Method for producing catalyst for vinyl acetate production and method for producing vinyl acetate

Abstract

The present invention provides a method for producing a catalyst that makes it possible to produce vinyl acetate with improved selectivity while ensuring high catalytic activity. Provided is a method for producing a catalyst that is for vinyl acetate production and that contains a carrier, palladium, gold, copper, and an acetate, said method comprising: step 1, which is for impregnating an alkaline solution into the carrier; step 2, which is for causing a solution containing a compound that includes palladium, a compound that includes gold, and a compound that includes copper to come into contact with and impregnate the carrier; step 5, which is for performing a liquid phase reduction treatment in the range of 0-15°C; and step 6, which is for causing the carrier to support the acetate.

Description

Method for producing a catalyst for producing vinyl acetate and method for producing vinyl acetate

[0001] The present disclosure relates to a method for producing a catalyst for producing vinyl acetate, which is used in producing vinyl acetate from acetic acid, ethylene, and oxygen as raw materials, and a method for producing vinyl acetate using the catalyst.

[0002] Vinyl acetate is an important industrial material that is used in a wide range of fields, such as paints, adhesives, and fiber treatment agents, as a raw material for vinyl acetate resins, a raw material for polyvinyl alcohol, and as a copolymerization monomer with ethylene, styrene, acrylates, methacrylates, etc.

[0003] Catalysts in which palladium, gold, and potassium acetate are supported on silica are widely used as catalysts for producing vinyl acetate from acetic acid, ethylene, and oxygen. Palladium is thought to be the active site in this reaction, and gold not only inhibits palladium aggregation but also reduces the production of carbon dioxide, a by-product, thereby improving the selectivity for vinyl acetate. For this effect of gold to be realized, the gold atoms must be present in close proximity to the palladium. In Patent Document 1, the impregnation process on the support is devised to support the palladium and gold in such a way that their supported sites are close to each other.

[0004] In the production of vinyl acetate, increasing the selectivity of vinyl acetate is an important technical challenge, and from the viewpoint of environmental load, suppressing the generation of carbon dioxide gas is also desired.

[0005] In Patent Document 2, the selectivity for vinyl acetate is improved by supporting copper in addition to palladium and gold.

[0006] In Patent Document 3, in a method for producing a catalyst containing palladium, gold, and copper, a palladium-containing compound, a gold-containing compound, and a copper-containing compound are supported on a carrier in the same process, thereby improving the selectivity for vinyl acetate.

[0007] Japanese Patent Application Laid-Open No. 2008-080326 Japanese Patent Application Laid-Open No. 2002-516749 International Publication No. 2022 / 113429

[0008] In Patent Document 3, an alkaline component is loaded onto a carrier, and then the carrier is impregnated with a solution containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound in the same process. Each compound is then hydrolyzed, resulting in the loading of palladium hydroxide, gold hydroxide, and copper hydroxide onto the carrier. Gold-containing compounds, such as chloroauric acid, generally undergo slow hydrolysis and are loaded onto the carrier at a slow rate. Therefore, even if a palladium-containing compound and a gold-containing compound are contacted with an alkaline component-loaded carrier in the same process, the difference in the hydrolysis rates of palladium and gold can result in the generation of gold atoms that are not adjacent to palladium, or the gold-containing compound remaining in the solution can aggregate and coarsen, forming aggregates of gold particles. However, if a copper-containing compound is present during the hydrolysis of the gold-containing compound, the copper-containing compound is rapidly hydrolyzed and loaded onto the carrier. Subsequently, the gold-containing compound is adsorbed onto the hydrolyzate of the copper-containing compound loaded onto the carrier, thereby increasing the hydrolysis rate of the gold-containing compound. Therefore, compared to when no copper-containing compound is added in the same process, gold can be supported in close proximity to palladium and coarsening of gold particles in solution can be suppressed, resulting in improved vinyl acetate selectivity. However, since aggregation of gold particles is observed even in catalysts produced by this method, further improvement in catalyst performance can be expected if gold aggregation can be further improved in the hydrolysis and reduction steps of catalyst production.

[0009] The present disclosure provides a method for producing a catalyst capable of producing vinyl acetate with improved selectivity while ensuring high catalytic activity.

[0010] As a result of extensive research into solving the above problems, the present inventors have discovered a method for producing a catalyst comprising supporting a compound containing palladium, gold, and copper on a carrier while reacting the compound with an alkaline component, and then carrying out a liquid-phase reduction treatment in a temperature range of 0°C to 15°C, and have succeeded in producing vinyl acetate with improved selectivity.

[0011] That is, the present disclosure encompasses the following [1] to [9]. [1] A method for producing a catalyst for vinyl acetate production, comprising a support, palladium, gold, copper, and an acetate salt, comprising: Step 1. Impregnating a support with an alkaline solution; Step 2. Contacting and impregnating the support with a solution containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound; Step 5. Performing a liquid-phase reduction treatment at a temperature ranging from 0°C to 15°C; and Step 6. Supporting an acetate salt on the support. [2] The method according to [1], further comprising, between Steps 2 and 5: Step 3. Separating the support from the solution of Step 2 when the desired amounts of each catalyst component have been supported on the support. [3] The method according to [2], further comprising, between Steps 3 and 5: Step 4. Contacting the support with water or an aqueous solution having a pH of 7.0 to 11.5. [4] The production method according to any one of [1] to [3], wherein the mass of the supported metallic palladium per 1 kg of the support is 5.00 g to 20.0 g. [5] The production method according to any one of [1] to [4], wherein the mass of the supported metallic gold per 1 kg of the support is 4.00 g to 20.0 g. [6] The production method according to any one of [1] to [5], wherein the mass of the supported metallic copper per 1 kg of the support is 0.25 g to 5.00 g. [7] The production method according to any one of [1] to [6], wherein the mass of the supported acetate salt per 1 kg of the support is 40 g to 125 g. [8] The production method according to any one of [1] to [7], wherein the mass ratio of palladium to gold to copper is 100:70 to 130:8.3 to 9.5. [9] A production method for vinyl acetate using a catalyst for vinyl acetate production obtained by the method according to any one of [1] to [8], and using ethylene, oxygen, and acetic acid as raw materials.

[0012] According to the method of the present disclosure, it is possible to significantly improve the selectivity for vinyl acetate while ensuring high catalytic activity, as compared with conventional methods.

[0013] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments and various modifications are possible within the scope of the present invention. In this disclosure, when "to" is used to describe a numerical range, the numerical values ​​at both ends are the upper and lower limits, respectively, and are included in the numerical range. When multiple upper or lower limits are listed, numerical ranges can be created from all combinations of the upper and lower limits. Similarly, when multiple numerical ranges are listed, separate numerical ranges can be created by individually selecting and combining upper and lower limits from those numerical ranges.

[0014] [Method for Producing a Catalyst for Vinyl Acetate Production] In one embodiment, a method for producing a catalyst for vinyl acetate production comprises the steps shown below, preferably in the following order. Palladium, gold, and copper are referred to as the "catalyst components," and a palladium-containing compound, a gold-containing compound, and a copper-containing compound may be collectively referred to as the "raw material compound," or each metal may be referred to as the "raw material compound." Steps 3 and 4 are optional steps that are preferably performed. Step 1: Impregnating a carrier with an alkaline solution; Step 2: Contacting and impregnating a carrier with a solution containing palladium, gold, and copper as catalyst components, a palladium-containing compound, a gold-containing compound, and a copper-containing compound (hereinafter referred to as "solution A"); Step 3: Separating the carrier from solution A when the desired amounts of each catalyst component have been supported on the carrier (draining step); Step 4: Contacting the carrier with water or an aqueous solution having a pH of 7.0 to 11.5 (buffer step); Step 5: Performing a liquid-phase reduction treatment in the range of 0°C to 15°C; Step 6: Supporting acetate on a carrier

[0015] In one embodiment, step 2 is carried out after step 1, in which a support is contact-impregnated with solution A containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound to form a catalyst precursor in which the reaction products of these compounds with an alkaline compound are supported on the support. In step 2, the amounts of the palladium-containing compound, the gold-containing compound, and the copper-containing compound in solution A are preferably in excess of the desired supported amounts of each catalyst component.

[0016] Steps 1 to 6 are performed in the above order, but other steps may be included for the purpose of improving the performance of the catalyst, for example. For example, a step of washing the support with water after step 5 may be included. The liquid-phase reduction treatment in step 5 is a treatment for converting the reaction products of the raw material compound with the alkaline compound into metallic palladium, metallic gold, and metallic copper, respectively, and therefore must be performed after step 2 or 3. Exceptionally, steps 5 and 6 may be interchanged. Each step will be described in detail below.

[0017] <Step 1: Impregnating the carrier with an alkaline solution> In this step, the carrier is impregnated with an alkaline solution. This step can be performed at room temperature. After the impregnation operation is completed, the carrier may be dried, or the carrier may proceed to the next step without drying or other operations.

[0018] The carrier is not particularly limited, and any porous material generally used as a catalyst carrier can be used. The carrier is preferably silica, alumina, silica-alumina, diatomaceous earth, montmorillonite, or titania, and more preferably silica. When a material containing silica as a main component is used as the carrier, the silica content of the carrier is usually at least 50 mass %, and preferably at least 90 mass %, based on the mass of the carrier.

[0019] The support has a specific surface area of ​​at least 1 m2 as measured by the BET method. ２ / g, and 10 to 1000m ２ / g, and more preferably in the range of 100 to 500m ２ / g is particularly preferred. The bulk density of the support is preferably in the range of 50 to 1000 g / L, and particularly preferably in the range of 400 to 500 g / L. The water absorption of the support is preferably in the range of 0.05 to 3 g-water / g-support, and particularly preferably in the range of 0.1 to 2 g-water / g-support. With regard to the pore structure of the support, the average pore diameter is preferably in the range of 1 to 1000 nm, and particularly preferably in the range of 2 to 800 nm. An average pore diameter of 1 nm or more can facilitate gas diffusion. On the other hand, an average pore diameter of 1000 nm or less can ensure the specific surface area of ​​the support necessary to obtain catalytic activity.

[0020] Mercury porosimetry and gas adsorption (BJH) method are widely used to measure the pore size distribution of supports. According to the pore classification of IUPAC (International Union of Pure and Applied Chemistry), mercury porosimetry can measure macropores of 50 nm or more and some mesopores of 2 nm to less than 50 nm, while gas adsorption can measure mesopores and micropores of 2 nm or less. An appropriate measurement method can be selected depending on the pore diameter.

[0021] In this disclosure, the water absorption rate of a carrier refers to a value measured using the following measurement method. 1. Approximately 5 g of carrier is weighed (W1 g) on ​​a balance and placed in a 100 mL beaker. 2. Approximately 15 mL of pure water (ion-exchanged water) is added to the beaker so that the carrier is completely covered. 3. Leave for 30 minutes. 4. The contents of the beaker are placed on a 1 mm mesh wire screen and the pure water is drained. 5. The water adhering to the surface of the carrier is removed by gently pressing with a paper towel until the surface is no longer glossy. 6. The total mass of the carrier and pure water is measured (W2 g). 7. The water absorption rate of the carrier is calculated using the following formula: Water absorption rate (g-water / g-carrier) = (W2 - W1) / W1 Therefore, the amount of water absorption (g) of the carrier is calculated by multiplying the water absorption rate of the carrier (g-water / g-carrier) by the mass (g) of the carrier used.

[0022] The shape of the carrier is not particularly limited. Specific examples include, but are not limited to, powder, spheres, and pellets. The optimal shape can be selected depending on the reaction type, reactor, etc. used.

[0023] There are no particular limitations on the particle size of the support. When the support is spherical, the particle diameter is preferably in the range of 1 to 10 mm, more preferably in the range of 3 to 8 mm. When a tubular reactor is filled with a catalyst to carry out a gas-phase reaction, a particle diameter of 1 mm or more can prevent an excessive increase in pressure loss during gas flow and enable effective gas circulation. On the other hand, a particle diameter of 10 mm or less can facilitate diffusion of the raw material gas into the catalyst interior, allowing the catalytic reaction to proceed effectively. Furthermore, since the number of catalyst particles filled into the tubular reactor is not excessively reduced, a total surface area of ​​the catalyst particles sufficient to ensure that the metal components (palladium, gold, copper, etc.) dispersed on the surface of the support are in an amount appropriate for the reaction can be secured.

[0024] The alkaline solution may be a solution of any alkaline compound. Examples of alkaline compounds include hydroxides of alkali metals or alkaline earth metals, bicarbonates of alkali metals or alkaline earth metals, carbonates of alkali metals or alkaline earth metals, and silicates of alkali metals or alkaline earth metals. Examples of alkali metals that can be used include lithium, sodium, or potassium. Examples of alkaline earth metals that can be used include barium or strontium. Examples of alkaline compounds that can be used include sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, barium hydroxide, and strontium hydroxide.

[0025] The solvent for the alkaline solution is not particularly limited, and examples thereof include water, methanol, and ethanol, with water being preferred.

[0026] The alkaline compound is used in excess relative to the total amount of palladium, gold, and copper described below. For example, the product of the molar amount of the alkaline compound and the valence of the alkaline compound is preferably more than 1.1 times and not more than 3.0 times, more preferably more than 1.5 times and not more than 2.0 times, the sum of the product of the molar amount of palladium element contained in the palladium-containing compound and the valence of palladium, the product of the molar amount of gold element contained in the gold-containing compound and the valence of gold, and the product of the molar amount of copper element contained in the copper-containing compound and the valence of copper.

[0027] There are no particular limitations on the method for impregnating the carrier with the alkaline solution. Examples include (I) a method in which the carrier is immersed in a large amount of alkaline solution for a while, and then the carrier is taken out after being impregnated with the alkaline solution in an amount corresponding to the amount of water absorbed, and (II) a method in which an alkaline compound is dissolved in a solvent, and the solution is made up to a volume equivalent to the amount of water absorbed by the carrier, and the carrier is then impregnated with the solution. From the viewpoint of waste liquid treatment, method (II) is preferred.

[0028] The alkaline solution is preferably impregnated into the carrier in an amount equivalent to 0.9 to 1.0 times the water absorption of the carrier by mass, and more preferably 0.95 to 1.0 times the water absorption of the carrier by mass. If the amount of alkaline solution is 0.9 times or more the water absorption of the carrier, uneven impregnation of the alkaline solution is unlikely to occur. If the amount of alkaline solution is 1.0 times or less the water absorption of the carrier by mass, the entire amount of alkaline solution can be reliably absorbed into the carrier. In the present disclosure, the water absorption of the carrier is a value measured using pure water, which is strictly different from the value for the alkaline solution, but for convenience it is used as is.

[0029] <Step 2: Step of contact-impregnating the support with solution A> In this step, the support impregnated with the alkaline solution is contact-impregnated with solution A. Solution A is a solution containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound. Solution A may contain other components as necessary.

[0030] The amounts of the raw material compounds (palladium-containing compound, gold-containing compound, and copper-containing compound) contained in solution A may be equal to the desired catalyst composition, i.e., the amounts of the catalyst components (metallic palladium, metallic gold, and metallic copper) supported in the final catalyst. However, it is preferable to charge an excess amount of each raw material compound (palladium-containing compound, gold-containing compound, and copper-containing compound) relative to the amount of the catalyst components in the final catalyst. That is, the raw material compounds are dissolved in amounts calculated by multiplying the amount of raw material compound corresponding to the desired amount of catalyst component supported by the respective excess rates so that each of the palladium-containing compound, gold-containing compound, and copper-containing compound is in excess relative to the desired amount of catalyst component supported. The concentrations of the raw material compounds of the catalyst components (palladium, gold, and copper) in solution A can be calculated from the amounts of raw material compounds calculated as above and the amount of solution. In actual operation, the required amount (g) of raw material compound is weighed and dissolved in a solvent to obtain the desired amount of solution.

[0031] The excess rate of the raw material compound of each catalyst component charged in solution A is calculated by the following formula: (Amount (mass) of catalyst component in charged raw material compound - Amount (mass) of desired catalyst component to be supported) / (Amount (mass) of desired catalyst component to be supported) x 100 (%)

[0032] When the catalyst component is gold, the amount (g) of a compound containing gold (e.g., chloroauric acid) corresponding to the amount (g) to be supported per 1 kg of support is calculated, and this amount (g) of the compound containing gold is multiplied by the amount of support (kg) and (excess rate of the compound containing gold + 100) / 100, and the resulting amount (g) is dissolved in the solvent of solution A. Specifically, if the amount (g) of gold to be supported per 1 kg of support is 10 g, then chloroauric acid (HAuCl) containing 10 g of gold atoms is dissolved in the solvent of solution A. ４ When the excess rate is 80%, the amount of chloroauric acid to be charged per kg of carrier is 31.068 g (= 17.26 × ((80 + 100) / 100). This value is multiplied by the amount of carrier (kg) to be used, and the resulting amount of chloroauric acid is dissolved in the solvent for Solution A. Solutions A are prepared in the same manner for palladium and copper.

[0033] With respect to the excess ratio of the raw material compounds of each catalyst component in Solution A, the excess ratio of the palladium-containing compound is preferably 2% to 50%, more preferably 5% to 40%, and even more preferably 10% to 20%. The excess ratio of the gold-containing compound is preferably 2% to 150%, more preferably 10% to 100%, and even more preferably 25% to 90%. The excess ratio of the copper-containing compound is preferably 2% to 50%, more preferably 5% to 40%, and even more preferably 8% to 15%.

[0034] By using solution A containing an excess amount of raw compound relative to the desired catalyst component loading, the contact time between the carrier and solution A required to obtain the desired catalyst component loading can be shortened. This suppresses coarsening of gold particles due to the dissolution and reprecipitation process. When solution A containing an excess amount of raw compound relative to the desired catalyst component loading is used, it is preferable to perform step 3 (draining step) when the desired catalyst component loading amount has been loaded on the carrier. The timing to proceed to step 3 is determined based on a preliminary experiment, the details of which are described below.

[0035] A palladium precursor convertible to metallic palladium can be used as the palladium-containing compound in Solution A. Examples of palladium precursors convertible to metallic palladium include palladium chloride, palladium nitrate, palladium sulfate, sodium chloropalladate, potassium chloropalladate, barium chloropalladate, and palladium acetate, with sodium chloropalladate being preferred.

[0036] A gold precursor that can be converted into metallic gold can be used as the gold-containing compound in Solution A. Examples of gold precursors include chloroauric acid, sodium chloroaurate, and potassium chloroaurate, with chloroauric acid being preferred.

[0037] A copper precursor that can be converted into metallic copper can be used as the copper-containing compound in Solution A. Examples of copper precursors that can be converted into metallic copper include copper chloride, copper acetate, and copper nitrate, and copper chloride is preferably used.

[0038] Examples of the solvent for solution A include water, alcohol, and organic acid. Water is preferred because it does not damage the support and is not reactive with the compounds contained in solution A.

[0039] The amount of solution A is preferably 1.0 to 10.0 times by mass, more preferably 2.0 to 8.0 times by mass, and particularly preferably 2.0 to 5.0 times by mass the water absorption amount of the carrier.

[0040] By contacting and impregnating the support impregnated with the alkaline solution with solution A, the raw material metal compounds are converted into water-insoluble substances, and a shell-type catalyst precursor can be formed in which metal components such as palladium, gold, and copper are unevenly distributed and supported on the surface portion of the support.

[0041] The contact temperature is not particularly limited, but is preferably 10 to 80° C., more preferably 20 to 60° C. A contact temperature of 10° C. or higher allows the conversion reaction to proceed sufficiently. A contact temperature of 80° C. or lower can suppress aggregation of gold, palladium, and copper.

[0042] The contact time is determined by repeating preliminary experiments to confirm the change over time in the loading rate of the catalyst component at a predetermined contact temperature, and is set to the time required to achieve the desired loading amount. Since the contact time cannot be changed for each catalyst component, the excess rate of the charged amount of each raw material compound is adjusted so that the desired loading amount is achieved within the contact time. The contact time is preferably 0.5 to 100 hours, and more preferably 1 to 20 hours. By setting the contact time to 100 hours or less, it is possible to suppress degradation of the carrier.

[0043] <Step 3: Draining Step> In this step, only the carrier is extracted from the mixture of carrier and solution obtained in Step 2. Gold-containing compounds, such as chloroauric acid, have a significantly slower hydrolysis rate than palladium-containing compounds and copper-containing compounds. Therefore, if the carrier is immersed in Solution A for a long period of time, compositional irregularities are likely to occur within the carrier. In addition, if the carrier is immersed in Solution A for a long period of time, coarsening of gold particles is likely to occur during the dissolution and reprecipitation process. In contrast, by separating the carrier from Solution A once the desired amount of catalyst component has been supported on the carrier, the occurrence of compositional irregularities and coarsening of gold particles can be suppressed. The method for separating the carrier from the solution is not particularly limited and can be appropriately determined from conventional methods taking into account the shape and morphology of the catalyst. For example, filtration, centrifugation, sedimentation, etc. can be used, with filtration being preferred. Examples of filtration methods include passing the carrier through a mesh smaller than the size of the carrier. When the carrier size is 3 to 8 mm, for example, passing the carrier through a mesh with a 1 mm mesh opening is sufficient. It is preferable to separate the solution by solid-liquid separation to a level not exceeding 1.2 times the water absorption rate of the carrier.

[0044] <Step 4. Buffer Solution Step> In this step, the carrier separated from the solution after impregnation with Solution A is brought into contact with water or an aqueous solution having a pH of 7.0 to 11.5 (hereinafter collectively referred to as "Solution B"). It is presumed that the operation of Step 4 changes the state of gold to Cl. － Au(OH) without coordination ３ This is expected to have the effect of suppressing the aggregation of gold in the next step 5 (liquid-phase reduction treatment step). Solution B may be gently stirred, but it is preferable to leave it to stand to prevent damage to the carrier.

[0045] Compounds containing gold, such as chloroauric acid, react with alkaline components to produce AuCl ３－ｎ (OH) ｎ and Au(OH) ３ In the liquid phase reduction treatment step of step 5, Cl is added to the gold. － When the gold particles are reduced in a coordinated state, the gold particles are more likely to increase in size and aggregate with each other. － On the other hand, if the pH of the solution becomes too high, the substitution of [Au(OH)４ ] － Furthermore, if the solution temperature is too high, the gold particles tend to increase in size and aggregate together.

[0046] By carrying out the buffer step, the pH of the solution after reaction with the alkaline component is adjusted to the state of gold. － In the uncoordinated state, i.e., Au(OH) ３ By controlling the reduction temperature to a range in which the redissolution of gold does not occur and by carrying out the reduction at a low temperature, it is possible to suppress the aggregation of gold particles in the liquid-phase reduction treatment step and to produce a catalyst for producing vinyl acetate that has a palladium-gold alloy state suitable for the vinyl acetate production reaction.

[0047] Solution B may be water or an aqueous solution having a pH of 7.0 to 11.5 at the operating temperature in step 4 (for example, room temperature (20°C)). The above pH is the pH of Solution B before it is brought into contact with the carrier. The above pH is preferably 8.0 to 11.0. During step 4, the pH may deviate from the above range, but it is preferable to maintain the pH within the above range. In the present disclosure, the pH is a value measured using a pH meter (desktop pH meter, Horiba Advanced Techno Co., Ltd.) at the temperature in step 4. Solution B may be water alone or an alkaline aqueous solution. Other components may be dissolved in Solution B as necessary.

[0048] When solution B is an alkaline aqueous solution, the solution may be an aqueous solution of any alkaline compound. Examples of alkaline compounds include hydroxides of alkali metals or alkaline earth metals, bicarbonates of alkali metals or alkaline earth metals, carbonates of alkali metals or alkaline earth metals, and silicates of alkali metals or alkaline earth metals. Examples of alkali metals that can be used include lithium, sodium, or potassium. Examples of alkaline earth metals that can be used include barium or strontium. Examples of alkaline compounds that can be used include sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, barium hydroxide, and strontium hydroxide.

[0049] It is preferable to use a pH buffer solution as Solution B because this reduces the pH change during Step 4. The pH of the pH buffer solution before contact with the support is preferably 7.0 to 11.5, and more preferably 8.0 to 11.0. Using a pH buffer solution can prevent the pH of Solution B from becoming too high, which would otherwise cause re-dissolution of gold. Examples of pH buffer solutions include phosphate (sodium) buffer solutions (pH 5.8-7.8), citrate (sodium) buffer solutions (pH 6.0-8.0), phosphate buffered saline (pH 6.4-8.4), ethylenediaminetetraacetic acid (sodium) buffer solutions (pH 7.0-9.0), Tris-HCl buffer solutions (pH 7.0-9.0), Tris-EDTA buffer solutions (pH 7.0-9.0), acetate-ethanolamine buffer solutions (pH 8.6-10.6), boric acid (potassium) buffer solutions (e.g., pH 8.1-10.1), boric acid (sodium) buffer solutions (e.g., pH 9.1), and carbonate-bicarbonate buffer solutions (e.g., pH 10.0). Preferably, boric acid (potassium) buffer solutions, boric acid (sodium) buffer solutions, or carbonate-bicarbonate buffer solutions are used, and more preferably, carbonate-bicarbonate buffer solutions are used. Note that for each buffer solution, (sodium) or (potassium) means that the counter ion is sodium or potassium, respectively.

[0050] The amount of solution B is preferably 1.0 to 10.0 times by mass, more preferably 2.0 to 8.0 times by mass, and particularly preferably 2.0 to 5.0 times by mass the amount of water absorption of the carrier.

[0051] The temperature of Solution B in Step 4 is not particularly limited, but is preferably 10 to 80°C, more preferably 20 to 60°C. A contact temperature of 10°C or higher allows the conversion reaction to proceed sufficiently. A contact temperature of 80°C or lower can prevent aggregation of gold, palladium, and copper.

[0052] The contact time with Solution B is preferably 0.1 to 48 hours, more preferably 1.0 to 24 hours.

[0053] <Step 5. Liquid-Phase Reduction Treatment Step> It is desirable to perform a reduction treatment on the support carrying the reaction product of the raw material compound and the alkaline compound, thereby converting the reaction product into metallic palladium, metallic gold, and metallic copper. In the present disclosure, "metallic copper," "metallic palladium," and "metallic gold" refer to metal species with a valence of zero. The reduction treatment is performed in a liquid phase. It is not necessary for all palladium, gold, and copper to be reduced to the metallic state, i.e., to a valence of zero, by the reduction treatment.

[0054] Liquid-phase reduction can be carried out in either a non-aqueous system using alcohols or hydrocarbons, or an aqueous system. Examples of reducing agents that can be used include carboxylic acids and their salts, aldehydes, hydrogen peroxide, sugars, polyhydric phenols, boron compounds, amines, and hydrazine. Examples of carboxylic acids and their salts include oxalic acid, potassium oxalate, formic acid, potassium formate, potassium citrate, and ammonium citrate. Examples of aldehydes include formaldehyde and acetaldehyde. Examples of sugars include glucose. Examples of polyhydric phenols include hydroquinone. Examples of boron compounds include diborane and sodium borohydride. Examples of reducing agents include hydrazine, formaldehyde, acetaldehyde, hydroquinone, sodium borohydride, and potassium citrate, with hydrazine being particularly preferred.

[0055] In the liquid-phase reduction treatment, the liquid-phase temperature is in the range of 0 to 15°C. It is preferably in the range of 0 to 13°C, more preferably in the range of 0 to 10°C, and even more preferably in the range of 3 to 7°C. When the liquid-phase temperature, i.e., the liquid-phase reduction treatment temperature, is in the range of 0 to 15°C, the selectivity to vinyl acetate can be increased. The reduction time is preferably in the range of 0.5 to 24 hours, more preferably in the range of 1 to 10 hours. When the reduction time is 0.5 hours or more, the reduction can proceed sufficiently. On the other hand, when the reduction time is 24 hours or less, the aggregation of palladium, gold, and copper can be suppressed.

[0056] The reduced support is washed with pure water or the like as needed. Washing may be carried out continuously or batchwise. The washing temperature is preferably in the range of 5 to 200°C, more preferably in the range of 15 to 80°C. There are no particular limitations on the washing time, and it is sufficient to select conditions sufficient for the purpose of removing remaining undesirable impurities. Examples of undesirable impurities include chlorine-containing compounds and chloride ions. After washing, the support may be dried by heating as needed.

[0057] Step 6: Supporting Acetate on a Carrier The acetate can be supported on a carrier by impregnating the carrier with a solution containing the required amount of acetate and drying. The amount of acetate solution used is preferably 0.9 to 1 times the mass of the carrier's water absorption. Supporting the acetate is typically performed after the reduction treatment, but can also be performed before the reduction treatment.

[0058] The acetate is preferably at least one compound selected from the group consisting of alkali metal acetates and alkaline earth metal acetates, more preferably an alkali metal acetate. Examples of the alkali metal acetate include acetates of lithium, sodium, and potassium. Preferred acetates are sodium acetate and potassium acetate, with potassium acetate being particularly preferred.

[0059] The amount of acetate supported is preferably set so that the mass of acetate supported per 1 kg of carrier is 40 g to 125 g.

[0060] [Catalyst for producing vinyl acetate] The mass of supported metallic palladium per kg of carrier is preferably 5.00 g to 20.0 g, more preferably 8.0 g to 17.0 g, and even more preferably 10.0 g to 15.0 g.

[0061] The mass of metallic gold carried per 1 kg of carrier is preferably 4.00 g to 20.0 g, more preferably 6.00 g to 18.0 g, and even more preferably 10.0 g to 17.0 g.

[0062] The mass of metallic copper carried per 1 kg of carrier is preferably 0.25 g to 5.00 g, more preferably 0.60 g to 2.50 g, and even more preferably 0.80 g to 1.5 g.

[0063] The mass of the supported acetate salt per 1 kg of the carrier is preferably 40 g to 125 g, more preferably 50 g to 88 g.

[0064] The mass ratio of palladium, gold, and copper is preferably palladium:gold:copper=100:70 to 130:8.3 to 9.5.

[0065] The amounts of the metal element and the acetate salt supported are measured by the method described in the Examples.

[0066] The catalyst for vinyl acetate production obtained by the method of the present disclosure has an eggshell structure in which most of the palladium, gold, and copper are supported on the surface of the carrier. The thickness of the shell portion varies depending on the type of carrier, alkaline solution, and solution containing a compound containing a catalytic metal element used. When spherical silica with a diameter of 5 mm is used as the carrier, the shell portion preferably has a thickness of 0.05 to 0.5 mm, and more preferably a thickness of 0.1 to 0.3 mm. When the shell portion is 0.05 mm or thicker, catalytic activity can be maintained even if the surface portion of the carrier peels off during the reaction. When the shell portion is 0.5 mm or thinner, the catalyst concentration on the surface of the carrier can be sufficiently increased, allowing the benefits of shell-type support to be economically enjoyed. The acetate does not need to be supported in a shell form and may be uniformly present throughout the catalyst.

[0067] [Specific Example of Catalyst Production] A preferred specific example of catalyst production is as follows: 1. Impregnate the support with an alkaline solution in an amount equivalent to the water absorption capacity of the support. 2. Dilute pure water to obtain Solution A, which is prepared by adding an excess amount of a palladium-containing compound, a gold-containing compound, and a copper-containing compound relative to the desired amounts of catalyst components, to twice the mass of the water absorption capacity of the support. The support is then immersed in this solution for a predetermined period of time to allow contact impregnation with Solution A, thereby forming a catalyst precursor carrying the desired amounts of catalyst components. 3. The contact-impregnated catalyst precursor is separated from the solution obtained in 2. 4. The catalyst precursor obtained in 3 is allowed to stand in water or an aqueous solution with a pH of 7.0 to 11.5. 5. The catalyst precursor obtained in 4 is brought into contact with a reducing agent to perform a liquid-phase reduction treatment. 6. Wash the reduced support with pure water. 7. Dry the washed support. 8. A predetermined amount of acetate is supported on the support. 9. Dry the support carrying the catalyst components.

[0068] [Production of Vinyl Acetate] A method for producing vinyl acetate using a catalyst for producing vinyl acetate produced by the method of the present disclosure will now be described. The reaction for producing vinyl acetate is preferably carried out in the gas phase using acetic acid, ethylene, and oxygen as reaction raw materials. The gas phase reaction may be in any conventionally known form, but is preferably a fixed-bed flow reaction.

[0069] The reaction formula is as follows: CH ２ =CH ２ +CH ３ COOH + 1 / 2O ２ →CH ２ = CHOCOCH ３ +H ２ O

[0070] The molar ratio of acetic acid, ethylene, and oxygen in the raw material gas is preferably acetic acid:ethylene:oxygen=1:0.08-16:0.01-4, and more preferably acetic acid:ethylene:oxygen=1:0.2-9:0.07-2.

[0071] The raw material gas contains ethylene, acetic acid (gas), and oxygen gas, and may further contain nitrogen gas, carbon dioxide, a rare gas, or the like as a diluent, as necessary. When ethylene, acetic acid, and oxygen are defined as the reaction raw materials, the ratio of the reaction raw materials to the diluent is preferably reaction raw materials:diluent=1:0.05-9 in molar ratio, and more preferably reaction raw materials:diluent=1:0.1-3 in molar ratio.

[0072] When the reaction is carried out in a fixed bed flow reactor, the raw material gas is supplied at a space velocity (SV) of 10 to 15,000 hr under standard conditions. －１ It is preferable that the temperature is 300 to 12,000 hr －１ It is more preferable that the space velocity is 10 hr －１ By setting the space velocity at 15,000 hr or more, the reaction heat can be appropriately removed. －１ By satisfying the following, the equipment such as the compressor can be made to have a practical size.

[0073] It is preferable to add water as steam to the raw material gas in an amount of 0.5 to 20 mol %, and more preferably 1 to 18 mol %. Without being bound by any theory, it is believed that the presence of water in the reaction system suppresses the outflow of acetate from the catalyst. Adding water in an amount greater than 20 mol % not only does not improve the above-mentioned effect, but also may accelerate the hydrolysis of vinyl acetate, so it is not preferable to have a large amount of water present in the raw material gas.

[0074] There are no particular restrictions on the material of the reactor, but it is preferable that the material be corrosion-resistant.

[0075] The reaction temperature is preferably in the range of 100 to 300°C, more preferably in the range of 120 to 250°C. If the reaction temperature is 100°C or higher, an appropriate reaction rate can be maintained. If the reaction temperature is 300°C or lower, the heat of reaction can be easily removed.

[0076] The reaction pressure is preferably in the range of 0 to 3 MPaG (gauge pressure), more preferably in the range of 0.1 to 1.5 MPaG. If the reaction pressure is 0 MPaG or higher, an appropriate reaction rate can be maintained. If the reaction pressure is 3 MPaG or lower, there is no need to make equipment such as reaction tubes highly pressure-resistant, and equipment costs can be reduced.

[0077] It is preferable to use high-purity ethylene as the reaction raw material, but it may be contaminated with lower saturated hydrocarbons such as methane, ethane, and propane.

[0078] The reaction raw materials ethylene and acetic acid may be produced from fossil fuels or biomass materials, or may be a mixture of these. １４ The concentration of C carbon atoms is 1 × 10 relative to the total number of carbon atoms. －１４ ~2 x 10 －１２ may be.

[0079] There are no particular limitations on the oxygen gas, and it can be supplied in the form of air, for example, diluted with an inert gas such as nitrogen gas or carbon dioxide gas, but when circulating the reaction gas, it is generally advantageous to use a highly concentrated oxygen gas, preferably an oxygen gas with a purity of 99% or more.

[0080] The present invention will be further explained below with reference to examples, but the present invention is not limited to these examples.

[0081] (Example 1) Preparation of Catalyst A A commercially available silica spherical support (particle diameter: 5 mm, BET specific surface area: 176 m) was used as a support. ２ / g, bulk density 470 g / L, water absorption 0.85 g-water / g-carrier, average pore diameter 17.2 nm, hereinafter simply referred to as "carrier"), a catalyst was prepared by the following procedure.

[0082] Step 1. Add 23.5 g of carrier (water absorption: 20.0 g) to Na ２ SiO ３ ・9H ２The carrier containing 4.9 g of PO was impregnated with an aqueous solution in an amount equivalent to the carrier's water absorption (1.1 times by mass). The container containing the carrier and aqueous solution was shaken to completely impregnate the carrier with the solution, and the container was left to stand for 3 hours in a sealed container. The water absorption was calculated from the carrier weight of 23.5 g and the water absorption rate of 0.85 g - water / g - carrier (the same applies to the following Examples and Comparative Examples).

[0083] Step 2: The support obtained in step 1 is treated with Na ２ PdCl ４ : 1.06g, HAuCl ４ The carrier was immersed in an aqueous solution containing 0.80 g of palladium and 0.074 g of copper chloride dihydrate in an amount twice the mass of the carrier's water absorption, and allowed to stand at room temperature (25°C) for 2 hours to obtain a catalyst precursor carrying the desired amount of catalyst component. The standing time was determined from the time required to achieve the desired amount of catalyst component supported, based on a preliminary experiment in which the relationship between the amount and time required for the catalyst component to be supported was determined. The desired catalyst component loading amounts were 13.8 g / kg of palladium, 12.5 g / kg of gold, and 1.15 g / kg of copper per kg of carrier, and the excess amounts of the raw material compounds charged relative to these were set to 18.3% for the palladium-containing compound, 56.8% for the gold-containing compound, and 2.0% for the copper-containing compound.

[0084] Step 3: The catalyst precursor was separated from the dispersion obtained in step 2 using a metal mesh with 1 mm openings, and the liquid was drained off.

[0085] Step 4. The catalyst precursor obtained in step 3 was immersed in ion-exchanged water (pH = 7.0) at 25°C in an amount four times the mass of the carrier water absorption, and allowed to stand at room temperature (25°C) for 18 hours.

[0086] Step 5. The catalyst precursor was separated from the dispersion obtained in Step 4 using the same metal mesh as above, and the liquid was drained. The separated catalyst precursor was immersed in an aqueous solution containing 5.9 g of 52 mass% hydrazine hydrate aqueous solution in an amount twice the mass of the carrier's water absorption, and left to stand in an ice bath (5°C) for 4 hours to perform a liquid-phase reduction treatment. Next, the palladium / gold / copper / carrier composition was washed with deionized water, and the water washing was continued until chloride ions disappeared in the water after washing. The washed palladium / gold / copper / carrier composition was dried with hot air at 110°C for 4 hours.

[0087] Step 6: The palladium / gold / copper / carrier composition obtained in Step 5 was impregnated at room temperature (25°C) with an aqueous solution containing 1.7 g of potassium acetate in an amount equivalent to 0.9 times the mass of the water absorption of the carrier, and then dried with hot air at 110°C for 4 hours to obtain catalyst A.

[0088] Example 2 Preparation of Catalyst B Using the same silica sphere carrier as in Example 1, a catalyst was prepared according to the following procedure.

[0089] Step 1. Add 23.5 g of carrier (water absorption: 20.0 g) to Na ２ SiO ３ ・9H ２ The carrier containing 4.4 g of O was impregnated with an aqueous solution in an amount equivalent to the carrier's water absorption (1.1 times by mass). The container containing the carrier and the aqueous solution was shaken to completely impregnate the carrier with the solution, and the container was left to stand for 3 hours in a sealed container.

[0090] Step 2: The support obtained in step 1 is treated with Na ２ PdCl ４ : 1.06g, HAuCl ４ The carrier was immersed in an aqueous solution containing 0.80 g of palladium and 0.074 g of copper chloride dihydrate in an amount twice the mass of the carrier's water absorption, and allowed to stand at room temperature (25°C) for 20 hours to obtain a catalyst precursor carrying the desired amount of catalyst component. The standing time was determined from the time required to achieve the desired amount of catalyst component supported, based on a preliminary experiment in which the relationship between the amount and time required for the catalyst component to be supported was determined. The desired catalyst component loading amounts were 13.4 g / kg of palladium, 16.8 g / kg of gold, and 1.13 g / kg of copper per kg of carrier, and the excess amounts of the raw material compounds charged relative to these were set to 22.0% for the palladium-containing compound, 17.0% for the gold-containing compound, and 4.0% for the copper-containing compound.

[0091] Step 3: The catalyst precursor was separated from the dispersion obtained in step 2 using a metal mesh with 1 mm openings, and the liquid was drained off.

[0092] Step 5. The separated catalyst precursor was immersed in an aqueous solution containing 5.9 g of 52% by mass hydrazine hydrate aqueous solution in an amount twice the mass of the carrier's water absorption, and allowed to stand in an ice bath (5°C) for 4 hours to carry out a liquid-phase reduction treatment. The palladium / gold / copper / carrier composition was then washed with deionized water, and continued to be washed until chloride ions disappeared in the water after washing. The washed palladium / gold / copper / carrier composition was then dried with hot air at 110°C for 4 hours.

[0093] Step 6: The palladium / gold / copper / carrier composition obtained in Step 5 was impregnated at room temperature (25°C) with an aqueous solution containing 1.7 g of potassium acetate in an amount equivalent to 0.9 times the mass of the water absorption of the carrier, and then dried with hot air at 110°C for 4 hours to obtain catalyst B.

[0094] Example 3 Preparation of Catalyst C Using the same silica sphere carrier as in Example 1, a catalyst was prepared according to the following procedure.

[0095] Step 1. Add 23.5 g of carrier (water absorption: 20.0 g) to Na ２ SiO ３ ・9H ２ The carrier containing 4.9 g of O was impregnated with an aqueous solution in an amount equivalent to the carrier's water absorption (1.1 times by mass). The container containing the carrier and the aqueous solution was shaken to completely impregnate the carrier with the solution, and the container was left to stand for 3 hours in a sealed container.

[0096] Step 2: The support obtained in step 1 is treated with Na ２ PdCl ４ :0.89g, HAuCl ４ The carrier was immersed in an aqueous solution containing 0.62 g of palladium and 0.091 g of copper chloride dihydrate in an amount twice the mass of the carrier's water absorption, and allowed to stand at room temperature (25°C) for 20 hours to obtain a catalyst precursor carrying the desired amount of catalyst component. The standing time was determined from the time required to achieve the desired amount of catalyst component supported, based on a preliminary experiment in which the relationship between the amount and time required for the catalyst component to be supported was determined. The desired catalyst component loading amounts were 12.9 g / kg of palladium, 12.0 g / kg of gold, and 1.17 g / kg of copper per kg of carrier, and the excess amounts of the raw material compounds charged relative to these were set to 6.8% for the palladium-containing compound, 28.1% for the gold-containing compound, and 23.6% for the copper-containing compound.

[0097] Step 3: The catalyst precursor was separated from the dispersion obtained in step 2 using a metal mesh with 1 mm openings, and the liquid was drained off.

[0098] Step 4. The catalyst precursor obtained in step 3 is dissolved in NaHCO at 25 ° C. ３ : 0.86 g, and Na ２ CO ３ The carrier containing 0.68 g of the polymer was immersed in a pH buffer solution (pH = 10.0) having a mass four times the amount of water absorption, and allowed to stand at 25°C for 3 hours.

[0099] Step 5. The catalyst precursor was separated from the dispersion obtained in Step 4 using the same metal mesh as above, and the liquid was drained. The separated catalyst precursor was immersed in an aqueous solution containing 4.8 g of 52 mass% hydrazine hydrate aqueous solution in an amount twice the mass of the carrier's water absorption, and left to stand at 5°C for 4 hours to perform a liquid-phase reduction treatment. Next, the palladium / gold / copper / carrier composition was washed with deionized water, and the water washing was continued until chloride ions disappeared in the water after washing. The washed palladium / gold / copper / carrier composition was dried with hot air at 110°C for 4 hours.

[0100] Step 6: The palladium / gold / copper / carrier composition obtained in Step 5 was impregnated at 25°C with an aqueous solution containing 1.7 g of potassium acetate in an amount equivalent to 0.9 times the mass of the water absorption of the carrier, and then dried with hot air at 110°C for 4 hours to obtain catalyst C.

[0101] Example 4 Preparation of Catalyst D Catalyst D was obtained in the same manner as in Example 3, except that in step 5 of Example 3, the liquid-phase reduction treatment temperature was changed to 15°C.

[0102] Comparative Example 1 Preparation of Catalyst E Catalyst E was obtained in the same manner as in Example 1, except that in step 5 of Example 1, the liquid-phase reduction treatment temperature was changed to 25°C.

[0103] Comparative Example 2 Preparation of Catalyst F Using the same silica sphere carrier as in Example 1, a catalyst was prepared according to the following procedure.

[0104] Step 1. Add 23.5 g of carrier (water absorption: 20.0 g) to Na ２ SiO ３ ・9H ２The carrier containing 7.5 g of O was impregnated with an aqueous solution in an amount equivalent to the carrier's water absorption (2.9 times by mass). The container containing the carrier and aqueous solution was shaken to completely impregnate the carrier with the solution, and the carrier was air-dried for 5 minutes. The water absorption was calculated from the carrier weight of 23.5 g and the water absorption rate of 0.85 g - water / g - carrier.

[0105] Step 2: The support obtained in step 1 is treated with Na ２ PdCl ４ :0.87g, HAuCl ４ The carrier was immersed in an aqueous solution containing 0.38 g of copper chloride and 0.04 g of copper chloride dihydrate in an amount twice the mass of the carrier's water absorption, and allowed to stand at room temperature for 20 hours.

[0106] Step 5. 1.9 g of a 52% by mass aqueous solution of hydrazine hydrate was added to the dispersion obtained in Step 2, gently mixed, and allowed to stand at 25°C for 4 hours to carry out a liquid-phase reduction treatment. Next, the palladium / gold / copper / carrier composition obtained in the previous step was washed with deionized water, and the washing was continued until chloride ions were no longer present in the water after washing. The washed palladium / gold / copper / carrier composition was dried with hot air at 110°C for 4 hours.

[0107] Step 6: The palladium / gold / copper / carrier composition obtained in Step 5 was impregnated at room temperature (25°C) with an aqueous solution containing 1.7 g of potassium acetate in an amount equivalent to 0.9 times the mass of the water absorption of the carrier, and then dried with hot air at 110°C for 4 hours to obtain catalyst F.

[0108] [Catalyst Evaluation] <Measurement of Metal (Palladium, Gold, and Copper) and Potassium Acetate Support Amounts> 3 g of a supported catalyst sample was crushed and pressed into a disk with an inner diameter of 3 cm. The metal amounts of the disks were measured using a ZSX Primus II X-ray fluorescence spectrometer manufactured by Rigaku Corporation. For potassium acetate, the amount of potassium atoms was quantified and converted into the amount of potassium acetate.

[0109] <Catalytic Activity Evaluation Test> 6.7 mL of catalyst was diluted with 75 mL of glass beads and packed into a reaction tube (made of SUS316L, inner diameter 22 mm, length 480 mm). ２ H ４ / O ２ / H ２ O / HOAc / N ２= 45 / 6 / 5 / 23 / 21 (mol%) gas at a flow rate of 66.7 NL / h (SV: 10000 h －１ ) for 240 hours to evaluate catalytic activity and selectivity. Generally, the higher the vinyl acetate activity (STY) (g / L-cat h), the lower the vinyl acetate selectivity. Therefore, the vinyl acetate selectivity at the same vinyl acetate activity for each catalyst was compared. For example, the vinyl acetate selectivity at a vinyl acetate activity of 750 (g / L-cat h) was calculated by interpolation from a polynomial approximation curve consisting of a plot of vinyl acetate activity and vinyl acetate selectivity for each reaction temperature.

[0110] The reactor outlet gas was analyzed using the following method.

[0111] 1. Oxygen Using the absolute calibration curve method, 50 mL of effluent gas was collected and the entire amount was passed through a 1 mL gas sampler attached to the gas chromatograph, and analysis was performed under the following conditions: Gas chromatography: Gas chromatograph (Shimadzu Corporation GC-14B) equipped with a Shimadzu gas chromatograph gas sampler (MGS-4: 1 mL measuring tube) Column: MS-5A IS 60 / 80 mesh (3 mm diameter x 3 m) Carrier gas: Helium (flow rate 20 mL / min) Temperature conditions: Detector temperature and vaporizer temperature 110°C, column temperature constant at 70°C Detector: TCD (He pressure 70 kPaG, Current 100 mA)

[0112] 2. Acetic acid: Using the internal standard method, 1 mL of 1,4-dioxane was added as an internal standard to 10 mL of the reaction solution to form the analytical solution, and 0.2 μL of this was injected and analyzed under the following conditions: Gas chromatography: Shimadzu Corporation GC-14B Column: Packed column Thermon 3000 (length 3 m, inner diameter 0.3 mm) Carrier gas: Nitrogen (flow rate 20 mL / min) Temperature conditions: Detector temperature and vaporizer temperature 180°C, column temperature was maintained at 50°C for 6 minutes from the start of analysis, then heated to 150°C at a rate of 10°C / min and maintained at 150°C for 10 minutes Detector: FID (H ２ pressure 40kPaG, air pressure 100kPaG)

[0113] 3. Vinyl acetate Using the internal standard method, 1 g of 1,4-dioxane was added as an internal standard to 6 g of the reaction solution to form the analytical solution, and 0.3 μL of this solution was injected and analyzed under the following conditions: Gas chromatography: Shimadzu Corporation GC-9A Column: Capillary column TC-WAX (length 30 m, inner diameter 0.25 mm, film thickness 0.5 μm) Carrier gas: Nitrogen (flow rate 30 mL / min) Temperature conditions: Detector temperature and vaporizer temperature 200°C, column temperature was maintained at 45°C for 2 minutes from the start of analysis, then heated to 130°C at a heating rate of 4°C / min and maintained at 130°C for 15 minutes, then heated to 200°C at a heating rate of 25°C / min and maintained at 200°C for 10 minutes Detector: FID (H ２ pressure 60kPaG, air pressure 100kPaG)

[0114] The catalyst evaluation results are shown in Table 1. The selectivity for vinyl acetate is based on ethylene.

[0115]

[0116] Comparing Examples 1 to 4 with Comparative Examples 1 and 2, it was found that by lowering the temperature of the solution containing the reducing agent used in reducing the compounds containing palladium, gold, and copper supported on the carrier to metals from 25° C. to 15° C. or less, the vinyl acetate selectivity improved by 1.0 to 1.7 points, demonstrating a significant effect. This effect is presumably due to the difference in the alloy state.

Claims

1. A method for producing a catalyst for use in the production of vinyl acetate, comprising a support, palladium, gold, copper, and an acetate salt, the method comprising: Step 1. Impregnating a support with an alkaline solution; Step 2. Contacting and impregnating the support with a solution containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound; Step 5. Performing a liquid-phase reduction treatment at a temperature ranging from 0°C to 15°C; and Step 6. Supporting an acetate salt on the support.

2. The method according to claim 1, further comprising, between steps 2 and 5: step 3. separating the support from the solution of step 2 when a desired amount of each catalyst component has been supported on the support.

3. The method according to claim 2, further comprising, between steps 3 and 5: step 4. contacting the carrier with water or an aqueous solution having a pH of 7.0 to 11.

5.

4. The method according to any one of claims 1 to 3, wherein the mass of the supported metallic palladium per kg of the support is 5.00 g to 20.0 g.

5. The method according to any one of claims 1 to 3, wherein the mass of metallic gold carried per 1 kg of the support is 4.00 g to 20.0 g.

6. The method according to any one of claims 1 to 3, wherein the mass of metallic copper carried per kg of the carrier is 0.25 g to 5.00 g.

7. The method according to any one of claims 1 to 3, wherein the mass of the supported acetate salt per kg of the support is 40 g to 125 g.

8. The manufacturing method according to any one of claims 1 to 3, wherein the mass ratio of palladium, gold, and copper is 100:70 to 130:8.3 to 9.

5.

9. A method for producing vinyl acetate using the catalyst for producing vinyl acetate obtained by the method according to any one of claims 1 to 3 and ethylene, oxygen and acetic acid as raw materials.

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