MXPA06006167A - Zirconia containing support material for catalysts - Google Patents

Abstract

The present invention addresses at aeast four different aspects relating to catalyat structure, method of making those catalysts and methods of using those catalysts for making allcenyl alkanoates. Separately or together incombination, the various aspects of the invention are directed at improving the production of alkenyl alkanoates and VA in particular, including reduction of by-products and improved production efficiency. A first aspect of the presente invention pertains to a unique palladium/gold catalyst or pre-catalyst (optionally calcined) that includes rhodium or another metal. A second aspect pertains to a palladium/gold catalyst or precatalyst at is based on a layered support material where one layer of the support materiel is substantially free of catalytic components. A third aspect pertains to a palladium/gold catalyst or precatalysts on a zirconia containing support material. A fourth aspect pertains to a palladium gold catalyst or pre-catalyst that is produced from substantially chloride free catalytic components.

Description

SUPPORT MATERIAL THAT CONTAINS ZIRCONIA FOR CATALYST PRIORITY CLAIM This application claims the benefit of United States Provisional Application No. 60/531, 415 filed December 19, 2003, which is therefore incorporated for reference.

FIELD OF THE INVENTION The present invention relates to catalysts, methods of making the catalysts, and methods of making alkenyl alkanoates. More particularly, the invention relates to methods for making vinyl acetate.

BACKGROUND OF THE INVENTION Certain alkenyl alkanoates, such as vinyl acetate (VA), are commercial chemicals with high demand in their monomeric form. For example, VA is used to make polyvinyl acetate (PVAc), which is commonly used for adhesives, and is considered for a large portion of VA use. Other uses for the VA include polyvinyl alcohol (PVOH), ethylene-vinyl acetate (EVA), vinyl acetate-ethylene (VAE), polyvinyl butyral (PVB), ethylene-vinyl alcohol (EVOH), polyvinyl formal ( PVF), and vinyl chloride-vinyl acetate copolymer. PVOH is normally used for textiles, films, adhesives and photosensitive coatings. Films and wire and insulation for cable sometimes use EVA in some proportion. Most applications for the vinyl chloride-vinyl acetate copolymer include coatings, paints and adhesives, sometimes using VAE that has VA in some proportion. The VAE, which contains more than 50% VA, is mainly used as an additive for cement, paints and adhesives. The PVB is mainly used for a sub-layer in laminated screens, coatings, inks. The EVOH is used for barrier films and polymers for use in engineering. The PVF is used for wire enamel and magnetic tape. Because VA is the basis for many materials and commercially significant products, the demand for VA is large, and VA production is often done on a relatively large scale, for example, 5 x 107 kg or more per year. This large scale production refers to significant scale savings are possible and relatively slight changes in the procedure, process conditions or catalyst characteristics can have a significant economic impact on the cost of VA production. Many techniques for the production of alkenyl alkanoates have been mentioned. For example, in VA processing, a widely used technique includes a catalysed gas phase reaction of ethylene with acetic acid and oxygen, as observed in the following reaction: C2H4 + CH3COOH + 0.5 O2? CH3COOCH = CH2 + H2O several side reactions can take place, including such as, the formation of CO2. The results of this reaction are discussed in terms of the yield in grams / cm3 (STY) time of the reaction system, where the STY is the grams of VA produced per liter of catalyst per hour of reaction time (g / l * h ). The composition of the feed of the starting material can vary within wide limits. Normally, the feed of the starting material includes 30-70% ethylene, 10-30% acetic acid and 4-16% oxygen. The feed may also include inert materials such as C02, nitrogen, methane, ethane, propane, argon and / or helium. The primary restriction in feed composition is that the oxygen level in the effluent stream leaving the reactor should be low enough so that the current is outside the flammability zone. The oxygen level in the effluent is affected by the oxygen level in the starting material stream, the conversion rate of 02 of the reaction and the amount of any inert material in the effluent. The gas phase reaction is performed when a feed of the starting materials passes over or through fixed bed reactors. Successful results are obtained with the use of reaction temperatures in the range of -125 ° C to 200 ° C, while reaction pressures of 1 to 15 atmospheres are typical. Although these systems provide adequate yields, there remains a need for reduced production of byproducts, higher VA production rates, and lower energy use during production. One approach is to improve the characteristics of the catalyst, particularly as it relates to the selectivity of C02 and / or catalyst activity. Another approach is the modification of reaction conditions, such as the ratio of starting materials to each other, the conversion of 02 of the reaction, the spatial velocity (SV) of the feed of the starting material, and operating temperatures and pressures. . The formation of C02 is an aspect that can be reduced by the use of improved catalysts. The selectivity of C02 is the percentage of the converted ethylene that moves towards CO2. The decrease in C02 selectivity allows a large amount of VA per unit volume and unit time in existing plants, while retaining all other reaction conditions. The VA production of a particular reaction system is affected by several other factors including catalyst activity, the ratio of starting materials to one another, the conversion of 02 from the reaction, the spatial velocity (SV) of the feed of the starting material, and the operating temperatures and pressures. All these factors cooperate to determine the yield in grams / cm3 (STY) time of the reaction system, when the STY is discussed in terms of grams of VA produced per liter of catalyst per hour of reaction time or g / l * h. In general terms, activity is a significant factor in determining the STY, but other factors in the STY still have a significant impact. Normally, the higher the activity of a catalyst, the higher the STY and the catalyst will have the production capacity. The conversion of 02 is a measure of how much oxygen reacts in the presence of the catalyst. The conversion rate of 02 is temperature dependent such that the talk rate generally rises with the reaction temperature. However, the amount of C02 produced also increases along with the conversion of 02. In this way, the conversion rate of 02 is selected to provide the desired VA output balanced against the amount of C02 produced. A catalyst with higher activity means that the overall reaction temperature can be decreased while maintaining the same conversion of 02. Alternatively, a catalyst with higher activity will provide a higher conversion rate of 02 at a temperature and space velocity Given It is common for the catalysts to employ one or more catalytic components carried in a relatively inert support material. In the case of VA catalysts, the catalytic components are usually a mixture of metals that can be distributed evenly throughout the support material ("global coverage catalysts"), just on the surface of the support material (" shell catalysts "), just below a shell of support material (" egg white catalysts ") or in the core of the support material (" egg yolk catalysts "). Numerous different types of support materials have been suggested for use in a VA catalyst that includes silica, silica contaminated with cerium, alumina, titania, zirconia, and mixtures of oxides. But a very small investigation of the differences between the support materials has been made. For the most part, only silica and alumina are actually marketed as support materials. A useful combination of metals for VA catalysts is palladium and gold. Pd / Au catalysts provide adequate selectivity and activity of C02, but the need for improved catalysts remains, given the scale savings that are possible in the production of GOES. A process for the preparation of Pd / Au catalysts typically includes the steps of: impregnation of the support with aqueous solutions of water soluble salts of palladium and gold; reaction of the water-soluble salts impregnated with an appropriate alkaline compound, for example, sodium hydroxide, to precipitate (sometimes called fixation) the metallic elements such as the water-insoluble compounds, for example, the hydroxides; washing the fixed support material to remove unfixed compounds and otherwise cleaning the catalyst from any potential poison, for example, a chloride; the reduction of insoluble compounds in water with a typical reducing agent such as hydrogen, ethylene or hydrazine, and the addition of an alkaline metal compound such as potassium or sodium acetate. Various modifications to this basic procedure have been suggested. For example, in the patent of E.U.A. No. 5,990,344, it is suggested that palladium sintering is taken after reduction to its free metal form. In the patent of E.U.A. No. 6,022,823, it is suggested that the calcination of the support in a non-reducing atmosphere may be desirable after impregnation with palladium and gold salts. In W094 / 21374, it is suggested that after reduction and activation, but before its first use, the catalyst can be pre-treated with successive heating in oxidation, inert and reduction atmospheres. In the patent of E.U.A. No. 5,466,652, it is suggested that the palladium and gold salts that are free of hydroxyl, halide and barium and soluble in acetic acid are useful for impregnating the support material. A similar suggestion is made in the patent of E.U.A. No. 4,902,823, that is to say the use of salts and complexes of halide and sulfur free palladium soluble in unsubstituted carboxylic acids having from 2 to 10 carbon atoms. In the patent of E.U.A. No. 6,486,370 it is proposed that a stratified catalyst can be used in a dehydrogenation process when the support material of the inner layer differs from the support material of the outer layer. Similarly, the US patent. No. 5,935,889 proposes that a stratified catalyst is useful as acid catalysts. But none of the documents raises the use of stratified catalysts in the production of alkenyl alkanoates. Unifying, the inventors have recognized and prosecuted the need for continuous improvements in the field of VA catalysts to provide improved VA production at low costs.

BRIEF DESCRIPTION OF THE INVENTION The present invention addresses at least four different aspects that relate to the structure of the catalyst, methods of making those catalysts and methods of using those catalysts to make the alkenyl alkanoates. Separately or jointly in combination, the various aspects of the invention are directed to improve the production of alkenyl alkanoates and VA in particular, including the reduction of side products and improved production efficiency. A first aspect of the present invention pertains to a unique palladium / gold catalyst or pre-catalyst (optionally calcined) that includes rhodium or other metal. A second aspect pertains to a palladium / gold catalyst or precatalyst that is based on a layered support material where a layer of the support material is substantially free of catalyst components. A third aspect pertains to a palladium / gold catalyst or precatalyst in a support material containing zirconia. A fourth aspect relates to a palladium / gold catalyst or precatalyst that is produced from substantially free chloride catalyst components.

DETAILED DESCRIPTION OF THE INVENTION Catalysts For the purposes of the present, a catalyst is any support material that contains at least one catalytic component and that has the ability to catalyze a reaction, whereas a pre-catalyst is any material that results from any of the catalyst preparation stages discussed herein. The catalysts and pre-catalysts of the present invention can include those having at least one of the following attributes: 1) the catalyst will be a catalyst containing palladium and gold that includes at least one other catalyst component, for example, rhodium where one or more of the catalytic components have been calcined; 2) the catalyst will be carried on a stratified support; 3) the catalyst will be carried in a support material containing zirconia; 4) The catalyst will be produced with chloride free precursors or any combination of the above. The effective use of the catalysts will consequently help to improve C02 selectivity, activity, or both, particularly as it pertains to VA production. It will be appreciated that the present invention is described in the answer to certain illustrative embodiments, but may vary in any of a number of aspects depending on the needs of a particular application. By way of example, without limitation, the catalysts may have the catalyst components uniformly distributed throughout the support material or they may be shell catalysts where the catalyst components are in a relatively thin shell around the core of support material . Egg white catalysts are also suitable, when the catalyst components reside substantially at a distance from the center of the support material. Egg yolk catalysts may also be suitable.

Catalyst Components In general, the catalysts and pre-catalysts of the present invention include metals and particularly include a combination of at least two metals. In particular, the metal combination includes at least one of group VIIIB and at least one of group IB. It will be appreciated that the "catalytic component" is used to make known the metal that ultimately provides the catalytic functionality to the catalyst, but also includes the metal in a variety of states, such as a salt, solution, sol-gel, suspensions , colloidal suspensions, free metal, alloys or their combinations. Preferred catalysts include palladium and gold as the catalyst components. One embodiment of the catalyst includes a combination of catalyst components having palladium and gold combined with a third catalyst component. The third catalyst component is preferably selected from group VIIIB, with Rh being most preferred. Other preferred catalysts include those where the third catalyst component is selected from W, Ni, Nb, Ta, Ti, Zr, Y, Re, Os, Fe, Cu, Co, Zn, In, Sn, Ce, Ge, Ga and their combinations Another embodiment of the catalysts includes a combination of catalyst components that includes proportions of palladium, gold and rhodium. Optionally a third catalyst component (as listed above) can also be included in this embodiment instead of Rh. In another embodiment, two or more catalytic components from the above list may be employed. In one example, palladium and gold can be combined with Rh to form a catalyst that shows improved C02 selectivity (ie, decreased CO2 formation) compared to Pd / Au catalysts lacking Rh. Also, the addition of Rh does not appear to reverse the activity of the catalyst. The C02 selectivity of the palladium, gold, rhodium catalyst can also be improved by calcination during catalyst preparation and / or by the use of water-soluble halide precursors (both discussed below), although these are not necessary to observe the effect of Rh. The atomic ratio of the third catalytic component to the palladium can vary in the range of from about 0.005 to about 1.0, more preferably from about 0.01 to about 1.0. In one embodiment, the catalyst contains between about 0.01 and about 5.0 g of the third catalyst component per liter of catalyst. Another preferred embodiment of the catalyst includes between about 1 to about 10 grams of palladium, and about 0.5 to about 10 grams of gold per liter of catalyst. The amount of gold is preferably from about 10 to about 125% by weight based on the weight of the palladium. In an embodiment for crushed catalysts, the atomic ratios of Au to Pd between about 0.5 and about 1.00 are preferred for crushed catalysts. The atomic ratio can be adjusted to balance the activity and selectivity of C02. The use of atomic and weight ratios of higher Au / Pd tends to favor more active and more selective catalysts. Alternatively it is determined that, a catalyst with an atomic ratio of about 0.6 is less effective for C02, but also has less activity than a catalyst with a ratio of about 0.8. The effect of the high atomic ratio of Au / Pd in the crushed support material can also be improved by the use of a relatively slight excess of hydroxide ion, as will be discussed later with respect to the fixing step. A crushed catalyst can be one where the catalyst components are connected to the support material followed by a reduction in particle size (for example, by grinding or by grinding in a ball mill) or one where the catalyst components are contacted with the support material after the size of the support material has been reduced. For shell catalysts, the thickness of the shell of the catalyst components in the support material ranges from about 5 μm to about 500 μm. The most preferred scales include from about 5 μm to about 300 μm.

Support Materials As already indicated, in one aspect of the invention, the catalyst components of the present invention will generally be carried through a support material. Suitable support materials typically include materials that are substantially uniform in identity or a mixture of materials. Generally, the support materials are usually inert in the reaction that is carried out. The support materials may be composed of any suitable substance preferably selected so that the support materials have a relatively high surface area per mass or unit volume, such as a porous structure, a molecular sieve structure, a honeycomb structure, or another adequate structure. For example, the support material may contain silica, alumina, silica-alumina, titania, zirconia, niobia, silicates, aluminosilicates, titanates, spinel, silicon carbide, silicon nitride, carbon, cordierite, steatite, bentonite, clays, metals , glass, quartz, pumice stone, zeolites, non-zeolitic molecular sieves, combinations thereof and the like. Any of the different crystalline forms of the materials may also be suitable, for example, alpha or gamma alumina. Support materials containing silica and zirconia are most preferred. In addition, the layered support materials are also suitable for use in the present invention. The support material in the catalyst of this invention can be composed of particles having any of the various regular or irregular shapes, such as spheres, tablets, cylinders, discs, rings, stars or other shapes. The support material may have dimensions such as diameter, length or width of from about 1 to about 10 mm; preferably about 3 to about 9 mm. In particular, having a regular (e.g., spherical) shape will have as its preferred longer dimension of about 4 mm to about 8 mm. In addition, a crushed or powdered backing material may be suitable in such a way that the backing material has a regular or irregular shape with a diameter of between about 10 microns and about 1000 microns, with preferred sizes being between about 10 and about 700 microns, the most preferred sizes still being between approximately 180 microns and approximately 450 microns. Larger or smaller sizes can be used, as well as polydispersity collections of particle sizes. For example, for a fluidized bed catalyst a preferred size scale can include from 10 to 150 microns. For the precursors used in the stratified catalysts, a size scale of 10 to 250 microns is preferred. The surface areas available for the support catalyst components, as measured by the BET method (Brunauer, Emmett, and Teller), can generally be between about 1 m2 / g and about 500 m2 / g, preferably about 100 m2 / g about 200. m2 / g. For example, for a porous support, the pore volume of the support material will generally be from about 0.1 to about 2 ml / g, and preferably from about 0.4 to about 1.2 ml / g. An average pore size on the scale, for example, from about 50 to about 2000 angstroms is desirable, but not required. Examples of suitable support materials containing silica include KA160 from Sud Chemie, Aerolyst350 from Degussa and other pyrogenic or micro-free silicas with a particle size of between about 1 mm to about 10 mm. Examples of suitable support materials containing zirconia include those from NorPro, Zirconia Sales (America), Inc., Daichi Kigenso Kagaku Kogyo, and Magnesium Elektron Inc (MEI). Suitable zirconia support materials have a wide variety of surface areas of less than about 5 m2 / g to more than 300 m2 / g. Preferred zirconia support materials have surface areas of about 10 m2 / g to about 135 m2 / g. The support materials may have their surfaces treated with a calcination stage where the virgin support material is heated. The heating reduces the surface area of the support material (for example, calcination). This provides a method to create support materials with specific surface areas that can not easily be otherwise available from suppliers. In another embodiment, it is contemplated to employ at least one plural combination of support materials, each having different characteristics. For example, at least two support materials (eg, zirconia) with different characteristics can exhibit different C02 activities and selectivities, thus allowing the preparation of catalysts with a desired set of characteristics, i.e., the activity of a catalyst that can be balanced against the C02 selectivity of the catalyst. In one embodiment, different plural supports are employed in a stratified configuration. The stratification can be achieved in any number of different methods, such as a plurality of lamellae which are generally flat, corrugated or a combination thereof. A particular method is to use wrapping layers successively in relation to an initial core layer. In general, herein, the layered support materials usually include at least one inner layer and one outer layer at least partially surrounding the inner layer. The outer layer preferably contains substantially more catalyst components than the inner layer. In one modality, the inner and outer layers are made of different materials; but the materials can be the same. Although the inner layer may not be porous, other embodiments include an inner layer that is porous. The layered support material is preferably in the form of a shell catalyst. But the stratified support material offers a well-defined boundary between the areas of the support material that have catalytic components and the areas that do not. Also, the outer layer can be constructed consistently with a desired thickness. Together the limit and the uniform thickness of the outer layer result in a shell catalyst which is a shell of catalytic components which is of a uniform and known thickness. Various techniques are known for creating layered backing materials including those described in U.S. Patent No. 6,486,370; 5,935,889; and 5,200,382, each of which is incorporated for reference. In one embodiment, the materials of the inner layer are not substantially penetrated by liquids, for example, metals including, but not limited to, aluminum, titanium and zirconium. Examples of other materials for the inner layer include, but are not limited to, alumina, silica, silica-alumina, titania, zirconia, niobia, silicates, aluminosilicates, titanates, spinel, silicon carbide, silicon nitride, carbon, cordierite, soapstone, bentonite, clays, metals, glasses, quartz, pumice, zeolites, non-zeolitic molecular sieves and their combinations. A preferred inner layer is silica and KA160, in particular. These materials that make up the inner layer can be found in a variety of forms such as regularly shaped particulate materials, irregularly shaped particulate materials, pellets, discs, rings, stars, van wheels, combs or other shaped bodies. An inner layer in spherical particles is preferred. The inner layer, whether spherical or not, has an effective diameter of about 0.02 mm to about 10.0 mm and preferably about 0.04 mm to about 8.0 mm. The outermost layer of any multi-layer structure is one that is porous, having a surface area in the range of about 5 m2 / g to about 300 m2 / g. The material of the outer layer is a metal, ceramic, or a combination thereof, and in one embodiment is selected from alumina, silica, silica-alumina, titanium, zirconia, niobia, silicates, aluminosilicates, titanates, spinel, carbide silicon, silicon nitride, carbon, cordierite, steatite, bentonite, clays, metals, glasses, quartz, pumice, zeolites, non-zeolitic molecular sieves, their combinations and preferably include alumina, silica, silica / alumina, zeolites, non-zeolitic molecular sieves (NZMS), titania, zirconia, and their mixtures. Specific examples include zirconia, silica and alumina or combinations thereof. Although the outer layer normally substantially surrounds the entire inner layer, this is not necessarily the case and a selective coating on the inner layer through the outer layer may be employed. The outer layer can be coated on the subtended layer in a suitable manner. In one embodiment, a suspension of the outer layer material is employed. The coating of the inner layer with the suspension can be carried out by methods such as rolling, dipping, spraying, coating with washing, or other coating techniques with suspension, combinations of the above or the like. A preferred technique involves the use of a fixed or fluidized bed of internal layer particles and the spraying of the suspension in the bed to cover the particles uniformly. The suspension can be applied repeatedly in small amounts, with drying intervention, to provide an outer layer that is highly uniform in thickness. The suspension used to coat the inner layer also includes any of a number of additives such as surfactants, an organic or inorganic binder agent that aids in adhesion of the outer layer to an underlay layer, or combinations thereof. Examples of this organic binder include, but are not limited to, PVA, hydroxypropylcellulose, methylcellulose and carboxymethylcellulose. The amount of organic binder that is added to the suspension can vary, such as from about 1% by weight to about 15% by weight of the combination of the outer layer and the binder. Examples of inorganic binding agents are selected from an alumina binder (eg, Bohmite), a silica binder (eg, Ludox, Teos), zirconia binder (eg, zirconia acetate or colloidal zirconia) or your combinations Examples of silica binding agents include silica sol and silica gel, although examples of alumina binding agents include alumina sol, bentonite, bohmite and aluminum nitrate. The amount of inorganic binder can vary from about 2% by weight to about 15% by weight of the combination of the outer layer and the binder. The thickness of the outer layer may vary from about 5 microns to about 500 microns and preferably between about 20 microns and about 250 microns. Once the inner layer is covered with the outer layer, the resulting laminated support will be dried, for example with heating at a temperature of about 100 ° C to about 320 ° C (for example, for a time from about 1 to about 24 hours) and subsequently optionally calcined at a temperature of about 300 ° C to about 900 ° C (for example, for a time from about 0.5 to about 10 hours) to increase the bonding of the outer layer with its layer subtended for at least a portion of its surface and provide a stratified catalyst support. The drying and calcination steps can be combined in one step. The resulting layered support material can be contacted with the catalyst components just like any other support material in the production of catalysts, as described below. Alternatively, the external layered support material is contacted with the catalyst components before coating on the subtended layer. In another embodiment of the laminated support, a second external layer is added to surround the initial outer layer to form at least three layers. The material for the second outer layer may be the same as or different from that of the first outer layer. Suitable materials include those discussed with respect to the first outer layer. The method for applying the second outer layer may be the same as or different from the method used to apply the intermediate layer and suitable methods include those discussed with respect to the first outer layer. Organic or inorganic binding agents such as those described can be suitably used in the formation of the second outer layer. The initial outer layer may or may not contain catalytic components. Similarly, the second outer layer may or may not contain catalytic components. If both outer layers contain a catalytic component, different catalytic components are preferably used in each layer, although this does not necessarily have to be the case. In a preferred embodiment, the initial outer layer does not contain a catalytic component. The contact of the catalytic component with the outer layers can be carried out with impregnation or spray coating, as discussed below. In embodiments where the initial outer layer contains the catalytic component, one method to achieve this is to contact the catalytic component with the material of the initial outer layer before applying the material to the inner layer. The second outer layer can be applied to the pure initial outer layer or containing the catalytic component. Other suitable techniques can be used to achieve a three layer backing material wherein one or more of the outer layers contain catalyst components. Really, the layered support material is not limited to three layers, but may include four, five or more layers, some or all of which may contain catalytic components. In addition, the number and type of catalyst components that vary between the layers of the layered support material, other characteristics (e.g., porosity, particle size, surface area, pore volume, or the like) of the support material, may vary between the layers.

Methods for the preparation of catalysts In general, the method includes the contact of the catalytic components of the support material and the reduction of the catalytic components. Preferred methods of the present invention include impregnation of the catalyst components in the support material, calcination of the support material containing a catalyst component, reduction of the catalyst components and modification of the reduced catalyst components on the support material. Additional steps, such as fixing the catalytic components on the support material and washing the fixed catalytic components, can be included in the method for the preparation of catalysts or pre-catalysts. Some of the stages listed above are optional and others can be eliminated (for example, the washing and / or fixing stages). In addition, some steps may be repeated (e.g., impregnation or multiple fixation stages) and the order of the steps may be different from that enumerated above (e.g., the reduction stage precedes the calcination step). Up to a certain degree, the contact stage will determine what later stages are needed for catalyst formation.

Contact step A particular approach to making the contact is one in which an egg yolk catalyst or precatalyst is formed, an egg white catalyst or precatalyst is formed, a catalyst or a pre-catalyst from the egg is formed. overall coverage, or a shell catalyst or pre-catalyst, or one of its combinations, is formed. In one embodiment, the techniques that form the shell catalysts are preferred.

The contacting step can be carried out using any of the support materials described above, with silica, zirconia, and stratified support materials containing zirconium which are the most favored. Preferably the contact stage is carried out at ambient temperature and pressure conditions; however, reduced or high temperatures or pressures may be employed. In a preferred contacting step, a support material is impregnated with one or more aqueous solutions of the catalyst components (referred to as precursor solutions). The physical state of the support material during the contacting step can be a dry solid, a suspension, a sol-gel, a colloidal suspension and the like. In one embodiment, the catalyst components contained in the precursor solution are water soluble salts made from the catalyst components, including without limitation, chlorides, other halides, nitrates, nitrites, hydroxides, oxides, oxalates, acetates (OAc) and amines with salts halide-free being preferred and chloride-free salts being more preferred. Examples of palladium salts suitable for use in precursor solutions include PdCI2, Na2PdCl4, Pd (NH3) 2 (N02) 2, Pd (NH3) 4 (OH) 2, Pd (NH3) 4 (N03) 2, Pd (N03) ) 2, Pd (NH3) 4 (OAc) 2, Pd (NH3) 2 (OAc) 2, Pd (OAc) 2 in KOH and / or NMe4OH and / or NaOH, Pd (NH3) 4 (HC03) 2 and oxalate of palladium. Of the palladium precursors containing chloride, Na 2 PdCl 4 is most preferred. Of the chloride-free palladium precursor salts, the following four are most preferred: Pd (NH3) 4 (N03) 2, Pd (N03) 2, Pd (NH3) 2 (N02) 2, Pd (NH3) 4 ( OH) 2. Examples of gold salts suitable for use in the precursor solution include AuCI3, HAuCI4, NaAuCI4, KAu02, NaAu02, NMe4Au02, Au (OAc) 3 in KOH and / or NMe4OH as well as HAu (N03) 4 in nitric acid, the most preferred KAu02 of chloride-free gold precursors. Examples of rhodium salts suitable for use in precursor solutions include RhCl3, Rh (OAc) 3, and Rh (N03) 2. Similar salts of the third catalytic components described above can be selected. In addition, more than one salt can be used in a given precursor solution. For example, a palladium salt can be combined with a gold salt or two different palladium salts can be combined together in a single precursor solution. Precursor solutions can usually be obtained by dissolving the selected salt or salts in water, with or without solubility modifiers such as acids, bases or other solvents. Other non-aqueous solvents may also be suitable. The precursor solutions can be impregnated onto the support material simultaneously (e.g., co-impregnated) or sequentially and can be impregnated by the use of one or multiple precursor solutions. With three or more catalytic components, a combination of simultaneous and sequential impregnation can be used. For example, palladium and rhodium can be impregnated by the use of a simple precursor solution (referred to as a co-impregnation), followed by impregnation with a gold precursor solution. In addition, a catalytic component can be impregnated on the support material in multiple steps, such that a portion of the catalyst component is in contact at each moment. For example, a suitable protocol may include impregnation with Pd, followed by impregnation with Au, followed by impregnation with Au again. The order of impregnation of the support material with the precursor solutions is not critical; although there are some advantages in certain orders, as will be discussed later, with respect to the calcination stage. Preferably, the palladium catalyst component is impregnated on the support material first, being impregnated with gold after palladium, or the latter. Rhodium or another third catalytic component, when used, can be impregnated with palladium, with gold or with itself. Also, the support material can be impregnated multiple times with the same catalyst component. For example, a portion of the global gold contained in the catalyst may first be contacted, followed by the contact of a second portion of the gold. A more different stage may intervene between the steps where the gold is brought into contact with the support material, for example, calcination, reduction, and / or fixation. The acid-base profile of the percussive solutions can have an influence whether a co-impregnation or a sequential impregnation is used. Thus, only precursor solutions with similar acid-base profiles can be used together with a co-impregnation step; this eliminates that any of the acid-base reactions alter the precursor solutions. For the impregnation step, the volume of the precursor solution is selected such that it corresponds to between about 85% and about 110% of the pore volume of the support material. Volumes between about 95% and about 100% of the pore volume of the support material are preferred, and more preferably between about 98% and about 99% of the pore volume. Typically, the precursor solution is added to the support material and the support material is allowed to absorb the precursor solution.

This can be done in a drip mode until the incipient moisture of the support material is substantially achieved. Alternatively, the support material can be placed by aliquots or in the form of batches in the precursor solution. A roto-immersor or other auxiliary apparatus can be used to achieve complete contact between the support material and the precursor solution. In addition, a spray device can be used in such a way that the precursor solution is sprayed through a nozzle onto the support material, where it is absorbed. Optionally, settling, heat or reduced pressure can be used to remove any excess liquid not absorbed by the support material or to dry the support material after impregnation. For the impregnation step, the volume of the precursor solution is selected to correspond to between about 85% and about 110% of the pore volume of the support material. Volumes between about 95% and about 100% of the pore volume of the support material are preferred, and more preferably between about 98% and about 99% of the pore volume. Normally, the precursor solution is added to the support material and the support material is allowed to absorb the precursor solution. This can be done in a drip mode until the incipient moisture of the support material is substantially achieved. Alternatively, the support material can be placed with aliquots or in the form of batches in the precursor solution. A roto-immersor or other auxiliary apparatus can be used to achieve complete contact between the support material and the precursor solution. In addition, a spray device can be used in such a way that the precursor solution is sprayed through a nozzle onto the support material, where it is absorbed. Optionally, settling, heat or reduced pressure can be used to remove any excess liquid not absorbed by the support material or to dry the support material after impregnation. Other contacting techniques can be used to avoid a fixing cap while achieving a shell catalyst. For example, the catalyst components can be contacted with a support material through a chemical vapor deposition process, such as described in US2001 / 0048970, which is incorporated for reference. Also, the spray coating or stratification of a different way of a uniformly pre-impregnated support material, such as an outer layer, on an inner layer effectively forms the shell catalyst which can be described as a layered support material. In another technique, organometallic precursors of catalyst components, particularly with respect to gold, can be used to form shell catalysts, as described in U.S. Patent No. 5,700,753, which is incorporated by reference. A physical shell formation technique may also be suitable for the production of shell catalysts. Therefore, the precursor solution can be sprayed onto a hot support material or a layered support material, wherein the solvent in the precursor solution evaporates during contact with the heated support material, thereby depositing the catalyst components in a shell on the support material. Preferably, the temperature between about 40 and 140 ° C can be used. The thickness of the shell can be controlled by selecting the temperature of the support material and the flow rate of the solution through the spray nozzle. For example, at temperatures above about 100 ° C, a relatively thin shell is formed. This embodiment may be particularly useful when using chloride-free precursors to help improve the formation of the shell in the support material.

One skilled in the art will understand that a combination of the contacting steps may be an appropriate method for forming a contacted support material.Fixing step It is advisable to transform at least a portion of the catalytic components on the contact material contacted from a water-soluble form to a water-insoluble form. Such a stage can be referred to as a fixing step. This can be done by applying a fixing agent (eg, dispersion in a liquid, such as a solution) to the impregnated support material which causes at least a portion of the catalyst components to precipitate. The fixing step helps to form a shell catalyst, but is not required to form shell catalysts. Any of the suitable fixing agents can be used, with hydroxides (for example, alkali metal hydroxides), silicates, borates, carbonates and bicarbonates being preferred in aqueous solutions. The preferred binding agent is NaOH. The fixation can be carried out by adding the fixing agent to the support material before, during or after the precursor solutions are impregnated onto the support material. Normally, the fixing agent is used after the contacting step in such a way that the contacted support material is allowed to impregnate with the fixing solution for about 1 to about 24 hours. The specific time depends on the combination of the precursor solution and the fixing agent. As in the impregnation step, an auxiliary device, such as a roto-dip apparatus as described in U.S. Patent No. 5,332,710, which is incorporated herein by reference, can be conveniently used in the step of fixation. The fixing step can be carried out in one or multiple steps, referred to as co-fixation or a separate fixation. In a co-fixation, one or more volumes of a fixing agent solution is applied to the contacted support material after all the important precursor solutions have made contact with the support material, whether the contact is made through of the use of one or multiple precursor solutions.

For example, the fixation after sequential impregnation with a palladium precursor solution, a gold precursor solution and a rhodium precursor solution can be a co-fixation, such as a fixation after a co-impregnation with a precursor solution. of palladium / rhodium followed by impregnation with a gold precursor solution.

An example of a co-fixation can be found in the United States patent United No. 5,314,888, which is incorporated for reference. A separate fixation, on the other hand, may include applying a solution of fixing agent during or after each impregnation with a precursor solution. For example, the following protocols may be a separate fixation: a) palladium impregnation followed by fixation followed by impregnation with gold followed by fixation; or b) co-impregnation with palladium and rhodium followed by fixation followed by impregnation with gold followed by fixation. Between a fixation and subsequent impregnation, any excess liquid can be removed and the support material dried, although this is not necessarily the case. An example of a separate fixation can be found in U.S. Patent No. 6,034,030, which is incorporated by reference. In another embodiment, the fixing step and the contacting step are performed simultaneously, an example of which is described in U.S. Patent No. 4,048,096, which is incorporated for reference. For example, a simultaneous fixation may be: impregnation with palladium followed by fixation followed by impregnation with gold and fixing agent. In a variation of this embodiment, the fixation can be conducted twice for a catalytic component. A catalytic component can be partially fixed when in contact with the support material (called a "pre-fixation"), followed by an additional, final fixation. For example: impregnation with palladium followed by impregnation with gold and a pre-fixing agent followed by fixation with a final fixing agent. This technique can be used to help ensure the formation of the shell catalyst contrary to a global coverage catalyst. In another modality, particularly suitable for use with chloride-free precursors, the support material is pre-treated with a fixing agent to adjust the properties of the support material. In this mode, first the support material is impregnated with an acid solution or with a basic solution, normally free of metals. After drying, the support material is impregnated with a precursor solution having opposite acidity / alkalinity as the dry support material. The resulting acid-base reaction forms a shell of catalytic components on the support material. For example, nitric acid can be used to pre-treat a support material which in turn is impregnated with a basic precursor solution such as Pd (OH) 2 or Au (OH) 3. This forming technique can be considered using a fastening cap followed by a contacting stage. The concentration of the fixing agent in the solution is usually a molar excess of the amount of catalyst components impregnated on the support material. The amount of binding agent may be between about 1.0 to about 2.0, preferably about 1.1 to about 1.8 times the amount necessary to react with the catalytically active cations present in the water soluble salt. In an embodiment using an atomic ratio or high weight ratio of Au / Pd, an increased molar excess of hydroxide ion increases the selectivity and CO 2 activity of the resulting catalyst. The volume of the fixing agent solution supplied generally can be a sufficient amount to cover the available free surfaces of the impregnated support material. This can be done by introducing, for example, a volume that is greater than the pore volume of the contact material contacted.

The combination of the impregnation and fixing steps can form a shell catalyst. However, the use of halide-free precursor solutions also allows the formation of a shell catalyst while optionally removing the fixing step. In the absence of a chloride precursor, a washing step, as discussed below, can be obviated. In addition, the process may be free of a step of fixing catalytic components that may be otherwise needed to survive the washing step. Because no washing step is needed, the catalyst components do not need to be fixed to survive the washing step. The subsequent steps in the method of making the catalyst do not require that the catalyst components are fixed and therefore the rest of the step can be carried out without further preparatory steps. In general, the use of chloride-free precursors allows a catalyst or pre-catalyst production method to be free of a washing step, thereby reducing the number of steps needed to produce the catalyst and eliminating the need for treat waste that contains chloride.

Washing step Particularly, when using halide-containing precursor solutions, and in other applications as desired, after the fixing step, the fixed support material can be washed to remove any halide residue on the support or it can be treated otherwise to eliminate the potential negative effect of a contaminant on the support material. The washing step includes rinsing the fixed support material in water, preferably deionized water. The washing can be carried out in a batch or continuous mode. Washing at room temperature should continue until the effluent wash water has a halide ion content of less than 1000 ppm, and more preferably until the final effluent gives a negative result to a silver nitrate test. The washing step can be carried out after or simultaneously with the reduction step, as will be discussed later, but preferably it is carried out before. As already discussed, the use of halide-free precursor solutions allows the elimination of the washing step.

Calcination step After the catalytic component has been contacted, at least with the support material, a calcination step can be employed. Normally the calcination step is before the reduction step and after the fixation step (if said step is used) but it can take place in another part of the procedure. In another embodiment, the calcination step is carried out after the reduction step. The calcination step includes heating the support material in a non-reducing atmosphere (i.e., oxidation or inert atmosphere). During calcination, the catalytic components on the support material are at least partially decomposed from their salts to a mixture of their oxide form and free metal form. For example, the calcination step is carried out at a temperature in the range from about 100 ° C to about 700 ° C, preferably between about 200 ° C and about 500 ° C. Non-reduction gases used for the calcination may include one or more inert or oxidation gases such as helium, nitrogen, argon, neon, nitrogen oxides, oxygen, air, carbon dioxide, their combinations or the like.

In one embodiment, the calcining step is carried out in an atmosphere of substantially pure nitrogen, oxygen, air or combinations thereof. The calcination times may vary but are preferably between about 1 and 5 hours. The degree of decomposition of the salts of the catalyst component depends on the temperature used and the length of time in which the impregnated catalyst is calcined and can be followed by monitoring the volatile decomposition products. One or more calcining stages can be used, so that at any point after at least one catalytic component is contacted with the support material, it can be calcined. Preferably, the last calcining step occurs prior to contacting the gold catalyst component with a zirconia support material. Alternatively, the calcination of a gold containing zirconia support material is carried out at temperatures below about 300 ° C. By preventing calcination of the zirconia support material containing gold at temperatures above 300 ° C, the risk that the C02 selectivity of the resulting catalyst is adversely affected is reduced. Exemplary protocols including a calcination step include: a) impregnating with palladium followed by calcination followed by impregnation with gold; b) co-impregnating palladium and rhodium followed by calcination followed by impregnation with Au; c) impregnation with palladium followed by calcination followed by impregnation with rhodium followed by calcination followed by impregnation with gold; or d) impregnate with palladium and rhodium, followed by impregnation with gold, followed by calcination.

Reduction stage Another step generally employed herein to at least partially transform any remaining catalyst component of a salt or oxide form into a catalytically active state, such as by a reduction step. Typically this is done by exposing salts or oxides to a reducing agent, examples of which include ammonia, carbon monoxide, hydrogen, hydrocarbons, olefins, aldehydes, alcohols, hydrazine, primary amines, carboxylic acids, carboxylic acid salts, esters of carboxylic acid and combinations thereof. Hydrogen, ethylene, propylene, alkaline hydrazine and alkaline formaldehyde and combinations thereof are preferred reducing agents with ethylene and hydrogen mixed with particularly preferred inert gases. Although the reduction employing a gaseous environment is preferred, a reduction step carried out with a liquid environment can also be used (for example, by using a reducing solution). The temperature selected for the reduction can range from room to approximately 550 ° C. Reduction times will typically vary from about 1 to about 5 hours. Since the procedure used to reduce the catalytic components may influence the characteristics of the final catalyst, the conditions used for the reduction may vary depending on whether you want high activity, high selectivity or some balance of these properties. In one embodiment, the palladium is contacted with the support material, fixed and reduced before the gold is contacted and reduced, as described in the U.S. patent. Nos. 6,486,093, 6,015,769 and related applications, which are incorporated by reference. Exemplary protocols that include a reduction step include: a) impregnating with palladium followed by optional calcination followed by impregnation with gold followed by reduction; b) co-impregnating with palladium and gold followed by optional calcination followed by reduction; or c) impregnating with palladium followed by optional calcination followed by reduction followed by impregnation with gold.

Modification stage Generally after the reduction stage and before the catalyst is used, a modification step is desirable. Although the catalyst can be used with the modification pass, the stage has several beneficial results, including prolongation of the operating lifetime of the catalyst. The modification stage is sometimes called an activation stage and can be accomplished in accordance with conventional practice. Primarily, the reduced support material is contacted with a modifying agent, such as an alkali metal carboxylate and / or alkali metal hydroxide, before being used. Conventional alkali metal carboxylates such as sodium, potassium, lithium and cesium salts of C2.4 aliphatic carboxylic acids are used for this purpose. A preferred activating agent in the production of VA is an alkaline acetate, potassium acetate (KOAc) being most preferred. The support material may optionally be impregnated with a solution of the modifying agent. After drying, the catalyst may contain, for example, about 10 to about 70, preferably about 20 to about 60 grams of modifying agent per liter of catalyst.

Methods for making alkenyl alkanoates The present invention can be used to produce alkenyl alkanoates from an alkene, alkanoic acid and an oxygen-containing gas in the presence of a catalyst. Preferred alkene starting materials contain from two to four carbon atoms (eg, ethylene, propylene and n-butene). The preferred alkanoic acid starting materials used in the process of this invention to produce alkenyl alkanoates contain from two to four carbon atoms (e.g., acetic, propionic and butyric acid). Preferred products of the process are VA, vinyl propionate, vinyl butyrate, and allyl acetate. The most preferred starting materials are ethylene and acetic acid with the VA being the most preferred product. Thus, the present invention is useful in the production of olefinically unsaturated carboxylic esters from an olefinically unsaturated compound, a carboxylic acid and oxygen in the presence of a catalyst. Although the remainder of the specification discusses VA exclusively, it should be understood that the catalysts, method for making the catalysts and production methods apply equally to other alkenyl alkanoates, and the disclosure is not intended to limit the application of the invention to VA. When VA is produced using the catalyst of the present invention, a stream of gas, which contains ethylene, oxygen or air, and acetic acid is passed over the catalyst. The composition of the gas stream can vary within wide limits, taking into account the flammability zone of the effluent. For example, the molar ratio of ethylene to oxygen may be from about 80:20 to about 98: 2, the molar ratio of acetic acid to ethylene may be from about 100: 1 to about 1: 100, preferably about 10: 1 to 1:10, and more preferably from about 1: 1 to about 1: 8. The gas stream may also contain gaseous alkali metal acetate and / or inert gases, such as nitrogen, carbon dioxide and / or saturated hydrocarbons. The reaction temperatures that can be used are elevated temperatures, preferably those in the range of about 125-220 ° C. The pressure used can be a somewhat reduced pressure, a normal pressure or high pressure, preferably a pressure of up to about 20 atmospheres gauge. In addition to fixed bed reactors, the methods for producing alkenyl alkanoates and catalysts of the present invention are also suitably employed in other types of reaction, for example, fluidized bed reactors.

EXAMPLES The following examples are provided for illustration only and are not intended to be limiting. The amounts of solvents and reagents are approximate. The atomic ratio Au / Pd can be converted to a weight ratio Au / Pd and vice versa by the following equations: atomic ratio Au / Pd = 0.54 * (Au / Pd weight ratio) and weight ratio Au / Pd = 1.85 (ratio atomic Au / Pd). The reduction can be abbreviated 'R' followed by the temperature in ° C at which the reduction can be carried out. Similarly, the calcination can be abbreviated 'C followed by the temperature in ° C at which the calcination can be carried out, while the drying step can be abbreviated as' dry'. The catalyst of examples 1-11 can be prepared as described in the example and analyzed according to the following procedure, wherein the catalyst of examples 1-7 can be compared with each other and the catalyst of 8-11 can be compared with each other . The results are provided where useful. The catalysts of the examples were analyzed for their activity and selectivity in various by-products in the production of vinyl acetate by reaction of ethylene, oxygen and acetic acid. To achieve this, approximately 60 ml of the catalyst prepared as described was placed in a stainless steel basket with the temperature capable of being measured by a thermocouple on both the top and the bottom of the basket. The basket was placed in a Berty continuously stirred tank reactor of recirculation type and maintained at a temperature that provided approximately 45% oxygen conversion with an electric heating mantle. A gas mixture of about 50 normal liters (measured in NTP) of ethylene, about 10 normal liters of oxygen, about 49 normal liters of nitrogen, about 50 grams of acetic acid, and about 4 mg of potassium acetate, caused it will move under pressure at about 12 atmospheres through the basket, and the catalyst aged under these reaction conditions for at least 16 hours before a two-hour run, after which the reaction was terminated. Product analysis was achieved by on-line gas chromatographic analysis combining with an off-line liquid product analysis by condensing the product stream to around 10 ° C to obtain the optimal carbon dioxide analysis (C02). ) of end products, heavy ends (HE) and ethyl acetate (EtOAc), the results of which can be used to calculate the percentage selectivities (CO2 selectivity) of these materials for each example. The relative activity of the reaction expressed as an activity factor (activity) can be computed by computer using a series of equations that correlate the activity factor with the catalyst temperature (during the reaction), oxygen conversion, and a series of parameters kinetics for the reactions to be carried out during VA synthesis. More generally, the activity factor is typically inversely related to the temperature required to achieve constant oxygen conversion.

EXAMPLES OF RHODIUM CATALYST EXAMPLE 1 A support material containing palladium metal and rhodium was prepared as follows: the support material in an amount of 250 ml consisting of Sud Chemie KA-160 silica spheres having a nominal diameter of 7 mm, a density of about 0.569 g / ml, in absorbance of about 0.568 g H20 / g of support, a surface area of about 160 to 175 m2 / g and a pore volume of about 0.68 ml / g, was first impregnated by moisture with 82.5 ml of an aqueous solution of tetrachloropalladium (II) sodium (Na2PdCl4) and rhodium chloride trihydrate (RhCl3 * 3H20) sufficient to provide about 7 grams of palladium elemental and around 0.29 grams of elemental rhodium per liter of catalyst. The support was stirred in a solution for 5 minutes to ensure complete absorption of the solution. Palladium and rhodium were then fixed to the support as palladium (H) and rhodium (III) hydroxides by contacting the treated support by roto-immersion for 2.5 hours at about 5 rpm with 283 ml of an aqueous sodium hydroxide solution prepared from 50% w / w NaOH / H20 in an amount of 120% of what is needed to convert palladium and rhodium to its hydroxides. The solution was drained from the treated support and the support was then rinsed with deionized water and dried at 100 ° C in a fluid bed dryer for 1.2 hours. The support material containing palladium and rhodium hydroxides was then impregnated with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl and 2.71 g of 50% NaOH solution (1.8 equivalents with respect to Au ) using the incipient moisture method. The NaOH-treated pills were allowed to stand overnight to ensure precipitation of the Au salt to the insoluble hydroxide. The pills were washed with deionized water (~ 5 hours) to remove chloride ions and subsequently dried at 100 ° C in a fluid bed dryer for 1.2 hours. Support containing palladium, rhodium and gold were then calcined at 400 ° C for two hours under air and then allowed to cool naturally to room temperature. Palladium, rhodium and gold were reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally, the catalyst was impregnated by incipient moisture with an aqueous solution of 10 g of potassium acetate in 81 ml of H20 and dried in a fluidized bed drier at 100 ° C for 1.2 hours.

EXAMPLE 2 A support material using palladium and rhodium hydroxides was prepared as described in example 1. The support containing palladium and rhodium was then calcined at 400 ° C for 2 hours under air and then allowed to cool naturally to room temperature. The calcined support material containing palladium and rhodium hydroxides was then impregnated with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl 4 and 2.71 g of 50% NaOH solution (1.8 equivalents with respect to Au ) using the incipient moisture method. The NaOH-treated pills were allowed to stand overnight to ensure precipitation of the Au salt to the insoluble hydroxide. The pills were washed with deionized water (~ 5 hours) to remove the chloride ions and subsequently dried at 100 ° C in a fluid bed dryer for 1.2 hours. The palladium, rhodium and gold were then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally the catalyst was impregnated by incipient humidity with an aqueous solution of 10 g of potassium acetate in 81 ml of H20 and dried in a fluidized bed drier at 100 ° C for 1.2 hours.

EXAMPLE 3 A support material containing palladium and rhodium hydroxides was prepared as described in Example 1. The support containing palladium and rhodium was then calcined at 400 ° C for 2 hours under air and then allowed to cool naturally to room temperature. The calcined support material containing palladium and rhodium hydroxides was then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. The support containing palladium metal and rhodium was subsequently impregnated with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl 4 and 2.71 g of 50% NaOH solution (1.8 equivalents with respect to Au) using the incipient humidity method. The NaOH-treated pills were allowed to stand overnight to ensure precipitation of the Au salt to the insoluble hydroxide. The pills were washed with deionized water (~ 5 hours) to remove the chloride ions and subsequently dried at 100 ° C in a fluid bed dryer for 1.2 hours. The palladium, rhodium and gold were then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally, the catalyst was impregnated by incipient moisture with an aqueous solution of 10 g of potassium acetate in 81 ml of H20 and dried in a fluidized bed drier at 100 ° C for 1.2 hours.

EXAMPLE 4 A support material containing palladium and rhodium hydroxides was prepared as described in Example 1. The support containing palladium and rhodium was then calcined at 400 ° C for 2 hours under air and then allowed to cool naturally to room temperature. The calcined support material containing palladium and rhodium hydroxides was then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. The support containing palladium metal and rhodium was subsequently impregnated with an aqueous solution (81 ml) containing 1.1 g Au from KAu02 using the incipient damp method. The pills were subsequently dried at 100 ° C in a fluid bed dryer for 1.2 hours. The palladium, rhodium and gold were then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally, the catalyst was impregnated by incipient humidity with an aqueous solution of 10 g of potassium acetate in 81 ml of H 2 O and dried in a fluidized bed drier at 100 ° C for 1.2 hours.

EXAMPLE 5 A support material containing palladium and rhodium hydroxides was prepared as described in Example 1. The support containing palladium and rhodium was then calcined at 400 ° C for 2 hours under air and then allowed to cool naturally to room temperature. The calcined support containing palladium and rhodium hydroxides was subsequently impregnated with an aqueous solution (81 ml) containing 1.1 g of Au from KAu02 using the incipient damp method. The pills were then dried at 100 ° C in a fluid bed dryer for 1.2 hours. Palladium, rhodium and gold were then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally, the catalyst was impregnated by incipient moisture with an aqueous solution of 10 g of potassium acetate in 81 ml of H20 and dried in a fluidized bed drier at 100 ° C for 1.2 hours.

EXAMPLE 6 A support material containing palladium and rhodium hydroxides was prepared as described in Example 1. The support containing palladium and rhodium was then calcined at 400 ° C for 2 hours under air and then allowed to cool naturally to room temperature. The calcined support material containing palladium and rhodium hydroxides was then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. The support containing palladium metal and rhodium was subsequently impregnated with an aqueous solution (81 ml) containing 1.1 g of Au from KAu02 and 10 g of potassium acetate using the incipient damp method. The pills were subsequently dried at 100 ° C in a fluid bed dryer for 1.2 hours.

EXAMPLE 7 (REFERENCE CATALYST) A support material containing palladium metal was prepared as follows: The support material in an amount of 250 ml consisting of Sud Chemie KA-160 silica spheres with a nominal diameter of 7 mm, a density of about 0.569 g / ml, in absorbency of about 0.568g of H20 / g of support, a surface area of about 160 to 175 m2 / g, and a pore volume of about 0.68 ml / g, was first impregnated by incipient moisture with 82.5 ml of an aqueous solution of sodium tetrachloropalladium (II) (Na2PDCI) sufficient to provide about 7 grams of elemental palladium per liter of catalyst. The support was stirred in the solution for 5 minutes to ensure complete absorption of the solution. The palladium was then fixed to the support as palladium (II) hydroxides by contacting the treated support by roto-immersion for 2.5 hours at about 5 rpm with 283 m of an aqueous sodium hydroxide solution prepared from NaCH / H20. at 50% w / w in an amount of 110% of what is needed to convert palladium to its hydroxide. The solution was drained from the treated support and the support was then rinsed with deionized water and dried at 100 ° C in a fluid bed dryer for 1.2 hours. The support material containing the palladium hydroxide was then impregnated with an aqueous solution (81 m!) Containing 1.24 g of Au from NaAuCI4 and 2.71 g of NaOH solution a! 50% (1.8 equivalents with respect to Au) using the incipient humidity method. The NaOH-treated pills were allowed to stand overnight to ensure precipitation of the Au salt to the insoluble hydroxide. The pills were washed with deionized water (~ 5 hours) to remove the chloride ions and subsequently dried at 100 ° C in a fluid bed dryer for 1.2 hours. The support containing palladium and gold was then reduced by contacting the support with C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally the catalyst was impregnated by incipient humidity with an aqueous solution of 10 g of potassium acetate in 81 ml of H20 and dried in a fluidized bed drier at 100 ° C for 1.2 hours. Table 1 shows the comparison of C02 selectivity and activity for the catalyst of examples 1 and 7.

TABLE 1 Selectivity of C02 Activity Example 1 9.89 2.32 Example 7 (reference catalyst) 11.13 2.36 EXAMPLES OF STRATIFIED SUPPORT EXAMPLE 8 40 g of Zr02 (RC-100, supplied by DKK) was calcined at 650 ° C for 3 hours. The resulting material has a BET surface area of 38 m2 / g. The material was ground by ball with 120 ml of DI water for 6 hours. The sol was mixed with 22.5 g of zirconium binder acetate supplied by DKK (ZA-20) and sprayed on 55 g of Bentonite Wares KA-160 with OD-7.5 mm. The coated spheres were calcined for 3 hours at 600 ° C. Examination under a microscope showed uniform shell formation with a thickness of 250 μm.

EXAMPLE 9 g of Zr02 (XZ16075, surface area of BET 55 m2 / g) were impregnated with Pd (N03) 2 solution (Aldrich) to give a Pd load of 39 mg / g of Zr02. The impregnated material was dried and calcined at 450 ° C for 4 hours. The material was triturated by ball with 60 ml of DI water for 4 hours, mixed with 11 g of a binder (ZA-20) and sprayed on 30 g of KA-160 bentonite spheres. The spheres were calcined at 450 ° C for 3 hours. This procedure results in the formation of a strong uniform shell with a thickness of 160 μm.

EXAMPLE 10 The spheres of Example 8 were impregnated with potassium acetate solution to give a loading of 40 mg KOAc / ml KA-160, dried and calcined at 300 ° C for 4 hours. After that the solution, which contains 9.4 mM Pd (from Pd (NH3) 4 (OH) 2 supplied by Heraeus) and 4.7 mM Au (from a 1 M solution, Au (OH) 3"Alpha" dissolved in KOH 1.6 M) was sprayed in these areas. The material was reduced with the mixture: 5% H2, 95% N2 at 200 ° C for 4 hours. The spheres were crushed and tested in a fixed bed micro reactor under conditions described in the section experimental. The C02 selectivity of ~ 6% was achieved at one conversion 45% oxygen.

EXAMPLE 11: (REFERENCE CATALYST) The same catalyst prepared in Example 7 was used as a reference catalyst herein. Table 2 shows the comparison of CO2 selectivity and activity for the catalyst of examples 9-11.

TABLE 2 Selective CO2 activity Example 9 9.33 2.08 Example 10 9.03 1.69 Example 11 (reference catalyst) 11.13 2.36 Examples of the zirconia support material and the chloride free precursor The following general procedure was used for this set of examples. The zirconia support material catalysts were made in the following manner: several formed catalytic carriers were ground and sieved. The zirconia support materials were supplied by NorPro (XZ16052 and XZ16075), DKK and MEI. The silica support materials were supplied by Degussa and Sud Chemie. The sieve fraction of 180-425 μm was impregnated (either simultaneously or sequentially with an intermediate drying stage at 110 ° C and optionally with an intermediate calcination stage) to incipient humidity with a precursor solution of Pd and Au, optionally calcined in air, reduced with formation gas 5% H2 / N2 post-impregnated with KOAc solution, dried at 100 ° C under N2, and sieved in a fixed-channel reactor with multiple channels 8x6. A solution of Au (OH) 3 in KOH was used as the Au precursor. Aqueous solutions of Pd (NH3) 4 (OH) 2, Pd (NH3) 2 (N02) 2, Pd (NH3) 4 (N03) 2 and Pd (B03) 2 were used as Pd precursors. A reference was made to the catalyst of silica support material in the following manner: a support material containing palladium metal and rhodium was prepared as follows: the support material in an amount of 250 ml consisting of spheres of Sud Chemie KA-160 silica with a nominal diameter of 7 mm, a density of around 0.569 g / ml, an absorption of around 0.568 g H2? / g of support, a surface area of around 160 to 175 m2 / g a pore volume of about 0.68 ml / g., was first impregnated with incipient humidity with 82.5 ml of an aqueous solution of tetrachloropalladium (II) sodium (Na2PdCl) sufficient to provide about 7 grams of elemental palladium per liter of catalyst. The support was stirred in the solution for 5 minutes to ensure complete absorption of the solution. The palladium was then fixed to the support as palladium (II) hydroxides by contacting the treated support by roto-immersion for 2.5 hours at about 5 rpm with 283 ml of aqueous sodium hydroxide solution prepared from NaOH / H20 at 50% p / p in an amount of 110% of that needed to convert palladium to its hydroxide. The solution was drained from the treated support and the support was then rinsed with deionized water and dried at 100 ° C in a fluid bed dryer for 1.2 hrs. The support material containing palladium hydroxide was then impregnated with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl 4 and 2.71 g of 50% NaOH solution (1.8 equivalents with respect to Au) using the incipient moisture method. The NaOH-treated pills were allowed to stand overnight to ensure precipitation of the Au salt to the insoluble hydroxide. The pills were washed with deionized water (~ 5 hours) to remove the chloride ions and subsequently dried at 100 ° C in a fluidized bed drier for 1.2 hours. The support containing palladium and gold was then reduced by contacting the support C2H4 (1% in nitrogen) in the vapor phase at 150 ° C for 5 hours. Finally the catalyst was impregnated by incipient humidity with an aqueous solution of 10 g of potassium acetate in 81 ml of H20 and dried in a fluidized bed drier at 100 ° C for 1.2 hours. Before analyzing, the catalyst was crushed and sieved. The sieved fraction in the size scale of 180-425 um was used. The arrays of arrays of 8 row by 6 column catalysts in glass jars were designated and a grid of 36 glass jars was mounted on a vortex stirrer and stirred while supplying metal precursor solutions using Cavro ™ liquid dispensing robots. 0.4 ml of support were used for each library element, for the synthesis of the glass bottle as well as for loading into a reactor vessel. The KOAc load is reported as grams of KOAc per liter of catalyst volume in liters or as μmol KOAc in a 0.4 ml support. For the specification of the Au load, the relative atomic ratio of Au to Pd is reported as Au / Pd. The Pd loading is specified as mg of Pd per support volume of 0.4 ml (ie, absolute amount of Pd in a reactor vessel). The analysis protocol used a temperature ramp of 145 ° C to 165 ° C in increments of 5 ° C, as a fixed space velocity of 175% (with 1.5 mg of Pd in a 0.4 ml support). A space velocity at 100% is defined as the following flows: 5.75 sccm of Nitrogen, 0.94 sccm of Oxygen, 5.94 sccm of Ethylene, and 5.38 microliters per minute of acetic acid through each of the 48 catalyst vessels (all which had an inner diameter of approximately 4 mm). The C02 selectivity was plotted against the oxygen conversion, a linear adjustment performed, and the C02 selectivity calculated (interpolated in most cases) to a 45% oxygen conversion is reported in the performance summary tables below. The temperature in the conversion of oxygen to 45% calculated from the T ramp (linear adjustments of C02 selectivity and conversion of oxygen to reaction temperature are also reported).

The lower the calculated temperature, the higher the catalyst activity. The yield in time in grams / cubic centimeter (STY; g of VA produced by my catalyst volume per h) at a conversion of 45% oxygen is a measure of catalyst productivity.

EXAMPLE 12 400 ul of Zr02 carriers XZ16075 (55 m2 / g as supplied) and XZ16052 (precalcined at 650 ° C / 2h to lower the surface area to 42 m2 / g) were impregnated with 3 different Pd solutions at incipient humidity, dried at 110 ° C for 5 hours, impregnated with KAu02 (Au supply solution 0.97M) to incipient humidity, dried at 110 ° C for 5 hours, reduced to 350 ° C for 4 hours in gas formation 5% H2 / N2, were post-impregnated with KOAc and dried at 110 ° C for 5 hours. Samples of Pd / Au / Zr02 (shells) were then diluted 1 / 9.3 with a KA160 diluter (preloaded with 40 g / 1 KOAc), ie 43 ul of Pd / Au / Zr02 shell and 357ul of a diluter (volume 400 ul total fixed bed) were loaded into the reactor vessels. The loading of Pd was 14 mg Pd in 400 ul of Zr02 shell (or 14 * 43/400 = 14 / 9.3 = 1.5 mg Pd in the reactor vessel for all the library elements.) Pd precursors were Pd (NH3) ) 2 (N02) 2 in columns 1 and 4, Pd (NH3) 4 (OH) 2 in columns 2 and 5, Pd (NH3) 4 (N03) 2 in columns 3 and 6. Au / Pd = 0.3 in row 2 and row 5, Au / Pd = 0.6 in row 3, Au / Pd = 0.9 in row 4, row 6 and row 7. The KOAc load was 114 umol in rows 2, 3, 5 and 147 umol in rows 4, 6, 7. The Silica reference catalyst was loaded in row 1. The library was analyzed using the analysis protocol of the T ramp in fixed SV. The results of the analysis are summarized in Table 3.

TABLE 3 CO2 Selectivity Temp. a STY C1 precursors in SiO2 7.37 156.6 729 Pd (NH4) 2 (OH) 2 in Zr02 5.79 152.4 787 Pd (NH3) 4 (N03) 2 in Zr02 5.90 152.3 783 Pd (NH3) 2 (N02) 2 in Zr02 5.57 150.7 795 * The data shown are taken from an average of two atomic ratios Au / Pd (mainly 0.3 and 0.6) and two different ZrO2 supports.

EXAMPLE 13 400 ul of carriers of Zr02 XZ16075 (55 m2 / g as supplied) and XZ16052 (precalcined at 650 ° C / 2h to lower the surface area at 42 m2 / g) were impregnated with Pd (NH3) 4 (OH) 2 (supply solution 1,117M Pd) to incipient humidity, calcined at 350 ° C for 4 hours in air, impregnated with KAuO2 (supply solution 0.97M Au) at incipient humidity, dried at 110 ° C for 5 hours, reduced at 350 ° C for 4 hours in 5% H2 / N2 formation gas, post-impregnated with KOAc and dried at 110 ° C for 5 hours. The samples of Pd / Au / Zr02 (shells) were then diluted 1/12 with a KA160 diluter (preloaded with 40 g / 1 KOAc), ie 33.3 ul of Pd / Au / Zr02 catalyst and a 366.7ul diluter (volume 400 ul total fixed bed) were loaded into the reactor vessels. The library design and the library element compositions were the following: Zr02 XZ16075 in columns 1-3 (left half of the library) and Zr02 XZ16052 (650 ° C) in columns 4-6 (right half of the library) ). The loading of Pd was 18 mg Pd in a shell of Zr02 400 ul (or 18 * 33/400 = 18/12 mg Pd in a reactor vessel) in a cell G2, column 3 (cells B3-G3), cell G5 , column (cells B6-G6); 10 mg Pd in a shell of Zr02 400ul (or 10 * 33/400 = 10/12 mg Pd in a reactor vessel) in column 1 (cells A1-G1) and column 4 (cells A4-G4); 14 mg of Pd in Zr02 400ul (or 14 * 33/400 = 14/12 mg Pd in a reactor vessel) in column 2 (cells B2-F2) and column 5 (cells B5-F5). Au / Pd = 0.3 in row 2 and row 5, Au / Pd = 0.5 in row 3 and row 6, Au / Pd = 0.7 in row 4 and row 7 (except for cells A1, A4, G2, G5 in where Au / Pd was 0.3). The KOAc load was 114 umol (except cells D3, G3, D6, G6 where the KOAc load was 147 umol). The silica reference catalyst was loaded in row 1. The library was analyzed using the T ramp analysis protocol in fixed SV. The results of the analysis are summarized in table 4.

TABLE 4 Selectivity of CO2 Temp at 45% Conv ST? Atomic ratio of Au / Pd 0.3 0.5 0.7 0.3 0.5 0.7 0.3 0.5 0.7 Precursors of Ci in 6.98 - - 154.8 - 742.8 - - S02 ZrO2: XZ16052 6.06 5.31 5.38 153.7 152.3 154.9 776.8 806.0 803.0 ZrO2: XZ16075 6.18 5.62 5.71 147.5 151.0 154.4 773.8 791.6 790.3 EXAMPLE 14 Carrier Zr02 (supplied by NorPro, XZ16075, sieve fraction 180-425 μm, density 1.15 g / ml, pore volume 475 ul / g, surface area of 55 m2 / g) was impregnated with a Pd precursor solution (N03) 2 to incipient humidity, dried at 110 ° C, calcined at 250 ° C (columns 1-2), 350 ° C (columns 3-4), 450 ° C (columns 5-6) in air, impregnated with solution of KAu02 (prepared by dissolving Au (OH) 3 in KOH), dried at 110 ° C, reduced with formation gas 5% H2 / N2 at 350 ° C for 4 hours, and post-impregnated with solution of KOAC. The library has a KOAc gradient of 25 to 50 g / 1 in row 2 to row 7. The Pd load adds 1.5 mg Pd to the 0.4 ml support. Two different loads of Au were chosen (Au / Pd = 0.5 in columns 1, 3, 5 and Au / Pd = 0.7 in columns 2, 4, 6). The silica reference catalyst was loaded in row 1. The library was analyzed using the T ramp analysis protocol in the VA MCFB48 reactor in fixed SV. The results of the analysis are summarized in table 5.

TABLE 5 Selectivity of CO2 Temp to 45% STY Conv Ci precursors in SiO2 7.21 154.7 734 Pd (NO3) 2 in ZrO2 6.10 145.3 775 * The data shown are taken from an average of two atomic ratios of Au / Pd (mainly 0.5 to 0.7) at 40 g / L KOAc, calcination at 450oC, and reduction at 350 ° C.

EXAMPLE 15 Carrier Zr02 (supplied by NorPro, XZ16075, fraction of sieve 180-425 μm, density 1.15 g / ml, pore volume 575 μl / g, area surface area of BET 55 m2 / g) was impregnated with Pd (N03) 2 precursor solution at incipient humidity, dried at 110 ° C, calcined at 450 ° C in air, impregnated with KAu02 solution (prepared by dissolution of Au (OH) 3 in KOH), dried at 110 ° C, reduced with formation gas 5% H2 / N2 at 200 ° C (columns 1-2), 300 ° C (columns 3-4), or 400 ° C (columns 5-6), and post-impregnated with KOAc solution. The library has a KOAc gradient of 15 to 40 g / l in row 2 to row 7. The Pd load adds 1.5 mg Pd to a 0.4 ml support. Two different loads of Au were chosen (Au / Pd = 0.5 in columns 1, 3, 5 and Au / Pd / = 0.7 in columns 2, 4, 6). The silica reference catalyst is loaded in row 1. The library was analyzed in a VA MCFB48 reactor using a T ramp analysis protocol in fixed SV. The results of The analyzes are summarized in table 6.

TABLE 6 Selectivity of CO2 Temp to 45% Conv STY Precursors Ci in SiO2 7.11 154.2 738 Pd (NO3) 2 in ZrO2 5.51 145.4 797 * The data shown are taken from an average of two atomic ratios Au / Pd (mainly 0.5 and 0.7) in 40 g / L KOAc calcination at 450 ° C, and reduction at 400 ° C.

It will further be appreciated that the functions or structures of a plurality of components or steps may be combined into a single component or stage, or the functions structures of a stage or component may be divided among several stages or components. The present invention contemplates all these combinations. Unless stated otherwise, the dimensions and geometries of various structures shown herein are not intended to be restrictive of the invention, and others are possible. dimensions or geometries. The various structural components or steps may be provided by a single integrated structure or stage.

Alternatively, a single integrated structure or stage can be divided into several separate components or stages. Furthermore, although a feature of the present invention can be described in the context of only one of the illustrated embodiments, said feature can be combined with one or more of the features of other embodiments, for any application Dadaist. It will be apparent from the foregoing that the manufacture of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention.

The explanations and illustrations presented herein are intended to inform other experts in the art of the invention, its principles and its practical application. Those skilled in the art can adapt and apply the invention in its many forms, as best suited to the requirements of particular use. Also, the specific embodiments of the present invention as set forth are not intended to be detailed or limiting of the invention. The scope of the invention should, therefore, be determined not with reference to the foregoing description, but instead determined with reference to the appended claims, together with the full scope of the equivalents to which said claims are qualified. Descriptions of all articles and references, including patent applications and publications, are incorporated by reference for all purposes.

Claims (46)

NOVELTY OF THE INVENTION REINVIDICATIONS

1. - A method for producing a catalyst or suitable pre-catalyst to aid in the production of alkenyl alkanoates, comprising; contacting the palladium and gold precursors with a zirconia support material consisting essentially of zirconia; and reducing at least the palladium precursor by contacting a reducing environment with the zirconia support material.

2. The method according to claim 1, further characterized in that the zirconia support material has a BET surface area of between about 5 m / g and about 300 m2 / g.

3. The method according to claim 1 or 2, further characterized in that the zirconia support material has a particle size between 5 μm and about 10 mm.

4. The method according to any of claims 1-3, further characterized in that it comprises calcining the zirconia support material contacted, in a non-reducing atmosphere before the reduction step.

5. The method according to any of claims 1-4, further characterized in that the step of contacting comprises impregnating the support material of zirconia with palladium and gold precursors.

6. The method according to any of claims 1-5, further characterized in that the impregnation step comprises sequential impregnation of palladium and gold precursors in the zirconia support material.

7. The method according to any of claims 1-6, further characterized in that the calcination step occurs before the impregnation of the gold precursor.

8. The method according to any of claims 1-7, further characterized in that it comprises at least one fixing step using a fixing agent.

9. The method according to any of claims 1-8, further characterized in that the reduction step occurs before impregnating the gold precursor.

10. The method according to any of claims 1-9, further characterized in that the impregnation step comprises co-impregnating palladium and gold precursors.

11. The method according to any of claims 1-10, further characterized in that the impregnation step comprises impregnating the zirconia support material with water-soluble substantially chloride-free precursor solutions.

12. - The method according to any of claims 1-11, further characterized in that the substantially free precursors of palladium chloride comprise Pd (NH3) 2 (N02) 2, Pd (NH3) 4 (OH) 2, Pd (NH3) 4 (N03) 2, Pd (N03) 2, Pd (NH 3) 4 (OAc) 2, Pd (NH 3) 2 (OAc) 2, Pd (OAc) 2, in KOH or NMe 4 OH or NaOH, Pd (NH 3) 4 (HC03) 2, palladium oxalate or combinations thereof.

13. The method according to any of claims 1-12, further characterized in that the substantially gold-free precursors of chlorine comprise KAu02, NaAu02, NMe4Au02, Au (OAc) 3 in KOH or NMe4OH, HAu (N03) 4 in nitric acid or combinations thereof.

14. The method according to any of claims 1-13, further characterized in that the impregnation step comprises impregnating the zirconia support material with chloride-containing precursor solutions and followed by a fixing step comprising fixing with an agent Fixing.

15. The method according to any of claims 1-14, further characterized in that the step of contacting further comprises contacting a precursor of the third component.

16. The method according to any of claims 1-15, further characterized in that the third component precursor comprises W, Ni, Nb, Ta, Ti, Zr, Y, Re, Os, Fe, Cu, Co, Zn , In, Sn, Ce, Ge, Rh, Ga and combinations thereof.

17. The method according to any of claims 1-16, further characterized in that the step of contacting comprises contacting the third component and palladium in a palladium third component atomic ratio of between about 0.01 and about 0.5.

18. The method according to any of claims 1-17, further characterized in that the calcination step comprises heating the zirconia support material contacted at a temperature between about 200 ° C and about 700 ° C.

19. The method according to any of claims 1-18, further characterized in that it comprises contacting an alkali metal acetate with the zirconia support material.

20. The method according to any of claims 1-19, further characterized in that the alkali metal acetate is potassium acetate.

21. The method according to any of claims 1-20, further characterized in that the potassium acetate is present in an amount between about 10 and 70 grams per liter of catalyst.

22. The method according to any of claims 1-21, further characterized in that the step of contacting comprises contacting between about 1 to about 10 grams of palladium, and about 0.5 to about 10 grams of gold per liter of catalyst, with the amount of gold being between about 10 to about 125% by weight based on the weight of palladium.

23. The method according to any of claims 1-22, further characterized in that the atomic ratio of gold to palladium is between about 0.50 and about 1.00.

24. The method according to any of claims 1-23, further characterized in that the steps of the method result in a catalyst or a shell pre-catalyst, a catalyst or egg yolk pre-catalyst, a catalyst or egg white pre-catalyst, or a catalyst or pre-catalyst for global coverage.

25. The method according to any of claims 1-24, further characterized in that the shell has a thickness between about 5 and about 300 microns.

26. A composition for catalyzing the production of alkenyl alkanoates, comprising: a zirconia support material consisting essentially of zirconia with at least one palladium and gold contacted therein to form a catalyst or precatalyst .

27. The composition according to claim 26, further characterized in that the palladium and gold have been calcined.

28. - The composition according to any of claims 26-27, further characterized in that palladium and gold have been reduced.

29. The composition according to any of claims 26-28, further characterized in that the gold has been calcined before being reduced.

30. The composition according to any of claims 26-29, further characterized because the gold has been reduced.

31. The composition according to any of claims 26-30, further characterized in that the catalyst or pre-catalyst comprises a third component.

32. The composition according to any of claims 26-31, further characterized in that the third component is selected from W, Ni, Nb, Ta, Ti, Zr, Y, Re, Os, Fe, Cu, Co, Zn , In, Sn, Ce, Ge, Rh, Ga and combinations thereof.

33. The composition according to any of claims 26-32, further characterized in that the atomic ratio of the third component to the palladium is between about 0.01 and about 0.5.

34. The composition according to any of claims 26-33, further characterized in that the catalyst or pre-catalyst comprises between about 1 to about 10 grams of palladium, and about 0.5 to about 10 grams of gold per liter of catalyst, with the amount of gold being from about 10 to about 125% by weight based on the weight of palladium.

35.- The composition according to any of claims 26-34, further characterized in that the catalyst or pre-catalyst comprises an alkali metal acetate.

36. The composition according to any of claims 26-35, further characterized in that the alkali metal acetate is potassium acetate.

37. The composition according to any of claims 26-36, further characterized in that the potassium acetate is present in an amount between about 10 and 70 grams per liter of catalyst.

38.- The composition according to any of claims 26-37, further characterized in that the catalyst or pre-catalyst comprises a catalyst or shell pre-catalyst, a catalyst or egg yolk pre-catalyst, a catalyst or pre-catalyst. -catalyst of egg white, or a catalyst or pre-catalyst of global coverage.

39.- The composition according to any of claims 26-38, further characterized in that the zirconia support material comprises a particulate support material or a crushed support material.

40. - A method for producing alkenyl alkanoates, comprising: contacting a food comprising an alkene, an alkanoic acid and an oxidant with a catalyst or precatalyst comprising palladium and gold in a zirconia support material consisting essentially of in zirconia.

41. The method according to claim 40, further characterized in that the alkene is ethylene, the alkanoic acid is acetic acid and the oxidant is an oxygen gas.

42. The method according to any of claims 40 or 41, further characterized in that the catalyst or pre-catalyst comprises a third component.

43.- The method according to any of claims 40-42, further characterized in that the third component is selected from W, Ni, Nb, Ta, Ti, Zr, Y, Re, Os, Fe, Cu, Co, Zn , In, Sn, Ce, Ge, Rh, Ga, and combinations thereof.

44. The method according to any of claims 40-43, further characterized in that the catalyst or precatalyst comprises a third component and a palladium in an atomic ratio of third component to palladium of between about 0.01 and about 0.5.

45. The method according to any of claims 40-44, further characterized in that the catalyst or pre-catalyst comprises between about 1 to about 10 grams of palladium, and about 0.5 to about 10 grams of gold per liter of catalyst, with the amount of gold being from about 10 to about 125% by weight based on the weight of the palladium. 46.- The method according to any of claims 40-45, further characterized in that the catalyst or pre-catalyst is a catalyst or a shell pre-catalyst, a catalyst or egg yolk pre-catalyst, a catalyst or egg white pre-catalyst, or a catalyst or pre-catalyst for global coverage.