RU2077382C1 - Method of preparing catalyst for synthesis of carboxylic acid alkenyl esters - Google Patents

Abstract

FIELD: catalysts for organic syntheses. SUBSTANCE: invention relates to preparing improved catalysts for synthesis of carboxylic acid alkenyl esters from alkenes, carboxylic acids, and oxygen-containing gas. Catalysts contain palladium, gold, potassium promoter and are characterized by reduced content of sodium. The latter is achieved by (i) preparing catalyst using practically sodium-free reactants, (ii) washing catalyst with water or aqueous solution of potassium promoter after catalyst has been impregnated with the latter, and (iii) washing catalyst at a certain step of its preparation with cation-exchange solution. EFFECT: increased activity of catalyst. 2 cl, 4 dwg, 19 tbl

Description

 The present invention relates to a method for producing catalysts for the synthesis of alkenyl esters of carboxylic acids, the catalyst itself and a method for producing alkenyl esters of carboxylic acids from alkenes, carboxylic acids and an oxygen-containing gas.

 Known methods for producing catalysts for the synthesis of alkenyl esters of carboxylic acids.

For example, U.S. Patent N4048096 describes a catalyst having a specific activity of at least about 83 g vinyl acetate per 1 g of noble metal per hour, measured at 150 ^° C. This vinyl acetate synthesis catalyst consists essentially of: (1) a carrier a catalyst having a particle diameter of from about 3 to about 7 mm and a pore volume of from about 0.2 to about 7 mm and a pore volume of from about 0.2 to about 1.5 ml / g, and 10% (wt.) an aqueous suspension of a catalyst carrier has a pH of from about 3.0 to about 9.0; (2) a palladium-gold alloy distributed in the surface layer of the catalyst carrier, the surface layer extending to a depth of less than about 0.5 mm from the surface of the carrier, palladium in the alloy is present in an amount of from about 1.5 to about 5.0 g per liter of catalyst, and gold is present in an amount of from about 0.5 to 2.25 g per liter of catalyst, and (3) from about 5 to about 60 g of alkali metal acetate per liter of catalyst. The patent says that palladium is an active catalyst metal, and gold is a catalyst promoter.

 The said patent also describes a method for producing a catalyst, which involves the deposition of metal salts on a catalyst support. The method, in particular, includes: (1) impregnation of the catalyst support with an aqueous solution of water-soluble palladium and gold compounds, (2) precipitation on the support of water-insoluble palladium and gold compounds by contacting the impregnated catalyst support with a solution of compounds (preferably sodium metasilicate) capable of interact with water-soluble compounds of palladium and gold to form water-insoluble compounds of palladium and gold, (3) the conversion of water-insoluble compounds of palladium and gold lots in metallic palladium and metallic gold on a carrier by treatment with a reducing agent, (4) washing the catalyst with water, (5) drying the catalyst (see patent example 1), (6) impregnating the catalyst with an alkali metal acetate promoter (e.g., potassium promoter ) and (7) drying the catalyst.

 The usefulness of the method described in the patent includes the distribution of palladium and gold in the form of an alloy in the surface layer of the catalyst carrier, the surface layer extending to a depth of less than about 0.5 mm from the surface of the carrier. The impregnation step is carried out using an aqueous solution of palladium and gold compounds, and the total volume of the solution is from about 95% to about 100% of the absorption capacity of the catalyst carrier. The precipitation step is carried out by keeping the wet catalyst support in an alkali metal silicate solution, the amount of alkali metal silicate being such that after the alkali metal silicate solution has been in contact with the catalyst carrier for about 12 to 24 hours, the pH of the solution is from about 6.5 to about 9.5.

 The patent does not disclose the sodium content in the catalysts of the examples. Example 1 indicates that the catalyst of this example had an activity of 560 g of vinyl acetate per liter of catalyst per hour. In the following Example 3, it was found that the two catalysts prepared in accordance with the description of Example 1 had a sodium content of 0.32 and 0.38% (wt.) And activities of 551 and 535 g of vinyl acetate per liter of catalyst in hour.

 Given the methods of the prior art, it is desirable to further improve the activity of the catalysts for the synthesis of alkenyl esters of carboxylic acids.

 The present invention relates to a method for producing improved catalysts for the production of alkenyl esters of carboxylic acids by reaction of an alkene, a carboxylic acid and an oxygen-containing gas. The catalysts contain palladium, gold and a cadmium promoter and are characterized by a low sodium content, which leads to increased activity of the catalyst. The main invention consists of three embodiments (i.e., embodiment A, embodiment B and embodiment C), described in detail below.

 In Embodiment A of the invention, a reduced sodium content is obtained using substantially no sodium starting materials in the process for preparing the catalysts.

 In an embodiment of the present invention, a reduced sodium content is obtained by washing the catalyst with water or an aqueous solution of a potassium promoter after the catalyst has been impregnated with a potassium promoter.

 In Embodiment C of the present invention, a reduced sodium content is obtained by washing the catalyst at a particular intermediate point in time of its preparation with a cation exchange solution.

 Embodiment A of the present invention is based in part on the discovery that the activity of catalysts for the synthesis of alkenyl esters of carboxylic acids is increased if, when preparing the catalysts, their sodium content is reduced using substantially no sodium-containing starting materials.

More specifically, Embodiment A of the present invention provides a method for producing a catalyst suitable for catalyzing a reaction of an alkene, a carboxylic acid and an oxygen-containing gas to produce an alkenyl ester of a carboxylic acid and containing carrier particles capable of exchanging cations and impregnated with palladium, gold and potassium acetate;
wherein said method comprises the steps of:
(a) impregnating the carrier particles with aqueous solutions of water-soluble compounds of palladium and gold;
(c) precipitating water-insoluble palladium and gold compounds from such solutions on carrier particles using a precipitating agent;
(c) converting precipitated water-insoluble palladium and gold compounds to palladium and gold on carrier particles using a reducing agent;
(d) washing the carrier particles with water;
(e) drying the carrier particles;
(f) additionally impregnating the carrier particles with a potassium promoter; and
(g) drying the impregnated particles to obtain a catalyst; moreover, the specified method is carried out using, at stages (b) and (c), essentially, not containing sodium starting materials in order to reduce the amount of sodium in the catalyst and thereby increase the activity of the catalyst.

 FIG. 1 shows the effect of sodium on the behavior of the catalysts prepared in accordance with Embodiment A of the present invention in the synthesis of vinyl acetate prepared in accordance with Embodiment A of the present invention.

 When using option A of the method of the present invention, it is usually possible to use sodium-containing water-soluble compounds of palladium and / or gold, since they are usually not used in amounts leading to catalysts containing significant amounts of sodium. The main sources of sodium in catalysts for the synthesis of alkenyl esters of carboxylic acids are sodium-containing precipitating agents (e.g., sodium metasilicate) and / or sodium-containing promoters or activators (e.g., sodium acetate). To a lesser extent, significant amounts of sodium can be added to the catalyst by some carriers and some reducing agents (e.g. sodium borohydride). Accordingly, in the application of the present invention, substantially sodium-free precipitating agents (e.g., potassium hydroxide), promoters (e.g., potassium acetate), reducing agents (e.g., hydrazine) and carriers are used. When potassium hydroxide is used as the precipitating agent in the precipitation step, the corresponding potassium salt (for example, potassium acetate) can also be used in order to help potassium displace any amount of sodium bound to the carrier. Preferably, potassium hydroxide and potassium salt are used in an aqueous solution. Salt is used in an amount providing from 1 to 10% (wt.) Potassium, based on the total weight of the solution. Care should be taken to ensure that the resulting catalyst does not contain such an amount of potassium that the activity of the catalyst is less than desired.

 The carrier particles used in embodiment A of the method of the present invention are solid particulate materials capable of exchanging cations (for example, due to the presence of SiOH or AlOH groups), as well as being able to be impregnated with palladium, gold and potassium promoter compounds, and inert under the conditions used to obtain alkenyl esters of carboxylic acids. Examples of such carrier particles are ground silica, alumina, and aluminosilicates. Silica is the preferred carrier. The carrier preferably has a specific surface area of 100 to 800 square meters per gram.

Aqueous solutions of water-soluble palladium and gold compounds used in embodiment A of the method of the present invention include aqueous solutions of any suitable palladium or gold compound, for example palladium (P) chloride, sodium tetrachloropalladate (II) (Na ₂ PdCl ₄ , palladium (II) nitrate palladium (II) sulfate, gold (III) chloride or gold (III) - hydrochloric acid (HAuCl ₄ ) The volume of the solution preferably corresponds to from 95 to 100% (more preferably from 98 to 99%) of the pore volume of the carrier.

 Precipitating agents used in embodiment A of the method of the present invention include silicates and hydroxides of lithium and potassium. Precipitating agents are preferably used in the form of aqueous solutions containing from 1.6 to 1.8 molar excess of precipitating agent. The used volume of such a solution is preferably just sufficient to cover the carrier particles. In order to avoid possible destruction of the carrier, the weight ratio between the precipitating agent and the carrier should not be too high. As an illustration, the weight ratio between potassium hydroxide and the carrier of about 0.08: 1 did not lead to a noticeable destruction of the carrier.

Reducing agents used in embodiment A of the method of the present invention include ethylene, hydrazine, formaldehyde and hydrogen. Reducing agents are preferably used in the form of aqueous solutions containing 50: 1 (or more, preferably 10: 1) molar excess of reducing agents. If hydrogen is used, it is usually necessary to heat the catalyst to 100-300 ^{° C.} to complete the reduction.

 The potassium promoters used in embodiment A of the method of the present invention include the potassium salts of carboxylic acids and any potassium compound that is converted to the potassium salt of the carboxylic acid during the formation of alkenyl esters of the carboxylic acid (i.e., the reaction of ethylene, carboxylic acid and an oxygen-containing gas in the presence of a catalyst to give an alkenyl carboxylic acid ester). Suitable potassium compounds include acetate, bicarbonate, nitrate and (when a stable carrier is used) potassium hydroxide. Promoters are preferably used in the form of aqueous solutions.

The washing step in embodiment A of the method of the present invention can be carried out periodically or continuously. Continuous washing is more effective, but may not be most suitable for large-scale (for example, factory scale) preparation of the catalyst. With continuous washing, the washing water slowly and continuously passes through the catalyst for a certain period of time (for example, from 8 to 24 hours). During periodic washing, the catalyst is brought into contact with washing water, the mixture is allowed to stand (for example, from 0.5 to 2.0 hours) and the water and the catalyst are separated. During periodic washing, in order to lower the content of impurities (for example, halides) in the catalyst to the desired level, several such washes are often required (for example, from 2 to 10 or, preferably, from 4 to 6 washes). Temperatures from 20 ^o to 80 ^o C and volume ratios between the wash water and the catalyst, comprising from 2: 1 to 100: 1, can be used either in batch or continuous washing. In the washing step, some impurities, in particular chlorides, are removed from the catalyst.

The drying of the catalyst in step (e) and step (g) of embodiment A of the method of the present invention can be carried out by any standard method. For example, drying can be carried out at 40 ^{° C.} to 120 ^{° C.} in a furnace with forced air circulation for 15-30 hours.

 Embodiment In the implementation of the present invention, it is partly based on the fact that the activity of the catalyst for the synthesis of alkenyl esters of carboxylic acids described in US Pat. No. 4,048,096 increases if, after the above-described step (7) of the method of this patent (drying after washing with a promoter) decreases the sodium content in catalyst by washing the catalyst with water or an aqueous solution of a potassium promoter.

More specifically, Embodiment B of the present invention is to provide a catalyst suitable for catalyzing a reaction of an alkene, a carboxylic acid and an oxygen-containing gas to produce an alkenyl ester of a carboxylic acid, and containing carrier particles capable of exchanging cations and impregnated with a palladium, gold and potassium promoter, wherein said method comprises the steps of:
(a) impregnating the carrier particles with aqueous solutions of water-soluble compounds of palladium and gold;
(b) precipitating water-insoluble palladium and gold compounds from such solutions on carrier particles using a precipitating agent;
(c) converting precipitated water-insoluble palladium and gold compounds to palladium and gold on carrier particles using a reducing agent; and
(d) washing the impregnated carrier with water;
(e) drying the washed impregnated carrier;
(f) additionally impregnating the carrier particles with a potassium promoter;
(g) drying the carrier so impregnated to obtain a dried catalyst containing sodium, due to the presence of sodium in one or more of the substances used in steps (a) (f);
(h) washing the dried catalyst with water or an aqueous solution containing a potassium promoter so as to reduce the amount of sodium in the catalyst and thereby increase the activity of the catalyst, and
(i) drying the catalyst.

 When using Embodiment B of the method of the present invention, it is preferable to use an aqueous solution containing a potassium promoter in step (h) in order to avoid lowering the concentration of the potassium promoter (by which the carrier was impregnated in step (f) below the desired level. Such an undesirable decrease in the concentration of the promoter occur if water as such is used in step (h), however, if water is used in step (h) and the promoter concentration is thereby undesirably reduced, then after step (i) stage (j), which is the second impregnation with the potassium promoter, and then stage (k), which is the third drying. In some cases, when the initial impregnation with the potassium promoter (stage (f)), an excess amount of the potassium promoter can be used to ensure that the product of step (i) has the desired potassium promoter content even after washing with water (step (h). The latter procedure also removes the need for steps (j) and (k).

 Apparently, the potassium promoter used in the preparation of the catalysts of the US patent displaces at least a portion of the sodium bound to the ion exchange centers of the catalyst support. The source of sodium is the starting materials (especially the precipitating agent) used in the preparation of the catalysts of US Pat. No. 4,048,096). Although displaced by the potassium promoter, such sodium remains in the catalyst obtained by the method according to US patent as a suppressing activity of impurities. In the method of the present invention, displaced sodium is readily removed from the catalyst by simply washing the catalyst with water or an aqueous solution containing a potassium promoter (step (h)). Prior to being displaced by the potassium promoter in step (f), sodium cannot be effectively removed from the catalyst by simple washing with water (i.e., as in step (d)), since sodium is too tightly bound to the support. However, step (d) is effective for removing unbound impurities, especially chlorides and excess amounts of the reactants of steps (a) (c).

 FIG. 1 shows the predicted effect of sodium on the behavior of vinyl acetate synthesis catalysts prepared according to Embodiment B of the process of the present invention.

 The carrier particles used in the embodiment In the method of the present invention are solid particulate particles capable of cation exchange and impregnation with palladium, gold and potassium promoter compounds and inert under the conditions used to produce alkenyl esters of carboxylic acids.

 Examples of such carrier particles are ground silica, alumina, and aluminosilicates. Silica is the preferred carrier. The carrier preferably has a specific surface area of 100 to 800 square meters per gram.

Aqueous solutions of water-soluble palladium and gold compounds used in the embodiment In an embodiment of the method of the present invention, include aqueous solutions of any suitable palladium or gold compound, for example palladium (II) chloride, sodium tetrachloropalladate (II) (Na ₂ Pd Cl ₄ , palladium (III) nitrate ), palladium (III) sulfate, gold (III) chloride or gold (III) hydrochloric acid (HAu Cl _4. The solution volume preferably corresponds to 95 to 100 (more preferably 98 to 99%) of the pore volume of the carrier.

 Precipitating agents used in Embodiment In a process for preparing the catalysts of the present invention include silicates and hydroxides of sodium, lithium and potassium. Precipitating agents are preferably used in the form of aqueous solutions containing from 1.6 to 1.8 molar excess of precipitating agents. The used volume of such solutions is preferably just enough to cover the carrier particles.

Reducing agents used in Embodiment In the method of the present invention include hydrazine, ethylene, formaldehyde, hydrogen and sodium borohydride. Reducing agents are preferably used in the form of aqueous solutions containing 50: 1 (or more, preferably 10: 1) molar excesses of reducing agents. If you use hydrogen, usually in order to complete the recovery, it is necessary to heat the catalyst to 100 300 ^o C.

 Potassium Promoters Used in Embodiment In the method of the present invention, include potassium salts of carboxylic acids and any potassium compound that is converted to a potassium salt of carboxylic acid during the reaction to produce alkenyl esters of carboxylic acids (i.e., the reaction of ethylene, carboxylic acid and oxygen-containing gas) in the presence of a catalyst to give an alkenyl carboxylic acid ester). Suitable potassium compounds include acetate, bicarbonate, nitrate and (when a stable carrier is used) potassium hydroxide. Promoters are preferably used in the form of aqueous solutions.

The washing steps (d) and (h) of Embodiment B of the method of the present invention can be carried out periodically or continuously. Continuous washing is more effective, but may not be most suitable for large-scale (for example, factory scale) preparation of the catalyst. With continuous washing, the washing liquid slowly and continuously passes through the catalyst for a certain period of time (for example, from 8 to 24 hours). During periodic washing, the catalyst is brought into contact with the washing liquid, the mixture is allowed to stand (for example, for 0.5 to 2.0 hours), and the liquid and the catalyst are separated. With periodic washing, often several such washes are required (for example, from 2 to 10, or preferably from 4 to 6 washes). Temperatures from 2 ^{° C.} to 80 ^{° C.} and volume ratios between the washing liquid and the catalyst, comprising from 2: 1 to 100: 1, can be used either in batch or continuous washing.

 Washing the catalyst with water or an aqueous solution containing a potassium promoter in step (h) of an embodiment of the method of the present invention differs from the steps of impregnation with a potassium promoter in the prototype method. Similar stages of soaking in the prototype are carried out using the initial wetting method or the decantation method. In the initial wetting method (see Example 5 of U.K. Patent N1215210 (National Distillers)), the catalyst is contacted with the minimum amount of aqueous solution of the potassium promoter required to fill the pores of the support and to impregnate the catalyst with the desired amount of potassium promoter. Then the water is evaporated. Using this method, sodium cannot be removed from the catalyst. In the decantation method, the catalyst (preferably dry) is immersed in a larger volume of an aqueous solution of the potassium promoter than is used in the initial wetting method. After the pores are filled with the solution, the excess solution is decanted and the catalyst is dried. Only one dipping and decanting operation is carried out, and the contact time is relatively short. Therefore, only a minimal amount of sodium can be removed from the catalyst by decantation. Example 9 of US patent N3743607 Sennewald and others illustrates the method of decantation using a wet catalyst.

Drying of the catalyst in steps (e), (g), (i) or (k) of an embodiment of the method of the present invention can be carried out by any standard method. By way of illustration, drying can be carried out at 40 ^{° C.} to 120 ^{° C.} in an oven with forced air circulation for 15-30 hours.

 Embodiment c of the present invention is based in part on the fact that the activity of the catalysts for the synthesis of alkenyl esters of carboxylic acids increases if their sodium content is lowered by washing the catalysts at a particular intermediate point in time to obtain a cation exchange solution.

More specifically, an embodiment of the present invention is a process for preparing a catalyst for catalyzing a reaction of alkene, carboxylic acid and an oxygen-containing gas to produce an alkenyl carboxylic acid ester containing carrier particles capable of exchanging cations and impregnated with palladium, gold and potassium acetate, said process comprising from the stages:
(a) impregnating the carrier particles with aqueous solutions of water-soluble compounds of palladium and gold;
(b) precipitating water-insoluble palladium and gold compounds from such solutions on carrier particles using a precipitating agent;
(c) the conversion of precipitated water-insoluble compounds of palladium and gold into palladium and gold on carrier particles using a reducing agent to obtain an impregnated carrier containing sodium, due to the presence of sodium in one or more substances used in stages (a) to (c );
(d) washing the impregnated carrier particles with a cation exchange solution so that the amount of sodium in the catalyst decreases and the activity of the catalyst increases; and
(e) drying the washed and impregnated carrier particles to form a catalyst.

If it is desired to further increase the activity of the catalyst obtained by the process embodiment of the present invention, the above steps may be followed by the steps of:
(f) impregnating the dried carrier particles with a potassium promoter; and (g) drying the catalyst (see the following experiment 1 2A and figure 1).

 However, such an additional increase in catalyst activity is preferably achieved by the preferred embodiment of the present invention, which involves the use of specific concentrations and amounts of specific cation exchange solutions (i.e., potassium promoter solutions) for the purpose (see also the following examples VII XII and FIG. 3).

 Embodiment c of the present invention also provides catalysts for the synthesis of alkenyl esters of carboxylic acids having a reduced sodium content and a method for producing alkenyl esters of carboxylic acids using such catalysts.

 Apparently, the sodium impurities in the catalysts for the synthesis of alkenyl esters of carboxylic acids reduce the activity of the catalysts and cations in the cation exchange solutions used in step (d) of the embodiment of the method of the present invention, displace sodium (and, possibly, other impurities subjected to ion exchange) with carriers, so that impurities can be washed from the carriers in step (d). As a result of a decrease in sodium, the activity of the catalysts increases.

 FIG. 1 shows the effect of sodium on the behavior of vinyl acetate synthesis catalysts prepared in accordance with the present invention.

 FIG. 2 shows various batch washing experiments in accordance with Embodiment c of the present invention.

 FIG. 3 shows a procedure for preparing catalysts for the synthesis of vinyl acetate according to US Pat. No. 4,048,096 and a method for preparing catalysts of a preferred embodiment of the present invention.

 FIG. 4 shows the effect of the washing procedure on the activity of the catalyst according to Embodiment c of the present invention.

Description of the preferred implementation of option c
The method of producing catalysts
The cation exchange solutions used in the embodiment of the method of the present invention for preparing catalysts for the synthesis of alkenyl esters of carboxylic acids are solutions containing a cation which is exchanged with sodium on a carrier and which does not impair, but preferably promotes, the activity of the catalyst. Suitable cation exchange solutions include, but are not limited to, potassium promoter solutions. Preferred cation exchange solutions are aqueous solutions containing from 0.01 to 20% (wt.) Of a compound containing a suitable cation. Such compounds include, but are not limited to, potassium acetate, lithium acetate, potassium nitrate, potassium carbonate, ammonium carbonate, ammonium acetate, and magnesium acetate. More preferred are solutions containing from 0.1 to 10% (wt.) (And most preferably from 0.5 to 7% (wt.)) Of a compound containing a suitable cation.

 In order to save the amount of the cation-containing compound in the cation exchange solutions used in embodiment c of the method of the present invention, washing with a cation exchange solution may be preceded by one or more washes with water to remove impurities that are not firmly bound to the carrier (e.g., chloride and unbound sodium).

 The optimal concentration of the ion exchange solution used in embodiment c of the method of the present invention will depend on a number of factors, for example, the sodium content of the catalyst, the volume of the washing solution used, the total washing time, etc., and is best determined experimentally. Concentrations of a compound containing a suitable cation of about 10% or higher are less preferred since they consume many compounds and sometimes give catalysts having lower activities.

 The potassium promoters used in step (d) or step (f) of embodiment c of the method of the present invention include the potassium salts of carboxylic acids and any potassium compound that is converted to the potassium salt of the carboxylic acid during the formation of the alkenyl ester of the carboxylic acid (i.e. reaction of alkene, carboxylic acid and oxygen-containing gas in the presence of a catalyst to produce an alkenyl carboxylic acid ester). Suitable potassium compounds include acetate, bicarbonate, nitrate and (when a stable carrier is used) potassium hydroxide. Promoters are preferably used in the form of aqueous solutions.

 When the cation in the cation exchange solution used in step (d) of embodiment c of the method of the present invention is potassium, it is thereby introduced into the catalyst. In such cases, the catalyst should be dried and analyzed for potassium to determine how much more potassium should be added in step (f). This procedure is necessary in order to avoid obtaining a catalyst having an excess or deficiency of potassium, each of which can cause a decrease in the activity of the catalyst.

 A preferred embodiment of embodiment c of the method of the present invention includes using a potassium promoter solution as a cation exchange solution in step (d) and using a sufficient concentration and amount of a potassium promoter solution in this step, so that the step is impregnated with potassium acetate (step (f) and step two drying (step (g)) is not required. This embodiment is illustrated in Fig. 3.

More specifically, a preferred embodiment of embodiment c of the method of the present invention for preparing catalysts for the synthesis of alkenyl esters of carboxylic acids includes the steps of:
(a) impregnating the carrier particles with aqueous solutions of water-soluble compounds of palladium and gold;
(b) precipitating water-insoluble palladium and gold compounds from such solutions on carrier particles using a precipitating agent;
(c) converting precipitated water-insoluble palladium and gold compounds to palladium and gold on carrier particles using a reducing agent, wherein the impregnated carrier contains sodium due to the presence of sodium in one or more of the substances used in steps (a) (c);
(d) washing the carrier particles with a solution of a potassium promoter with a concentration and in an amount sufficient both to (I) reduce the amount of sodium in the catalyst in order to increase the activity of the catalyst, and in order to (II) additionally impregnate the catalyst with an amount potassium, necessary for additional promotion of catalyst activity; and
(e) drying the washed and further impregnated carrier particles to form a catalyst.

 Preferably, the appropriate concentration of the potassium promoter in the cationic solution used in the washing step (d) of embodiment c of the present invention depends on factors such as the ion-exchange properties of the support material and its pore volume, and the desired catalyst activity. For this reason, the optimal concentration is best determined experimentally. It was found that a five percent aqueous solution of potassium acetate gives good results.

 When using the catalyst preparation method described in US Pat. No. 4,048,096, a certain amount of colloidal palladium and gold is washed off the catalyst carrier during the washing step. Another benefit of the application of the present invention is the more efficient use of metals during the preparation of the catalyst when a potassium acetate solution is used as the cation exchange solution. A noticeable amount of palladium or gold is not removed from the catalyst support when a potassium acetate solution is used as the cation exchange solution when using the present invention. The following Examples 9 1A and 9 2A show that one weight percent of palladium and gold was washed out of the catalyst using the method of US Patent, but notable amounts of these metals were not washed out in the method of the present invention. This benefit not only leads to improved metal deposition efficiency, but also serves to lower the cost of precious metal recovery from washes.

 The carrier particles used in the embodiment of the method of the present invention are solid particulate matter capable of exchanging cations, capable of being impregnated with palladium, gold and a potassium promoter and inert under the conditions used to produce alkenyl esters of carboxylic acids. Examples of such carrier particles are ground silica, alumina, and aluminosilicates. Silica is the preferred carrier. The carrier preferably has a specific surface area of 100 to 800 square meters per gram.

Aqueous solutions of water-soluble compounds of palladium and gold used in embodiment c of the method of the present invention for preparing catalysts for the synthesis of alkenyl esters of carboxylic acids include aqueous solutions of any suitable compound of palladium or gold, for example, palladium (P) chloride, sodium tetrachloropalladate (P) (Na) ₂ PdCl _4, palladium nitrate (II) sulfate, palladium (II) sulfate, palladium (II) chloride, gold (III) or gold (III) with hydrochloric acid (HAuCl _4. The volume of the solution preferably corresponds to from 95 about 100 (more preferably from 98 to 99%) volume of the support pores.

 Precipitating agents used in embodiment c of the method of the present invention include silicates and hydroxides of sodium, lithium and potassium. Precipitating agents are preferably used in the form of aqueous solutions containing 1.6 to 1.8 molar excess of precipitating agents. The volume of such solutions used is preferably just sufficient to cover the carrier particles.

Reducing agents used in embodiment c of the method of the present invention include hydrazine, ethylene, formaldehyde, hydrogen and sodium borohydride. Reducing agents are preferably used in the form of aqueous solutions containing 50: 1 (or more preferably 10: 1) molar excesses of reducing agents. If hydrogen is used, it is usually necessary to heat the catalyst to 100 300 ^o C. to complete the reduction.

The washing step (step (d)) used in the embodiment of the method of the present invention can be carried out periodically or continuously. Continuous washing is more effective, but may not be most suitable for large-scale (for example, factory scale) preparation of the catalyst. With continuous washing, the cation exchange solution passes slowly and continuously through the catalyst over a period of time (for example, for 8 to 24 hours). During periodic washing, the catalyst is brought into contact with a cation exchange solution, the mixture is allowed to stand (for example, for 0.5 to 2.0 hours), and the solution and the catalyst are separated. With periodic washing, in order to lower the sodium content of the catalyst to the desired level, it is often necessary to have several washes (for example, from 2 to 10, or preferably from 4 to 6 washes). Temperatures from 20 ^o C to 80 ^o C and the ratio between the cation exchange solution and the catalyst, comprising from 2: 1 to 100: 1, can be used either in batch or continuous washing.

 The washing of the catalyst with a cation exchange solution in accordance with step (d) of embodiment c of the method of the present invention differs from the steps of impregnation with a potassium promoter in known methods for preparing catalysts for the synthesis of alkenyl esters of carboxylic acids. Such impregnation steps of the prior art are carried out by means of an initial wetting technique or a decantation technique. In an initial wetting technique (see Example 5 of U.K. Patent No. 1,215,210), the catalyst is contacted with the minimum amount of potassium promoter aqueous solution required to fill the pores of the support and impregnate the catalyst with the desired amount of potassium promoter. Then the water is evaporated. Using this technique, sodium cannot be removed from the catalyst. In the decantation technique (preferably dry), the catalyst is immersed in a larger volume of an aqueous solution of the potassium promoter than is used in the initial wetting technique. After the pores are filled with the solution, the excess solution is decanted and the catalyst is dried. Only one dipping and decanting operation is carried out, and the contact time is relatively short. Therefore, only a minimal amount of sodium can be removed from the catalyst by decantation technique. Example 9 of US patent N3743607 illustrates the method of decantation using a wet catalyst.

Drying of the catalyst according to step (e) of embodiment c of the method of the present invention can be carried out in any standard manner. By way of illustration, drying can be carried out at 40-120 ^{° C.} in an oven with forced air circulation for 15-30 hours.

 The catalysts of the present invention obtained by any of the above embodiments (i.e., embodiments A, B and C) catalyzing the reaction of an alkene, a carboxylic acid and an oxygen-containing gas to produce an alkenyl ester of a carboxylic acid include carrier particles capable of exchanging cations for which are deposited and reduced palladium and gold, as well as the potassium promoter, and the sodium in the catalyst is present in an amount not exceeding 0.3% (wt.), calculated on the total weight of the catalyst a.

 The catalysts of the present invention obtained by any of the above embodiments preferably have a palladium content of more than 0.25% (weight) based on the total weight of the catalyst, more preferably more than 0.5% (weight) based on the total weight of the catalyst and most preferably, from 0.5 to 1.7% (wt.) based on the total weight of the catalyst. Preferably, the weight ratio between gold and palladium catalyst is from 0.2 to 1.5, and most preferably from 0.4 to 1.2.

 Preferably, the catalysts of the present invention, obtained by any of the above embodiments, are impregnated in the outer layer of the catalysts in which the catalyst carrier has a particle diameter of from about 3 to about 7 mm and a pore volume of 0.2 to 1.5 mm per gram. Palladium and gold are preferably distributed in a layer with a thickness of at most 1.0 mm of the catalyst support particles. The catalysts preferably contain from about 1.4 to about 3.8 weight. (more preferably 2 to 3.6 wt.) potassium formed from the potassium promoter.

 The catalysts of the present invention obtained by any of the above embodiments have a reduced sodium content. Preferably, the catalysts contain no more than 0.3 weight. sodium based on the weight of the catalyst. More preferably, the catalysts contain no more than 0.2 weight. sodium and, most preferably, the catalysts contain not more than about 0.1 weight. sodium based on the weight of the catalyst. The amount of sodium in the catalysts of the present invention will depend on such factors as the starting materials used, the number of washes, the total washing time, the volume of washing solutions and the concentration of cation in the cation exchange solution.

 The catalysts of the present invention, obtained by any of the above embodiments, can be obtained using the above method of the present invention.

The method of the present invention for producing alkenyl esters of carboxylic acids involves reacting an alkene, a carboxylic acid and an oxygen-containing gas in the presence of a catalytic amount of a catalyst of the present invention as described above. The method is preferably carried out at a temperature of from 100 to 250 ^o C (and most preferably at a temperature of from 140 to 200 ^o C) and at a pressure of from 15 to 300 psi (from 1.05 to 21 atm) (most preferably at a pressure of from 90 pounds per square inch to 150 pounds per square inch) (6.3 to 10.5 atm). The method is preferably carried out continuously in the vapor phase.

 The method of the present invention for producing alkenyl esters of carboxylic acids is characterized by a higher activity of the catalyst. Typically, the activity of the catalysts is 5 25% higher (in terms of the number of alkenyl esters of carboxylic acids per unit of catalyst per unit time) compared with other identical catalysts containing from above 0.3 to about 1.0 weight. sodium. Although the selectivity of the catalyst (i.e., the tendency to produce alkenyl esters of carboxylic acids rather than by-products such as carbon dioxide) partially decreases with decreasing sodium content, this disadvantage is more than offset by the increased activity of the catalyst, especially in the range of sodium found in industrial catalysts for the synthesis of alkenyl esters of carboxylic acids (for example, up to 1.0 wt. sodium).

 Preferably used in the method of the present invention for producing alkenyl esters of carboxylic acids, carboxylic acid starting materials contain from two to four carbon atoms (for example, acetic, propionic and butyric acid). Preferred alkaline starting materials contain from two to four carbon atoms (e.g., ethylene, propylene and n-butene), four carbon atoms (e.g., ethylene, propylene and n-butane). Preferred products of the process are vinyl acetate, vinyl propionate, vinyl butyrate and allyl acetate.

 One aspect of the method of the present invention for the production of alkenyl esters of carboxylic acids is the use of the models shown in Table 3 below to predict the conversion of oxygen to vinyl acetate, catalyst activity, catalyst selectivity with respect to vinyl acetate, production of ethyl acetate by-product and / or severe by-products products.

 Alkenyl esters of carboxylic acids obtained by the method of the present invention are known compounds having known uses (for example, vinyl acetate is useful in the production of polyvinyl acetate).

 Below the invention is illustrated by examples of its implementation.

Examples of Embodiment A
The following abbreviations are used in the following examples.

 Abbreviation.

 Media 1.

 Value.

 Silicon oxide balls having an average diameter of 5-6 mm and containing about 0.1% (wt.) Sodium. Balls have a specific surface area of 150 to 200 square meters per gram and a pore volume of 0.6 to 0.7 mm per gram. Carrier 1 contains SiOH groups capable of exchanging cations. Carrier 1 is sold by Sud Chemic AG under the brand name "KA 160".

OD ^x
Volumetric productivity (a measure of catalyst activity), expressed in grams of vinyl acetate per liter of catalyst per hour.

^X selectivity
Selectivity was calculated as follows. Selectivity 100 x (number of moles of vinyl acetate) / (number of moles of vinyl acetate + 1/2 x number of moles of CO ₂ ).

 AA analysis.

 Atomic absorption spectroscopy.

 COI.

 Inductively coupled plasma optical emission spectrometry.

g VA / l cat./h
The number of grams of vinyl acetate obtained per liter of catalyst per hour.

^x All activities and selectivities given in the following examples are based on activities and selectivities measured 26 hours after the complete supply of oxygen feed was achieved in the catalyst test method described below.

VA Vinyl Acetate
KOAs Potassium Acetate
EtOAc Ethyl Acetate
NaCAc Sodium Acetate
Weight percentage
g gram
ml milliliter
mm millimeter
hour hour
min minute
In the following examples, the following methods were used.

 The method of obtaining the catalyst.

Carrier 1 (15 g) was added to a solution of Na ₂ PdCl ₄ (35.86% Pd 0.258 g) and HAuCl ₄ (48.95 Au, 0.094 g) dissolved in 9.0 ml of deionized water. The mixture thus formed was carefully mixed until all moisture was adsorbed onto the carriers, and then left to stand in a closed flask for about one hour at room temperature in order to impregnate the carrier with palladium and gold salts. The wet catalyst was coated with a solution of potassium hydroxide (0.371 g in 28 ml of water) as a precipitating agent. In a preferred embodiment of the present invention, potassium acetate was used together with potassium hydroxide in the precipitation step. After mixing for several seconds, the mixture was left to stand covered with liquid and not stirred for 23 hours at room temperature in order to precipitate palladium and gold compounds on the support. Palladium and gold were then reduced by adding 1.0 to 85% hydrazine hydrate to the above mixture. The mixture was stirred for several seconds and left to stand covered with liquid and not stirred at room temperature for another 23 hours. The liquid above was discharged from the catalyst by decantation, and the catalyst was washed four times with water to remove a small amount of metal contamination. The catalyst was thoroughly washed using the column washing procedure described below to remove chlorides and residual reagents. The catalyst was dried on a stainless steel grate in an oven with forced air circulation at 60 ^o C for 20 24 hours. The catalyst was analyzed for potassium using an AA analysis. The catalyst was then impregnated with the desired amount of potassium acetate in water using the impregnation method described above for the palladium and gold salts. Then, the impregnated catalyst was dried at 60 ^{° C.} for 20 to 24 hours. The content of palladium, gold, sodium and potassium in the final catalysts was determined by ICP analysis, and the content of sodium and potassium for greater accuracy was also determined by AA analysis. The catalysts thus obtained were impregnated in the outer layer (i.e., essentially all palladium and all gold were present in the outer layer within 0.5 mm of the surface of the carrier beads 1).

Column Wash Procedure
The catalysts were washed or re-washed in a glass chromatographic column with an outer diameter of 1.24 inches (31.5 mm) and a height of 24 inches (650 mm) equipped with a Teflon stopcock. Typically, 15 g of catalyst was loaded into the column and the column was then filled with water. The stopcock was adjusted to allow fluid to flow out of the column so that at room temperature for about 24 hours, about 1 liter passed through the catalyst. After this period of time, excess liquid was removed from the column, and the catalyst was discharged and dried in accordance with the procedure described above for the preparation of the catalyst.

Catalyst Test Method
The catalyst (2.5 gram samples of catalyst balls with a diameter of 5 to 6 mm) was diluted with 10.5 ml glass beads with a diameter of 0.5 mm and the mixture was uniformly distributed in both elbows of the reactor in the form of a U-shaped tube made of stainless steel 316. The reactor had an outer diameter of 3/8 inch (9.6 mm) and a total height of about 6 inches (152.4 mm). An ethylene stream of 151 ml / min was started to flow through the reactor, after which the catalyst was heated in an oven maintained at 150 ^° C, while simultaneously increasing the pressure in the system to 115 psid (10.5 ati). After keeping under these conditions for 1.5 hours, acetic acid vapors were added to ethylene and the mixture was passed through the catalyst for 45 minutes. Air was added to the feed gas at a slowly increasing rate over a 45-minute period until a total flow of 105 ml / min was reached. The catalyst was allowed to stabilize for two hours before data collection began. The final gas composition was ethylene: acetic acid: oxygen: nitrogen 52.9: 10.7: 7.7: 28.7, the total hourly space velocity of the gas was about 3800 h ^-1 , and the hourly space velocity of the acetic acid liquid was about 1 hour ^-1 . The product was analyzed by gas chromatography. The reproducibility from experience to experience of the microreactors used in these experiments is about ± 10 OD units.

 Example 1

 Carrier 1 contains about 0.1 (wt.) Sodium as received from the manufacturer. An additional 0.4 to 0.8% (w / w) sodium is added during the precipitation step when sodium hydroxide or sodium metasilicate is used as the precipitating agent. Three catalysts were prepared using potassium hydroxide as a precipitating agent to lower the sodium content in the final catalyst. In order to further shift the ion-exchange equilibrium towards potassium, varying concentrations of potassium acetate were added to the precipitated solution. Catalysts were prepared from the same mother liquor having a nominal palladium content of 0.5% (wt.) And an Au / Pd ratio of 0.46. After reduction with hydrazine and washing using a column washing procedure, the catalysts were analyzed for sodium and potassium. Then added additional potassium acetate, since it was required to obtain a final potassium acetate content of about 5.3% (wt.). The results shown in table 1 show that the sodium content in the catalysts decreased. The sodium content in the catalysts decreased uniformly, and the catalytic activity improved as the concentration of potassium in the precipitated solution increased.

 A similar catalyst obtained using sodium metasilicate as a precipitating agent (instead of potassium hydroxide) had an OH of 544, a selectivity of 93.6, and a sodium content of 0.44% (wt.). No potassium acetate was added in the precipitation step.

 Example 2

 The effect of sodium on the behavior of the catalysts for the synthesis of vinyl acetate was studied using statistically designed experiments. Models were obtained that are useful in predicting the behavior of vinyl acetate synthesis catalysts obtained by any of the process embodiments of the present invention (i.e., embodiments A, B and C), as well as vinyl acetate synthesis catalysts obtained by the methods of both of the aforementioned US patents . Models predict the activity and selectivity of the catalyst as a function of sodium, palladium, weight ratio between gold and palladium, potassium and catalyst weight. These models and the results are presented in table. 2 and 3, respectively.

Since the degree of conversion has a major influence on both productivity and selectivity of the catalyst, reasonable comparisons of the properties of the catalyst can only be made with a constant degree of conversion. In order to predict the effects of catalyst composition on continuous conversion, the oxygen conversion model in Table. 2 were converted to express the weight of the catalyst as a function of palladium content, gold / palladium ratio, potassium content, sodium content and conversion. This is an expression of the weight of the catalyst in OH models and selectivity. The predicted effects of increasing sodium on the activity and selectivity of the catalyst for the synthesis of vinyl acetate are plotted in FIG. 1. The abbreviations used in the table. 2 and 3 have the following meanings:
Pd is the weight percent of palladium in the catalyst.

 Au / Pd weight ratio between gold and palladium in the catalyst.

 Cat. weight. catalyst weight in grams.

 To the weight percent of potassium in the catalyst.

 Na weight percent of sodium in the catalyst.

 OD volumetric productivity in grams of vinyl acetate per liter of catalyst per hour.

R ² correlation coefficients indicating the quality of compliance with these models.

 CCA relative standard deviation.

 EtOAc by-product formation rate ethyl acetate production in moles / kilogram of catalyst / hour.

 heavy by-products in VA heavy by-products, expressed as a weight percent of vinyl acetate obtained. Severe by-products are defined as all products coming out after acetic acid in a gas chromatographic analytical procedure.

 Tab. 4 shows the effect of varying sodium content on catalyst activity as predicted by the models in the table. 2.

 Example 3

The procedure of example 1 of US patent N4048096 was repeated as follows: two samples were obtained (samples 1 and 2), each using 15 g of support 1, 0.315 g of Na ₂ PdCl ₄ , 0.085 g of HAuCl ₄ , 0.0585 g of Na ₂ SiO ₃ • 9H ₂ O, 0.59 g of 85% hydrazine hydrate and 0.823 g of potassium acetate. Since the exact washing procedure is not described in Example 1 of the US patent, sample 1 was washed using a column washing procedure for 16 hours using 23 ml of H ₂ O per gram of catalyst, while sample 2 was washed in a similar manner, but using 31 ml of water per gram of catalyst. Samples of catalyst 1 and 2 were analyzed by ICP for the content of palladium and gold and by AA analysis for the content of potassium and sodium. It was found that the experimental error in the determination of sodium is about +0.01 relative percent. The catalyst sample 1 was analyzed twice. The results are presented in table. 5.

 Example 4

 The measured activities of three industrial catalysts (catalysts X, Y and Z) are presented in table. 6. In the table. 6, the activities of the catalysts X and Y are compared with the predicted activities of the catalysts of any embodiment of the present invention having the same composition (model catalysts). Predicted activities were determined from the models of the table. 2, suggesting 0.15% sodium. Model catalysts had significantly higher predicted activities. A similar comparison cannot be made for catalyst Z, since its composition is outside the models of the table. 2.

 Catalyst X was prepared using a catalyst preparation procedure. The preparation of catalyst X was different from the preparation of catalyst U in that, upon preparation of catalyst U: (1) the catalyst was dried before precipitation and (2) the precipitating agent used was sodium hydroxide rather than sodium metasilicate. The stages of reduction, washing, drying and impregnation with potassium acetate were the same for both catalyst preparations.

 As for the catalyst Y, the indices A, B and C in the table. 6 indicate different samples (batches) of nominally the same catalyst and, as for catalysts Y and Z, indices 1 and 2 indicate double analyzes of different samples from the same batch of catalysts.

 Catalyst Z has a high palladium content and contains cadmium rather than gold as a cocatalyst. Cadmium is significantly more toxic than gold. In addition, the catalyst Z is obtained by a method significantly different from the method of the present invention, that is, catalyst Z is obtained by impregnating the support with a solution of palladium, cadmium and potassium acetate and drying. In the method used to prepare catalyst Z, there are no precipitation, reduction, or washing steps.

Examples illustrating embodiment B
In the following examples illustrating embodiment B, the abbreviations have the same meaning as the above abbreviations used in the examples illustrating embodiment A.

 In the following examples illustrating Embodiment B, the following procedures were used.

Catalyst Preparation Procedure
A. Carrier 1 (15 g) was added to a solution of Na ₂ PdCl ₄ (35.86% Pd 0.258 g) and HAuCl ₄ 48.95% Au, 0.094 g) dissolved in 9.0 ml of deionized water. The mixture thus formed was carefully mixed until all moisture was adsorbed onto the carrier, and then left to stand in a closed flask for about one hour at room temperature in order to impregnate the carrier with palladium and gold salts. The wet catalyst was coated with a solution of either sodium hydroxide (0.236 g in 28 ml of water) or sodium metasilicate Na ₂ SiO ₃ (0.837 g in 28 ml of water) as a precipitating agent. After stirring for several seconds, the mixture was allowed to stand coated with a liquid and not stirred for 23 hours to precipitate water-insoluble compounds of palladium and gold on the support. Palladium and gold were then reduced by adding 1.0 g of 85% hydrazine hydrate to the above mixture. The mixture was stirred for several seconds and allowed to stand covered with liquid and not stirred at room temperature for another 23 hours. The liquid above was discharged from the catalyst by decantation and the catalyst was washed four times with water to remove a small amount of metal contamination. The catalyst was thoroughly washed using either a column washing procedure or a batch washing procedure described below. The catalyst was dried on a stainless steel grate at 60 ^{° C.} in an oven with forced air circulation for 20 to 24 hours. The catalyst was analyzed for potassium using an AA analyzer. The catalyst was then impregnated with the desired amount of potassium acetate in water using the impregnation method described above for the palladium and gold salts. Then, the impregnated catalyst was dried at 60 ^{° C.} for 20 to 24 hours. The method of the prototype of US patent N4048096 (i.e., the above steps (a) (g)) is completed at this stage. The method of Embodiment In the implementation of the present invention comprises additional steps (h) and (i), followed by steps (j) and (k) as necessary, as illustrated below.

 B. The content of palladium, gold, sodium and potassium in the final catalysts was determined by analysis of ICP. In most cases, sodium and potassium were also determined by AA analysis for greater accuracy.

 C. Unless otherwise noted, the above procedure was used to prepare all of the catalysts mentioned in the following examples. When various amounts of carrier 1 were used, the amounts of other starting materials used were changed accordingly.

 D. All catalysts prepared as described in the examples below were impregnated in the outer layer (i.e., essentially all palladium and all gold was present in the outer layer within 0.5 mm of the surface of the carrier beads 1).

 The catalyst washing procedures (the same as for the above examples illustrating embodiment A).

 The catalyst test method (the same as for the above examples illustrating embodiment A).

 Example 5

 A. Comparative.

 An important step in the preparation of catalysts for the synthesis of alkenyl esters of carboxylic acids is the washing step with water, which is known to remove the separated chloride and residual starting materials. In the laboratory, catalysts are traditionally washed on a column for a 20 24-hour period using about 60 to 80 ml of water per gram of catalyst. For practical and economic reasons, large-scale (for example, semi-plant) catalysts are washed periodically for a shorter time, using significantly smaller volumes of water per volume of the washed catalyst. It was found that the catalysts obtained on large-scale equipment are less active than the catalysts obtained on laboratory-scale equipment. It was suggested that differences in activity were caused by less efficient flushing on large-scale equipment.

 In the table. 7 compare typical behavior results of catalysts obtained in a laboratory with catalysts obtained on large-scale equipment in accordance with the method of US Pat. No. 4,048,096. In particular, all catalysts were prepared using a catalyst preparation procedure using sodium metasilicate as a precipitating agent, except that in large-scale preparations, the amounts of the starting material were proportionally increased, and with the exception of differences in washing procedures. Column washing was used in laboratory samples, and batch washing was used in large-scale samples. Catalysts obtained using large-scale equipment include samples from 80-liter semi-refineries, as well as samples from 260-liter equipment, typical of equipment intended for industrial production. The catalysts obtained using large-scale equipment usually contained about 5 10% (wt.) More palladium than the catalysts obtained in the laboratory, however, the OP of the catalysts obtained on large-scale equipment was about 5 10% less.

B. The implementation of option In the present invention
The data table. 7 show that catalysts prepared on a large scale had lower activities than catalysts prepared on a laboratory scale. In order to determine whether insufficient washing explains the lower activity of the catalysts obtained on a large scale, four of the catalysts obtained on large-scale equipment (i.e., 1-7, 1-9, 1-12, and 1 17 of Table 7 ) repeatedly washed (step (h) of the method of the present invention) with water using a column washing technique, and then dried (step (i) of Embodiment B of the method of the present invention). A fifth catalyst was obtained on a laboratory scale using a catalyst preparation method and a periodic washing method, and a portion of this catalyst was repeatedly washed with water (step (h) of embodiment B of the method of the present invention) using a column washing method, and then dried (step (i) an implementation option In the method of the present invention). Each of the five re-washed and re-dried catalysts was re-impregnated (step (j) of embodiment B of the method of the present invention) with 5% potassium acetate to replace the potassium acetate supposedly removed during the re-washing and dried again (step (k) an implementation option In the method of the present invention). The results are presented in table. 8 and indicate that in each case, repeated washing improved activity by 5-10%
Example 6

 In the experiments described in Example 5, it was suggested that by repeated washing (step (h)) of the method of the present invention) all potassium acetate was also removed. Therefore, in these experiments, potassium acetate was reused (step (i) of the method of the present invention) after repeated washing in an amount equal to the amount used in the initial impregnation of the catalysts. The assumption made in connection with Example 5 was verified using yet another series of eight catalysts having varying palladium contents. The analysis results for these eight catalysts (P-1 P-8 catalysts), obtained before and after repeated washing, are presented in table. 9. These analysis results show that re-washing, as described in Example 1 above, did not actually remove all potassium acetate. The results presented in table. 9 show that about 0.9% (weight) of potassium remained continuously in the catalyst after repeated washing. It is believed that potassium is bound to the carrier via an ion-exchange mechanism.

 Example 7

 Based on the results presented in table. 9, two of the re-washed catalysts shown in table. 8 were analyzed before reapplying potassium acetate. The results presented below were mainly consistent with the data in table. 9.

Re-washed retained K catalyst
1 12 0.88
1 17 1.19
As a result, the potassium content in all re-washed catalysts mentioned in the table. 8 may have been about 0.8 1.2% higher than expected. It could be expected that a higher than required potassium content would lower the activity of the catalyst. These data suggest that improvements in activity, even greater than the observed 5 10% are presented in table. 8 would be possible with an appropriate (lower) final potassium content. This was confirmed when the amount of potassium added after repeated washing was only the amount required to reach the initial content, as shown by the following experiments from 7-1 to 7-7.

 Comparative experience 7-1.

 2.5 g of catalyst P was evaluated to obtain vinyl acetate, obtaining the result shown in table. 10. Parts of this catalyst were re-washed as described in the following experiments 7-2 and 7-3.

 Experience 7-2.

Three portions of 50 g of the catalyst from experiment 7-1 were washed using a column washing method, and then analyzed for potassium content, which gave a potassium content of 0.92% (wt.). A 15-gram sample of the catalyst was re-impregnated with 0.469 g of potassium acetate in 9.0 ml of water, then dried for 18 hours at 60 ^o C. The results of the analysis and testing of the catalyst are presented in table. 10.

 Experience 7-3.

The procedure of the above experiment 7-2 was used, except that four samples of catalyst P were used, and each part (200 g) was washed with 2 gallons (7.57 L) for a 48-hour period using the column washing method. It was determined that the potassium content is 0.86% after mixing the washed substance. A sample weighing 15 g was impregnated with a solution of 0.556 g of potassium acetate in 9.0 ml of water, then dried for 24 hours at 60 ^o C. The results of the analysis and testing of the catalyst are presented in table. 10.

 Comparative experience 7-4.

 This catalyst was prepared using the catalyst preparation procedure, except that the concentrations of palladium and gold salts in the impregnation solution and other starting materials were refined to obtain the contents shown in Table 1. 10. Evaluation was carried out using the catalyst test method described above, with a total of 0.75 g of catalyst used. The results of the analysis and testing are presented in table. ten.

 Experience 7-5.

 2.75 g of the catalyst from experiment 7-4 was washed using a column washing method using 500 ml of water for 24 hours. After drying, the catalyst was impregnated with a sufficient amount of potassium acetate, obtaining about 3% potassium in the final catalyst. Evaluation was carried out using a catalyst test method, with a total of 0.75 g of catalyst being used. The results of the analysis and testing are presented in table. ten.

 Comparative experience 7-6.

 This catalyst was obtained, as in the above experiment 7-4, except that the concentrations of palladium and gold salts in the solution for impregnation and other starting materials were refined to obtain the contents shown in table. 10. Evaluation was carried out using a catalyst testing method, wherein only 0.75 g of catalyst was used. The results of the analysis and testing of the catalyst are presented in table. ten.

 Experience 7-7.

 The catalyst sample from Experiment 7-6 was repeatedly washed with water using a column washing procedure. Evaluation was performed using the catalyst test method described above, except that only 0.75 g of catalyst was used. The results of the analysis and testing of the catalyst are presented in table. ten.

 Based on the above results, studies were conducted to determine if other impurities can explain the described effects. A comparison of the ICP analysis data of the initial catalysts and their re-washed analogs revealed significant differences in the sodium content, but no significant differences in the content of other impurities were observed.

 Example 8

 To check the effect of sodium on the activity of the catalyst, a series of experiments was carried out, where the sodium content was changed and the potassium content was kept constant. In another series of experiments, the ratio between sodium and potassium was changed, keeping the total number of moles of alkali metals constant. The results of both series of experiments are presented in table. 11, and these results confirm that increasing sodium levels actually result in decreased activity.

 In the experiment, 2 tablets. 11 re-washed catalyst, which was impregnated with a solution with a sodium content similar to the sodium content in the original non-washed analogue (experiment 4 of Table 11), showed a significantly higher activity. This suggests that other undesirable impurities may also be removed by repeated washing.

Examples illustrating embodiment c
In the following examples illustrating embodiment c, the abbreviations used have the same meaning as those used for examples illustrating embodiment A.

 In the following examples, the following methods were used.

Catalyst Preparation Procedure
A. Carrier 1 (15 g) was added to a solution of Na ₂ PdCl ₄ (35.86% Pd, 0.258 g) and HAuCl ₄ (48.95% Au 0.094 g) dissolved in 9.0 ml of deionized water. The mixture thus formed was carefully mixed until all moisture was adsorbed onto the carrier, and then left to stand in a closed flask for about one hour at room temperature in order to impregnate the carrier with palladium and gold salts. The wet catalyst was coated with a solution of either sodium hydroxide (0.236 g in 28 ml of water) or sodium metasilicate Na ₂ SiO ₃ (0.837 g in 28 ml of water) as a precipitating agent. After stirring for several seconds, the mixture was allowed to stand coated with a liquid and not stirred for 23 hours at room temperature in order to precipitate water-insoluble compounds of palladium and gold on the support. Palladium and gold were then reduced by adding 1.0 g of 85% hydrazine hydrate to the above mixture. The mixture was stirred for several seconds and left to stand covered with liquid and not stirred at room temperature for another 23 hours. The liquid on top was discharged from the catalyst by decantation and the catalyst was washed four times with water to remove a small amount of metal contamination. The catalyst was thoroughly washed using either a column washing procedure or a batch washing procedure described below. The catalyst was dried on a stainless steel steel grate in an oven with forced air circulation at 60 ^o C for 20 24 hours. Using the preferred embodiment of embodiment c of the present invention, the catalyst preparation procedure was completed at this stage.

B. When applying other embodiments of embodiment c of the present invention and using known methods and the comparative examples described below, the catalyst preparation procedure also included the following additional steps: the catalyst was analyzed for potassium using an AA analysis. The catalyst was then impregnated with the required amount of potassium acetate in water using the impregnation procedure described above for the palladium and gold salts. The impregnated catalyst was then dried at 60 ^{° C.} for 20 to 24 hours.

 C. The content of palladium, gold, sodium and potassium in the final catalyst was determined by ICP analysis. In most cases, sodium and potassium were also determined for greater accuracy by AA analysis.

 D. Unless otherwise indicated, the above procedure was used to prepare all of the catalysts mentioned in the following examples. When various amounts of carrier were used, the amounts of other starting materials were changed accordingly.

 E. All catalysts prepared in accordance with the examples below were impregnated in the outer layer (that is, essentially all palladium and all gold were present in the outer layer within 0.5 mm of the surface of the carrier beads 1).

 The catalyst washing procedures and the catalyst test method were the same as those used in the above examples illustrating embodiment A.

 Example 9

 Comparative experience 9-1A.

A sample of carrier 1 weighing 90 g was impregnated as described in the catalyst preparation procedure using sodium metasilicate as a precipitating agent. After the reduction step, the liquid on top was decanted, the wet balls were divided into three equal parts, designated as samples A, B and C. Samples B and C were stored for future use. Sample A was transferred without drying to a washing apparatus and washed with water using a column washing technique. The black opaque washings taken from the column were analyzed for palladium and gold using COI. The results showed that about 1% of each metal was lost from the catalyst during washing. The catalyst was dried at 60 ^{° C.} in an oven with forced air circulation for 4.5 hours, then analyzed for potassium content (0.31%). The catalyst (30.4 g) was impregnated with a solution of 1.62 g of potassium acetate in 18.3 ml of water, using the procedure described above in the catalyst preparation procedure. After drying at 60 ^{° C.} for 24 hours, the catalyst was tested for activity. The results are shown in FIG. one.

 Experience 9-1B.

 A portion of the catalyst obtained from sample A described in the above test 9-1A was re-washed with water using a column washing procedure and dried. Then, the amount of potassium acetate necessary to increase the content of potassium acetate to its initial level was added. The results are shown in FIG. one.

 Experience 9-2A.

Sample B from the still wet catalyst obtained in the above test 9-1A was washed using a column washing procedure as described above, except that a 1% potassium acetate solution (cation exchange solution) was used, and not water. The washings were colorless and did not show a noticeable amount of palladium or gold in the ICP analysis. The washed catalyst was dried as described above and analyzed for potassium content (1.41%). The catalyst was impregnated with a solution of 0.608 g of potassium acetate in 17.8 ml of water, then dried at 60 ^{° C.} for 24 hours. The test results are shown in FIG. one.

 Experience 9-2V.

 A portion of the catalyst from the above Test 9-2A was repeatedly washed with water using a column washing technique and dried. Then the amount of potassium acetate needed was added in order to increase the potassium acetate content back to its initial level. The results are shown in FIG. one.

 Experience 9-3.

 Sample C from the above test 9-1A was treated similarly to sample B from the above test 9-2A, except that in the washing step, a 1% potassium acetate solution was replaced with a 1% potassium hydroxide solution. It was found that after standing for about 12 hours, the silica support was very destroyed and the catalyst had to be discarded. This experiment shows that under the conditions used, potassium hydroxide is not suitable for use as a cation exchange solution in the present invention when carriers are used that are sensitive to a strong base.

 The results in FIG. 1 show that the same improvement in activity is obtained by immediately using a rinse with potassium acetate or using an initial water rinse and then rinsing with water after soaking in potassium acetate. These results show the presence of a harmful impurity on the catalyst and confirm the theory that the addition of potassium helps to remove this impurity.

 Example 1

 Chloride was supposed to be, at least in part, an impurity removed by the experiments described in Example 9 above. However, subsequent chloride analyzes performed on the catalysts obtained in Example 9 (see FIG. 4) showed only slight differences in the chlorine content before and after washing. Additional experiments in which varying amounts of potassium chloride were added to the catalysts also showed a minimal effect on activity (see table 12).

 The catalysts used to obtain the results presented in table. 12, was obtained using the method of obtaining a catalyst from the same mother liquor having a nominal palladium content of 0.58% Au / Pd ratio of 0.5, KOAc content of 5.3% and the established initial chloride content, equal to about 200 ppm. Chloride was added as KCl to the KOAc solution for soaking.

 Based on the results described above, studies were carried out to determine whether other impurities can explain the effects described. A comparison of the ICP analysis data of the initial catalysts and their re-washed analogues showed significant differences in the sodium content, but no significant differences in the content of other impurities were observed.

 Example 11

 In order to check the effect of sodium on the activity of the catalyst, a series of experiments was carried out in which the sodium content was changed and the potassium content was kept constant. In another series of experiments, the ratio between sodium and potassium was changed, keeping the total number of moles of alkali metals constant. The results of both series of experiments are presented in table. 13, and the results confirm that increasing amounts of sodium do lead to decreased activity.

 In the experiment, 2 tablets. 13 re-washed catalyst, which was impregnated with an amount of sodium similar to the amount in the original non-washed analogue (experiment 4 of Table 13), showed a significantly higher activity. This suggests that other harmful impurities may also be removed by repeated washing.

 Example 12

 A series of experiments (the following experiments 12-1 to 12-4) were carried out in order to further illustrate the effects shown in the above example 9. An additional goal was to demonstrate that the benefits of the present invention can also be obtained using a periodic washing technique , which is more affordable for large-scale preparation of catalysts than the column washing method used in Example 9.

 Comparative experience 12-1.

The catalyst was prepared with 80 g of support 1 using a catalyst preparation procedure. Sodium hydroxide was used as the precipitating agent. Following the reduction step, the liquid was discharged from the catalyst beads, and then the beads were quickly washed with a volume of water approximately equal to the volume of the catalyst. The catalyst was divided into four equal parts, labeled samples A, B, C and D. Samples B, C and D were stored for use in the following examples. Sample A was washed using a batch washing technique that included coating the catalyst with 23 ml of deionized water and settling for 36 minutes. The water was decanted and the catalyst was covered with another 23 ml of fresh water. Washing was continued in this way for 5 washes performed over 3 hours. After the last washing, the balls were washed again with water, then dried overnight at 60 ^° C. The catalyst was analyzed for potassium (0.30%) and then soaked in a solution of 0.955 g of potassium acetate in 11.7 ml of water. After drying at 60 ^{° C.} overnight, the evaluation of the catalyst gave the results shown in the table. one.

 Experience 12-2.

Sample B from the above experiment 12-1 was washed in a batch process 5 times for three hours in 23 ml of a 5% aqueous potassium acetate solution using the procedure specified in experiment 12-1. After washing the balls with water, the catalyst was dried overnight at 60 ^° C, then analyzed for potassium content (1.42%). The catalyst was then impregnated with a solution of 0.359 g of potassium acetate in 11.7 ml of water. After drying at 60 ^{° C.} overnight, the evaluation of the catalyst gave the results shown in the table. 14.

 Comparative experience 12-3.

Sample C from the above experiment 12-1 was washed five times with water in a manner similar to the method of the above experiment 12-1, except that the duration of each washing was 96 minutes for a total washing time of 8 hours. Analysis for potassium showed 0.33% after washing. The sample was impregnated with a solution of 0.934 g of potassium acetate in 11.7 ml of water, then dried overnight at 60 ^o C. The test results are presented in table. 14.

 Experience 12-4.

Sample D from test 12-1 above was washed five times with a 5% potassium acetate solution using the procedure of test 12-3 above. Analysis for potassium showed 1.69% after washing. The sample was impregnated with a solution of 0.216 g of potassium acetate in 11.7 ml of water, then dried overnight at 60 ^o C. The test results are presented in table. 14.

 Example 13

 An additional series of experiments was carried out in order to determine the most cost-effective amount of potassium acetate required in order to give a significant improvement in activity. In these experiments, a large batch of catalyst was divided immediately before the washing step (i.e., step (d) of the method of the present invention) into six equal parts as shown in FIG. 2. All catalysts were washed periodically five times using a periodic washing technique. The composition of the wash solutions was changed in accordance with that indicated in FIG. 2. For example, the first part of the catalyst was washed periodically five times with water, the second part was washed three times with water, and then twice with a 5% potassium acetate solution, etc. The catalysts were dried and analyzed for potassium and sodium by atomic adsorption spectroscopy. Each catalyst was again divided into parts A and B. Each part was then treated with potassium acetate in an amount sufficient to bring the potassium content in the final catalyst to about 2.9%. The catalyst fractions labeled A also received enough sodium acetate to return the final sodium content in them is approximately the same as that found in the water-washed catalyst (for example, the level in the water-washed catalyst of the following experiment 13-1).

 Thus, two series of catalysts were obtained; one series (series A) shows the effect of washing with potassium acetate on the behavior of the catalyst, and the second series (series B) shows that the removal of sodium adequately explains this effect. These results are summarized in table. 15.

 Comparative experience 13-1.

The catalyst was prepared using a catalyst preparation procedure with 100 g of support 1 and sodium metasilicate. After the reduction step, the solution was decanted and the catalyst was washed four times with water. The precipitating agent and reducing agent solutions were poured and the still wet catalyst was divided into six equal parts, labeled samples A, B, C, D, E and F. BF samples were stored for use in the following examples. Sample A was washed periodically five times with about 20 ml of water for 8 hours. After drying overnight at 60 ^{° C., the} catalyst was impregnated with a solution of 1.098 g of potassium acetate in 9.6 ml of water and dried at 60 ^° C. The final catalyst, which had the calculated amount of potassium and sodium, is shown in the table. 15, was evaluated for activity in the synthesis of vinyl acetate. The results are presented in table. 15.

 Experience 13-2.

Sample B from the above experiment 13-1 was washed in a batch manner similar to the method of experiment 13-1, except that the first three washes were carried out with water and the last two with a 5% potassium acetate solution. After drying overnight at 60 ^{° C., the} catalyst was divided into equal parts. The first part was impregnated with 0.26 g of potassium acetate and 4.6 ml of water. After drying at 60 ^o With the catalyst, which had the calculated composition shown in table. 15 (experiment 13-2A), gave the results presented in the same table. The second half of the sample was impregnated with a solution of 0.26 g of potassium acetate and 0.090 g of sodium acetate in 4.6 ml of water. The calculated composition and results are presented in table. 15 (experiment 13-2V).

 Experience 13-3.

Sample C from the above experiment 13-1 was washed periodically in a manner analogous to the method of experiment 13-1, except that the first two washes were carried out with water and the last three were washed with 5% potassium acetate solution. After drying overnight at 60 ^{° C., the} catalyst was divided into equal parts. The first part was soaked in 0.20 g of potassium acetate in 4.6 ml of water. After drying, the catalyst, which had the calculated composition shown in table. 15 (experiment 13-3A), gave the results presented in the same table. The second half of the sample was impregnated with a solution of 0.20 g of potassium acetate and 0.097 g of sodium acetate in 4.6 ml of water. The calculated composition and test results are given in table. 15 (experiment 13-3V).

 Experience 13-4.

Sample D from the above experiment 13-1 was washed periodically in a manner analogous to the above experiment 13-1, except that the first washing was carried out with water and the last four with a 5% potassium acetate solution. After drying overnight at 60 ^{° C., the} catalyst was divided into equal parts. The first part was soaked in 0.155 g of potassium acetate in 4.6 ml of water. After drying, the catalyst, which had the calculated composition shown in table. 15 (experiment 13-4A), gave the results presented in the same table. The second half of the sample was impregnated with a solution of 0.155 g of potassium acetate and 0.094 g of sodium acetate in 4.6 ml of water. The calculated composition after drying and the test results are presented in table. 15 (experiment 13-4V).

 Experience 13-5.

Sample E from the above experiment 13-1 was washed in a batch manner similar to the above experiment 13-7, except that the first three washes were carried out with water and the last two were washed with 10% potassium acetate solution. After drying at 60 ^{° C.} overnight, the catalyst was divided into equal parts. The first part was soaked in 0.32 g of potassium acetate in 4.6 ml of water. After drying, the catalyst, which had the calculated composition shown in table. 15 (experiment 13-5A), gave the results presented in the same table. The second half of the sample was impregnated with a solution of 0.032 g of potassium acetate and 0.098 g of sodium acetate in 4.6 ml of water. The calculated composition after drying and the test results are presented in table. 15 (experiment 13-5V).

 Experience 13-6.

The sample from the above experiment 13-1 was washed in a batch manner similar to the above 13-1, except that the first two washes were carried out with water and the last three were washed with a 10% potassium acetate solution. After drying at 60 ^{° C.} overnight, the catalyst was divided into equal parts. The first part was dried and divided without additional impregnation with potassium acetate. The catalyst, which had the calculated composition shown in the table (experiment 13-6A), gave the results presented in the same table. The second half of the sample was impregnated with a solution of 0.12 g of sodium acetate in 4.6 ml of water. The calculated composition after drying and the test results are presented in table. 15 (experiment 13-6B).

 Significant improvements in activity are visible in table. 15 in series A catalysts (compare experiment 13-1 with experiments 13-2A 13-6A), and these improvements mainly correspond to lower sodium contents of these catalysts. Catalysts of series B show that the repeated addition of sodium to the catalysts of series A reduces the activity of the catalyst to the level of the initial water-washed catalyst (compare experiment 13-1 with experiments 13-2V to 13-6V). These results again confirm the theory that sodium removal is responsible for the observed increases in activity.

 Example 14

 Ion chromatography was used to analyze the wastewater from the column washing procedure and the periodic washing method from several catalyst preparations. The experiments included the use of both water and potassium acetate solutions as washing liquids, and were carried out in order to detect any impurity that could pass unnoticed by ICP analyzes. Sulfate, apparently, is the main impurity, however, it was estimated that in the initial catalyst it is less than 100 million dollars. Less phosphate and chloride were also found. In order to determine whether sulfate could have a detrimental effect on activity, potassium sulfate was added to the two catalysts in amounts of $ 500 and $ 1,000 million. The effect on activity was negligible, in accordance with the table. sixteen.

 The following Examples 15 to 20 illustrate the preferred embodiment of the present invention shown in FIG. 3.

 Example 15

Using a catalyst preparation technique, a catalyst was prepared per 50 g of support 1 using sodium hydroxide as a precipitating agent. After the reduction step, the liquid was discharged from the catalyst and the balls were washed four times with water to remove metal contaminants. The wet catalyst was divided into three equal parts, placed samples A, B and C. Samples B and C were stored for use in the following examples. Sample A was washed five times in 23 ml of a 5% potassium acetate solution for 8 hours using the periodic washing procedure of Test 12-4. Each wash had a duration of 96 minutes. The catalyst was dried at 60 ^{° C.} without washing with water and evaluated for activity in the synthesis of vinyl acetate without additional addition of potassium acetate. The results of the analysis and testing are presented in table. 17.

 Example 16

Sample B obtained in Example 15 above was washed as described in Example 15, except that the first four washes with 5% potassium acetate had a duration of 1 hour each and the last washing had a duration of 4 hours. The catalyst was dried at 60 ^{° C.} without washing with water. The results of the analysis and testing are presented in table. 17.

 Example 17

Sample C obtained in Example 15 was washed as described in Example VII, except that a 7% potassium acetate solution was used. The catalyst was dried at 60 ^{° C.} without washing with water. The results of the analysis and testing are presented in table. 17.

 Comparative example 18.

 20 L of the catalyst was prepared in a semi-refinery using the catalyst preparation procedure and washed with water using the periodic washing procedure. The results of the analysis and testing are presented in table. 17.

 Example 19

 20 l of catalyst was prepared using the method described in example 15. The results of the analysis and testing are presented in table. 17.

 Example 20

 520 L of the catalyst was obtained at the factory using the method described in example 15. The results of the analysis and testing are presented in table. 17.

 The data in the table. 17 show the improvements achieved by using the present invention.

 Example 21

 The catalyst sample from Example 20 above was impregnated with a potassium acetate solution at a concentration calculated in order to increase the potassium content by about 0.8%. The resulting catalyst contained 0.56 Pd, 0.25% Au, 3.7% K and 0.17 % Na and had an OD of 550.

 The purpose of the following Examples 22 to 32 was to demonstrate the suitability of various cation exchange solutions in Embodiment C of the present invention.

 Comparative example 22.

 The catalyst was prepared using a catalyst preparation technique with 90 g of support and sodium hydroxide as the precipitating agent. Following the reduction step, the catalyst was dried and the balls washed four times with water. The wet catalyst was divided into six equal parts, labeled Samples A, B, C, D, E, and F. Samples B-F were stored for use in the following examples. Sample A was washed with five 20 ml portions of water using a batch washing procedure as described in Test 12-3 above. Evaluation of the final catalyst gave the results presented in table. 18.

 Example 23

 Sample B from Example 22 above was washed with 20 ml portions of 2% ammonium carbonate in water using the procedure described in Example 22. Evaluation of the final catalyst gave the results shown in Table 1. 18.

 Example 24

 Sample C from Example 22 above was washed with 20 ml portions of 2% lithium acetate in water using the procedure described in Example 22. Evaluation of the catalyst gave the results shown in Table 1. 18. Through AA analysis, it was found that the lithium content in the final catalyst is 0.18.

 Comparative example 25.

 Sample D from Example 22 above was washed with 20 ml portions of 2% sodium acetate in water using the procedure described in Example 22. Evaluation of the catalyst gave the results shown in Table 1. 18.

 Example 26

 Sample E from Example 22 above was washed with 20 ml portions of 2% potassium nitrate in water using the procedure described in Example 2. Evaluation of the catalyst gave the results shown in table. 18.

 Example 27

 Sample F from Example 22 above was washed with 20 ml portions of 2% potassium carbonate in water, using the procedure described in Example 22. The results of the evaluation of the catalyst are presented in table. 18.

 Comparative example 28.

 Catalysts were prepared according to the procedure of Example 23 above. Following the reduction, the wet catalyst was divided into six equal parts, labeled Samples A, B, C, D, E, and F. Samples B-F were stored for use in the following examples. Sample A was washed with five 20 ml portions of water as described in Example 23 above. Evaluation of the catalyst gave the results shown in Table 1. 19.

 Example 29

 Sample B from Example 28 above was washed with 20 ml portions of 2% ammonium acetate in water as described in Example 23 above. Evaluation of the catalyst gave the results shown in Table 1. 19.

 Example 30

 Sample C from the above example 28 was washed with 20 ml portions of 2% potassium acetate in water as described in the above example 23. The evaluation of the catalyst gave the results shown in table. 19.

 Example 31

 Sample D from Example 28 was washed with 20 ml portions of 2% potassium sulfate in water as described in Example 23 above. Evaluation of the catalyst gave the results shown in Table 1. 19. The potassium sulfate solution is a less suitable cation exchange solution because it appears to be converted into effective species (potassium acetate) relatively slowly.

 Example 32

 Sample F from Example 28 above was washed with 20 ml portions of 2% magnesium acetate in water using the procedure described in Example 23. Evaluation of the catalyst gave the results shown in Table 1. 19.

Claims (1)

1 1. A method of producing a catalyst for the synthesis of alkenyl ethers of carboxylic acids containing palladium, gold and an alkaline promoter on a cation exchangeable carrier by impregnating the carrier with a solution of water-soluble palladium and gold compounds taken in an amount that provides 0.5 palladium in the finished catalyst 1.7 wt. and gold 0.1 to 2.55 wt. treating the impregnated carrier with a solution of the compound converting the water-soluble compounds of palladium and gold to water-insoluble, reducing the water-soluble compounds of palladium and gold to metallic palladium and gold, drying, applying the potassium promoter compound and drying, characterized in that the catalyst is further washed with water, followed by impregnation with potassium, after drying after drying, the promoter or catalyst is further washed with an aqueous solution of the potassium promoter until the content of lia 1.4 3.8 wt. and sodium not more than 0.3 wt. followed by drying of the catalyst. 2 2. The method according to claim 1, characterized in that after processing the impregnated carrier with a solution of a compound converting water-soluble compounds of palladium and gold into water-soluble, it is washed with a solution of a cation exchanger, followed by drying.

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