiment of the present invention, the alkali metal acetate content in the prepared catalyst is 10–100 g / L, preferably 20–40 g / L. This significantly reduces the impurity content of ethylene diacetate in the product.

[0027] According to a preferred embodiment of the present invention, any Group IB metal can be used. Specifically, according to a preferred embodiment of the present invention, the Group IB metal is Au and / or Cu, preferably Au. This significantly reduces the impurity content of ethylene diacetate in the product.

[0028] According to a preferred embodiment of the present invention, the alkali metal element is selected from one or more of Li, Na, K, Rb, Cs, and Fr, preferably one or more of Na and K; preferably, the alkali metal acetate is potassium acetate.

[0029] According to a preferred embodiment of the present invention, the concentration of the N,N-methylenebisacrylamide solution is 0.1 to 1.0 g / L.

[0030] According to a preferred embodiment of the present invention, the solvent of the N,N-methylenebisacrylamide solution is one or both of water and ethanol.

[0031] In this invention, there are no special requirements for the carrier source; commonly used carrier sources in the field can achieve the purpose of this invention. The carrier source is selected, for example, from one or more of silica and alumina. Preferably, the carrier source is selected from spherical silica, and more preferably, the diameter of the spherical silica is 2-8 mm, and the specific surface area is 150-200 m². 2 / g, pore volume 0.6-1cm 3 / g.

[0032] In this invention, the range of alkaline compounds that can be selected is relatively wide. According to a preferred embodiment of this invention, in step (b), the alkaline compound includes, but is not limited to, one or more of sodium silicate and sodium hydroxide.

[0033] According to a preferred embodiment of the present invention, in step (c), the reducing agent includes, but is not limited to, one or more of hydrazine hydrate and sodium citrate.

[0034] According to a preferred embodiment of the present invention, the conditions in step (a) include: the conditions for impregnating the catalyst support source with the N,N-methylenebisacrylamide solution include: the volume ratio of the N,N-methylenebisacrylamide solution to the support volume is 1-1.5:1.

[0035] According to a preferred embodiment of the present invention, the conditions in step (a) include: a solid-liquid volume ratio of 1:1 to 1:1.2, and in the solution containing a Pd source and a Group IB metal source, the content of Pd is 1 to 12 g / L, preferably 2 to 3 g / L, and the content of Group IB metal is 0.1 to 10 g / L, preferably 0.4 to 0.8 g / L.

[0036] According to a preferred embodiment of the present invention, the conditions in step (b) include: the volume ratio of the alkaline compound solution to the carrier is 0.05 to 0.5, preferably 0.07 to 0.1.

[0037] According to a preferred embodiment of the present invention, the conditions in step (b) include: the concentration of the alkaline compound solution is 10-30% by weight.

[0038] In this invention, there are no special requirements for the conditions of reduction, washing, and drying. Commonly used reduction, washing, and drying conditions can all be used in this invention. According to the preferred embodiment of this invention, the conditions in step (c) include: reduction time of 1-10 hours; washing time of 1-20 hours; drying temperature of 60-100℃; and drying time of 1-10 hours.

[0039] According to a preferred embodiment of the present invention, the conditions in step (d) include: a solid-liquid volume ratio of 1:1-1.2 and a Pd content of 0.5-2 g / L in the solution.

[0040] According to a preferred embodiment of the present invention, step (d) is preferably carried out in the presence of acetic acid, wherein the amount of acetic acid is 1-10 g / L solid, preferably 5-8 g / L solid.

[0041] According to a preferred embodiment of the present invention, the conditions in step (e) include: a drying temperature of 60-100°C and a drying time of 1-10 hours.

[0042] In this invention, steps (a) to (e) involve allowing the liquid to stand as needed, with the aim of ensuring sufficient contact between the solid and liquid.

[0043] In this invention, step (a) can optionally be left to stand for 0.5-3 hours as needed.

[0044] In this invention, step (b) can optionally be left to stand for 12-24 hours as needed.

[0045] In this invention, step (c) can optionally be left to stand for 3-6 hours as needed.

[0046] In this invention, step (d) can optionally be left to stand for 3-6 hours as needed.

[0047] In this invention, step (e) can optionally be left to stand for 3-6 hours as needed.

[0048] In this invention, the purpose of drying is to remove liquid substances from solids. Generally, drying results in a solid content of 95 wt% or more, and there are no special technical requirements for it.

[0049] This invention provides a catalyst prepared by the preparation method described herein.

[0050] This invention provides a method for synthesizing vinyl acetate, wherein the raw material gas for synthesizing vinyl acetate undergoes a gas-phase catalytic synthesis reaction in the presence of a catalyst, wherein the catalyst includes the catalyst described in this invention.

[0051] According to a preferred embodiment of the present invention, the raw material gas for synthesizing vinyl acetate includes oxygen, ethylene, nitrogen and acetic acid; preferably, the raw material gas composition in molar ratio is oxygen:ethylene:nitrogen:acetic acid = 1:(5-7):(4-8):(1-2).

[0052] According to a preferred embodiment of the present invention, the conditions for the gas-phase catalytic synthesis reaction include a reaction pressure of 0.5 to 0.9 MPa.

[0053] According to a preferred embodiment of the present invention, the conditions for the gas-phase catalytic synthesis reaction include a reaction temperature of 130–200°C.

[0054] According to a preferred embodiment of the present invention, the conditions for the gas-phase catalytic synthesis reaction include: a feed gas volume hourly space velocity of 1600–3000 hr. -1 .

[0055] Unless otherwise specified, this invention is operated at room temperature.

[0056] Unless otherwise specified, the solvent of the solution in this invention is water.

[0057] In this invention, the method for testing the content of each component in the catalyst is as follows: the content of different valence states of elements is represented by the peak area of ​​XPS spectrum, and the ratio of their peak areas can represent the content ratio of different valence states of elements.

[0058] In this invention, STY refers to the space-time yield of vinyl acetate, which is calculated as: STY(t / dm 3 = 86 * ethylene consumption (mol / d) * 1000 / catalyst dosage (m³) 3).

[0059] The catalyst with the features of this invention can reduce the reaction temperature and significantly reduce the impurity content of ethylene diacetate in the product. Detailed Implementation

[0060] 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.

[0061] The advantages of the present invention will be described in detail below through examples, but the present invention is not limited thereto.

[0062] Example 1

[0063] 1. Catalyst Preparation

[0064] (a) Take 1100 ml of spherical silica carrier (5 mm in diameter, with a specific surface area of ​​175 μm). 2 / g, pore volume 0.8cm 3 The catalyst precursor I' was impregnated in an ethanol solution of N,N-methylenebisacrylamide (wherein the concentration of N,N-methylenebisacrylamide was 0.1 g / L; the ratio of impregnation liquid volume to support volume was 1.5). After impregnation for half an hour, it was dried to obtain precursor I'. Then, it was impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid. According to the solid-liquid volume ratio of 1:1.2, the palladium (as an element, the same below) content in the solution was 2.75 g / L, and the gold (as an element, the same below) content was 0.625 g / L. After standing for 3 hours, the drying conditions included drying at 80℃ for 30 minutes to prepare catalyst precursor I.

[0065] (b) Add 100 ml of sodium silicate aqueous solution (prepared by dissolving 27.5 g of Na2SiO3·9H2O in 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;

[0066] (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.

[0067] (d) Catalyst precursor III was immersed in an aqueous solution of chloropalladic acid with a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution was 0.50 g / L. After mixing evenly, the solution was allowed to stand for 6 hours and then dried at 80 °C for 12 hours to prepare catalyst precursor IV.

[0068] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0069] 2. Catalyst Evaluation

[0070] The evaluation was conducted using a fixed-bed reactor, under the following conditions:

[0071] Catalyst loading volume: 40 ml;

[0072] Composition of reaction raw materials (in molar ratio): Oxygen: Ethylene: Nitrogen: Acetic acid = 1:6.9:7.0:2.0;

[0073] Reactant feed volume hourly space velocity: 2020 hr -1 ;

[0074] Reaction pressure: 0.7 MPa;

[0075] Reaction temperature: 132℃;

[0076] Reaction time: 100 hours;

[0077] The content of each component in the reaction product was analyzed by gas chromatography, and then the space-time yield of the catalyst was calculated.

[0078] For ease of comparison, the experimental results are listed in Table 1.

[0079] Example 2

[0080] 1. Catalyst Preparation

[0081] (a) Take 1100 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 an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 1.0 g / L; the ratio of impregnation liquid volume to support volume was 1.5), and after impregnation for half an hour, it was dried and then impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid. According to the solid-liquid volume ratio of 1:1.2, the palladium content in the solution used was 2.75 g / L and the gold content was 0.625 g / L. After standing for 3 hours, the drying conditions included drying at 80℃ for 30 minutes to prepare catalyst precursor I;

[0082] (b) Add 100 ml of sodium silicate aqueous solution (prepared by dissolving 27.5 g of Na2SiO3·9H2O in 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;

[0083] (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.

[0084] (d) Catalyst precursor III was immersed in an aqueous solution of chloropalladic acid with a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution was 0.92 g / L. After mixing evenly, the solution was allowed to stand for 6 hours and then dried at 80 °C for 12 hours to prepare catalyst precursor IV.

[0085] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0086] 2. Catalyst Evaluation

[0087] The catalyst evaluation method is the same as in Example 1.

[0088] For ease of comparison, the experimental results are listed in Table 1.

[0089] Example 3

[0090] 1. Catalyst Preparation

[0091] (a) Take 1100 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 an aqueous solution of N,N-methylenebisacrylamide (wherein, the concentration of N,N-methylenebisacrylamide was 0.6 g / L; the ratio of impregnation liquid volume to support volume was 1.5), and dried after impregnation for half an hour; impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid, and allowed to stand for 3 hours. Calculated according to a solid-liquid volume ratio of 1:1.2, the palladium content in the solution used was 2.75 g / L and the gold content was 0.625 g / L. The drying conditions included drying at 80℃ for 30 minutes to prepare catalyst precursor I;

[0092] (b) Add 100 ml of sodium silicate aqueous solution (prepared by dissolving 27.5 g of Na2SiO3·9H2O in 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;

[0093] (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.

[0094] (d) Catalyst precursor III was immersed in an aqueous solution of chloropalladium acid. The solid-liquid volume ratio was 1:1.2, and the palladium content in the solution was 1.18 g / L. After mixing evenly, the solution was allowed to stand for 6 hours and then dried at 80 °C for 12 hours to prepare catalyst precursor IV.

[0095] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0096] 2. Catalyst Evaluation

[0097] The catalyst evaluation method is the same as in Example 1.

[0098] For ease of comparison, the experimental results are listed in Table 1.

[0099] Example 4

[0100] 1. Catalyst Preparation

[0101] (a) Take 1100 ml of spherical silica carrier (5 mm in diameter, with a specific surface area of ​​175 μm). 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 1.0 g / L and the ratio of impregnation volume to support volume was 1.5) for half an hour and then drying it. Afterward, it was impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid, with a solid-liquid volume ratio of 1:1.2, where the palladium content in the solution was 2.75 g / L and the gold content was 0.625 g / L. The solution was allowed to stand for 3 hours, and the drying conditions included drying at 80°C for 30 minutes.

[0102] (b) Add 100 ml of sodium silicate aqueous solution (prepared by dissolving 27.5 g of Na2SiO3·9H2O in 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;

[0103] (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.

[0104] (d) Catalyst precursor III was immersed in an aqueous solution of chloropalladium acid with a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution was 2.0 g / L. After mixing evenly, the solution was allowed to stand for 6 hours and then dried at 80 °C for 12 hours to prepare catalyst precursor IV.

[0105] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0106] 2. Catalyst Evaluation

[0107] The catalyst evaluation method is the same as in Example 1.

[0108] For ease of comparison, the experimental results are listed in Table 1.

[0109] Example 5

[0110] The method is the same as in Example 1, except that 6g of acetic acid is added to the solution in step (d).

[0111] Comparative Example 1

[0112] 1. Catalyst Preparation

[0113] (a) Take 1100 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, with a solid-liquid volume ratio of 1:1.2. The palladium content in the solution was 2.75 g / L and the gold content was 0.625 g / L. The drying conditions included drying at 80°C for 30 minutes to prepare catalyst precursor I.

[0114] (b) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), with a solid-liquid volume ratio of 1:1.2; after mixing evenly, let stand for 24 hours, and then dry at 80 °C for 8 hours to obtain catalyst precursor II;

[0115] (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.

[0116] (d) The catalyst precursor III was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0117] 2. Catalyst Evaluation

[0118] The catalyst evaluation method is the same as in Example 1.

[0119] For ease of comparison, the experimental results are listed in Table 1.

[0120] Comparative Example 2

[0121] 1. Catalyst Preparation

[0122] (a) Take 1100 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) is impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid, with a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution is 1 g / L and the gold content is 0.1 g / L. The drying conditions include drying at 80℃ for 30 minutes to prepare catalyst precursor I.

[0123] (b) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), with a solid-liquid volume ratio of 1:1.2; after mixing evenly, let stand for 24 hours, and then dry at 80 °C for 8 hours to obtain catalyst precursor II;

[0124] (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.

[0125] (d) Catalyst precursor III was immersed in an aqueous solution of chloropalladic acid with a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution was 0.92 g / L. After mixing evenly, the solution was allowed to stand for 6 hours and then dried at 80 °C for 12 hours to prepare catalyst precursor IV.

[0126] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0127] 2. Catalyst Evaluation

[0128] The catalyst evaluation method is the same as in Example 1.

[0129] For ease of comparison, the experimental results are listed in Table 1.

[0130] Comparative Example 3

[0131] 1. Catalyst Preparation

[0132] (a) Take 1100 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) is impregnated in a mixed aqueous solution of chloropalladic acid and chloroauric acid, with a solid-liquid volume ratio of 1:1.2. The palladium content in the solution is 12 g / L and the gold content is 10 g / L. The drying conditions include drying at 80℃ for 30 minutes to prepare catalyst precursor I.

[0133] (b) Add 100 ml of sodium silicate aqueous solution (27.5 g Na2SiO3·9H2O was prepared into 100 ml of aqueous solution), with a solid-liquid volume ratio of 1:1.2; after mixing evenly, let stand for 24 hours, and then dry at 80 °C for 8 hours to obtain catalyst precursor II;

[0134] (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.

[0135] (d) Catalyst precursor III was immersed in an aqueous solution of chloropalladic acid with a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution was 0.92 g / L. After mixing evenly, the solution was allowed to stand for 6 hours and then dried at 80 °C for 12 hours to prepare catalyst precursor IV.

[0136] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate and dried at 80°C for 6 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst was 30 g / L.

[0137] 2. Catalyst Evaluation

[0138] The catalyst evaluation method is the same as in Example 1.

[0139] For ease of comparison, the experimental results are listed in Table 1.

[0140] Table 1

[0141]

[0142] 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 comprises a support and Pd, Group IB metals, and alkali metal acetates supported on the support. The X-ray photoelectron spectroscopy (XPS) of the catalyst shows Pd... 2+ The content of the state accounts for 10% to 45% of the total Pd element content; the optimal reaction temperature point in the temperature-programmed surface reaction (TPSR) process of the catalyst is 125 to 135°C; The total pd element only includes pd 2+ and PD 0+ .

2. The catalyst according to claim 1, wherein, X-ray photoelectron spectroscopy of the catalyst showed that Pd 2+ The content of this state accounts for 15-42% of the total Pd element content; and / or In the catalyst, the total Pd content, calculated as elemental, is 1~12 g / L; and / or The catalyst contains, on an elemental basis, 0.1–10 g / L of Group IB metals; and / or The catalyst contains 10~100 g / L of alkali metal acetate.

3. The catalyst according to claim 2, wherein, In the catalyst, the total Pd content, calculated as elemental, is 2~5 g / L; and / or The catalyst contains 0.4–0.8 g / L of Group IB metals (based on elemental composition); and / or The catalyst contains 20-40 g / L of alkali metal acetate.

4. The catalyst according to claim 1, wherein, Group IB metals are Au and / or Cu; and / or The alkali metal element is selected from one or more of Li, Na, K, Rb, Cs, and Fr; and / or The carrier is selected from one or more of silicon oxide and aluminum oxide.

5. The catalyst according to claim 4, wherein, Group IB metals are Au; and / or The alkali metal element is one or more of Na and K; and / or The carrier is selected from spherical silica.

6. The catalyst according to claim 5, wherein, The alkali metal acetate is potassium acetate; and / or The spherical silica particles have a diameter of 2-8 mm and a specific surface area of ​​150-200 m². 2 / g, pore volume 0.6-1cm 3 / g.

7. A method for preparing a catalyst for the ethylene-to-vinyl acetate synthesis process according to any one of claims 1-6, characterized in that, The method includes: (a) The catalyst support source was impregnated in N,N-methylenebisacrylamide solution and dried to obtain precursor I'; then impregnated in a solution containing Pd source and Group IB metal source and dried to obtain precursor I; (b) Precursor I is mixed and contacted with a solution of an alkaline compound, and then dried to obtain precursor II; (c) Reduce precursor II with a reducing agent, wash with water and dry to obtain precursor III; (d) Precursor III was immersed in a solution containing a Pd source and dried to prepare precursor IV; (e) Impregnate precursor IV with alkali metal acetate, dry, and obtain the finished catalyst.

8. The preparation method according to claim 7, wherein, In step (a), the carrier source is selected from one or more of silica and alumina; The concentration of the N,N-methylenebisacrylamide solution is 0.1 ~ 1.0 g / L; and / or The solvent for the N,N-methylenebisacrylamide solution is one or both of water and ethanol; and / or In step (b), the alkaline compound is selected from one or more of sodium silicate and sodium hydroxide; and / or In step (c), the reducing agent is selected from one or more of hydrazine hydrate and sodium citrate.

9. The preparation method according to claim 8, wherein, In step (a), the carrier source is selected from spherical silica.

10. The preparation method according to claim 9, wherein, The spherical silica particles have a diameter of 2-8 mm and a specific surface area of ​​150-200 m². 2 / g, pore volume 0.6-1cm 3 / g.

11. The preparation method according to claim 7, wherein, The conditions in step (a) include: The conditions for impregnating the catalyst support source with N,N-methylenebisacrylamide solution include: the volume ratio of the N,N-methylenebisacrylamide solution to the volume of the support source is 1-1.5:1; and / or The immersion conditions for immersion in a solution containing a Pd source and a Group IB metal source include: a solid-liquid volume ratio of 1:1-1.2, and in the solution containing a Pd source and a Group IB metal source, the Pd content is 1~12 g / L and the Group IB metal content is 0.1~10 g / L. and / or The conditions in step (b) include: the concentration of the alkaline compound solution is 10-30% by weight, and the volume ratio of the alkaline compound solution to the carrier source is 0.05-0.

5. The conditions in step (d) include: a solid-liquid volume ratio of 1:1-1.2 and a Pd content of 0.5-2 g / L in the solution.

12. The preparation method according to claim 11, wherein, The conditions in step (a) include: The immersion conditions for immersion in a solution containing a Pd source and a Group IB metal source include: the Pd content in the solution containing the Pd source and the Group IB metal source is 2~3 g / L; the Group IB metal content is 0.4~0.8 g / L. and / or The conditions in step (b) include: the volume ratio of the alkaline compound solution to the carrier source is 0.07 to 0.1; Step (d) is carried out in the presence of acetic acid, with an amount of 1-10 g / L solid.

13. The preparation method according to claim 12, wherein, In step (d), the amount of acetic acid used is 5-8 g / L solid.

14. The catalyst prepared by the method according to any one of claims 7-13.

15. A method for synthesizing vinyl acetate, wherein the raw material gas for synthesizing vinyl acetate undergoes a gas-phase catalytic synthesis reaction in the presence of a catalyst, characterized in that, The catalyst comprises the catalyst according to any one of claims 1-6 and 14.

16. The synthesis method according to claim 15, wherein, The raw materials for synthesizing vinyl acetate include oxygen, ethylene, nitrogen, and acetic acid; and / or The conditions for gas-phase catalytic synthesis reactions include: The reaction pressure is 0.5–0.9 MPa, and / or The reaction temperature is 130–200℃, and / or The feed gas volume hourly space velocity is 1600–3000 hr. -1 .

17. The synthesis method according to claim 16, wherein, In the raw material gas for synthesizing vinyl acetate, the molar ratio of oxygen, ethylene, nitrogen and acetic acid is 1:(5-7):(4-8):(1-2).

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