Method for manufacturing catalyst for vinyl acetate and method for manufacturing vinyl acetate

Abstract

A method for manufacturing a catalyst is provided, which can produce vinyl acetate with improved selectivity while ensuring high catalyst activity. The method for manufacturing a vinyl acetate catalyst comprises a carrier, palladium, gold, copper, and acetate, and includes the following steps: Step 1. Impregnating the carrier with an alkaline solution; Step 2. Contacting the aforementioned carrier with a solution impregnating a palladium-containing compound, a gold-containing compound, and a copper-containing compound; Step 5. Performing a liquid-phase reduction treatment within a temperature range of 0°C to 15°C; and Step 6. Supporting the aforementioned carrier with acetate.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing a catalyst for vinyl acetate production, which is used in the production of vinyl acetate from acetic acid, ethylene and oxygen as raw materials, and a method for manufacturing vinyl acetate using the catalyst. [Previous Technology]

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

[0003] As a catalyst for manufacturing vinyl acetate using acetic acid, ethylene, and oxygen as raw materials, catalysts formed by supporting palladium, gold, and potassium acetate in silicon dioxide are widely used. Palladium is considered the active site in this reaction, and gold is believed to not only inhibit palladium aggregation but also reduce the formation of the byproduct carbon dioxide, thereby increasing the selectivity of vinyl acetate. To achieve the effect of gold, the gold atoms must be present in close proximity to the palladium. In Patent Document 1, efforts are made in the impregnation step to support the metals in a state where the supporting sites of palladium and gold are close to each other.

[0004] In the manufacture of vinyl acetate, improving the selectivity of vinyl acetate is an important technical issue. From the perspective of environmental impact, it is also desirable to suppress the generation of carbon dioxide.

[0005] In Patent Document 2, in addition to palladium and gold, copper is also used to increase the selectivity of vinyl acetate.

[0006] In Patent Document 3, in a method for manufacturing a catalyst containing palladium, gold, and copper, a carrier is used to support the palladium-containing compound, the gold-containing compound, and the copper-containing compound in the same step, thereby improving the selectivity of vinyl acetate. [Prior Art Documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2008-080326 [Patent Document 2] Japanese Patent Publication No. 2002-516749 [Patent Document 3] International Publication No. 2022 / 113429 [Summary of the Invention]

[0008] [Problem to be Solved by the Invention] In Patent Document 3, an alkaline component is supported on a carrier, and then, in the same step, the carrier is impregnated with a solution containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound. Each compound is hydrolyzed, and palladium hydroxide, gold hydroxide, and copper hydroxide are supported on the carrier. Gold-containing compounds, such as chloroauric acid, typically hydrolyze slowly, resulting in slow support on the carrier. Therefore, even if the carrier supporting the alkaline component comes into contact with the palladium-containing compound and the gold-containing compound in the same step, due to the difference in the hydrolysis rates of palladium and gold, gold atoms that are not close to palladium are generated, or the gold-containing compound system remaining in the solution agglomerates, becoming coarse and forming gold particle aggregates. However, if a copper-containing compound coexists during the hydrolysis of the gold-containing compound, the copper-containing compound hydrolyzes rapidly and is supported on the carrier. Then, the gold-containing compound adsorbs onto the hydrolysate of the copper-containing compound supported on the carrier, thereby increasing the hydrolysis rate of the gold-containing compound. Therefore, compared to the case where no copper-containing compound is added in the same step, gold can be held in a state close to that of palladium, and the coarsening of gold particles in the solution can be suppressed, resulting in improved selectivity for vinyl acetate. However, since gold particle aggregation has also been observed in the catalyst produced by this method, further improvements in gold aggregation during the hydrolysis and reduction steps of catalyst manufacturing can be expected to further enhance the catalyst's performance.

[0009] This disclosure provides a method for manufacturing a catalyst that can produce vinyl acetate with improved selectivity while ensuring high catalyst activity. [Means of Problem Solving]

[0010] As a result of repeated and dedicated research by the inventors in order to solve the above-mentioned problems, a method for manufacturing a catalyst has been discovered, characterized in that a compound containing palladium, gold and copper is reacted with an alkaline component, and then the compound is supported on a carrier and subjected to liquid-phase reduction treatment in a temperature range of 0°C to 15°C, thereby successfully manufacturing vinyl acetate with an improved selectivity.

[0011] That is, the contents of this disclosure include the following [1] to [9]. [1] A method for manufacturing a catalyst for vinyl acetate manufacturing, which is a method for manufacturing a catalyst for vinyl acetate manufacturing containing a carrier, palladium, gold, copper and acetate, comprising the following steps: Step 1. A step of impregnating the carrier with an alkaline solution; Step 2. A step of contacting the aforementioned carrier with a solution impregnating a compound containing palladium, a compound containing gold and a compound containing copper; Step 5. A step of performing liquid-phase reduction treatment in the range of 0°C to 15°C; and Step 6. A step of supporting acetate on the aforementioned carrier. [2] The manufacturing method described in [1] further comprises between step 2 and step 5: Step 3. A step of separating the aforementioned carrier from the solution prior to step 2 when the aforementioned carrier is supported with the desired amount of each catalyst component. [3] The manufacturing method described in [2] further includes, between step 3 and step 5: step 4. contacting the aforementioned carrier with water or an aqueous solution at pH = 7.0 to 11.5. [4] The manufacturing method described in any one of [1] to [3], wherein the mass of palladium supported per 1 kg of the aforementioned carrier is 5.00 g to 20.0 g. [5] The manufacturing method described in any one of [1] to [4], wherein the mass of gold supported per 1 kg of the aforementioned carrier is 4.00 g to 20.0 g. [6] The manufacturing method described in any one of [1] to [5], wherein the mass of copper supported per 1 kg of the aforementioned carrier is 0.25 g to 5.00 g. [7] The manufacturing method described in any one of [1] to [6], wherein the mass of acetate supported per 1 kg of the aforementioned carrier is 40 g to 125 g. [8] The manufacturing method described in any 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 method for manufacturing vinyl acetate, wherein a vinyl acetate manufacturing catalyst obtained by any of [1] to [8] is used, and ethylene, oxygen, and acetic acid are used as raw materials. [Effects of the Invention]

[0012] According to the method disclosed herein, compared with conventional methods, high catalyst activity can be ensured while significantly improving the selectivity of vinyl acetate.

Implementation Method

[0013] [Forms of the Invention] The following describes various forms of the invention, but the invention is not limited to these forms and can be modified in various ways within the scope of the invention. Furthermore, in this disclosure, when "~" is used to refer to a numerical range, the values ​​at both ends are the upper and lower limits, respectively, and are included within the numerical range. When a plurality of upper or lower limits are recorded, the numerical range can be created by combining all the upper and lower limits. Similarly, when a plurality of numerical ranges are recorded, individual numerical ranges can be created by individually selecting and combining the upper and lower limits from those numerical ranges.

[0014] [Method for Manufacturing a Catalyst for Vinyl Acetate Production] One embodiment of the method for manufacturing a catalyst for vinyl acetate production includes the steps shown below, preferably in the order shown. Furthermore, palladium, gold, and copper are referred to as "catalyst components," and sometimes palladium-containing compounds, gold-containing compounds, and copper-containing compounds are combined, or each metal is referred to as a "raw material compound." Steps 3 and 4 are preferably either steps. Step 1. Impregnating the carrier with an alkaline solution. Step 2. Contacting the carrier with a solution containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound (hereinafter referred to as "Solution A"), using palladium, gold, and copper as catalyst components. Step 3. Separating the carrier from Solution A when it has the desired amount of each catalyst component (liquid removal step). Step 4. Contacting the carrier with water or an aqueous solution at pH 7.0–11.5 (buffer solution step). Step 5. Performing liquid-phase reduction treatment within the range of 0°C–15°C. Step 6. Supporting acetate on the carrier.

[0015] In one embodiment, step 2 is performed after step 1, in which the support is contacted with a solution A containing a palladium-containing compound, a gold-containing compound, and a copper-containing compound to form a catalyst precursor on the support carrying the reactant of the compounds and the basic compound. 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 relative to the desired carrying amount of each catalyst component.

[0016] Steps 1 to 6 are performed in the order described above, but other steps may be included for purposes such as improving the performance of the catalyst. For example, a step of washing the carrier with water after step 5 can be cited. The liquid-phase reduction treatment in step 5 is a process of converting the reactants of the raw material compound and the basic compound into metallic palladium, metallic gold, and metallic copper, respectively, and therefore must be performed after step 2 or 3. Alternatively, steps 5 and 6 can be interchanged. Each step will be explained in detail below.

[0017] <Step 1. Step of impregnating the carrier with alkaline solution> In this step, the carrier is impregnated with alkaline solution. This step can be carried out at room temperature. If the impregnation operation is completed, the carrier can be dried, or the following steps can be carried out without drying.

[0018] There are no particular restrictions on the carrier; any porous material commonly used as a carrier for catalysts can be used. Preferred carriers are silica, alumina, silica-alumina, diatomaceous earth, montmorillonite, or titanium dioxide, with silica being more preferred. When using a material with silica as the main component as the carrier, the silica content of the carrier is typically at least 50% by mass, and preferably at least 90% by mass, relative to the mass of the carrier.

[0019] The specific surface area of ​​the carrier, as determined by the BET method, is preferably at least 1 m² / g, more preferably in the range of 10 to 1000 m² / g, and particularly preferably in the range of 100 to 500 m² / g. The bulk density of the carrier 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 rate of the carrier is preferably in the range of 0.05 to 3 g-water / g-carrier, and particularly preferably in the range of 0.1 to 2 g-water / g-carrier. Regarding the micropore structure of the carrier, the average micropore diameter is preferably in the range of 1 to 1000 nm, and particularly preferably in the range of 2 to 800 nm. If the average micropore diameter is 1 nm or more, gas diffusion is facilitated. On the other hand, if the average micropore diameter is 1000 nm or less, the specific surface area of ​​the carrier required for obtaining catalytic activity can be ensured.

[0020] In the determination of the pore size distribution of a carrier, the mercury infiltration method and the gas adsorption method (BJH method) are widely used. According to the IUPAC (International Union of Pure and Applied Chemistry) classification of pores, the mercury infiltration method can determine large pores larger than 50 nm and a portion of medium-sized pores from 2 nm to less than 50 nm, while the gas adsorption method can determine medium-sized pores and micropores smaller than 2 nm. An appropriate determination method can be selected based on the size of the pores.

[0021] In this disclosure, the water absorption rate of the carrier refers to the value determined by the following method: 1. Measure approximately 5g of carrier (W1g) using a balance and place it into a 100mL beaker. 2. Add approximately 15mL of pure water (ion-exchanged water) to the beaker to completely cover the carrier. 3. Let stand for 30 minutes. 4. Place the contents of the beaker through a 1mm mesh sieve to remove the pure water. 5. Gently press and remove the water adhering to the surface of the carrier with a paper towel until the surface gloss disappears. 6. Measure the total mass of the carrier and pure water (W2g). 7. Calculate the water absorption rate of the carrier using the following formula: Water absorption rate (g - water / g - carrier) = (W2 - W1) / W1 Therefore, the water absorption (g) of the carrier is calculated by multiplying the water absorption rate (g - water / g - carrier) by the mass (g) of the carrier used.

[0022] There are no particular restrictions on the shape of the carrier. Specific examples include powder, spheres, and granules, but it is not limited to these. The most suitable shape can be selected according to the reaction method, reactor, etc. used.

[0023] There are no particular limitations on the size of the carrier particles. When the carrier is spherical, the particle diameter is preferably in the range of 1 to 10 mm, and more preferably in the range of 3 to 8 mm. When the catalyst is filled into a tubular reactor for gas-phase reaction, if the particle diameter is 1 mm or more, excessive pressure loss during gas flow can be prevented, and gas circulation can be effectively carried out. On the other hand, if the particle diameter is 10 mm or less, the raw material gas can easily diffuse into the interior of the diffusion catalyst, and the catalytic reaction can be effectively carried out. Furthermore, the number of catalyst particles filled into the tubular reactor is not excessively reduced, thus ensuring a sufficient total surface area of ​​the catalyst particles, so that the metal components (copper, palladium, gold, etc.) dispersed on the surface of the carrier are in a suitable amount for the reaction.

[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. Lithium, sodium, or potassium may be used as the alkali metal. Barium or strontium may be used as the alkaline earth metal. Sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, barium hydroxide, or strontium hydroxide are preferred as the alkaline compound.

[0025] There are no particular limitations on the solvent used as an alkaline solution; water, methanol, and ethanol are examples, with water being the preferred choice.

[0026] The basic compound is used excessively relative to the total of palladium, gold, and copper described below. For example, the product of the molar amount of the basic compound and the valence of the basic compound is preferably more than 1.1 times and less than 3.0 times the sum of the molar amount of palladium in the palladium-containing compound and the valence of palladium, the molar amount of gold in the gold-containing compound and the valence of gold, and the molar amount of copper in the copper-containing compound and the valence of copper.

[0027] There are no particular limitations on the method of impregnating the carrier with an alkaline solution. For example, (I) a method in which the carrier is briefly impregnated in a large amount of alkaline solution and then removed, the carrier having absorbed a portion of the water-absorbing alkaline solution, and (II) a method in which an alkaline compound is dissolved in a solvent and diluted in such a way that it is diluted with an amount equivalent to the water-absorbing capacity of the carrier, is impregnated with the carrier. From the viewpoint of wastewater treatment, method (II) is preferable.

[0028] Preferably, the carrier is impregnated with an alkaline solution in an amount equivalent to 0.9 to 1.0 times the water absorption of the carrier; more preferably, the carrier is impregnated with an alkaline solution in an amount equivalent to 0.95 to 1.0 times the water absorption of the carrier. 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 less likely to occur. If the amount of alkaline solution is less than 1.0 times the water absorption of the carrier, the complete absorption of the alkaline solution into the carrier can be reliably ensured. In this disclosure, the water absorption of the carrier is a value measured with pure water, which, although strictly speaking, differs from the value for alkaline solutions, is conveniently used directly.

[0029] <Step 2. Step of contacting the carrier with impregnation solution A> In this step, the carrier impregnated with the alkaline solution is contacted with impregnation solution A. Solution A is a solution containing a copper-containing compound, a palladium-containing compound, and a gold-containing compound. Solution A may contain other components as needed.

[0030] The amount of each raw material compound (palladium-containing compound, gold-containing compound, and copper-containing compound) contained in solution A can be equal to the carrying amount of each catalyst component (metallic palladium, metallic gold, and metallic copper) in the desired catalyst composition, i.e., the final obtained catalyst. However, it is preferable to pre-add an excess amount of each raw material compound (palladium-containing compound, gold-containing compound, and copper-containing compound) relative to the amount of catalyst component in the final obtained catalyst. That is, the palladium-containing compound, gold-containing compound, and copper-containing compound are all in excess relative to the desired catalyst component carrying amount, so that the amount of raw material compound equivalent to the desired catalyst component carrying amount is multiplied by the respective excess rate and dissolved. The concentration of the catalyst component (palladium, gold, and copper) raw material compounds in solution A can be calculated from the amount of raw material compounds and the solution volume as calculated above. In practice, it is only necessary to measure the required amount (g) of raw material compound and dissolve it in the solvent in a manner that yields the preferred solution volume.

[0031] The excess rate of the raw material compounds of each catalyst component in solution A is calculated using the following formula: (Amount of catalyst component (mass) in the added raw material compounds - Desired amount of catalyst component (mass) to be maintained) / (Desired amount of catalyst component (mass) to be maintained) × 100 (%)

[0032] When the catalyst component is gold, calculate the amount (g) of gold-containing compound (e.g., chloroauric acid) equivalent to the amount (g) that should be held by each 1 kg of carrier. Multiply this amount by the carrier amount (kg) and (excess rate of gold-containing compound + 100) / 100 to obtain the amount (g) of gold-containing compound, then dissolve it in the solvent of solution A. Specifically, if the amount (g) of gold that should be held by each 1 kg of carrier is set to 10 g, then the amount of chloroauric acid (HAuCl4) containing 10 g of gold atoms becomes 17.26 g. When the excess rate is set to 80%, the amount of chloroauric acid added per 1 kg of carrier becomes 31.068 g (= 17.26 × ((80 + 100) / 100). Multiply this value by the amount of carrier used (kg) to obtain the amount of chloroauric acid, then dissolve it in the solvent of solution A. Solution A is prepared in the same manner for palladium and copper.

[0033] Regarding the excess rate of the raw material compounds of each catalyst component in solution A, the excess rate of the palladium-containing compound is preferably 2% to 50%, more preferably 5% to 40%, and even more preferably 10% to 20%. The excess rate of the gold-containing compound is preferably 2% to 150%, more preferably 10% to 100%, and even more preferably 25% to 90%. The excess rate 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 a solution A containing an excess of the raw material compound relative to the desired catalyst component holding amount, the contact time between the carrier and solution A required to obtain the desired catalyst component holding amount can be shortened. This suppresses the coarsening of gold particles caused by the dissolution and redeposition processes. When using a solution A containing an excess of the raw material compound relative to the desired catalyst component holding amount, step 3 (the dehydration step) is preferably performed at the point in time when the carrier holds the desired catalyst component holding amount. The timing of moving to step 3 is determined based on preliminary experiments. Details are described below.

[0035] As the palladium-containing compound in solution A, a palladium precursor capable of being converted into metallic palladium can be used. Examples of palladium precursors capable of being converted into metallic palladium include palladium chloride, palladium nitrate, palladium sulfate, sodium chloropalladium, potassium chloropalladium, barium chloropalladium, and palladium acetate, with sodium chloropalladium being preferred.

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

[0037] As the copper-containing compound in solution A, a copper precursor capable of being converted into metallic copper can be used. Examples of copper precursors capable of being converted into metallic copper include copper chloride, copper acetate, and copper nitrate, with copper chloride being preferred.

[0038] Examples of solvents for solution A include water, alcohols, and organic acids. Water is preferred from the perspective of not causing damage to the carrier and not being reactive with the compounds contained in solution A.

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

[0040] By contacting a carrier impregnated with an alkaline solution with an impregnated solution A, the metal compound of the raw material can be converted into a water-insoluble substance, forming a shell-type catalyst precursor in which the metal components such as palladium, gold and copper are predominantly present on the surface of the carrier.

[0041] There are no particular limitations on the contact temperature, but it is preferably 10–80°C, and more preferably 20–60°C. Setting the contact temperature above 10°C allows the conversion reaction to proceed fully. Setting the contact temperature below 80°C inhibits the agglomeration of gold, palladium, and copper.

[0042] The contact time is the time change of the retention rate of the catalyst component at a specific contact temperature, which can be confirmed by repeating preliminary experiments, and is set at the time when the desired retention amount is reached. Since the contact time cannot be changed for each catalyst component, the excess rate of the added amount of each raw material compound is adjusted in such a way that the desired retention amount is achieved at that contact time. The contact time is preferably 0.5 to 100 hours, more preferably 1 to 20 hours. Setting the contact time to less than 100 hours can suppress the deterioration of the carrier.

[0043] <Step 3. Dehydration Step> In this step, only the carrier is removed from the mixture of carrier and solution obtained in step 2. Compared with palladium-containing compounds and copper-containing compounds, gold-containing compounds such as chloroauric acid have a significantly lower hydrolysis rate. Therefore, if the carrier is immersed in solution A for a long time, compositional inhomogeneity is likely to occur in the carrier. In addition, if the carrier is immersed in solution A for a long time, gold particles tend to coarsen during the dissolution and redeposition process. In contrast, when the carrier carries the desired amount of catalyst components, separating the carrier from solution A can suppress the occurrence of compositional inhomogeneity and the coarsening of gold particles. There are no particular restrictions on the method of separating the carrier from the solution, and a suitable method can be determined from common methods considering the shape and morphology of the catalyst. For example, filtration, centrifugation, sedimentation, etc. can be used, with filtration being preferred. As a filtration method, methods such as passing the carrier through a mesh smaller than the size of the carrier can be cited. The carrier size is 3–8 mm, for example, it can pass through a mesh with a pore size of 1 mm. Preferably, solid-liquid separation is used to separate the solution until the water absorption rate of the carrier is less than 1.2 times.

[0044] <Step 4. Buffer Solution Step> In this step, after impregnation in solution A, the carrier separated from the solution is brought into contact with water or an aqueous solution at pH 7.0–11.5 (hereinafter collectively referred to as "solution B"). It is presumed that by performing this step 4, the state of gold can be brought close to that of Cl- uncoordinated Au(OH)3, which is expected to inhibit the aggregation of gold in the next step 5 (liquid phase reduction treatment step). Solution B can be stirred slowly, but it is better to let it stand to prevent damage to the carrier.

[0045] Gold-containing compounds, such as chloroauric acid, react with alkaline components to form AuCl3-n(OH)n and Au(OH)3. In the liquid-phase reduction process of step 5, if reduction is performed with Cl- coordinated to gold, it is easy for the gold particle size to increase and for gold particles to aggregate. The higher the pH of the solution, the more it promotes the substitution from Cl- to OH-. On the other hand, if the pH of the solution is too high, it becomes [Au(OH)4]- and the gold will dissolve again. Furthermore, if the solution temperature is high, it is easier for the gold particle size to increase and for gold particles to aggregate.

[0046] By implementing the buffer solution step, the pH of the solution after reacting with the alkaline component can be controlled within the range where the gold is close to the Cl- uncoordinated state, that is, close to Au(OH)3, and the gold does not undergo redissolution. By reducing at low temperature, the aggregation of gold particles in the liquid phase reduction process can be suppressed, and a catalyst for the manufacture of vinyl acetate with an alloy state of palladium and gold suitable for the formation reaction of vinyl acetate can be manufactured.

[0047] Solution B can be any water or aqueous solution with a pH of 7.0 to 11.5 at the operating temperature of step 4 (e.g., room temperature (20°C)). The pH mentioned above refers to the pH of solution B before contact with the carrier. The pH is preferably 8.0 to 11.0. In step 4, the pH may deviate from the above range, but it is preferable to maintain the pH within the above range. In this disclosure, the pH is the value measured using a pH meter (desktop pH meter, Horiba Advanced Technology Co., Ltd.) at the temperature of step 4. Solution B can be water only or an alkaline aqueous solution. Other components may be dissolved in solution B as needed.

[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. Lithium, sodium, or potassium may be used as alkali metals. Barium or strontium may be used as alkaline earth metals. Sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, barium hydroxide, or strontium hydroxide are preferred as alkaline compounds.

[0049] For solution B, a pH buffer solution is preferably used to minimize pH changes in step 4. The pH of the pH buffer solution before contact with the carrier is preferably 7.0 to 11.5, more preferably 8.0 to 11.0. By using a pH buffer solution, the pH of solution B can be prevented from becoming too high, thus preventing the redissolution of gold. Examples of pH buffer solutions include sodium phosphate buffer (pH 5.8–7.8), sodium citrate buffer (pH 6.0–8.0), phosphate-buffered saline (pH 6.4–8.4), sodium ethylenediaminetetraacetic acid buffer (pH 7.0–9.0), hydrochloric acid buffer (pH 7.0–9.0), EDTA buffer (pH 7.0–9.0), acetate-ethanolamine buffer (pH 8.6–10.6), potassium borate buffer (e.g., pH 8.1–10.1), sodium borate buffer (e.g., pH 9.1), and carbonate-bicarbonate buffer (e.g., pH 10.0). Potassium borate buffer, sodium borate buffer, or carbonate-bicarbonate buffer are preferred, with carbonate-bicarbonate buffer being even more preferred. Furthermore, regarding each buffer solution, "(sodium)" or "(potassium)" respectively refers to the relative ion being sodium or potassium.

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

[0051] The temperature of solution B in step 4 is not particularly limited, but it is preferably 10–80°C, and more preferably 20–60°C. Setting the contact temperature above 10°C allows for sufficient conversion reaction. Setting the contact temperature below 80°C inhibits the aggregation of gold, palladium, and copper.

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

[0053] <Step 5. Liquid-phase reduction process> It is desired to reduce the carrier holding the reactants containing the raw material compound and the basic compound to metallic palladium, metallic gold, and metallic copper. In this disclosure, "metallic copper," "metallic palladium," and "metallic gold" refer to metals with a valence of 0. The reduction process can be carried out in the liquid phase. Through the reduction process, all palladium, gold, and copper can be reduced to their metallic state, i.e., 0 valence.

[0054] Liquid-phase reduction can be carried out using either non-aqueous or aqueous systems of alcohols or hydrocarbons. Examples of reducing agents include carboxylic acids and their salts, aldehydes, hydrogen peroxide, sugars, polyphenols, boron compounds, amines, or 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 polyphenols include hydroquinone. Examples of boron compounds include diborane and sodium borohydride. Hydrazine, formaldehyde, acetaldehyde, hydroquinone, sodium borohydride, and potassium citrate are preferred reducing agents, with hydrazine being particularly preferred.

[0055] The liquid phase temperature in the liquid-phase reduction treatment is in the range of 0–15°C. Preferably, it is in the range of 0–13°C, more preferably in the range of 0–10°C, and even more preferably in the range of 3–7°C. If the liquid phase temperature, i.e., the liquid-phase reduction treatment temperature, is in the range of 0–15°C, the selectivity of vinyl acetate can be improved. The reduction time is preferably in the range of 0.5–24 hours, more preferably in the range of 1–10 hours. If the reduction time is 0.5 hours or more, the reduction can be sufficiently carried out. On the other hand, if the reduction time is less than 24 hours, the aggregation of palladium, gold, and copper can be suppressed.

[0056] The reduced carrier system should be washed with pure water or the like as needed. Washing can be done continuously or in batches. The washing temperature is preferably in the range of 5 to 200°C, and more preferably in the range of 15 to 80°C. There is no particular limitation on the washing time, as long as the conditions are sufficient for removing any remaining undesirable impurities are selected. Examples of undesirable impurities include, for example, chlorine-containing compounds and chloride ions. After washing, the carrier can be dried by heating if necessary.

[0057] <Step 6. Step of supporting acetate on the carrier> Acetate can be supported by impregnating the carrier with a solution containing the required amount of acetate and then drying it. The amount of acetate solution used is preferably 0.9 to 1 times the mass of the water absorbed by the carrier. Acetate support is typically carried out after reduction treatment, but it can also be carried out before 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 alkali metal acetates include lithium, sodium, and potassium acetates. Sodium acetate and potassium acetate are preferred acetates, especially potassium acetate.

[0059] The better the acetate holding capacity, the mass of acetate held per 1 kg carrier is 40 g to 125 g.

[0060] [Catalyst for the manufacture of vinyl acetate] The mass of palladium supported on each 1 kg 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 gold held per 1 kg 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 copper carried per 1 kg 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 acetate supported per 1 kg of carrier is preferably 40 g to 125 g, more preferably 50 g to 88 g.

[0064] The best quality ratio of palladium to gold to copper is palladium: gold: copper = 100: 70-130: 8.3-9.5.

[0065] The holding amounts of metal elements and acetates were determined by the method described in the examples.

[0066] The vinyl acetate manufacturing catalyst obtained by the method disclosed herein has an eggshell structure in which palladium, gold, and copper are largely supported on the surface portion of a carrier. The thickness of the shell portion varies depending on the type of carrier, alkaline solution, and solution containing the catalyst metal element. When using 5 mm diameter spherical silicon dioxide as a carrier, the shell portion preferably has a thickness of 0.05 to 0.5 mm, and more preferably 0.1 to 0.3 mm. If the shell portion thickness is 0.05 mm or more, the catalyst activity can be maintained even when the surface portion of the carrier peels off during the reaction. If the shell portion thickness is less than 0.5 mm, the catalyst concentration on the surface portion of the carrier can be sufficiently increased, and the advantages of shell-type support can be enjoyed economically. Acetate does not necessarily need to be supported in a shell and can also exist uniformly throughout the catalyst.

[0067] [Specific Example of Catalyst Manufacturing] The following shows a preferred specific example of catalyst manufacturing. 1. Impregnate a carrier with an alkaline solution equivalent to the water absorption capacity of the carrier. 2. Dilute excess amounts of palladium-containing compounds, gold-containing compounds, and copper-containing compounds with pure water to twice the water absorption capacity of the carrier, relative to the desired amount of each catalyst component, to obtain solution A. By immersing the carrier in solution A for a specific time for contact impregnation, a catalyst precursor bearing the desired amount of catalyst components is formed. 3. Separate the contact-impregnated catalyst precursor from the solution obtained in step 2. 4. Place the catalyst precursor obtained in step 3 in water or an aqueous solution with a pH of 7.0 to 11.5. 5. Contact the catalyst precursor obtained in step 4 with a reducing agent for liquid-phase reduction treatment. 6. Wash the reduced carrier with pure water. 7. Dry the washed carrier. 8. Load the carrier with a specific amount of acetate. 9. Dry the carrier holding the catalyst components.

[0068] [Manufacturing of Vinyl Acetate] Hereinafter, a method for manufacturing vinyl acetate using a catalyst for manufacturing vinyl acetate produced by the method disclosed herein will be described. The reaction for manufacturing vinyl acetate preferably uses acetic acid, ethylene, and oxygen as reactants and is carried out in the gas phase. The gas-phase reaction can be any conventional form, but a fixed-bed flow reaction is preferred.

[0069] The reaction formula is as follows: CH2=CH2 + CH3COOH + 1 / 2O2 → CH2=CHOCOCH3 + H2O

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

[0071] The raw material gas includes ethylene, acetic acid (gas), and oxygen, and may further include nitrogen, carbon dioxide, or rare gases as diluents as needed. When ethylene, acetic acid, and oxygen are defined as reactants, the ratio of reactants to diluents, expressed in moles, is preferably reactants:diluent = 1:0.05 to 9, more preferably reactants:diluent = 1:0.1 to 3.

[0072] When the reaction is carried out in a fixed-bed flow-through reaction, the feed gas is preferably supplied to the reactor at a space velocity (SV) of 10 to 15,000 hr⁻¹ under standard conditions, and more preferably at 300 to 12,000 hr⁻¹. By setting the space velocity to 10 hr⁻¹ or more, the heat of reaction can be appropriately removed. On the other hand, by setting the space velocity to 15,000 hr⁻¹ or less, equipment such as compressors can be made to a practical size.

[0073] It is preferable to add 0.5 to 20 mol% water as water vapor to the feed gas, and more preferably 1 to 18 mol%. Although not bound by any theory, it is believed that the presence of water in the reaction system can inhibit the efflux of acetate from the catalyst. Even if more than 20 mol% water is added, the above effect will not be improved. Moreover, there is a risk of hydrolysis of vinyl acetate. Therefore, the presence of a large amount of water in the feed gas is not advisable.

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

[0075] The reaction temperature is preferably in the range of 100 to 300°C, and more preferably in the range of 120 to 250°C. If the reaction temperature is above 100°C, a suitable reaction rate can be maintained. As long as the reaction temperature is below 300°C, the heat of reaction is easily removed.

[0076] The reaction pressure is preferably in the range of 0 to 3 MPaG (gauge pressure), and more preferably in the range of 0.1 to 1.5 MPaG. As long as the reaction pressure is above 0 MPaG, an appropriate reaction rate can be maintained. As long as the reaction pressure is below 3 MPaG, it is not necessary to make the equipment such as the reaction tubes high-pressure resistant, and equipment costs can be reduced.

[0077] High-purity ethylene is preferred as the raw material for the reaction, but lower saturated hydrocarbons such as methane, ethane, and propane may also be mixed in.

[0078] The ethylene and acetic acid, the raw materials for the reaction, can each be produced from fossil raw materials, biomass raw materials, or a mixture thereof. The concentration of 14 carbon atoms in ethylene, acetic acid, and vinyl acetate, relative to the total number of carbon atoms, can be 1×10⁻¹⁴ to 2×10⁻¹².

[0079] There are no particular limitations on oxygen. It can also be diluted with inert gases such as nitrogen or carbon dioxide, or supplied in the form of air. However, when circulating the reaction gases, it is generally advantageous to use high-concentration oxygen, preferably oxygen with a purity of 99% or higher. [Example]

[0080] The present invention will be further illustrated by the following embodiments, but the present invention is not limited to these embodiments.

[0081] (Example 1) Modulation of catalyst A as a carrier, commercially available silica spherical carrier (particle diameter 5mm, BET specific surface area 176m2 / g, bulk density 470g / L, water absorption rate 0.85g-water / g-carrier, average pore size 17.2nm, hereinafter referred to as "carrier"), and the catalyst was modulated using the following procedure.

[0082] Step 1. Impregnate 23.5g of the carrier (water absorption capacity 20.0g) with an aqueous solution containing 4.9g of Na2SiO3・9H2O, equivalent to the water absorption capacity of the carrier (1.1 times by mass). Shake the container containing the carrier and the aqueous solution to ensure complete impregnation, and let it stand in a sealed container for 3 hours. The water absorption capacity is calculated from the carrier amount of 23.5g and the water absorption rate of 0.85g-water / g-carrier (the same applies to the following examples and comparative examples).

[0083] Step 2. The carrier obtained in Step 1 is immersed in an aqueous solution containing 1.06 g of Na2PdCl4, 0.80 g of HAuCl4, and 0.074 g of copper chloride dihydrate, in an amount twice the mass of the carrier's water absorption. The solution is left to stand at room temperature (25°C) for 2 hours to obtain a catalyst precursor carrying the desired amount of catalyst components. The standing time is determined in advance by a preliminary experiment based on the relationship between the amount of catalyst components carried and the time required to reach the desired carrying amount. The desired carrying amount of catalyst components is defined as 13.8 g / kg palladium, 12.5 g / kg gold, and 1.15 g / kg copper per 1 kg of carrier. The excess percentages of each raw material compound are set as follows: 18.3% for palladium-containing compounds, 56.8% for gold-containing compounds, and 2.0% for copper-containing compounds.

[0084] Step 3. Separate the catalyst precursor from the dispersion obtained in step 2 using a metal mesh with a pore size of 1 mm to perform liquid removal.

[0085] Step 4. Immerse the catalyst precursor obtained in step 3 in ion-exchange water (pH=7.0) with a mass of 4 times the water absorption of the carrier at 25°C, and let it stand at room temperature (25°C) for 18 hours.

[0086] Step 5. Separate the catalyst precursor from the dispersion obtained in Step 4 using the same metal mesh as described above, and perform dehydration. Immerse the separated catalyst precursor in an aqueous solution containing 5.9 g of 52% hydrazine hydrate aqueous solution, twice the mass of the water absorbed by the carrier, and allow it to stand in an ice bath (5°C) for 4 hours for liquid-phase reduction treatment. Next, wash the palladium / gold / copper / carrier composition with deionized water, continuing washing until chloride ions disappear from the washed water. Dry the washed palladium / gold / copper / carrier composition with hot air at 110°C for 4 hours.

[0087] Step 6. The palladium / gold / copper / carrier composition obtained in step 5 is impregnated at room temperature (25°C) with an aqueous solution containing 1.7g of potassium acetate in an amount equivalent to 0.9 times 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) The catalyst B was modulated using the same silica sphere carrier as in Example 1, and the catalyst was modulated using the following procedure.

[0089] Step 1. Impregnate 23.5g of the carrier (20.0g of water absorption) with an aqueous solution containing 4.4g of Na2SiO3・9H2O, which is equivalent to the amount of water absorbed by the carrier (1.1 times the mass). Shake the container containing the carrier and the aqueous solution to ensure complete impregnation, and let it stand in a sealed container for 3 hours.

[0090] Step 2. The carrier obtained in Step 1 is immersed in an aqueous solution containing 1.06 g Na2PdCl4, 0.80 g HAuCl4, and 0.074 g copper chloride dihydrate, in an amount twice the mass of the carrier's water absorption. The solution is left to stand at room temperature (25°C) for 20 hours to obtain a catalyst precursor carrying the desired amount of catalyst components. The standing time is determined in advance by using a preparatory experiment to establish the relationship between the amount of catalyst components carried and the time required to reach the desired carrying amount. The desired carrying amount of catalyst components is defined as 13.4 g / kg palladium, 16.8 g / kg gold, and 1.13 g / kg copper per 1 kg of carrier. The excess percentage of each raw material compound is set as follows: 22.0% for palladium-containing compounds, 17.0% for gold-containing compounds, and 4.0% for copper-containing compounds.

[0091] Step 3. Separate the catalyst precursor from the dispersion obtained in step 2 using a metal mesh with a pore size of 1 mm to perform dehydration.

[0092] Step 5. Immerse the separated catalyst precursor in an aqueous solution containing 5.9 g of 52% hydrazine hydrate aqueous solution, twice the mass of the carrier's water absorption, and allow it to stand in an ice bath (5°C) for 4 hours for liquid-phase reduction treatment. Next, wash the palladium / gold / copper / carrier composition with deionized water, continuing washing until chloride ions disappear from the washed water. Dry the washed palladium / gold / copper / carrier composition with hot air at 110°C for 4 hours.

[0093] Step 6. The palladium / gold / copper / carrier composition obtained in step 5 is impregnated at room temperature (25°C) with an aqueous solution containing 1.7g of potassium acetate in an amount equivalent to 0.9 times 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) The catalyst C was modulated using the same silica sphere carrier as in Example 1, and the catalyst was modulated using the following procedure.

[0095] Step 1. Impregnate 23.5g of the carrier (20.0g water absorption) with an aqueous solution containing 4.9g of Na2SiO3・9H2O, equivalent to 1.1 times the water absorption of the carrier. Shake the container containing the carrier and the aqueous solution to ensure complete impregnation, and let it stand in a sealed container for 3 hours.

[0096] Step 2. The carrier obtained in Step 1 is immersed in an aqueous solution containing 0.89 g of Na2PdCl4, 0.62 g of HAuCl4, and 0.091 g of copper chloride dihydrate, in an amount twice the mass of the carrier's water absorption. The solution is left to stand at room temperature (25°C) for 20 hours to obtain a catalyst precursor carrying the desired amount of catalyst components. The standing time is determined in advance by using a preparatory experiment to establish the relationship between the amount of catalyst components carried and the time required to reach the desired carrying amount. The desired carrying amount of catalyst components is defined as 12.9 g / kg palladium, 12.0 g / kg gold, and 1.17 g / kg copper per 1 kg of carrier. The excess percentages of each raw material compound are set as follows: 6.8% for palladium-containing compounds, 28.1% for gold-containing compounds, and 23.6% for copper-containing compounds.

[0097] Step 3. Separate the catalyst precursor from the dispersion obtained in step 2 using a metal mesh with a pore size of 1 mm to perform liquid removal.

[0098] Step 4. The catalyst precursor obtained in step 3 is immersed at 25°C in a pH buffer solution (pH=10.0) containing 4 times the mass of the carrier water absorption of NaHCO3: 0.86g and Na2CO3: 0.68g, and left to stand at 25°C for 3 hours.

[0099] Step 5. Separate the catalyst precursor from the dispersion obtained in Step 4 using the same metal mesh as described above, and perform dehydration. Immerse the separated catalyst precursor in an aqueous solution containing 4.8 g of 52% hydrazine hydrate aqueous solution, twice the mass of the water absorbed by the carrier, and allow it to stand at 5°C for 4 hours for liquid-phase reduction treatment. Next, wash the palladium / gold / copper / carrier composition with deionized water, continuing washing until chloride ions disappear from the washed water. Dry the washed palladium / gold / copper / carrier composition with hot air at 110°C for 4 hours.

[0100] Step 6. The palladium / gold / copper / carrier composition obtained in step 5 is impregnated at 25°C with an aqueous solution containing 1.7g of potassium acetate in an amount equivalent to 0.9 times 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) The catalyst D was prepared by the same operation as in Example 3 except that the liquid phase reduction treatment temperature was changed to 15°C in step 5 of Example 3, and catalyst D was obtained.

[0102] (Comparative Example 1) The catalyst E was prepared by performing the same operation as in Example 1 except that the liquid phase reduction treatment temperature was changed to 25°C in step 5 of Example 1, and thus catalyst E was obtained.

[0103] (Comparative Example 2) The catalyst F was modulated using the same silicon dioxide sphere carrier as in Example 1, and the catalyst was modulated using the following procedure.

[0104] Step 1. Impregnate 23.5g of the carrier (water absorption capacity 20.0g) with an aqueous solution containing 7.5g of Na2SiO3・9H2O, equivalent to the water absorption capacity of the carrier (2.9 times its mass). Shake the container containing the carrier and the aqueous solution to ensure complete impregnation, and air dry for 5 minutes. The water absorption capacity is calculated from the carrier weight of 23.5g and the water absorption rate of 0.85g-water / g-carrier.

[0105] Step 2. Immerse the carrier obtained in Step 1 in an aqueous solution containing twice the mass of the carrier's water absorption amount of Na2PdCl4: 0.87g, HAuCl4: 0.38g and copper chloride dihydrate: 0.04g, and let it stand at room temperature for 20 hours.

[0106] Step 5. Add 1.9 g of 52% (w / w) hydrazine hydrate aqueous solution to the dispersion obtained in Step 2, mix gently, and let stand at 25°C for 4 hours to perform liquid-phase reduction treatment. Next, wash the palladium / gold / copper / support composition obtained in the previous step with deionized water, continuing washing until chloride ions disappear from the washed water. Dry the washed palladium / gold / copper / support composition with hot air at 110°C for 4 hours.

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

[0108] [Evaluation of Catalyst] <Determination of Metal (Palladium, Gold, and Copper) and Potassium Acetate Support> 3g of catalyst sample was pulverized and pressed into a disc shape with an inner diameter of 3cm. The metal content of the disc was determined using a RIGAKU Corporation ZSX Primus II fluorescence X-ray spectrophotometer. Potassium acetate is a quantitative amount of potassium atoms, converted to potassium acetate content.

[0109] <Catalyst Activity Evaluation Test> 6.7 mL of catalyst was diluted with 75 mL of glass beads and filled into a reaction tube (SUS316L, inner diameter 22 mm, length 480 mm). Under reaction conditions of 150 °C and 0.6 MPaG, a gas with a composition of C2H4 / O2 / H2O / HOAc / N2 = 45 / 6 / 5 / 23 / 21 (mol%) was allowed to flow at a flow rate of 66.7 NL / h (SV: 10000 h⁻¹) for 240 hours to evaluate the catalyst 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 under the same vinyl acetate activity was compared among various catalysts. For example, the vinyl acetate selectivity at an activity of 750 (g / L-cat・h) is calculated by interpolation from multiple approximate curves formed by plotted points of vinyl acetate activity and vinyl acetate selectivity at various reaction temperatures.

[0110] The following method was used to analyze the reactor outlet gas.

[0111] 1. Oxygen was analyzed using the absolute calibration curve method. 50 mL of effluent gas was collected and allowed to flow completely into a 1 mL gas sampler attached to the gas chromatograph. Analysis was performed under the following conditions: Gas Chromatography Instrument: Gas chromatograph (Shimadzu Corporation GC-14B) equipped with a Shimadzu gas sampler (MGS-4: 1 mL metering tube) Column: MS-5A IS 60 / 80 mesh (3 mm Φ × 3 m) Carrier Gas: Helium (flow rate 20 mL / min) Temperature Conditions: Detector and vaporization chamber temperatures 110°C, column temperature 70°C Fixed Detector: TCD (He pressure 70 kPaG, current 100 mA)

[0112] 2. Acetic acid was analyzed using an internal standard method. 1 mL of 1,4-dimethyl ether was added to 10 mL of the reaction solution as an internal standard. 0.2 μL of this solution was injected, and analysis was performed under the following conditions: Gas Chromatography System: Shimadzu Corporation GC-14B; Column: Thermon 3000 packed column (3 m length, 0.3 mm inner diameter); Carrier Gas: Nitrogen (flow rate 20 mL / min); Temperature Conditions: Detector and vaporization chamber temperatures were 180 °C; column temperature was maintained at 50 °C for 6 minutes from the start of analysis, then increased to 150 °C at a rate of 10 °C / min and held at 150 °C for 10 minutes; Detector: FID (H2 pressure 40 kPaG, air pressure 100 kPaG).

[0113] 3. For vinyl acetate, the internal standard method was used. 1g of 1,4-dimethyl ether was added to 6g of the reaction solution as an internal standard, and 0.3μL of this solution was injected. Analysis was performed under the following conditions: Gas Chromatography: Shimadzu GC-9A; Column: TC-WAX capillary column (30m length, 0.25mm inner diameter, 0.5μm film thickness); Carrier gas: Nitrogen (flow rate 30mL / min); Temperature conditions: Detector and vaporization chamber temperatures were 200℃; column temperature was maintained at 45℃ for 2 minutes from the start of analysis, then increased to 130℃ at a rate of 4℃ / min, held at 130℃ for 15 minutes, then increased to 200℃ at a rate of 25℃ / min, held at 200℃ for 10 minutes; Detector: FID (H2 pressure 60kPaG, air pressure 100kPaG).

[0114] Table 1 shows the evaluation results of the catalyst. The selectivity of vinyl acetate is based on ethylene.

[0115] [Table 1] Example Comparative example catalyst Step 4 Step 5 Component content per 1kg of carrier [g / kg] Catalyst metal mass ratio Vinyl acetate selectivity [%] 1) Solution B pH reduction temperature [℃] Restore time [hr] Pd Au Cu CH3COOK Pd Au Cu Example 1 Catalyst A Ion-exchanged water 7.0 5 4 13.8 12.5 1.15 72.3 100.0 90.7 8.3 95.8 Example 2 Catalyst B none - 5 4 13.4 16.8 1.13 72.3 100.0 125.4 8.4 95.7 Example 3 Catalyst C pH buffer solution 10.0 5 4 12.9 12.0 1.17 72.3 100.0 93.4 9.1 95.9 Example 4 Catalyst D pH buffer solution 10.0 15 4 12.9 12.0 1.17 72.3 100.0 93.4 9.1 95.9 Comparative Example 1 Catalyst E Ion-exchanged water 7.0 25 4 13.8 12.5 1.15 72.3 100.0 90.7 8.3 94.7 Comparative Example 2 Catalyst F none - 25 4 13.0 8.3 1.08 72.3 100.0 63.9 8.4 94.2 1) Selectivity is the interpolation of vinyl acetate activity (STY) [g / L-cat・h] at a reaction temperature of 750°C.

[0116] When comparing Examples 1-4 with Comparative Examples 1-2, a significant effect was observed: by lowering the temperature of the solution containing the reducing agent (used when reducing compounds containing palladium, gold, and copper respectively supported on a carrier to metals) from 25°C to below 15°C, the selectivity of vinyl acetate increased by 1.0 to 1.7 points. It is speculated that this effect is due to the difference in alloy state.

Claims

1. A method for manufacturing a catalyst for vinyl acetate production, comprising a carrier, palladium, gold, copper, and acetate, comprising the following sequential steps: Step 1. Impregnating the carrier with an alkaline solution; Step 2. Contacting the aforementioned carrier with a solution impregnating a palladium-containing compound, a gold-containing compound, and a copper-containing compound; Step 3. Separating the aforementioned carrier from the solution preceding Step 2 while the aforementioned carrier is loaded with the desired amount of each catalyst component; Step 5. Performing a liquid-phase reduction treatment within a temperature range of 0°C to 15°C; and Step 6. Loading the aforementioned carrier with acetate.

2. The manufacturing method of claim 1 further includes, between step 3 and step 5: step 4. contacting the aforementioned carrier with water or an aqueous solution with pH = 7.0 to 11.

5.

3. The manufacturing method as claimed in claim 1 or 2, wherein the mass of palladium supported on each 1 kg of the aforementioned carrier is 5.00 g to 20.0 g.

4. The manufacturing method as claimed in claim 1 or 2, wherein the mass of the gold-bearing metal in each 1 kg of the aforementioned carrier is 4.00 g to 20.0 g.

5. The manufacturing method as claimed in claim 1 or 2, wherein the mass of copper supported by each 1 kg of the aforementioned carrier is 0.25 g to 5.00 g.

6. The manufacturing method as claimed in claim 1 or 2, wherein the mass of acetate supported on each 1 kg of the aforementioned carrier is 40 g to 125 g.

7. The manufacturing method as claimed in claim 1 or 2, wherein the mass ratio of palladium to gold to copper is 100:70 to 130:8.3 to 9.

5.

8. A method for manufacturing vinyl acetate, wherein a vinyl acetate manufacturing catalyst obtained by any one of claims 1 to 7 is used, and ethylene, oxygen and acetic acid are used as raw materials.