Synthesis methods of vinyl acetate, catalysts for vinyl acetate synthesis and their preparation methods

Abstract

This invention discloses a method for synthesizing vinyl acetate, a catalyst for the synthesis of vinyl acetate, and a method for preparing the catalyst. The catalyst includes a support and Pd, Group IB metal, and alkali metal acetates supported on the support. The ratio of the content of strongly acidic sites to the content of weakly acidic sites on the catalyst surface is 0.15–5, preferably 0.2–4. This invention can effectively improve the space-time yield of vinyl acetate and the selectivity of the vinyl acetate synthesis reaction.

Description

Technical Field

[0001] This invention relates to a catalyst for synthesizing vinyl acetate, its preparation method, and a method for synthesizing vinyl acetate. Background Technology

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

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

[0004] Currently, the raw materials used in the industrial synthesis of vinyl acetate via the ethylene process are mainly oxygen, ethylene, acetic acid, and some nitrogen, as exemplified by the patent CN101391215A of Saudi Basic Industries. The catalysts in these methods have low selectivity. Therefore, to address the above issues, we have developed a novel vinyl acetate catalyst that effectively solves the problem of low catalyst selectivity. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of low catalyst selectivity in the prior art and to provide a novel vinyl acetate catalyst and a method for synthesizing vinyl acetate, which has high space-time yield and target analyte selectivity.

[0006] To achieve the above objectives, the present invention provides a catalyst for synthesizing vinyl acetate, the catalyst comprising a support and Pd, Group IB metal and alkali metal acetates supported on the support, wherein the ratio of the content of strong acid sites to the content of weak acid sites on the catalyst surface is 0.15 to 5, preferably 0.2 to 4.

[0007] A second aspect of the present invention provides a method for preparing the catalyst for synthesizing vinyl acetate according to the present invention, the method comprising:

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

[0009] (b) Catalyst precursor I was mixed and contacted with a solution of an alkaline compound and dried to obtain catalyst precursor II;

[0010] (c) Reduce the metal ions of catalyst precursor II and dry them to obtain catalyst precursor III;

[0011] (d) Impregnate catalyst precursor III with alkali metal acetate and dry to obtain catalyst precursor IV;

[0012] (e) The catalyst precursor IV is impregnated in an aqueous solution containing phosphoric acid and dried to obtain the finished catalyst.

[0013] A third aspect of the present invention provides a method for synthesizing vinyl acetate, wherein a gaseous material 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 the present invention.

[0014] The above technical solutions can effectively improve the space-time yield of vinyl acetate and the selectivity of vinyl acetate synthesis reaction. Detailed Implementation

[0015] 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.

[0016] In this invention, the composition of each substance in the catalyst is obtained by calculation based on the amount of feed.

[0017] In this invention, the Group IB metals in the catalyst mainly exist in elemental form.

[0018] In this invention, Pd mainly exists in elemental form.

[0019] The present invention provides a catalyst for synthesizing vinyl acetate, the catalyst comprising a support and Pd, Group IB metal and alkali metal acetate supported on the support, wherein the ratio of the content of strong acid sites to the content of weak acid sites on the catalyst surface is 0.15 to 5, preferably 0.2 to 4.

[0020] 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.

[0021] According to one embodiment of the present invention, the Pd content, calculated by element, is 1–12 g / L, preferably 1–5 g / L; for example, 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L, 2.0 g / L, 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. The concentrations of these concentrations are 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, 4.0 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, and 5 g / L. This allows for improved catalyst selectivity.

[0022] According to one embodiment of the present invention, the content of Group IB metals, calculated by element, is 0.1–10 g / L, preferably 0.2–3 g / L; for example, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L, 1.1 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L, 2 g / L, 2.1 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.

[0023] According to one embodiment of the present invention, the catalyst contains a phosphoric acid-containing substance, preferably one or more of phosphoric acid and phosphorous acid. This allows for improved selectivity of the catalyst.

[0024] According to one embodiment of the present invention, preferably, the content of the phosphoric acid-containing substance is 5-500 mmol / L, more preferably 10-300 mmol / L. This can improve the selectivity of the catalyst.

[0025] According to one embodiment of the present invention, the catalyst more preferably contains a phosphate salt promoter, wherein the phosphate salt promoter is selected from one or more of sodium phosphate and potassium phosphate. This allows for improved selectivity of the catalyst.

[0026] According to one embodiment of the present invention, preferably, the molar ratio of the phosphate salt auxiliary to the phosphoric acid-containing substance is 0.005 to 0.5, more preferably 0.01 to 0.1. This can improve the selectivity of the catalyst.

[0027] According to one embodiment of the present invention, the content of alkali metal acetate is 10-100 g / L, preferably 20-50 g / L, for example 20 g / L, 30 g / L, 40 g / L, or 40 g / L. This enables the catalyst to achieve improved selectivity.

[0028] 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.

[0029] According to one embodiment of the present invention, the preferred Group IB metal is Au and / or Cu, with Au being more preferred.

[0030] 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.

[0031] 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, the present 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.

[0032] 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:

[0033] (a) The catalyst support source is immersed in a solution containing a palladium source and a group IB metal source, and then dried to obtain catalyst precursor I;

[0034] (b) Catalyst precursor I was mixed and contacted with a solution of an alkaline compound and dried to obtain catalyst precursor II;

[0035] (c) Reduce the metal ions of catalyst precursor II and dry them to obtain catalyst precursor III;

[0036] (d) Impregnate catalyst precursor III with alkali metal acetate and dry to obtain catalyst precursor IV;

[0037] (e) The catalyst precursor IV is impregnated in an aqueous solution containing phosphoric acid and dried to obtain the finished catalyst.

[0038] In this invention, the range of phosphoric acid-containing substances that can be selected in step (e) is relatively wide. The following is an illustrative description, but it is not intended to limit the scope of this invention. According to one embodiment of this invention, in step (e), the phosphoric acid-containing substance is a phosphoric oxyacid, preferably one or more of phosphoric acid and phosphorous acid. This can improve the selectivity of the catalyst.

[0039] According to a preferred embodiment of the present invention, step (e) is preferably carried out in the presence of an additive, preferably, the phosphate salt additive is selected from one or more of sodium phosphate and potassium phosphate, preferably the molar ratio of the amount of phosphate salt additive to the amount of phosphoric acid-containing substance is 0.005 to 0.5, more preferably 0.01 to 0.1; thereby improving the selectivity of the catalyst.

[0040] In this invention, the concentration of the phosphoric acid solution in step (e) can be selected from 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 the phosphoric acid in the aqueous solution is 5 to 500 mmol / L, preferably 10 to 200 mmol / L, 10 mmol / L, 15 mmol / L, 100 mmol / L, 185 mmol / L, or 200 mmol / L.

[0041] In this invention, the solid-liquid volume ratio in step (e) can be selected from a wide range. The following is an illustrative example, but it is not limited to the scope of this invention. Preferably, the solid-liquid volume ratio is 1:1 to 1:1.5. In this invention, a solid-liquid volume ratio of 1.5 is used as an example to illustrate the advantages of this invention.

[0042] In this invention, there are no special requirements for the immersion time in step (e), as long as sufficient immersion is achieved.

[0043] In this invention, there are no special requirements for the drying conditions in step (e). Commonly used drying conditions are applicable to this invention and will not be described in detail here. For example, drying is generally done at 40-60°C, and there are no special requirements for the drying time.

[0044] According to one embodiment of the present invention, the conditions in step (a) include: a solid-liquid volume ratio of 1:1 to 1:1.2. In this invention, a solid-liquid volume ratio of 1.2 is used as an example to illustrate the advantages of the present invention.

[0045] According to one embodiment of the present invention, the conditions in step (a) include: in the solution containing a Pd source and a Group IB metal source, the content of Pd, calculated by element, is 1 to 12 g / L, preferably 2 to 3 g / L.

[0046] According to one embodiment of the present invention, the conditions in step (a) include: the content of Group IB metals is 0.1 to 10 g / L, preferably 0.4 to 0.8 g / L.

[0047] 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.

[0048] In this invention, the range of possible conditions in step (b) 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 (b) 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 (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.

[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 (b), the alkaline compound includes, but is not limited to, one or more of sodium silicate and sodium hydroxide. According to this invention, sodium silicate is preferred.

[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.

[0052] 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.

[0053] In this invention, in step (d), catalyst precursor III is impregnated with alkali metal acetate and dried to obtain catalyst precursor IV; there are no special requirements for the impregnation conditions, and it can be carried out with reference to the prior art, for example, a solid-liquid volume ratio of 1:1 to 1.2; the concentration of alkali metal acetate in the impregnation solution is, for example, 5-50 g / L.

[0054] In this invention, the purpose of drying is to remove liquid substances from the solid. Generally, drying results in a solid content of 95 wt% or more.

[0055] In this invention, a wide range of alkali metal acetates can be selected, such as potassium acetate.

[0056] 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.

[0057] In this invention, step (a) can optionally be left to stand for 0.5-3 hours as needed.

[0058] In this invention, step (b) can optionally be left to stand for 12-24 hours as needed.

[0059] In this invention, step (c) can optionally be left to stand for 3-6 hours as needed.

[0060] In this invention, step (d) can optionally be left to stand for 3-6 hours as needed.

[0061] In this invention, step (e) can optionally be left to stand for 3-6 hours as needed.

[0062] 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.

[0063] 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.

[0064] 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).

[0065] 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.

[0066] According to a preferred embodiment of the present invention, the conditions for the gas-phase catalytic synthesis reaction include: a reaction temperature of 130 to 200°C, for example, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C.

[0067] 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 .

[0068] Unless otherwise specified, this invention is operated at room temperature.

[0069] Unless otherwise specified, the solvent of the solution in this invention is water.

[0070] In this invention, the method for testing acidic sites on the catalyst surface is as follows:

[0071] Acidic sites on the catalyst surface can be detected using NH3-TPD. The desorption temperature of NH3-TPD represents the strength of the acidic sites; desorption at low temperatures represents weak acidic sites, while desorption at high temperatures represents strong acidic sites. The peak area represents the amount of acidic sites. The ratio of strong acid to weak acidic sites is calculated based on the area ratio of the desorption peaks (strong acidic sites) at temperatures >400℃ and <400℃ (weak acidic sites).

[0072] The test conditions for NH3-TPD were as follows: the sample was first purged with helium at 50°C for 30 minutes (space velocity of 300 ml / min), then purged with NH3 for 2 hours (space velocity of 300 ml / min), and then the temperature was increased by gradient (heating rate of 5°C / min). The temperature range for the test was 100-750°C.

[0073] The catalyst space-time yield (STY) and selectivity (SEL) are calculated as follows:

[0074] 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.

[0075] X = (3A - B) / 2.5.

[0076] STY = 86X / catalyst amount (m 3 )×1000.

[0077] SEL = X / A × 100%.

[0078] Example 1

[0079] 1. Catalyst Preparation

[0080] (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 calculated according to a solid-liquid volume ratio of 1:1.2, wherein the palladium content in the solution used was 2.75 g / L and the gold content was 0.625 g / L, and dried at 60℃ for 8 h to obtain catalyst precursor I;

[0081] (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;

[0082] (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.

[0083] (d) The catalyst precursor III was impregnated with an aqueous solution of potassium acetate (potassium acetate content of 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain the catalyst precursor IV.

[0084] (e) The catalyst precursor IV was impregnated in an aqueous phosphoric acid solution (phosphoric acid concentration of 10 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0085] 2. Catalyst Evaluation

[0086] The evaluation was conducted using a fixed-bed reactor, under the following conditions:

[0087] Catalyst loading volume: 40 ml;

[0088] Composition of reaction raw materials (in molar ratio): Oxygen: Ethylene: Nitrogen: Acetic acid = 1:6.5:7.4:1.6;

[0089] Reactant feed volume hourly space velocity: 1950 hr -1 ;

[0090] Reaction pressure: 0.7 MPa;

[0091] Reaction temperature: 138℃;

[0092] Reaction time: 100 hours;

[0093] 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.

[0094] For ease of comparison, the experimental results are listed in Table 1.

[0095] Example 2

[0096] 1. Catalyst Preparation

[0097] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0098] (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;

[0099] (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.

[0100] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) for 6 hours, with a solid-liquid volume ratio of 1, and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0101] (e) The catalyst precursor IV was impregnated in an aqueous phosphoric acid solution (phosphoric acid concentration of 100 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0102] 2. Catalyst Evaluation

[0103] The catalyst evaluation method is the same as in Example 1.

[0104] For ease of comparison, the experimental results are listed in Table 1.

[0105] Example 3

[0106] 1. Catalyst Preparation

[0107] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0108] (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;

[0109] (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.

[0110] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0111] (e) The catalyst precursor IV was impregnated in an aqueous phosphoric acid solution (phosphoric acid concentration of 200 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0112] 2. Catalyst Evaluation

[0113] The catalyst evaluation method is the same as in Example 1.

[0114] For ease of comparison, the experimental results are listed in Table 1.

[0115] Example 4

[0116] 1. Catalyst Preparation

[0117] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0118] (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;

[0119] (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.

[0120] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0121] (e) The catalyst precursor IV was impregnated in an aqueous solution of phosphorous acid (phosphoric acid concentration of 100 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0122] 2. Catalyst Evaluation

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

[0124] For ease of comparison, the experimental results are listed in Table 1.

[0125] Example 5

[0126] 1. Catalyst Preparation

[0127] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0128] (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;

[0129] (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.

[0130] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0131] (e) The catalyst precursor IV was impregnated in an aqueous solution of phosphorous acid (phosphoric acid concentration of 185 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0132] 2. Catalyst Evaluation

[0133] The catalyst evaluation method is the same as in Example 1.

[0134] For ease of comparison, the experimental results are listed in Table 1.

[0135] Example 6

[0136] 1. Catalyst Preparation

[0137] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0138] (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;

[0139] (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.

[0140] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0141] (e) The catalyst precursor IV was impregnated in an aqueous solution of phosphorous acid (phosphoric acid concentration of 15 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0142] 2. Catalyst Evaluation

[0143] The catalyst evaluation method is the same as in Example 1.

[0144] For ease of comparison, the experimental results are listed in Table 1.

[0145] Example 7

[0146] 1. Catalyst Preparation

[0147] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0148] (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;

[0149] (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.

[0150] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0151] (e) The catalyst precursor IV was impregnated in a mixed aqueous solution of phosphoric acid and sodium phosphate (phosphoric acid concentration of 100 mmol / L and sodium phosphate concentration of 10 mmol / L) for 24 hours with a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0152] 2. Catalyst Evaluation

[0153] The catalyst evaluation method is the same as in Example 1.

[0154] For ease of comparison, the experimental results are listed in Table 1.

[0155] Example 8

[0156] 1. Catalyst Preparation

[0157] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0158] (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;

[0159] (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.

[0160] (d) Catalyst precursor III was impregnated with potassium acetate aqueous solution (potassium acetate content was 30 g / L) for 6 hours, with a solid-liquid volume ratio of 1, and dried at 80°C for 2 hours to obtain catalyst precursor IV.

[0161] (e) The catalyst precursor IV was impregnated in a mixed aqueous solution of phosphoric acid and potassium phosphate (phosphoric acid concentration of 100 mmol / L and sodium phosphate concentration of 1 mmol / L) for 24 hours at a solid-liquid volume ratio of 1:1.5, and then dried at 50 °C to obtain the finished catalyst.

[0162] 2. Catalyst Evaluation

[0163] The catalyst evaluation method is the same as in Example 1.

[0164] For ease of comparison, the experimental results are listed in Table 1.

[0165] Comparative Example 1

[0166] 1. Catalyst Preparation

[0167] (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. Based on 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 drying at 60 °C for 8 h, catalyst precursor I was obtained.

[0168] (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;

[0169] (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.

[0170] (d) The catalyst precursor III was impregnated with an aqueous solution of potassium acetate (potassium acetate content of 30 g / L) at a solid-liquid volume ratio of 1 for 6 hours and dried at 80°C for 2 hours to obtain the finished catalyst, so that the potassium acetate content in the catalyst is 30 g / L.

[0171] 2. Catalyst Evaluation

[0172] The catalyst evaluation method is the same as in Example 1.

[0173] For ease of comparison, the experimental results are listed in Table 1.

[0174] Table 1

[0175]

[0176] 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 synthesizing vinyl acetate, characterized in that, The catalyst comprises a support and Pd, Group IB metal and alkali metal acetate supported on the support, wherein the ratio of the content of strong acid sites to the content of weak acid sites on the catalyst surface is 0.2 to 5. The catalyst contains phosphoric acid-containing substances. The acidic sites on the catalyst surface were detected by NH3-TPD. The ratio of strong acid to weak acid sites was calculated based on the area ratio of the desorption peak at >400℃ and the desorption peak at <400℃. The desorption peak at >400℃ represents strong acid sites, and the desorption peak at <400℃ represents weak acid sites.

2. The catalyst according to claim 1, wherein, The ratio of strongly acidic sites to weakly acidic sites on the catalyst surface is 0.2 to 4; and / or The Pd content is 1~12 g / L based on elemental composition.

3. The catalyst according to claim 2, wherein, The Pd content is 1~5 g / L based on elemental composition.

4. The catalyst according to any one of claims 1-3, wherein, The content of Group IB metals, on an elemental basis, is 0.1~10 g / L; and / or Group IB metals are Au and / or Cu; and / or Phosphoric acid-containing substances are one or more of phosphoric acid and phosphorous acid.

5. The catalyst according to claim 4, wherein, The content of Group IB metals, on an elemental basis, is 0.2-3 g / L; and / or Group IB metals are Au; and / or The content of phosphoric acid substances is 5~500 mmol / L.

6. The catalyst according to claim 5, wherein, The content of phosphoric acid substances is 10~300 mmol / L; and / or The catalyst contains a phosphorus salt promoter, which is selected from one or more of sodium phosphate and potassium phosphate.

7. The catalyst according to claim 6, wherein, The molar ratio of phosphate salt auxiliaries to phosphoric acid-containing substances is 0.005~0.

5.

8. The catalyst according to claim 7, wherein, The molar ratio of phosphate salt auxiliaries to phosphoric acid-containing substances is 0.01~0.

1.

9. The catalyst according to any one of claims 1-3, wherein, The content of alkali metal acetate is 10~100g / L.

10. The catalyst according to claim 9, wherein, The content of alkali metal acetate is 20~50g / L.

11. The catalyst according to any one of claims 1-3, 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.

12. The catalyst according to claim 11, wherein, Alkali metal elements are selected from one or more of Na and K; and / or The carrier is selected from spherical silica.

13. The catalyst according to claim 12, 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.

14. A method for preparing a catalyst for the synthesis of vinyl acetate according to any one of claims 1-5, characterized in that, The method includes: (a) The catalyst support source is immersed in a solution containing a palladium source and a group IB metal source, and then dried to obtain catalyst precursor I; (b) Catalyst precursor I was mixed and contacted with a solution of an alkaline compound and dried to obtain catalyst precursor II; (c) Reduce the metal ions of catalyst precursor II and dry them to obtain catalyst precursor III; (d) Impregnate catalyst precursor III with alkali metal acetate and dry to obtain catalyst precursor IV; (e) The catalyst precursor IV is impregnated in an aqueous solution containing phosphoric acid and dried to obtain the finished catalyst.

15. The method according to claim 14, wherein, In step (e), Phosphoric substances are phosphoric oxyacids; and / or In aqueous solutions containing phosphoric acid, the concentration of phosphoric acid is 5-500 mmol / L; and / or The solid-liquid volume ratio is 1:1-1.

5.

16. The method according to claim 15, wherein, The phosphoric acid-containing substance is one or more of phosphoric acid and phosphorous acid; and / or Step (e) is carried out in the presence of a phosphate salt auxiliary; and / or In aqueous solutions containing phosphoric acid, the concentration of phosphoric acid is 10-200 mmol / L.

17. The method according to claim 16, wherein, The phosphate salt auxiliary is selected from one or more of sodium phosphate and potassium phosphate; and / or The molar ratio of the amount of phosphate salt adjuvant to the amount of phosphoric acid-containing substance is 0.005~0.

5.

18. The method according to claim 17, wherein, The molar ratio of the amount of phosphate salt adjuvant to the amount of phosphoric acid-containing substance is 0.01~0.

1.

19. The preparation method according to any one of claims 14-18, wherein, The conditions in step (a) include: a solid-liquid volume ratio of 1:1-1.2, and in the solution containing Pd source and Group IB metal source, the content of Pd is 1~12 g / L and the content of Group IB metal is 0.1~10 g / L. In step (a), the carrier source is selected from one or more of silica and alumina; 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. and / or In step (b), the alkaline compound is selected from one or more of sodium silicate and sodium hydroxide.

20. The preparation method according to claim 19, 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 The carrier source is selected from spherical silica; 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.

21. The preparation method according to claim 20, 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.

22. 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 includes the catalyst described in any one of claims 1-13.

23. The synthesis method according to claim 22, 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 .

24. The synthesis method according to claim 23, wherein, The molar ratio of oxygen, ethylene, nitrogen and acetic acid is 1:(5-7):(4-8):(1-2).

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