Methods for preparing vinyl acetate and catalysts for preparing vinyl acetate and their preparation methods

Abstract

This invention discloses a method for preparing vinyl acetate and a catalyst for preparing vinyl acetate, and the preparation method thereof. The catalyst has a surface Pd-N3 site coverage of 0-10%. The catalyst preparation method includes: (a) impregnating a support source in a C3N4 dispersion and calcining it to prepare catalyst precursor I; (b) impregnating catalyst precursor I in a solution containing palladium and Group IB metals and drying it to prepare catalyst precursor II; (c) treating catalyst precursor II with a solution of an alkaline compound and drying it to obtain catalyst precursor III; (d) reducing catalyst precursor III with noble metal ions and drying it to obtain catalyst precursor IV; (e) impregnating catalyst precursor IV with an alkali metal acetate and drying it. The catalyst of this invention can effectively improve the selectivity and space-time yield of the catalyst.

Description

Technical Field

[0001] This invention relates to a catalyst for preparing vinyl acetate, a method for preparing the same, and a method for preparing 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 GB1283737 discloses a method for controlling catalyst component loading by treating a porous shell with sodium carbonate or sodium hydroxide.

[0004] CN1107831A discloses a scheme to improve metal aging by introducing barium salts on the surface of a support; CN1226188A discloses a method for preparing a catalyst supported on a noble metal as the main catalyst, a metal as the co-catalyst, and an alkali metal or alkaline earth metal compound. Summary of the Invention

[0005] The object of this invention is to provide a catalyst for the preparation of vinyl acetate that can significantly improve catalytic selectivity. To achieve the above object, one aspect of this invention provides a catalyst for the preparation of vinyl acetate, wherein the surface Pd-N3 site coverage of the catalyst is 0-10%.

[0006] A second aspect of the present invention provides a method for preparing the catalyst described herein, the method comprising:

[0007] (a) The carrier source was impregnated in a C3N4 dispersion and calcined to prepare catalyst precursor I;

[0008] (b) Catalyst precursor I was immersed in a solution containing palladium and Group IB metals and dried to prepare catalyst precursor II;

[0009] (c) Catalyst precursor II is treated with a solution of an alkaline compound and dried to obtain catalyst precursor III;

[0010] (d) Reduce the noble metal ions of catalyst precursor III and dry them to obtain catalyst precursor IV;

[0011] (e) Impregnate catalyst precursor IV with alkali metal acetate and dry.

[0012] A third aspect of the present invention provides a method for preparing vinyl acetate, wherein a gaseous catalytic synthesis reaction of a raw material gas for synthesizing vinyl acetate is carried out in the presence of a catalyst, wherein the catalyst includes the catalyst described in the present invention.

[0013] The above technical solutions can effectively improve the selectivity and space-time yield of catalysts. Detailed Implementation

[0014] 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.

[0015] This invention provides a catalyst for preparing vinyl acetate, wherein the surface Pd-N3 sites of the catalyst have a coverage rate of 0-10%. In this invention, the term 0 refers to a value infinitely close to 0, indicating that the presence of these sites is sufficient to achieve the purpose of this invention.

[0016] According to a preferred embodiment of the present invention, the surface Pd-N3 site coverage of the catalyst is 2% to 10%. The catalyst of the present invention can effectively improve reaction selectivity.

[0017] This invention does not have special requirements for the composition of the catalyst. For example, commonly used Pd-containing catalysts can be used in this invention. The following is an illustrative description, but it is not intended to limit the scope of this invention.

[0018] According to one embodiment of the present invention, the catalyst comprises a support and Pd, Group IB metal and alkali metal acetate supported on the support.

[0019] In this invention, all Group IB metals can be used. The following is an illustrative description, but it does not limit the scope of the invention.

[0020] According to one embodiment of the present invention, the preferred Group IB metal is Au and / or Cu, with Au being more preferred.

[0021] In this invention, commonly used alkali metal elements can be used. The following is an illustrative description, but it does not limit the scope of the invention. According to one embodiment of the 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 selectivity of the catalyst can be improved.

[0022] 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. The following is an illustrative description, but it does not limit the scope of this invention. According to one 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, the carrier is preferably 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 a silica carrier with a diameter of 5mm and a specific surface area of ​​175µm. 2 / g, pore volume 0.8cm 3 / g is provided as an example to illustrate the advantages of the invention, but does not limit the scope of the invention.

[0023] In this invention, there are no special requirements for the content of each substance. The contents commonly used in the art can be used in this invention. The following is an illustrative description, but it does not limit the scope of this invention.

[0024] According to one embodiment of the present invention, the Pd content, calculated by element, is 1–12 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, or 3 g / L. This enables the improvement of catalyst selectivity.

[0025] According to one embodiment of the present invention, the content of Group IB metals is 0.1 to 10 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 enables the improvement of catalyst selectivity.

[0026] According to one 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 enables the catalyst to achieve improved selectivity.

[0027] In this invention, the composition of each substance in the catalyst is obtained by calculation based on the amount of feed.

[0028] In this invention, the Group IB metals in the catalyst mainly exist in elemental form.

[0029] In this invention, Pd mainly exists in elemental form.

[0030] Catalysts possessing the aforementioned characteristics 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 the catalyst for synthesizing vinyl acetate is provided, the method comprising:

[0031] (a) The carrier source was impregnated in a C3N4 dispersion and calcined to prepare catalyst precursor I;

[0032] (b) Catalyst precursor I was immersed in a solution containing palladium and Group IB metals and dried to prepare catalyst precursor II;

[0033] (c) Catalyst precursor II is treated with a solution of an alkaline compound and dried to obtain catalyst precursor III;

[0034] (d) Reduce the noble metal ions of catalyst precursor III and dry them to obtain catalyst precursor IV;

[0035] (e) Impregnate catalyst precursor IV with alkali metal acetate and dry.

[0036] In this invention, the concentration of C3N4 in the C3N4 dispersion can be selected within a wide range. The following is an illustrative description, but it is not limited to the scope of this invention. According to one embodiment of this invention, the content of C3N4 in the C3N4 dispersion is 5-20 wt%.

[0037] In this invention, the solid-liquid volume ratio in step (a) can be selected from a wide range. The following is an illustrative description, but it is not limited to the scope of this invention. Preferably, the solid-liquid volume ratio is 1:1 to 1.5.

[0038] According to one embodiment of the present invention, the diameter of C3N4 in the C3N4 dispersion is 0.1 to 10 micrometers, for example, 0.1 micrometer, 0.5 micrometer, 1 micrometer, 2 micrometer, 3 micrometer, 4 micrometer, 5 micrometer, 6 micrometer, 7 micrometer, 8 micrometer, 9 micrometer, 10 micrometer, preferably 2 to 8 micrometers; C3N4 with the aforementioned diameter range can achieve the purpose of the present invention.

[0039] In this invention, the range of solvents that can be selected for the dispersion is relatively wide, and commonly used solvents can all be used in this invention. For this invention, it is preferred that the solvent in the dispersion is selected from one or more of deionized water.

[0040] According to a preferred embodiment of the present invention, preferably, the dispersion in step (a) contains an auxiliary agent, preferably selected from one or more of acetic acid and ammonium acetate; more preferably, the content of the auxiliary agent is 0.1-10 mmol / L; thereby improving the selectivity of the catalyst.

[0041] According to a preferred embodiment of the present invention, drying is performed before calcination. Preferred calcination conditions include 300-500°C, such as 300°C, 350°C, 400°C, 450°C, and 500°C. The aforementioned calcination temperatures can all achieve the purpose of the present invention. In this embodiment of the present invention, 500°C is used as an example to illustrate the advantages of the present invention, but this does not limit the scope of the present invention.

[0042] In this invention, there are no special requirements for the roasting time, which can be 1-4 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours), preferably 2-3 hours.

[0043] In this invention, there are no special requirements for drying conditions, such as drying at 60-100°C, and no special requirements for drying time. The purpose is to dry as much liquid as possible, such as drying to a solid content of 95% by weight or more, and the drying time is generally 4-8 hours.

[0044] 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. For example, the carrier source is selected 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.

[0045] In this invention, the operating conditions in step (b) can be selected from a wide range. There are no special requirements in this invention. The following is an illustrative description, but it is not limited to the scope of this invention.

[0046] According to a preferred embodiment of the present invention, the operating conditions in step (b) include:

[0047] The solid-liquid volume ratio is 1:1-1.2. In the solution containing Pd source and Group IB metal source, the content of Pd is 1-12 g / L, preferably 2-3 g / L, based on elemental composition; the content of Group IB metal is 0.1-10 g / L, preferably 0.4-0.8 g / L.

[0048] In this invention, the range of possible conditions in step (c) is quite wide. Conditions commonly used in the art can all be used in this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to one embodiment of this invention, the conditions in step (c) include: the concentration of the alkaline compound solution is 10-30% by weight.

[0049] According to one embodiment of the present invention, the conditions in step (c) include: the volume ratio of the alkaline compound solution to the carrier is 0.05 to 0.5, preferably 0.07 to 0.1.

[0050] 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 (c), the alkaline compound includes, but is not limited to, one or more of sodium silicate and sodium hydroxide.

[0051] According to one embodiment of the present invention, the reducing agent used for reduction includes, but is not limited to, one or more of hydrazine hydrate and sodium citrate. There are no special requirements for the reduction conditions; commonly used reduction conditions are applicable to the present invention.

[0052] In this invention, steps (a) to (e) involve allowing the material to stand as needed, with the aim of ensuring sufficient contact.

[0053] In this invention, step (a) can optionally be left to stand for 12-48 hours as needed.

[0054] In this invention, step (c) can optionally be left to stand for 12-48 hours as needed.

[0055] In this invention, step (d) can optionally be left to stand for 3-6 hours as needed.

[0056] In this invention, step (e) can optionally be left to stand for 3-6 hours as needed.

[0057] In this invention, in steps (a)-(e), water washing is performed before drying as needed. The purpose of water washing is to remove impurity ions such as chloride ions.

[0058] In this invention, there are no special requirements for the conditions of reduction, optional washing, and drying. Common reduction, washing, and drying conditions can all be used in this invention. According to a 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.

[0059] This invention provides a method for preparing 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.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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 .

[0064] Unless otherwise specified, this invention is operated at room temperature.

[0065] Unless otherwise specified, the solvent of the solution in this invention is water.

[0066] The present invention will be described in detail below through embodiments. In the following embodiments,

[0067] The catalyst space-time yield (STY) and selectivity (SEL) are calculated as follows:

[0068] Let A be the amount of ethylene reacted in a day (kmol / d), B be the amount of oxygen reacted in a day, and X be the amount of ethylene consumed in the main reaction in a day.

[0069] X = (3A - B) / 2.5

[0070] STY = 86X / catalyst amount (m 3 )×1000

[0071] SEL = X / A × 100%.

[0072] Test method for Pd-N3 sites:

[0073] XPS spectra can be used for testing, with a focus on analyzing the peak positions of N atoms. N atoms in the Pd-N3 bond will concentrate on the 398-399 eV position. The proportion of this peak area represents the content of the Pd-N3 sites.

[0074] Example 1

[0075] 1. Catalyst Preparation

[0076] (a) The carrier (silica carrier, diameter 5 mm, specific surface area 175 μm) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous dispersion of C3N4 (where the concentration of C3N4 was 5wt% and the diameter of C3N4 was 5μm), allowed to stand for 24 hours, the solid-liquid volume ratio was 1:1.5, dried at 80℃ for 6 hours, and calcined at 500℃ for 2 hours to prepare catalyst precursor I.

[0077] (b) Take 1100 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid. Calculate the solid-liquid volume ratio as 1:1.2. The palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L. Then dry it at 80 °C for 8 hours to prepare catalyst precursor II.

[0078] (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;

[0079] (d) 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 IV.

[0080] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate 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.

[0081] 2. Catalyst Evaluation

[0082] The evaluation was conducted using a fixed-bed reactor, under the following conditions:

[0083] Catalyst loading volume: 40 ml;

[0084] Composition of reaction raw materials (in molar ratio): Oxygen: Ethylene: Nitrogen: Acetic acid = 1:6.8:7.5:1.8;

[0085] Reactant feed volume hourly space velocity: 1950 hr -1 ;

[0086] Reaction pressure: 0.7 MPa;

[0087] Reaction temperature: 134℃;

[0088] Reaction time: 100 hours;

[0089] 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.

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

[0091] Example 2

[0092] 1. Catalyst Preparation

[0093] (a) The carrier (silica carrier, diameter 5 mm, specific surface area 175 μm) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous dispersion of C3N4 (where the concentration of C3N4 was 11%wt and the diameter of C3N4 was 2 μm), allowed to stand for 24 hours, the solid-liquid volume ratio was 1:1.5, dried at 80℃ for 6 hours, and calcined at 500℃ for 2 hours to prepare catalyst precursor I.

[0094] (b) Take 1100 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid. Calculate the solid-liquid volume ratio as 1:1.2. The palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L. Then dry it at 80 °C for 8 hours to prepare catalyst precursor II.

[0095] (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;

[0096] (d) 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 IV.

[0097] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate 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.

[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 3

[0102] 1. Catalyst Preparation

[0103] (a) The carrier (silica carrier, diameter 5 mm, specific surface area 175 μm) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous dispersion of C3N4 (where the concentration of C3N4 was 20%wt and the diameter of C3N4 was 8 μm), allowed to stand for 24 hours, the solid-liquid volume ratio was 1:1.5, dried at 80℃ for 6 hours, and calcined at 500℃ for 2 hours to prepare catalyst precursor I.

[0104] (b) Take 1100 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid. Calculate the solid-liquid volume ratio as 1:1.2. The palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L. Then dry it at 80 °C for 8 hours to prepare catalyst precursor II.

[0105] (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;

[0106] (d) 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 IV.

[0107] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate 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.

[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 4

[0112] The method is the same as in Example 2, except that acetic acid is added to the dispersion at a concentration of 0.1 mmol / L.

[0113] Example 5

[0114] The method is the same as in Example 2, except that acetic acid is added to the dispersion at a concentration of 8.5 mmol / L.

[0115] Example 6

[0116] The method is the same as in Example 2, except that ammonium acetate is added to the dispersion at a concentration of 10 mmol / L.

[0117] Comparative Example 1

[0118] 1. Catalyst Preparation

[0119] (a) The carrier (silica carrier, diameter 5 mm, specific surface area 175 μm) 2 / g, pore volume 0.8cm 3 / g) was impregnated in an aqueous dispersion of C3N4 (where the concentration of C3N4 was 25wt%), allowed to stand for 24 hours, the solid-liquid volume ratio was 1:1.5, dried at 80℃ for 6 hours, and calcined at 500℃ for 2 hours to prepare catalyst precursor I.

[0120] (b) Take 1100 ml of catalyst precursor I and immerse it in a mixed aqueous solution of chloropalladic acid and chloroauric acid. Calculate the solid-liquid volume ratio as 1:1.2. The palladium content in the solution is 2.75 g / L and the gold content is 0.625 g / L. Then dry it at 80 °C for 8 hours to prepare catalyst precursor II.

[0121] (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;

[0122] (d) Add 60g of hydrazine hydrate with a concentration of 85wt% for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100℃ for 6 hours to obtain catalyst precursor IV.

[0123] (e) The catalyst precursor IV was impregnated with an aqueous solution of potassium acetate 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.

[0124] 2. Catalyst Evaluation

[0125] The catalyst evaluation method is the same as in Example 1.

[0126] For ease of comparison, the experimental results are listed in Table 1.

[0127] Comparative Example 2

[0128] 1. Catalyst Preparation

[0129] (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. Then it was dried at 80 °C for 8 hours to prepare catalyst precursor I.

[0130] (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;

[0131] (c) Add 60g of hydrazine hydrate with a concentration of 85wt% for reduction, let stand for 4 hours, then wash with deionized water, and dry at 100℃ for 6 hours to obtain catalyst precursor III.

[0132] (d) The catalyst precursor III was impregnated with an aqueous solution of potassium acetate 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.

[0133] 2. Catalyst Evaluation

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

[0135] For ease of comparison, the experimental results are listed in Table 1.

[0136] Table 1

[0137] Pd-N3 coverage on catalyst surface Catalyst space-time yield, g / L·hr Catalyst selectivity, % Example 1 2.4％ 448 94.5 Example 2 5.1％ 449 94.7 Example 3 9.8％ 443 94.4 Example 4 5.3％ 452 95.4 Example 5 5.8％ 458 95.9 Example 6 5.4％ 455 95.8 Comparative Example 1 11.8％ 383 93.0 Comparative Example 2 0 387 92.7

[0138] 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 preparing vinyl acetate, characterized in that, The catalyst has a surface Pd-N3 site coverage of 2% to 10%, and the catalyst includes a support and Pd, Group IB metal and alkali metal acetate supported on the support, wherein the Group IB metal is Au.

2. The catalyst according to claim 1, wherein, 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.

3. The catalyst according to claim 2, wherein, Alkali metal elements are selected from one or more of Na and K; and / or The carrier is selected from spherical silica.

4. The catalyst according to claim 3, wherein, 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.

5. The catalyst according to any one of claims 1-4, wherein, The Pd content is 1~12 g / L based on elemental composition.

6. The catalyst according to any one of claims 1-4, wherein, The amount of Au, measured as an element, is 0.1~10 g / L.

7. The catalyst according to any one of claims 1-4, wherein, The content of alkali metal acetate is 10~100g / L.

8. The catalyst according to any one of claims 1-4, wherein, The alkali metal acetate is potassium acetate.

9. A method for preparing the catalyst according to any one of claims 1-8, characterized in that, The method includes: (a) The support source was impregnated in a C3N4 dispersion and calcined to prepare catalyst precursor I; (b) Catalyst precursor I was immersed in a solution containing palladium and Group IB metals and dried to prepare catalyst precursor II; (c) Catalyst precursor II is treated with a solution of an alkaline compound and dried to obtain catalyst precursor III; (d) Reduce the noble metal ions of catalyst precursor III and dry them to obtain catalyst precursor IV; (e) Impregnate catalyst precursor IV with alkali metal acetate and dry.

10. The method according to claim 9, wherein, In step (a), The diameter of C3N4 in the C3N4 dispersion is 0.1~10 micrometers; and / or The C3N4 content in the C3N4 dispersion is 5-20 wt%; and / or The solvent in the dispersion is deionized water; and / or The solid-liquid volume ratio is 1:1 to 1.5; Dry before roasting; and / or The operating conditions in step (b) include: The solid-liquid volume ratio is 1:1-1.

2. In solutions containing palladium and Group IB metals, the content of Pd is 1~12 g / L and the content of Group IB metals is 0.1~10 g / L. and / or The conditions in step (c) 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. and / or In step (c), the alkaline compound is selected from one or more of sodium silicate and sodium hydroxide.

11. The method according to claim 10, wherein, The dispersion contains an auxiliary agent, which is selected from one or more of acetic acid and ammonium acetate; and / or Firing conditions include: 300-500℃; and / or The operating conditions in step (b) include: In solutions containing palladium and Group IB metals, the Pd content is 2-3 g / L (elementally); the Group IB metal content is 0.4-0.8 g / L; and / or The conditions in step (c) include: the volume ratio of the alkaline compound solution to the carrier source is 0.07 to 0.

1.

12. The method according to claim 11, wherein, The content of the auxiliary agent is 0.1-10 mmol / L.

13. A method for preparing vinyl acetate, wherein the feed 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 1-8.

14. The method according to claim 13, wherein, The raw materials for synthesizing vinyl acetate include oxygen, ethylene, nitrogen, and acetic acid.

15. The method according to claim 14, wherein, In terms of molar ratio, the molar ratio of oxygen, ethylene, nitrogen and acetic acid is 1:(5-7):(4-8):(1-2); 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 volumetric space velocity of the feed gas is 1600–3000 hr. -1 .