Process for producing catalyst for producing vinyl acetate and process for producing vinyl acetate

Abstract

Provided is a method for producing a catalyst capable of producing vinyl acetate at a particularly high selectivity while ensuring high catalytic activity. One method is a method for producing a catalyst for producing vinyl acetate, which comprises a carrier, copper, palladium, gold, and an acetate salt, and the method comprises the following steps in order: Step 1, a step of impregnating the carrier with an alkali solution; Step 2, a step of bringing the carrier into contact with a solution containing a compound containing copper, a compound containing palladium, and a compound containing gold; Step 3, a step of performing a reduction treatment; and Step 4, a step of supporting the carrier with an acetate salt.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a catalyst used in the production of vinyl acetate from acetic acid, ethylene, and oxygen, and a method for manufacturing vinyl acetate using the catalyst. Background Technology

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

[0003] As a catalyst for the production of vinyl acetate from acetic acid, ethylene, and oxygen, catalysts obtained by supporting palladium, gold, and potassium acetate on silica are widely used. Palladium is considered the active site in this reaction, and gold is believed to have the following effects: in addition to inhibiting palladium aggregation, it also reduces the formation of carbon dioxide as a byproduct, thereby improving the selectivity of vinyl acetate. For gold to exert its effect, gold atoms need to be present in close proximity to palladium. In Patent Document 1, efforts were made in the impregnation process into the support to achieve a state in which the palladium and gold are supported in close proximity.

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

[0005] In Patent Document 2, copper is added in addition to palladium and gold, thereby increasing the selectivity of vinyl acetate.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2008-080326

[0009] Patent Document 2: Japanese Patent Publication No. 2002-516749 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In Patent Document 2, a palladium-containing compound, a gold-containing compound, and a copper-containing compound are supported on a support in separate steps. The effect of the copper-containing compound in the support step on the final state of metallic palladium and metallic gold is significantly smaller compared to cases where they are supported in the same step. Previously, it was not known that a catalyst could be manufactured by supporting a palladium-containing compound, a gold-containing compound, and a copper-containing compound on a support in the same step, and that the selectivity of vinyl acetate would be improved when using the catalyst obtained in this way.

[0012] The objective of this invention is to provide a method for manufacturing a catalyst capable of producing vinyl acetate with particularly high selectivity while ensuring high catalytic activity.

[0013] Methods for solving problems

[0014] The inventors of this application, through repeated and in-depth research to solve the aforementioned problems, discovered a method for manufacturing a catalyst characterized by simultaneously loading a palladium-containing compound, a gold-containing compound, and a copper-containing compound with an alkaline component in the same step, thereby successfully producing vinyl acetate with a particularly high selectivity. Gold-containing compounds, such as chloroauric acid, typically hydrolyze slowly, resulting in slow loading onto a support. However, if a copper-containing compound coexists with the hydrolysis of the gold-containing compound, the copper-containing compound is rapidly hydrolyzed, and the copper-containing compound supported on the support adsorbs the gold-containing compound in the solution. As a result, the residence time of the gold-containing compound in solution is shortened, thus enabling the gold to be micronized compared to cases where the copper-containing compound is not added in the same step. The micronized gold significantly contributes to improving the selectivity of vinyl acetate. Catalysts prepared by the method described in Patent Document 2, which involves loading a copper-containing compound in a step different from the step of loading the palladium-containing compound and the gold-containing compound, do not exhibit the particularly high selectivity of this invention.

[0015] That is, the present invention includes the following [1] to [6]. [1]

[0017] A method for manufacturing a catalyst for the production of vinyl acetate comprising a support, copper, palladium, gold, and an acetate, the method comprising the following steps in sequence:

[0018] Process 1. The process of impregnating the carrier with an alkaline solution;

[0019] Step 2. A step of contacting the carrier with a solution containing a compound containing copper, a compound containing palladium, and a compound containing gold;

[0020] Step 3. The process of performing reduction treatment; and

[0021] Step 4. The step of loading the carrier with acetate. [2]

[0023] According to the method described in [1], the mass of copper supported on each 1 kg catalyst is more than 0.1 g and less than 1.6 g. [3]

[0025] According to the method described in [1] or [2], the mass of palladium supported on each 1 kg catalyst is more than 8.0 g and less than 16.0 g. [4]

[0027] According to any one of [1] to [3], the mass of gold supported on each 1 kg catalyst is more than 4.0 g and less than 12.0 g. [5]

[0029] According to any one of [1] to [4], the mass of acetate supported on each 1 kg catalyst is 40 g or more and 100 g or less. [6]

[0031] A method for manufacturing vinyl acetate, which uses ethylene, oxygen and acetic acid as raw materials, is characterized by using a catalyst for manufacturing vinyl acetate obtained by any one of [1] to [5].

[0032] Invention Effects

[0033] According to the method of the present invention, a catalyst for the production of vinyl acetate can be easily manufactured by supporting copper, palladium and gold on a support, and compared with conventional methods, the selectivity of vinyl acetate can be significantly improved while ensuring high catalytic activity. Attached Figure Description

[0034] [ Figure 1 [A graph showing the relationship between copper loading and vinyl acetate selectivity in the examples and comparative examples.]

[0035] [ Figure 2 [Graphic representation showing the relationship between gold loading and vinyl acetate selectivity in the examples and comparative examples.] Detailed Implementation

[0036] The embodiments of the present invention will be described below, but the present invention is not limited to these embodiments and various modifications can be made within the scope of the present invention.

[0037] [Method for manufacturing a catalyst for producing vinyl acetate]

[0038] One embodiment of the method for manufacturing a catalyst for producing vinyl acetate includes the steps shown below in sequence.

[0039] Step 1. The process of impregnating the carrier with an alkaline solution.

[0040] Step 2. The step of contacting the carrier with a solution containing a compound containing copper, a compound containing palladium, and a compound containing gold (hereinafter also referred to as "Solution A").

[0041] Step 3. The process of performing reduction treatment.

[0042] Step 4. The process of loading acetate onto the carrier.

[0043] In one embodiment, step 2 is performed after step 1, in which the support is contacted with a solution A containing a compound containing copper, a compound containing palladium, and a compound containing gold, to form a catalyst precursor supported on the support.

[0044] Steps 1 through 4 are preferably performed in the order described above, but other steps may be included to improve the performance of the catalyst. Solution A may contain other components. The reduction treatment in step 3 is to convert the copper-containing compound, the palladium-containing compound, and the gold-containing compound into metallic copper, metallic palladium, and metallic gold, respectively, and therefore must be performed after step 2. Each step will be described in detail below.

[0045] <Step 1. The process of impregnating the carrier with an alkaline solution>

[0046] In this process, the carrier is impregnated with an alkaline solution. This process can be carried out at room temperature. Once the impregnation is complete, the carrier can be dried, or it can proceed to the next process without drying.

[0047] There are no particular limitations on the support; porous materials commonly used as supports for catalysts can be used. Preferred supports include silica, alumina, silica-alumina, diatomaceous earth, montmorillonite, or titanium dioxide, with silica being more preferred. When using a material primarily composed of silica as the support, it is generally suitable that the silica content of the support is at least 50% by mass and at least 90% by mass relative to the mass of the support.

[0048] The specific surface area of ​​the carrier, as measured by the BET method, is preferably at least 0.01 m². 2 / g, more preferably 10 to 1000m 2 The range of g / g is particularly preferred to be 100–500 m. 2The bulk density of the support is preferably in the range of 50–1000 g / L, particularly preferably in the range of 300–500 g / L. The water absorption rate of the support is preferably in the range of 0.05–3 g-water / g-support, particularly preferably in the range of 0.1–2 g-water / g-support. Regarding the micropore structure of the support, the average micropore diameter is preferably in the range of 1–1000 nm, particularly preferably in the range of 2–800 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 support required to obtain catalytic activity can be ensured.

[0049] In determining the pore size distribution of a carrier, mercury porosimetry and gas adsorption (BJH) methods are widely used. According to the IUPAC (International Union of Pure and Applied Chemistry) classification of pores, mercury porosimetry can determine large pores larger than 50 nm and a portion of medium-sized pores larger than 2 nm but smaller than 50 nm, while gas adsorption can determine medium-sized pores and micropores smaller than 2 nm. An appropriate measurement method can be selected based on the pore size.

[0050] In this disclosure, the water absorption rate of the carrier refers to the value measured using the following measurement method.

[0051] 1. Measure approximately 5g (W1g) of the carrier using a balance and place it into a 100mL beaker.

[0052] 2. Add approximately 15 mL of pure water (ion-exchanged water) to the beaker, ensuring complete coverage of the carrier.

[0053] 3. Let it sit for 30 minutes.

[0054] 4. Place the contents of the beaker onto the metal mesh and sprinkle with pure water.

[0055] 5. Gently press with a paper towel to remove the water adhering to the surface of the carrier until the surface shine disappears.

[0056] 6. Determine the total mass of the carrier and pure water (W2g).

[0057] 7. Calculate the water absorption rate of the carrier using the following formula.

[0058] Water absorption rate (g-water / g-carrier) = (W2-W1) / W1

[0059] Therefore, the water absorption capacity (g) of the carrier can be calculated by the water absorption rate of the carrier (g-water / g-carrier) × the mass (g) of the carrier used.

[0060] 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 in accordance with the reaction method, reactor, etc., used.

[0061] 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, more preferably in the range of 3 to 8 mm. When filling a tubular reactor with catalyst and carrying out a gas-phase reaction, if the particle diameter is 1 mm or more, it is possible to prevent excessive increase in pressure loss during gas flow and to effectively circulate the gas. On the other hand, if the particle diameter is 10 mm or less, it becomes easier for the feed gas to diffuse into the interior of the catalyst, and the catalytic reaction can be carried out effectively. In addition, the number of catalyst particles filled into the tubular reactor is not excessively reduced, so it is possible to ensure that the total surface area of ​​the catalyst particles is sufficient to ensure that the metal components (copper, palladium, gold, etc.) dispersed on the surface of the carrier are in an amount suitable for the reaction.

[0062] The alkaline solution can be a solution of any alkaline compound. Examples of alkaline compounds include, for instance, 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 can be used as alkali metals. Barium or strontium can be used as alkaline earth metals. Sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, barium hydroxide, or strontium hydroxide are suitable alkaline compounds.

[0063] There are no particular limitations on the solvents used for alkaline solutions; examples include water, methanol, and ethanol, with water being the preferred choice.

[0064] The basic compound is used in excess relative to the total amount of copper, palladium, and gold described later. For example, the product of the molar amount of the basic compound and the valence of the basic compound is preferably greater than 1.1 times and less than 3.0 times, more preferably greater than 1.5 times and less than 2.0 times, of the sum of the products of the molar amount of the palladium-containing compound and the valence of palladium, the molar amount of the gold-containing compound and the valence of gold, and the molar amount of the copper-containing compound and the valence of copper.

[0065] There are no particular limitations on the method of impregnating the carrier with an alkaline solution. Examples include method (I), in which the carrier is briefly impregnated in a large amount of alkaline solution, and then the carrier is removed after impregnation with the alkaline solution containing a fraction of the water absorption amount; and method (II), in which an alkaline compound is dissolved in a solvent, and the carrier is impregnated with a solution diluted to a volume equivalent to the water absorption amount of the carrier. From the viewpoint of wastewater treatment, method (II) is preferred.

[0066] The alkaline solution is preferably impregnated in the carrier in an amount equivalent to 0.9 times or more but less than 1.0 times the water absorption of the carrier, and more preferably in an amount equivalent to 0.95 times or more but less than 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 carrier can reliably absorb the entire amount of alkaline solution. In this disclosure, the water absorption of the carrier is a value measured using pure water, which is strictly different from the value for alkaline solutions, but is used directly for convenience.

[0067] <Step 2. Step of contacting the carrier with impregnation solution A>

[0068] In this process, a carrier impregnated with an alkaline solution is brought into contact with impregnation solution A. Solution A is a solution containing compounds containing copper, palladium, and gold. Other components may also be dissolved in solution A as needed.

[0069] The raw material compounds of each catalyst component in solution A are adjusted to achieve the desired catalyst composition. The concentration of the raw material compounds of the catalyst components (copper, palladium, and gold) in solution A can be calculated from the amount of raw material compound to be supported on the support and the volume of the solution. In practice, the amount (g) of raw material compound to be supported on the support is measured and dissolved in the solvent in a manner that yields the preferred solution volume.

[0070] 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.

[0071] The palladium-containing compound in solution A may use a palladium precursor that can be converted into metallic palladium. Examples of palladium precursors that can be 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.

[0072] The gold-containing compound in solution A can use a gold precursor that can be converted into metallic gold. Examples of gold precursors include chloroauric acid, sodium chloroaurate, and potassium chloroaurate, with chloroauric acid being preferred.

[0073] Examples of solvents for solution A include water, alcohols, and organic acids. Water is preferred from the perspective of not damaging the carrier and not reacting with the compounds contained in solution A.

[0074] 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 particularly preferably 2.0 to 5.0 times the water absorption of the carrier.

[0075] By contacting a support impregnated with an alkaline solution with 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 metal components such as palladium, gold, and copper are supported in a manner that is biased towards the surface portion of the support.

[0076] There is no particular limitation on the contact time, but it is preferably 0.5 to 100 hours, more preferably 3 to 50 hours. By making the contact time 0.5 hours or more, the catalyst component can be supported in the desired amount, and sufficient catalytic performance can be obtained. By making the contact time 100 hours or less, the deterioration of the support can be suppressed.

[0077] There are no particular limitations on the contact temperature, but it is preferably 10–80°C, more preferably 20–60°C. By keeping the contact temperature above 10°C, the conversion reaction can proceed fully. By keeping the contact temperature below 80°C, the aggregation of copper, palladium, and gold can be suppressed.

[0078] <Step 3. The process of performing the reduction treatment>

[0079] It is desirable to reduce a support containing a copper-containing compound (such as copper chloride), a palladium-containing compound (such as palladium salts), and a gold-containing compound (such as chloroauric acid) to obtain 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 treatment can be carried out by any method, including liquid-phase reduction or gas-phase reduction. Even after the reduction treatment, not all palladium, gold, and copper may be reduced to their metallic state, i.e., 0 valence.

[0080] Liquid-phase reduction can be carried out in any system, whether in a non-aqueous or aqueous system, using alcohols or hydrocarbons. Reducing agents that can be used include, for example, carboxylic acids and their salts, aldehydes, hydrogen peroxide, sugars, polyphenols, boron compounds, amines, or hydrazine. Examples of carboxylic acids and their salts include, for example, oxalic acid, potassium oxalate, formic acid, potassium formate, potassium citrate, and ammonium citrate. Examples of aldehydes include, for example, formaldehyde and acetaldehyde. Examples of sugars include, for example, glucose. Examples of polyphenols include, for example, hydroquinone. Examples of boron compounds include, for example, diborane and sodium borohydride. Hydrazine, formaldehyde, acetaldehyde, hydroquinone, sodium borohydride, and potassium citrate are preferred reducing agents, with hydrazine being particularly preferred.

[0081] In the case of liquid-phase reduction, the temperature is not particularly limited, but it is preferable to set the liquid phase temperature in the range of 0 to 200°C, and more preferably in the range of 10 to 100°C. If the liquid phase temperature is above 0°C, a sufficient reduction rate can be obtained. On the other hand, if the liquid phase temperature is below 200°C, the aggregation of copper, palladium, and gold can be suppressed. The reduction time is not particularly limited, but it is preferably in the range of 0.5 to 24 hours, and more preferably in the range of 1 to 10 hours. If the reduction time is 0.5 hours or more, sufficient reduction can be achieved. On the other hand, if the reduction time is 24 hours or less, the aggregation of copper, palladium, and gold can be suppressed.

[0082] The reducing agent used in gas-phase reduction can be selected from hydrogen, carbon monoxide, alcohols, aldehydes, and olefins such as ethylene, propylene, and isobutylene. Hydrogen is preferred as the reducing agent. In gas-phase reduction, an inert gas can be added as a diluent. Examples of inert gases include helium, argon, and nitrogen.

[0083] In the case of gas-phase reduction, the temperature is not particularly limited, but it is preferable to heat the impregnation carrier to a range of 30–350°C, more preferably to a range of 100–300°C. A sufficient reduction rate can be obtained if the heating temperature is 30°C or higher. On the other hand, if the heating temperature is 300°C or lower, the aggregation of copper, palladium, and gold can be suppressed. The reduction time is not particularly limited, but it is preferably in the range of 0.5–24 hours, more preferably in the range of 1–10 hours. A reduction time of 0.5 hours or more allows for sufficient reduction. On the other hand, a reduction time of 24 hours or less can suppress the aggregation of copper, palladium, and gold.

[0084] There is no particular limitation on the pressure of gas phase reduction, but from the point of view of the equipment, it is preferably in the range of 0.0 to 3.0 MPaG (gauge pressure), and more preferably in the range of 0.1 to 1.0 MPaG (gauge pressure).

[0085] Regarding the supply rate of the reducing agent in the case of gas-phase reduction, under standard conditions, the space velocity (hereinafter referred to as SV) is preferably 10 to 15000 hr. -1 The range is particularly preferred to be 100–8000hr. -1 The range.

[0086] The reduced carrier is washed with pure water or the like as needed. Washing can be performed continuously or intermittently. The washing temperature is preferably in the range of 5 to 200°C, more preferably in the range of 15 to 80°C. There is no particular limitation on the washing time; any condition sufficient for removing residual unwanted impurities can be selected. Undesirable impurities include, for example, chlorine-containing compounds and chloride ions. After washing, the carrier can be heated and dried as needed.

[0087] <Step 4. Step to load acetate onto the carrier>

[0088] For acetate, loading can be achieved by impregnating the carrier with a solution containing the necessary 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 loading is typically carried out after reduction treatment, but it can also be carried out before reduction treatment.

[0089] The acetate is preferably a compound selected from alkali metal acetates and alkaline earth metal acetates, more preferably an alkali metal acetate. Examples of alkali metal acetates include, for example, lithium, sodium, and potassium acetates. Sodium acetate and potassium acetate are preferred as acetates, with potassium acetate being particularly preferred.

[0090] [Catalyst used in the production of vinyl acetate]

[0091] The mass of copper supported per 1 kg of catalyst (the total mass of the support, catalyst metal, acetate, and other components) is preferably 0.1 g or more and 1.6 g or less, more preferably 0.3 g or more and 1.4 g or less, and particularly preferably 0.6 g or more and 1.2 g or less.

[0092] The preferred mass of palladium supported per 1 kg of catalyst is 8.0 g or more and 16.0 g or less, more preferably 10.0 g or more and 14.0 g or less.

[0093] The preferred mass of gold supported per 1 kg of catalyst is 4.0 g or more and 12.0 g or less, more preferably 5.0 g or more and 10.0 g or less.

[0094] The preferred mass of acetate supported per 1 kg of catalyst is 40 g or more and 100 g or less, more preferably 50 g or more and 70 g or less.

[0095] The catalyst for producing vinyl acetate obtained by the method of this disclosure has an eggshell structure in which copper, palladium, and gold are mostly supported on the surface of a support. The thickness of the shell varies depending on the type of support, alkaline solution, and aqueous solution of the raw metal compound used. When using spherical silica with a diameter of 5 mm as the support, the shell preferably has a thickness of 0.05 to 0.5 mm, more preferably 0.1 to 0.3 mm. If the thickness of the shell is 0.05 mm or more, catalytic activity can be maintained even if the surface portion of the support peels off during the reaction. If the thickness of the shell is less than 0.5 mm, the catalyst concentration on the surface portion of the support can be sufficiently increased, economically enjoying the advantages of shell-type support. Acetates do not necessarily need to be supported in a shell shape and can also be present uniformly in the catalyst.

[0096] [Specific examples of catalyst manufacturing]

[0097] The following are specific examples of catalyst manufacturing.

[0098] 1. Impregnate the carrier with an amount of alkaline solution equivalent to the amount of water absorbed by the carrier.

[0099] 2. The support is impregnated in solution A, which is obtained by diluting the raw material metal compounds of copper, palladium and gold with pure water to twice the mass of the water absorbed by the support, thereby making it contact impregnated and forming a catalyst precursor.

[0100] 3. Add a reducing agent to the dispersion containing the catalyst precursor obtained in step 2 and perform reduction treatment.

[0101] 4. Wash the reduced catalyst precursor with pure water.

[0102] 5. Dry the washed catalyst precursor.

[0103] 6. To enable it to carry the specified amount of acetate.

[0104] 7. Dry the support containing the catalyst.

[0105] [Manufacturing of vinyl acetate]

[0106] The following describes a method for producing vinyl acetate using a catalyst prepared by the method of this disclosure. The reaction for producing vinyl acetate is preferably carried out in the gas phase using acetic acid, ethylene, and oxygen as reactants. The gas-phase reaction can be of any known form, but a fixed-bed flow reaction is preferred.

[0107] The reaction equation is shown below.

[0108] CH2=CH2+CH3COOH+1 / 2O2→CH2=CHOCOCH3+H2O

[0109] The ratio of acetic acid, ethylene, and oxygen in the raw material gas is expressed as a molar ratio. Preferably, the ratio of acetic acid:ethylene:oxygen is 1:0.08 to 16:0.01 to 4, and more preferably, the ratio of acetic acid:ethylene:oxygen is 1:0.2 to 9:0.07 to 2.

[0110] The raw material gas includes ethylene, acetic acid (gas), and oxygen, and may also 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 is expressed as a molar ratio, preferably reactants:diluent = 1:0.05 to 9, more preferably reactants:diluent = 1:0.1 to 3.

[0111] In the case of a reaction carried out via a fixed-bed flow reaction, the feed gas is preferably in the standard state at a flow rate of 10–15000 h⁻¹. -1 The space velocity (SV) is supplied to the reactor, more preferably at 300–8000 hr. -1 It is supplied to the reactor. The space velocity is maintained at 10 hr. -1 The above allows for the appropriate removal of the heat of reaction. On the other hand, by setting the space velocity to 15000hr... -1 The following are sizes that enable equipment such as compressors to be of practical size.

[0112] In the feed gas, it is preferable to add 0.5–20 mol% water in the form of water vapor, more preferably 1–18 mol% water. Although not limited by any theory, it is believed that the presence of water in the reaction system can suppress 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 concern about the hydrolysis progress of vinyl acetate. Therefore, the presence of a large amount of water in the feed gas is not preferred.

[0113] There are no particular restrictions on the material of the reactor, but a corrosion-resistant material is preferred.

[0114] The reaction temperature is preferably in the range of 100–300°C, more preferably in the range of 120–250°C. If the reaction temperature is above 100°C, a suitable reaction rate can be maintained. If the reaction temperature is below 300°C, the heat of reaction is easily removed.

[0115] 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 above 0 MPaG, an appropriate reaction rate can be maintained. If the reaction pressure is below 3 MPaG, it becomes unnecessary to make the reaction tubes and other equipment highly pressure-resistant, thus reducing equipment costs.

[0116] High-purity ethylene is preferred as the reactant, but it may also contain lower saturated hydrocarbons such as methane, ethane, and propane.

[0117] There are no particular restrictions on oxygen. It can also be supplied as oxygen diluted with inert gases such as nitrogen or carbon dioxide, or 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.

[0118] Example

[0119] The present invention will be further illustrated below by way of examples, but the present invention is not limited to these examples.

[0120] Example 1 Modulation of catalyst A

[0121] Silica spheres were used as carriers (sphere diameter 5mm, specific surface area 155m²). 2 The catalyst was prepared by means of a water absorption rate of 0.85 g-water / g-support, and was prepared by the following steps.

[0122] Step 1. Impregnate 23.5g of carrier (water absorption capacity 20.0g) with an aqueous solution containing 2.3g of Na2SiO3·9H2O, in an amount equivalent to (0.95 times by mass) the water absorption capacity of the carrier. 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 amount of 23.5g and the water absorption rate of 0.85g-water / g-carrier (the same applies in the following examples and comparative examples).

[0123] Step 2. The carrier obtained in Step 1 was immersed in an aqueous solution containing 0.92 g of Na2PdCl4, 0.28 g of HAuCl4, and 0.04 g of copper chloride dihydrate, which was twice the mass of the carrier's water absorption. The solution was left to stand at room temperature for 20 hours.

[0124] Step 3. Add 1.9 g of 52% (w / w) hydrazine hydrate aqueous solution to the carrier dispersion obtained in Step 2, mix gently, and let stand at room temperature for 4 hours. Next, wash the palladium / gold / copper / carrier composition obtained in the previous step with deionized water, continuing the washing until no chloride ions are present in the washing water. Dry the washed palladium / gold / copper / carrier composition at 110°C for 4 hours.

[0125] Step 4. Impregnate the palladium / gold / copper / support composition with an aqueous solution containing 1.7g potassium acetate in an amount equivalent to 0.9 times the water absorption of the support, and dry at 110°C for 4 hours to obtain catalyst A.

[0126] Example 2 Modulation of catalyst B

[0127] In step 2 of Example 1, the amount of copper chloride dihydrate used was changed to 0.07 g, and the operation of Example 1 was repeated to obtain catalyst B.

[0128] Example 3 Modulation of catalyst C

[0129] In step 2 of Example 1, the amount of copper chloride dihydrate used was changed to 0.09 g. Otherwise, the operation of Example 1 was repeated to obtain catalyst C.

[0130] Example 4 Modulation of catalyst D

[0131] In step 2 of Example 1, the amount of copper chloride dihydrate used was changed to 0.10 g, and the operation of Example 1 was repeated to obtain catalyst D.

[0132] Example 5 Modulation of catalyst E

[0133] In step 2 of Example 1, the amount of copper chloride dihydrate used was changed to 0.11 g, and the operation of Example 1 was repeated to obtain catalyst E.

[0134] Example 6 Modulation of catalyst F

[0135] In step 2 of Example 1, the amount of copper chloride dihydrate used was changed to 0.087 g, and the amount of HAuCl4 used was changed to 0.20 g. Otherwise, the operation of Example 1 was repeated to obtain catalyst F.

[0136] Example 7 Modulation of catalyst G

[0137] In step 2 of Example 1, the amount of copper chloride dihydrate used was changed to 0.087g, and the amount of HAuCl4 used was changed to 0.27g. Otherwise, the operation of Example 1 was repeated to obtain catalyst G.

[0138] Modulation of catalyst H in Comparative Example 1

[0139] In step 2 of Example 1, copper chloride dihydrate was not used. Otherwise, the operation of Example 1 was repeated to obtain catalyst H.

[0140] Modulation of Catalyst I in Comparative Example 2

[0141] In step 2 of Example 1, HAuCl4 was not used, and the amount of copper chloride dihydrate used was changed to 0.14g. Otherwise, the operation of Example 1 was repeated to obtain catalyst I.

[0142] Modulation of catalyst J in Comparative Example 3

[0143] Silica spheres were used as carriers (sphere diameter 5mm, specific surface area 155m²). 2 The catalyst was prepared according to the following steps, based on the description of the embodiment in Patent Document 2 (Japanese Patent Publication No. 2002-516749).

[0144] Step i. Impregnate 23.5g of carrier (absorbing 20.0g of water) with an aqueous solution containing 0.32g of Na2PdCl4 and 0.14g of copper chloride dihydrate, in an amount equivalent to (0.95 times the mass of) the water absorbed by the carrier. Shake the container containing the carrier and the aqueous solution to ensure complete impregnation.

[0145] Step ii. Contact the carrier dispersion obtained in step i with a solution made of 0.7 g of 50% NaOH aqueous solution and 35.7 g of distilled water for 2.5 hours to immobilize palladium and copper on the carrier in the form of palladium(II) and copper hydroxide.

[0146] Step iii. The palladium(II) / copper hydroxide / carrier composition obtained in step ii is washed with deionized water until chloride ions are no longer present in the washing water. After washing, it is dried for 10 hours at 150°C under nitrogen circulation. Next, it is reduced by contacting ethylene (5 mol% in nitrogen) in the gas phase at 150°C for 5 hours. After cooling for 10 hours, it is washed with deionized water for 2 hours and then dried in an oven at 150°C for 5 hours.

[0147] Step iv. Mix 0.2 g of gold hydroxide and 0.10 g of potassium hydroxide in 17 mL of water. Heat the resulting orange suspension to 85 °C and allow it to dissolve all the solids for 5 hours to prepare a transparent yellow solution of potassium aurate. Add this yellow solution to the palladium / copper / support composition obtained in step iii, and allow the support to impregnate for 30 minutes. Then, dry the composition in an oven at 100 °C under nitrogen circulation for 5 hours. Next, reduce the composition using ethylene (5 mol% in nitrogen) at 120 °C for 5 hours to obtain free metallic gold on the support.

[0148] Step v. Impregnate the palladium / gold / copper / support composition obtained in step iv with an aqueous solution containing 1.7 g potassium acetate in an amount equivalent to 0.9 times the water absorption of the support, and dry at 110°C for 4 hours to obtain catalyst J.

[0149] Comparative Example 4: Modulation of Catalyst K

[0150] In step 2 of Example 1, copper chloride dihydrate was not used. In step 4 of Example 1, the method was changed so that 0.01 g of copper acetate monohydrate and 1.7 g of potassium acetate were dissolved together in water in an amount of water equivalent to 0.9 times the mass of the water absorbed by the carrier. Otherwise, the operation of Example 1 was repeated to obtain catalyst K.

[0151] [Evaluation of Catalysts]

[0152] <Determination of Metal (Copper, Palladium, and Gold) and Potassium Acetate Loading>

[0153] 3g of the catalyst-supported 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 PW2404 fluorescence X-ray analyzer manufactured by Filipps. Regarding potassium acetate, the amount of potassium atoms was quantified and converted into the amount of potassium acetate.

[0154] <Catalytic Activity Evaluation Test>

[0155] 6.7 mL of catalyst was diluted with 75 mL of glass beads and filled into a reaction tube (SUS316L, 22 mm inner diameter, 480 mm length). The catalyst was stabilized by circulating a gas with a composition of C2H4 / O2 / H2O / HOAc / N2 = 45 / 6 / 5 / 23 / 21 (mol%) at a flow rate of 66.7 NL / h for 240 hours at a reaction temperature of 150 °C and a reaction pressure of 0.6 MPaG. The catalytic activity and selectivity were then evaluated by changing the gas flow rate to 20.0 NL / h and the reaction temperature to 145 °C, 150 °C, 155 °C, or 160 °C. The evaluation of catalytic activity and selectivity was performed after at least a 4-hour interval between changes in gas flow rate and reaction temperature, and after the apparatus and catalyst had stabilized. Generally, a higher vinyl acetate activity (STY) (g / L-cat·h) corresponds to a lower vinyl acetate selectivity. Therefore, the vinyl acetate selectivity at the same vinyl acetate activity was compared among the various catalysts. For example, the vinyl acetate selectivity at a vinyl acetate activity of 550 (g / L-cat·h) was calculated by extrapolation from multiple approximate curves formed by plotting points of vinyl acetate activity and vinyl acetate selectivity at various reaction temperatures.

[0156] The following method was used to analyze the reactor outlet gas.

[0157] 1. Oxygen

[0158] The absolute standard curve method was used. 50 mL of outflowing gas was collected and the entire amount was fed into a 1 mL gas sampler attached to the gas chromatograph. The analysis was performed under the following conditions.

[0159] Gas chromatography: Gas chromatograph (GC-14B manufactured by Shimadzu Corporation) equipped with a Shimadzu gas chromatograph gas sampler (MGS-4: 1 mL metering tube).

[0160] Column: MS-5A IS 60 / 80 mesh (3mmΦ×3m)

[0161] Carrier gas: Helium (flow rate 20 mL / min)

[0162] Temperature conditions: Detector temperature and vaporization chamber temperature are 110℃, column temperature is constant at 70℃.

[0163] Detector: TCD (He pressure 70 kPaG, current 100 mA)

[0164] 2. Acetic acid

[0165] The internal standard method was used. The liquid obtained by adding 1 mL of 1,4-dioxane as an internal standard to 10 mL of reaction solution was used as the analytical solution. 0.2 μL of the liquid was injected into the solution and analyzed under the following conditions.

[0166] Gas chromatography: GC-14B manufactured by Shimadzu Corporation

[0167] Column: Thermon 3000 infill column (3m in length, 0.3mm in inner diameter)

[0168] Carrier gas: Nitrogen (flow rate 20 mL / min)

[0169] Temperature conditions: Detector temperature and vaporization chamber temperature were 180℃. Column temperature was maintained at 50℃ for 6 minutes from the start of analysis, then increased to 150℃ at a rate of 10℃ / min and held at 150℃ for 10 minutes.

[0170] Detector: FID (H2 pressure 40 kPaG, air pressure 100 kPaG)

[0171] 3. Vinyl acetate

[0172] The internal standard method was used. The liquid obtained by adding 1 g of 1,4-dioxane as an internal standard to 6 g of reaction solution was used as the analytical solution. 0.3 μL of the liquid was injected into the solution and analyzed under the following conditions.

[0173] Gas chromatography: GC-9A manufactured by Shimadzu Corporation

[0174] Column: TC-WAX capillary column (30m in length, 0.25mm in inner diameter, 0.5μm in film thickness)

[0175] Carrier gas: Nitrogen (flow rate 30 mL / min)

[0176] Temperature conditions: Detector temperature and vaporization chamber temperature 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, and held at 200℃ for 10 minutes.

[0177] Detector: FID (H2 pressure 60 kPaG, air pressure 100 kPaG)

[0178] The evaluation results of the catalyst are shown in Table 1. Figure 1 and Figure 2 In the middle. It should be noted that, in Figure 1 and Figure 2Comparative Examples 2, 3, and 4 were not plotted due to their significantly low STY values. The selectivity of vinyl acetate was based on ethylene.

[0179] [Table 1]

[0180] Table 1

[0181]

[0182] 1) Catalysts A to H represent vinyl acetate activity (STY) [g / L-cat·h] values ​​at 550. Catalysts I to K exhibit significantly lower vinyl acetate activity, therefore these values ​​represent values ​​at a reaction temperature of 150℃.

[0183] 2) Values ​​at a reaction temperature of 150℃

[0184] When comparing Examples 1-7 with Comparative Example 1, the selectivity of vinyl acetate increased by 0.3-2.9% by supporting copper, confirming a significant effect. Looking at Examples 4 and 6, it was observed that even with the same copper loading, increasing the gold loading further improved the selectivity of vinyl acetate. In Comparative Example 2, a combination of palladium and copper was supported without gold; as a result, even at a reaction temperature of 160°C, the vinyl acetate activity (g / L-cat·h) did not reach 550, indicating significantly low activity. In Comparative Examples 3 and 4, catalysts obtained by adding a copper-containing compound in a different step than those containing palladium and gold were evaluated. The results showed that the vinyl acetate activity was significantly lower than that of Examples 1-7, and the vinyl acetate selectivity was also lower than in all examples except Example 5. As can be seen from the above, by employing the modulation methods of Examples 1-7, a particularly high vinyl acetate selectivity can be obtained while ensuring high vinyl acetate activity. The modulation method is characterized by not only combining palladium, gold, and copper, but also simultaneously loading the palladium-containing compound, the gold-containing compound, and the copper-containing compound with a base in the same step. Furthermore, as shown in Examples 1-7, a Cu loading of 0.1-1.6 g / kg and an Au loading of 4.0-12.0 g / kg are suitable.

[0185] Industry availability

[0186] This invention provides a catalyst for the production of vinyl acetate that ensures high catalytic activity while exhibiting excellent selectivity, making it industrially useful.

Claims

1. A method for manufacturing vinyl acetate, comprising using ethylene, oxygen, and acetic acid as raw materials, characterized in that, Vinyl acetate is produced using a catalyst comprising a support, copper, palladium, gold, and acetate, and the method for producing the catalyst for vinyl acetate comprises the following steps in sequence: Step 1 is the process of impregnating the carrier with an alkaline solution. Step 2 is a step of contacting the carrier with a solution containing a compound containing copper, a compound containing palladium, and a compound containing gold. Step 3 is the process of performing reduction treatment; as well as Step 4 is the step of loading acetate onto the carrier. The mass of copper supported per 1 kg of catalyst is more than 0.1 g and less than 1.6 g, and the mass of gold supported per 1 kg of catalyst is more than 4.0 g and less than 12.0 g.

2. In the method for manufacturing vinyl acetate according to claim 1, the mass of palladium supported on each 1 kg catalyst is more than 8.0 g and less than 16.0 g.

3. In the method for manufacturing vinyl acetate according to claim 1 or 2, the mass of acetate supported on each 1 kg catalyst is 40 g or more and 100 g or less.

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