Process for the synthesis of vinyl acetate and catalysts for the synthesis of vinyl acetate by the ethylene process and methods for their preparation

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 Pd in ​​this state accounts for 10% to 45% of the total Pd element content, preferably 15% to 42%. The vinyl acetate catalyst of this invention mainly solves the problem of high levels of diethylene acetate as a byproduct in the gas-phase synthesis of vinyl acetate from ethylene. This invention employs a vinyl acetate catalyst comprising a support and Pd, a first-group metal, and an alkali metal acetate supported on the support. The X-ray photoelectron spectroscopy of the catalyst shows that Pd... 2+ The content of ethylene glycol is in the range of 10% to 45%, preferably 15% to 42%, thereby the catalyst can effectively reduce the content of ethylene glycol diacetate in the product.

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] 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.

[0003] 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.

[0004] US3743607 discloses a catalyst containing palladium, gold, and alkali metal acetate. The catalyst is prepared by the following steps: impregnating a support, such as silicate, alumina, silicate, or aluminum phosphate, with an aqueous solution of palladium and gold salts; evaporating the resulting mixture to dryness; reducing the palladium and gold salts to their metallic state with a reducing agent; then washing the catalyst with water, impregnating it with a sodium acetate solution, and drying it for later use. 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 diacetate in a product.

[0006] To achieve the aforementioned objective, according to a first aspect of the present invention, a catalyst for the synthesis of vinyl acetate via the ethylene process is provided, comprising a support and Pd, Group IB metal, and alkali metal acetates supported on the support, wherein X-ray photoelectron spectroscopy (XPS) of the catalyst shows Pd... 2+ The content of this state accounts for 10% to 45% of the total Pd element content, preferably 15% to 42%.

[0007] According to a second aspect of the present invention, a method for preparing a catalyst for the ethylene synthesis of vinyl acetate is provided, the method comprising:

[0008] (a) The catalyst support source was immersed in a solution containing a Pd source and a Group IB metal source and dried to prepare precursor I;

[0009] (b) Precursor I is mixed and contacted with a solution of an alkaline compound, and then dried to obtain precursor II;

[0010] (c) Reduce precursor II with a reducing agent, wash with water and dry to prepare precursor III;

[0011] (d) Precursor III was immersed in a solution containing a Pd source and dried to prepare precursor IV;

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

[0013] According to a third aspect of the present invention, a catalyst prepared by the preparation method described herein is provided.

[0014] According to a fourth aspect of the present invention, a method for synthesizing vinyl acetate is provided, wherein a gaseous material for synthesizing vinyl acetate is subjected to a gas-phase catalytic synthesis reaction in the presence of a catalyst, wherein the catalyst includes the catalyst described in this invention.

[0015] Having the Pd of the present 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.

[0016] The vinyl acetate catalyst of this invention mainly solves the problem of high levels of diethylene acetate, a byproduct, in the gas-phase synthesis of vinyl acetate from ethylene. This invention employs a vinyl acetate catalyst comprising a support and Pd, a Group 1 subgroup metal, and an alkali metal acetate supported on the support. The catalyst exhibits high Pd content in its X-ray photoelectron spectroscopy. 2+ The content of ethylene glycol is in the range of 10% to 45%, preferably 15% to 42%, thereby the catalyst can effectively reduce the content of ethylene glycol diacetate in the product. 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] 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.

[0019] In this invention, the composition of each substance in the catalyst is obtained by calculation based on the amount of feed.

[0020] 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 this state accounts for 10% to 45% of the total Pd element content, preferably 15% to 42%. The Pd state 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.

[0021] In this invention, the Group IB metal in the catalyst exists in the form of elemental and / or oxide.

[0022] In this invention, Pd exists in the form of elemental form and / or oxide.

[0023] According to a preferred embodiment of the present invention, in the catalyst, Pd, calculated as an element, 0 The content of ethylene diacetate is 1–12 g / L, preferably 2–3 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, and 3 g / L. This can significantly reduce the impurity content of ethylene diacetate in the product.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Catalysts having the aforementioned features of the present invention can achieve the purpose of the present invention, and there are no special requirements for their preparation methods. In view of the present invention, a method for preparing a catalyst for the synthesis of vinyl acetate by the ethylene method is provided. The method includes: (a) immersing a catalyst support source in a solution containing a Pd source and a Group IB metal source, and drying to prepare precursor I;

[0030] (b) Precursor I is mixed and contacted with a solution of an alkaline compound, and then dried to obtain precursor II;

[0031] (c) Reduce precursor II with a reducing agent, wash with water and dry to prepare precursor III;

[0032] (d) Precursor III was immersed in a solution containing a Pd source and dried to prepare precursor IV;

[0033] (e) Impregnate precursor IV with alkali metal acetate, dry, and obtain the finished catalyst.

[0034] 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.

[0035] According to a preferred embodiment of the present invention, the prepared catalyst has a PdO content of 1 to 12 g / L, preferably 2 to 3 g / L, based on elemental composition; thereby significantly reducing the impurity content of ethylene diacetate in the product.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] According to a preferred embodiment of the present invention, the conditions in step (b) include: a solid-liquid volume ratio of 1:1-1.2, and a concentration of 10-30% by weight of the alkaline compound solution.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In this invention, step (a) can optionally be left to stand for 0.5-3 hours as needed.

[0051] In this invention, step (b) can optionally be left to stand for 12-24 hours as needed.

[0052] In this invention, step (c) can optionally be left to stand for 3-6 hours as needed.

[0053] In this invention, step (d) can optionally be left to stand for 3-6 hours as needed.

[0054] In this invention, step (e) can optionally be left to stand for 3-6 hours as needed.

[0055] This invention provides a catalyst prepared by the preparation method described herein.

[0056] 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.

[0057] 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).

[0058] 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.

[0059] 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.

[0060] 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 .

[0061] Unless otherwise specified, this invention is operated at room temperature.

[0062] Unless otherwise specified, the solvent of the solution in this invention is water.

[0063] 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.

[0064] Example 1

[0065] 1. Catalyst Preparation

[0066] (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 solution contained 2.75 g / L of palladium (as an element, the same below) and 0.625 g / L of gold (as an element, the same below). After standing for 3 hours, the drying conditions included drying at 80°C for 30 minutes to prepare catalyst precursor I.

[0067] (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;

[0068] (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.

[0069] (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.

[0070] (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.

[0071] 2. Catalyst Evaluation

[0072] The evaluation was conducted using a fixed-bed reactor, under the following conditions:

[0073] Catalyst loading volume: 40 ml;

[0074] Composition of reaction raw materials (in molar ratio): Oxygen: Ethylene: Nitrogen: Acetic acid = 1:6.8:7.2:1.7;

[0075] Reactant feed volume hourly space velocity: 2000 hr -1 ;

[0076] Reaction pressure: 0.7 MPa;

[0077] Reaction temperature: 135℃;

[0078] Reaction time: 100 hours;

[0079] 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.

[0080] For ease of comparison, the experimental results are listed in Table 1.

[0081] Example 2

[0082] 1. Catalyst Preparation

[0083] (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. After standing for 3 hours, the drying conditions included drying at 80℃ for 30 minutes to prepare catalyst precursor I.

[0084] (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;

[0085] (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.

[0086] (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.

[0087] (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.

[0088] 2. Catalyst Evaluation

[0089] The catalyst evaluation method is the same as in Example 1.

[0090] For ease of comparison, the experimental results are listed in Table 1.

[0091] Example 3

[0092] 1. Catalyst Preparation

[0093] (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, and allowed to stand for 3 hours. Based on 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.

[0094] (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;

[0095] (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.

[0096] (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.

[0097] (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.

[0098] 2. Catalyst Evaluation

[0099] The catalyst evaluation method is the same as in Example 1.

[0100] For ease of comparison, the experimental results are listed in Table 1.

[0101] Example 4

[0102] 1. Catalyst Preparation

[0103] (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. After standing for 3 hours, the drying conditions included drying at 80℃ for 30 minutes to prepare catalyst precursor I.

[0104] (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;

[0105] (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.

[0106] (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.

[0107] (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.

[0108] 2. Catalyst Evaluation

[0109] The catalyst evaluation method is the same as in Example 1.

[0110] For ease of comparison, the experimental results are listed in Table 1.

[0111] Example 5

[0112] The method is the same as in Example 1, except that 6g of acetic acid is added to the solution in step (d).

[0113] Comparative Example 1

[0114] 1. Catalyst Preparation

[0115] (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.

[0116] (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;

[0117] (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.

[0118] (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.

[0119] 2. Catalyst Evaluation

[0120] The catalyst evaluation method is the same as in Example 1.

[0121] For ease of comparison, the experimental results are listed in Table 1.

[0122] Comparative Example 2

[0123] 1. Catalyst Preparation

[0124] (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.

[0125] (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;

[0126] (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.

[0127] (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.

[0128] (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.

[0129] 2. Catalyst Evaluation

[0130] The catalyst evaluation method is the same as in Example 1.

[0131] For ease of comparison, the experimental results are listed in Table 1.

[0132] Comparative Example 3

[0133] 1. Catalyst Preparation

[0134] (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.

[0135] (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;

[0136] (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.

[0137] (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.

[0138] (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.

[0139] 2. Catalyst Evaluation

[0140] The catalyst evaluation method is the same as in Example 1.

[0141] For ease of comparison, the experimental results are listed in Table 1.

[0142] Table 1

[0143]

[0144] STY refers to the space-time yield of vinyl acetate, which is calculated as follows:

[0145] STY(t / dm 3 = 86 * ethylene consumption (mol / d) * 1000 / catalyst dosage (m³) 3 )

[0146] 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 metal and alkali metal acetates supported on the support. in, 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. The total Pd element content is composed of Pd 0 The content of state and Pd 2+ The composition of the state; In terms of elements, Pd 0 The content is 1~12g / L; The content of Group IB metals is 0.1~10 g / L, based on elemental composition. The content of alkali metal acetate is 10~100g / L.

2. The catalyst according to claim 1, wherein, In catalysts, Pd, on an elemental basis 0 The content is 2~3g / 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.

3. The catalyst according to claim 1 or 2, 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.

4. The catalyst according to claim 3, 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.

5. The catalyst according to claim 4, wherein, The alkali metal acetate is potassium acetate; and / or 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.

6. A method for preparing a catalyst for the synthesis of vinyl acetate via the ethylene process, characterized in that, The method includes: (a) The catalyst support source is immersed in a solution containing a Pd source and a Group IB metal source, and then dried to prepare precursor I; (b) Precursor I is mixed and contacted with a solution of an alkaline compound, and then dried to obtain precursor II; (c) Precursor II was reduced with a reducing agent, washed with water and dried to prepare 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; in, X-ray photoelectron spectroscopy of the prepared catalyst showed Pd 2+ The content of this state accounts for 15-42% of the total Pd element content. The total Pd element content is composed of Pd 0 The content of state and Pd 2+ The composition of the state; In terms of elements, Pd 0 The content is 1~12g / L; The content of Group IB metals is 0.1~10 g / L, based on elemental composition. The content of alkali metal acetate is 10~100g / L.

7. The preparation method according to claim 6, wherein, In the prepared catalyst, Pd, by elemental count 0 The content is 2~3g / L; and / or The prepared catalyst contains, by elemental calculation, 0.4–0.8 g / L of Group IB metals; and / or The prepared catalyst contains 20-40 g / L of alkali metal acetate.

8. The preparation method according to claim 6 or 7, 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 In step (a), the carrier source is selected from one or more of silica and alumina; 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, Group IB metals are Au; and / or The alkali metal element is one or more of Na and K; and / or In step (a), the carrier source is selected from spherical silica.

10. The preparation method according to claim 9, wherein, The alkali metal acetate is potassium acetate; and / or 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 6 or 7, wherein, The conditions in step (a) 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; the Group IB metal content is 0.1-10 g / L; and / or The conditions in step (b) include: a solid-liquid volume ratio of 1:1-1.2, and a concentration of 10-30% by weight of the alkaline compound solution. 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: in the solution containing a Pd source and a Group IB metal source, the Pd content is 2-3 g / L; the Group IB metal content is 0.4-0.8 g / L; and / or 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, Step (d) is carried out in the presence of acetic acid, with an amount of 5-8 g / L solid.

14. The catalyst prepared by the method according to any one of claims 6-13.

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 1-5 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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