CN1929916A - Layered support material for catalysts - Google Patents

Abstract

The present invention addresses at least four different aspects relating to catalyst structure, methods of making those catalysts and methods of using those catalysts for making alkenyl alkanoates. Separately or together in combination, 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 present 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 that is based on a layered support material where one layer of the support material is substantially free of catalytic components. A third aspect pertains to a palladium/gold catalyst or pre-catalyst 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

Layered support materials for catalysts

priority claim

This application claims the benefit of US Provisional Patent Application No. 60/531,415, filed December 19, 2003, which is hereby incorporated herein by reference.

field of invention

The present invention relates to a catalyst, a preparation method of the catalyst, and a preparation method of alkenyl alkanoate. More specifically, the present invention relates to a process for the production of vinyl acetate.

Background of the invention

Certain alkenyl alkanoates such as vinyl acetate (VA) are commodity chemicals in high demand in their monomeric form. For example, the use of VA to prepare polyvinyl acetate (PVAc), which is commonly used in adhesives, accounts for a large proportion of VA applications. Other applications of VA include polyvinyl alcohol (PVOH), ethylene-vinyl acetate (EVA), vinyl acetate-ethylene (VAE), polyvinyl butyral (PVB), ethylene-vinyl alcohol (EVOH), polyethylene Alcohol formal (PVF), and vinyl chloride-vinyl acetate copolymer. PVOH is commonly used in textiles, films, adhesives, and photosensitive coatings. Film and wire and cable insulation usually use a certain proportion of EVA. The main applications of vinyl chloride-vinyl acetate copolymers include coatings, paints, and adhesives, usually using VAE with a certain proportion of VA. VAEs containing more than 50% VA are mainly used as cement additives, paints, and adhesives. PVB is mainly used for the bottom layer, coating, and ink of laminated screens. EVOH is used in impermeable membranes and engineering polymers. PVF is used in cable enamels and tapes.

Since VA is the basis for many commercially valuable feedstocks and products, VA is in high demand and VA production is typically performed on a large scale (eg, 50,000 metric tons per year or more). This large-scale production means that considerable economies of scale are possible and that small changes in the process, process conditions or catalyst properties can have a considerable economic impact on the production cost of VA.

A number of techniques have been reported for the production of alkenyl alkanoates. For example, a widely used technique in the preparation of VA involves the catalytic gas phase reaction of ethylene with acetic acid and oxygen, as shown in the following reaction:

Some side reactions may occur including, for example, _CO2 formation. The results of this reaction are discussed in terms of the space-time yield (STY) of the reaction system, where STY is the grams of VA produced per liter of catalyst per hour of reaction time (g/l*h).

The composition of the starting materials can vary within wide limits. Typically, the feedstock includes 30-70% ethylene, 10-30% acetic acid and 4-16% oxygen. The feed may also include inerts such as _CO2 , nitrogen, methane, ethane, propane, argon and/or helium. The main constraint on the feed composition is that the oxygen content in the effluent gas stream leaving the reactor must be low enough to keep the gas stream outside the flammable zone. The oxygen content in the effluent gas stream is affected by the oxygen content in the feed stream, the _O2 conversion of the reaction, and the amount of any inerts in the effluent gas stream.

The gas phase reaction has been carried out with the feedstock passing through a fixed bed reactor. Successful results have been obtained by employing reaction temperatures in the range -125 to 200°C, while reaction pressures are typically 1-15 atmospheres.

While these systems provide adequate yields, there is still a need to reduce by-product yields, increase VA output rates, and reduce energy consumption during production. One avenue is to improve the performance of the catalyst, especially the _CO2 selectivity and/or activity of the catalyst. Another approach is to change the reaction conditions, such as the ratio of raw materials, the _O2 conversion of the reaction, the space velocity (SV) of the feed, and the operating temperature and pressure.

_CO2 production can be reduced by using improved catalysts. _CO2 selectivity is the percentage of ethylene converted to _CO2 . Reducing the _CO2 selectivity yielded a higher amount of VA per unit volume and unit time in existing equipment, even keeping all other reaction conditions.

The VA output of a particular reaction system is affected by other factors including catalyst activity, feedstock ratio, _O2 conversion of the reaction, space velocity (SV) of the feed, and operating temperature and pressure. All of these factors cooperate to determine the space-time yield (STY) of the reaction system, where STY is measured in grams of VA produced per liter of catalyst per hour of reaction time, or g/l*h.

In general, activity is an important factor in determining STY, but other factors may also have important effects on STY. Generally, the higher the activity of the catalyst, the higher the STY that the catalyst can produce.

O _conversion is a measure of how much oxygen reacts in the presence of a catalyst. _O2 conversion is temperature dependent such that the conversion generally increases with reaction temperature. But the amount of _CO2 produced also increases with the _O2 conversion. Therefore, the _O2 conversion is chosen to obtain the desired VA output in balance with the _CO2 production. A catalyst with higher activity means that the overall reaction temperature can be lowered while maintaining the same _O2 conversion. Alternatively, catalysts with higher activity give higher _O2 conversions at a given temperature and space velocity.

It is common for catalysts to employ one or more catalytic components supported on relatively inert support materials. In the case of VA catalysts, the catalytic component is usually a mixture of metals that can be distributed uniformly over the support material (“full-through catalyst”), only on the surface of the support material (“shell catalyst”), only on the support material Below the shell ("protein catalyst") or distributed within the core of the support material ("egg yolk catalyst").

Many different types of support materials have been suggested for VA catalysts, including silica, cerium-doped silica, alumina, titania, zirconia, and oxide mixtures. However, little research has been done on the differences between carrier materials. For the most part, only silica and alumina are actually used commercially as support materials.

A suitable combination of metals for VA catalysts is palladium and gold. Pd/Au catalysts provide adequate _CO2 selectivity and activity, but improved catalysts that can generate economies of scale in VA production are still needed.

One of the preparation methods of Pd/Au catalysts generally includes the following steps: impregnating the support with an aqueous solution of water-soluble salts of palladium and gold; Precipitation of insoluble compounds such as hydroxides (commonly referred to as immobilization); washing the immobilized support material to remove unimmobilized compounds and otherwise purifying the catalyst from any potential poisons such as chlorides; with typical reducing agents such as hydrogen, ethylene or hydrazine to reduce the water-insoluble compound; and adding an alkali metal compound such as potassium or sodium acetate.

Various improvements to this basic method have been proposed. For example, US 5,990,344 proposes sintering of palladium after reduction to free metal form. It may be advantageous to calcine the support in a non-reducing atmosphere after impregnation with palladium and gold salts as suggested in US 6,022,823. It is proposed in WO 94/21374 that after reduction and activation but before its first use, the catalyst can be pretreated by successively heating in an oxidizing, inert, and reducing atmosphere.

Palladium and gold salts free of hydroxyl, halide ions and barium and soluble in acetic acid are proposed in US 5,466,652 for impregnating support materials. A similar suggestion is also made in US 4,902,823 to use palladium salts and complexes soluble in unsubstituted carboxylic acids having 2 to 10 carbon atoms which are free of halide ions and sulfur.

No. 6,486,370 proposes a layered catalyst for dehydrogenation, wherein the support material of the inner layer is different from the support material of the outer layer. Similarly, US 5,935,889 proposes that a layered catalyst can be used as an acid catalyst. Neither suggests the use of layered catalysts in the production of alkenyl alkanoates.

Taken together, the present inventors have recognized a need for continued improvement in the field of VA catalysts to provide improved VA production methods at lower cost.

Contents of the invention

The present invention is concerned with at least four different aspects concerning the structure of the catalyst, the method of preparing the catalyst and the method of using the catalyst to prepare alkenyl alkanoates. Separately or in combination, various aspects of the invention aim to improve the production of alkenyl alkanoates, especially VA, including reduction of by-products and improved production efficiency. A first aspect of the present invention relates to a unique palladium/gold catalyst or procatalyst (optionally calcined) comprising rhodium or another metal. A second aspect relates to palladium/gold catalysts or procatalysts based on layered support materials, wherein one layer of the support material is substantially free of catalytic components. A third aspect relates to a palladium/gold catalyst or procatalyst supported on a zirconia-containing support material. A fourth aspect relates to a palladium/gold catalyst or procatalyst produced from a substantially chloride-free catalytic component.

Detailed description of the invention

catalyst

For purposes herein, a catalyst is any support material that contains at least one catalytic component and is capable of catalyzing a reaction, while a procatalyst is any material resulting from any of the catalyst preparation steps described herein.

Catalysts and procatalysts of the present invention may include catalysts and procatalysts having at least one of the following properties: 1) the catalyst is a palladium and gold containing catalyst comprising at least one other catalytic component such as rhodium, wherein the catalytic component One or more of them have been calcined; 2) the catalyst is loaded on a layered carrier; 3) the catalyst is loaded on a carrier material containing zirconia; 4) the catalyst is made of a chloride-free precursor Produced or any combination of the above. Therefore, efficient utilization of this catalyst will help to improve _CO2 selectivity, activity, or both, especially for VA production.

It is to be understood that the invention will be described in conjunction with certain illustrated embodiments, but that any aspect may be modified as may be required for a particular application. For example, without limitation, the catalyst may have a catalytic component uniformly distributed throughout the support material or may be a shell catalyst in which the catalytic component is present within a thinner shell surrounding a core of support material. Proteinaceous catalysts may also be suitable where the catalytic component is substantially outside the center of the support material. Egg yolk catalysts may also be suitable.

Catalytic component

In general, the catalysts and procatalysts of the present invention comprise metals, in particular combinations of at least two metals. In particular, said combination of metals comprises at least one from group VIIIB and at least one from group IB. It is to be understood that "catalytic component" is used to denote the metal that ultimately renders the catalyst catalytically functional, but also includes metals in various states such as salts, solutions, sol-gels, suspensions, colloidal suspensions, free metals, alloys, or combinations thereof. Preferred catalysts include palladium and gold as catalytic components.

One embodiment of the catalyst includes a combination of catalytic components having palladium and gold combined with a third catalytic component. The third catalytic component is preferably selected from Group VIIIB, Rh being most preferred. Other preferred catalysts include wherein the third catalytic component is selected from W, Ni, Nb, Ta, Ti, Zr, Y, Re, Os, Fe, Cu, Co, Zn, In, Sn, Ce, Ge, Ga and combined catalyst.

Another embodiment of the catalyst includes a combination of catalytic components including palladium, gold and rhodium. Optionally, a third catalytic component (listed above) instead of Rh may also be included in this embodiment. In another embodiment, two or more catalytic components selected from those listed above may be employed.

In one example, palladium and gold can be combined with Rh to form catalysts that exhibit improved _CO2 selectivity (ie, reduced _CO2 production) over Rh-free Pd/Au catalysts. Moreover, the addition of Rh does not appear to have an adverse effect on the activity of the catalyst. The _CO2 selectivity of palladium-gold-rhodium catalysts can also be improved by calcination during catalyst preparation and/or by using halide-free water-soluble precursors (as described later), but these are not the reasons for observing the effect of Rh. required.

The atomic ratio of the third catalytic component to palladium may range 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 grams of the third catalytic component per liter of catalyst.

Another preferred embodiment of the catalyst comprises between about 1 to about 10 grams of palladium and between 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 wt%, based on the weight of palladium.

In one embodiment of the powdered catalyst, an atomic ratio of Au to Pd between about 0.5 and about 1.00 may be preferred for the powdered catalyst. This atomic ratio can be tuned to balance activity with _CO2 selectivity. Using higher Au/Pd weight or atomic ratios tends to favor more active, more selective catalysts. In other words, a catalyst with an atomic ratio of about 0.6 is less selective for _CO2 than a catalyst with an atomic ratio of about 0.8, but also has a lower activity. The effect of high Au/Pd atomic ratios on pulverulent support materials can also be enhanced by using a greater excess of hydroxide ions, as described later for the immobilization step. Powdered catalysts may be catalysts in which the catalytic components are contacted with a support material and then reduced to a particulate size (for example by grinding or ball milling) or catalysts in which the catalytic components are contacted with a support material which has been reduced in size.

For shell catalysts, the thickness of the catalytic component shell on the support material ranges from about 5 μm to about 500 μm. More preferred ranges include about 5 μm to about 300 μm.

carrier material

As previously stated, in one aspect of the present invention, the catalytic component of the present invention is supported on a support material. Suitable carrier materials generally include materials or mixtures of materials with substantially uniform properties. In general, the support material is generally inert in the reaction to be carried out. The support material may consist of any suitable substance, preferably selected such that the support material has a relatively high surface area per unit mass or volume, such as a porous structure, molecular sieve structure, honeycomb structure, or other suitable structure. For example, the support material may contain silica, alumina, silica-alumina, titania, zirconia, niobium oxide, silicates, aluminosilicates, titanates, spinels, silicon carbide, silicon nitride , carbon, cordierite, talc, bentonite, clay, metal, glass, quartz, pumice, zeolite, non-zeolite molecular sieves and combinations thereof. Any of the different crystal forms of these materials may also be used, such as alpha or gamma alumina. Support materials containing silica and zirconia are most preferred. Furthermore, multilayer support materials are also suitable for use in the present invention.

The support material in the catalyst of the present invention may consist of any particle having various regular or irregular shapes, such as spheres, flakes, cylinders, discs, rings, stars, or other shapes. The support material may have dimensions such as diameter, length or width of about 1 to about 10 mm, preferably about 3 to about 9 mm. In particular, regular shapes (eg spherical) have a preferred largest dimension thereof of about 4 to about 8 mm. Additionally, powdered support materials may be used such that the support material has a regular or irregular shape with a diameter between about 10 and about 1000 μm, preferably between about 10 and about 700 μm in size, and most preferably between about 180 and about 450 μm in size. Larger or smaller sizes, as well as polydisperse particle size collections, are available. For example, for fluidized bed catalysts, preferred size ranges include 10 to 150 μm. For precursors used in layered catalysts, a size range of 10 to 250 μm is preferred.

The surface area available for supporting the catalytic component as measured by the BET (Brunauer, Emmett, and Teller) method may generally be between about 1 and about 500 m ² /g, preferably about 100 to about 200 m ² /g. For example, for porous supports, the support material may generally have a pore volume of from about 0.1 to about 2 ml/g, preferably from about 0.4 to about 1.2 ml/g. An average pore size in the range of, for example, about 50 to about 2000 A is desirable, but not required.

Examples of suitable silica-containing support materials include KA160 from Sud Chemie, Aerolyst 350 from Degussa and other fumed or non-porous silicas having a particle size of from about 1 mm to about 10 mm.

Examples of suitable zirconia-containing support materials include those from NorPro, Zirconia Sales (America), Inc., Daichi Kigenso Kagaku Kogyo, and MagnesiumElektron Inc (MEI). Suitable zirconia support materials have a surface area ranging from less than about 5 m ² /g to greater than 300 m ² /g. Preferred zirconia support materials have a surface area of from about 10 to about 135 ^m2 /g. The support material may have a surface treated by a firing step, in which the original support material is heated. This heating causes the surface area of the support material to be reduced (eg, fired). This provides a means of producing support materials with specific surface areas that may not otherwise be readily available from suppliers.

In another embodiment, it is contemplated to use a composite of carrier materials with different properties. For example, at least two support materials with different properties (such as zirconia) can exhibit different activities and _CO2 selectivities, so that a catalyst can be prepared with a desired set of properties, that is, the activity of the catalyst is compared with the _CO2 selectivity of the catalyst. balance.

In one embodiment, multiple different supports are used in a multilayer configuration. Layering can be achieved in any of a number of different ways, such as multiple thin layers, generally flat, undulating, or a combination thereof. One approach is to use encapsulation layers sequentially relative to the inner core layer. In general, layered support materials herein generally comprise at least one inner layer and an outer layer at least partially surrounding the inner layer. The outer layer preferably contains significantly more catalytic component than the inner layer. In one embodiment, the inner and outer layers are made of different materials; however, the material may be the same. While the inner layer may be non-porous, other embodiments include porous inner layers.

The layered support material preferably forms a shell catalyst. However, layered support materials present a well-defined boundary between areas of the support material with catalytic components and areas of the support material without catalytic components. Furthermore, the outer layer can be formed to have a uniform desired thickness. The boundary and the uniform thickness of the outer layer together produce a shell catalyst which is a shell of catalytic components of uniform and known thickness.

Several techniques are known for producing layered support materials, including those described in US 6,486,370; 5,935,889; and 5,200,382, all incorporated herein by reference. In one embodiment, the material of the inner layer is also substantially impermeable to 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, niobium oxide, silicates, aluminosilicates, titanates, spinels , silicon carbide, silicon nitride, carbon, cordierite, talc, bentonite, clay, metal, glass, quartz, pumice, zeolite, non-zeolite molecular sieves, and combinations thereof. A preferred inner layer is silicon oxide, especially KA160.

These materials making up the inner layer can be in various forms such as regularly shaped particles, irregularly shaped particles, pellets, discs, rings, stars, wheels, honeycombs or other shaped objects. Spherical particle inner layers are preferred. The effective diameter of the inner layer (whether spherical or not) is from about 0.02 to about 10.0 mm, preferably from about 0.04 to about 8.0 mm.

The outermost layer of any multilayer structure is porous with a surface area in the range of about 5 to about 300 ^m2 /g. The material of the outer layer is metal, ceramic, or a combination thereof, in one embodiment selected from the group consisting of alumina, silica, silica-alumina, titania, zirconia, niobium oxide, silicates, aluminosilicates Salt, titanate, spinel, silicon carbide, silicon nitride, carbon, cordierite, talc, bentonite, clay, metal, glass, quartz, pumice, zeolite, non-zeolitic molecular sieves, and combinations thereof, preferably including alumina, Silica, silica/alumina, zeolites, non-zeolitic molecular sieves (NZMS), titania, zirconia and mixtures thereof. Specific examples include zirconia, silica, and alumina, or combinations thereof.

While the outer layer typically surrounds substantially the entire inner layer, it need not be, and the outer layer can be selectively applied over the inner layer.

The outer layer can be applied over the underlying layer in a suitable manner. In one embodiment, a slurry of outer layer material is used. Slurry coating the inner layer can be accomplished by roll coating, dip coating, spray coating, wash coating, other slurry coating techniques, or combinations thereof. A preferred technique involves using a fixed or fluidized bed of inner layer particles and spraying the slurry into the bed to evenly coat the particles. The slurry can be recoated in small amounts, with drying in between, to provide an outer layer of very uniform thickness.

The slurry used to coat the inner layer may further include any of various additives such as surfactants, organic or inorganic binders to facilitate the adhesion of the outer layer to the lower layer, or combinations thereof. Examples of such organic binders include, but are not limited to, PVA, hydroxypropyl cellulose, methyl cellulose, and carboxymethyl cellulose. The amount of organic binder added to the slurry can vary, for example from about 1 to about 15 wt% of the combined outer layer and binder. Examples of inorganic binders are selected from alumina binders (e.g. Bohmite), silica binders (e.g. Ludox, Teos), zirconia binders (e.g. zirconia acetate or colloidal zirconia) or combination. Examples of silica binders include silica sol or silica gel, and examples of alumina binders include alumina sol, bentonite, Bohmite, and aluminum nitrate. The amount of the inorganic binder may range from about 2 to about 15% by weight of the sum of the outer layer and the binder. The thickness of the outer layer may be in the range of about 5 to about 500 μm, preferably between about 20 and about 250 μm.

After the inner layer has been coated with the outer layer, the resulting layered support will be dried, for example by heating at a temperature of from about 100°C to about 320°C (eg, for a period of about 1 to about 24 hours), and then optionally at about Calcining at a temperature of 300°C to about 900°C (eg, for a period of about 0.5 to about 10 hours) to enhance the adhesion of the outer layer to its underlying layer at at least a portion of its surface to provide a layered catalyst support. The drying and firing steps can be combined into one step. As with any other support material in catalyst production, the resulting layered support material can be contacted with catalytic components, as described hereinafter. Alternatively, the outer support material is contacted with the catalytic component before it is applied over the underlying layer.

In another embodiment of the layered support, a second outer layer is added to surround the initial outer layer to form at least three layers. The material of the second outer layer may be the same as or different from the first outer layer. Suitable materials include those described for the first outer layer. The method of applying the second outer layer may be the same as or different from the method used to apply the intermediate layer, suitable methods include those described for the first outer layer. The organic or inorganic binder may be suitably used in forming 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 a catalytic component. If both outer layers contain catalytic components, it is preferred, although not necessary, to use a different catalytic component in each layer. In a preferred embodiment, the initial outer layer is free of catalytic components. Contact of the catalytic component with the outer layer can be achieved by dipping or spraying, as described below.

In embodiments where the initial outer layer contains a catalytic component, one method of doing this is by contacting the material of the initial outer layer with the catalytic component before the material is applied to the inner layer. The second outer layer may be applied over the initial outer layer, either pure or containing a catalytic component.

Other suitable techniques can be used to obtain three-layer support materials, wherein one or more outer layers contain catalytic components. Of course, layered support materials are 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 amount and type of catalytic components can vary between layers of layered support materials, and other characteristics of the support material (eg, porosity, particle size, surface area, or pore volume, etc.) can vary between layers.

Catalyst preparation method

Generally, the methods include contacting the support material with a catalytic component and reducing the catalytic component. A preferred method of the invention involves impregnating the catalytic component into a support material, calcining the support material containing the catalytic component, reducing the catalytic component and modifying the reduced catalytic component on the support material. Additional steps such as immobilizing the catalytic component on the support material and washing the immobilized catalytic component may also be included in the method of preparing the catalyst or procatalyst. Some of the steps listed above are optional and others can be eliminated (such as washing and fixing steps). Furthermore, certain steps may be repeated (eg, multiple impregnation or fixation steps) and the order of steps may be different than listed above (eg, a reduction step precedes a firing step). To some extent, the contacting step will determine what subsequent steps are required to form the catalyst.

contact steps

One particular method of contacting is in accordance with forming an egg yolk catalyst or procatalyst, forming a protein catalyst or procatalyst, forming a full-through catalyst or procatalyst, or forming a shell catalyst or procatalyst, or combinations thereof. In one embodiment, techniques for forming shell catalysts are preferred.

The contacting step can be carried out with any of the support materials mentioned above, with silica, zirconia and layered support materials containing zirconia being most advantageous. The contacting step is preferably carried out under ambient temperature and pressure conditions; however, reduced or elevated temperatures or pressures may also be employed.

In a preferred contacting step, the support material is impregnated with an aqueous solution of one or more catalytic components, called the precursor solution. The physical state of the support material during the contacting step can be dry solid, slurry, sol-gel, or colloidal suspension, among others.

In one embodiment, the catalytic component contained in the precursor solution is a water-soluble salt made of the catalytic component, including but not limited to chlorides, other halides, nitrates, nitrites, hydroxides, oxidized salts, oxalates, acetates (OAc), and amines, the halide-free salts are preferred, and the chloride-free salts are more preferred. Examples of palladium salts suitable for precursor solutions include PdCl ₂ , Na ₂ PdCl ₄ , Pd(NH ₃ ) ₂ (NO ₂ ) ₂ , Pd(NH ₃ ) ₄ (OH) ₂ , Pd(NH ₃ ) ₄ (NO ₃ ) ₂ , Pd(NO ₃ ) ₂ , Pd(NH ₃ ) ₄ (OAc) ₂ , Pd(NH ₃ ) ₂ (OAc) ₂ , Pd(OAc) in KOH and/or NMe ₄ OH and/or NaOH ) ₂ , Pd(NH ₃ ) ₄ (HCO ₃ ) ₂ and palladium oxalate. Of the chloride _- containing palladium precursors, _Na2PdCl4 is most preferred. Among the chloride-free palladium precursor salts, the following four are most preferred: Pd(NH ₃ ) ₄ (NO ₃ ) ₂ , Pd(NO ₃ ) ₂ , Pd(NH ₃ ) ₂ (NO ₂ ) ₂ , Pd(NH ₃ ) ₄ (OH) ₂ . Examples of gold salts suitable for precursor solutions include AuCl ₃ , HAuCl ₄ , NaAuCl ₄ , KAuO ₂ , NaAuO ₂ , NMe ₄ AuO ₂ , Au(OAc) ₃ in KOH and/or NMe ₄ OH and in nitric acid HAu(NO ₃ ) ₄ , KAuO ₂ are the most preferred chloride-free gold precursors. Examples of rhodium salts suitable for use in the precursor solution include _RhCl3 , Rh(OAc) ₃ , and Rh( _NO3 ) ₂ . Similar salts of the third catalytic component described above may also be selected.

Furthermore, more than one salt may 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 generally be prepared by dissolving the selected salt in water, with or without solubility modifiers such as acids, bases or other solvents. Other non-aqueous solvents can also be used.

The precursor solutions may be impregnated onto the support material simultaneously (eg co-impregnation) or sequentially and may be impregnated with one or more precursor solutions. In the case of three or more catalytic components, a combination of simultaneous and sequential impregnations may be used. For example, palladium and rhodium may be impregnated with a single precursor solution (known as co-impregnation), followed by impregnation with a gold precursor solution. Furthermore, the catalytic component can be impregnated onto the support material in multiple steps such that a portion of the catalytic component is contacted each time. For example, one suitable scheme may include impregnation with Pd, then Au, and then Au.

The order in which the support material is impregnated with the precursor solution is not critical; although certain orders may have some advantages, as described later for the firing step. Preference is given to impregnating the palladium catalytic component on the support material first, followed by palladium or finally with gold. Rhodium or other third catalytic component (when used) can be impregnated with palladium, with gold or separately. Furthermore, the support material can be impregnated multiple times with the same catalytic component. For example, a portion of the total gold contained in the catalyst is contacted first, followed by a second portion of the gold. One or more other steps may be inserted between the step of contacting the gold with the support material, such as firing, reduction, and/or immobilization.

The acid-base distribution of the precursor solution may affect whether co-impregnation or sequential impregnation is used. Therefore, only precursor solutions with similar acid-base distributions can be used together in the co-impregnation step; this eliminates any acid-base reactions that might contaminate the precursor solutions.

For the impregnation step, the volume of the precursor solution is chosen such that it corresponds to between about 85% and about 110% of the pore volume of the support material. The volume is preferably between about 95% and about 100% of the pore volume of the support material, more preferably between about 98% and about 99% of the pore volume.

Typically, the precursor solution is added to the support material such that the support material absorbs the precursor solution. This can be done dropwise until the carrier material has substantially achieved incipient wetness. Alternatively, the support material may be placed in the precursor solution in fractions or in a batch manner. Thorough contact between the support material and the precursor solution may be achieved by rotary dipping or other auxiliary means. Spraying devices can also be used to spray the precursor solution onto the support material through a nozzle to be absorbed. Optionally, any excess liquid not absorbed by the support material may be removed by decantation, heat or reduced pressure or the support material may be dried after impregnation.

For the impregnation step, the volume of the precursor solution is selected to be between about 85% and about 110% of the pore volume of the support material. Preferably the volume is between about 95% and about 100% of the pore volume of the support material, more preferably between about 98% and about 99% of the pore volume.

Typically, the precursor solution is added to the support material such that the support material absorbs the precursor solution. This can be done dropwise until the carrier material has substantially achieved incipient wetness. Alternatively, the support material may be placed in the precursor solution in fractions or in a batch manner. Thorough contact between the support material and the precursor solution may be achieved by rotary dipping or other auxiliary means. Spraying devices can also be used to spray the precursor solution onto the support material through a nozzle to be absorbed. Optionally, any excess liquid not absorbed by the support material may be removed by decantation, heat or reduced pressure or the support material may be dried after impregnation.

Other contacting techniques can be used to avoid the fixation step and still obtain a shell catalyst. For example, the catalytic component is contacted with the support material by chemical vapor deposition, as described in US2001/0048970, incorporated herein by reference. Furthermore, spraying or otherwise layering a uniformly pre-impregnated support material on an inner layer (as an outer layer) effectively forms a shell catalyst, also described as a layered support material. In another technique, organometallic precursors of the catalytic components, especially for gold, can be used to form shell catalysts, as described in US 5,700,753, incorporated herein by reference.

Physical shell formation techniques can also be used to produce shell catalysts. Here, the precursor solution can be sprayed onto the heated support material or layered support material, the solvent of the precursor solution evaporates on contact with the heated support material, so that the catalytic component is deposited on the support material in the form of a shell. Preferably a temperature between about 40 and 140°C is employed. 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 nozzle. For example, at temperatures higher than 100° C., thinner shells are formed. This embodiment is particularly suitable when the formation of the shell on the support material is promoted with chloride-free precursors.

Those skilled in the art will understand that a combination of the contacting steps may be a suitable method for forming a contacted support material.

fixed steps

It may be desirable to convert at least a portion of the catalytic components contacting the support material from a water-soluble form to a water-insoluble form. This step may be referred to as a fixation step. This can be achieved by precipitating at least a part of the catalytic component by applying a fixative (eg a dispersion in a liquid, eg a solution) on the impregnated support material. This immobilization step is helpful for, but not required for, the formation of the shell catalyst.

Any suitable fixative may be used, hydroxides (eg alkali metal hydroxides), silicates, borates, carbonates and bicarbonates in aqueous solution are preferred. A preferred fixative is NaOH. Fixing can be achieved by adding a fixative to the support material before, during or after impregnation of the precursor solution on the support material. Typically, a fixative is used following the contacting step by soaking the contacted support material in a fixative solution for about 1 to about 24 hours. The exact time depends on the combination of precursor solution and fixative. As with the impregnation step, the fixation step may also advantageously use auxiliary devices, such as a rotary dipping device as described in US 5,332,710, incorporated herein by reference.

The fixation steps can be done in one or more steps, called joint fixation or separate fixation. In co-immobilization, regardless of whether contacting is accomplished with one or more precursor solutions, one or more volumes of fixative solution. For example, fixation following sequential impregnation with palladium precursor solution, gold precursor solution and rhodium precursor solution is co-fixation, as is fixation after co-impregnation with palladium/rhodium precursor solution followed by impregnation with gold precursor solution. Examples of co-immobilization are found in US 5,314,888, incorporated herein by reference.

In another aspect, separate fixation includes applying a fixative solution during or after each impregnation with the precursor solution. For example, the following protocols are separate fixations: a) palladium impregnation followed by fixation, then gold impregnation followed by fixation; or b) palladium and rhodium co-impregnation followed by fixation, followed by gold impregnation followed by fixation. Between fixation and subsequent impregnation, any excess liquid can be removed and the support material allowed to dry, but this is not required. Examples of separate immobilization are found in US 6,034,030, incorporated herein by reference.

In another embodiment, the immobilization step and the contacting step are performed simultaneously, an example of which is described in US 4,048,096, incorporated herein by reference. For example, simultaneous fixation can be: impregnation with palladium followed by fixation followed by impregnation with gold and fixative. In a variant of this embodiment, the catalytic component can be immobilized twice. The catalytic component can be partially immobilized (referred to as "pre-immobilized") while it is in contact with the support material, followed by an additional final immobilization. Example: impregnation with palladium followed by gold and prefix, followed by final fix. This technique can be used to help ensure the formation of shell catalysts as opposed to full-through catalysts.

In another embodiment, particularly suitable for chloride-free precursors, the support material is pretreated with a fixative to adjust the properties of the support material. In this embodiment, the support material is first impregnated with an acid or base solution (typically metal-free). After drying, the support material is impregnated with a precursor solution having an opposite acidity/basicity to the dried support material. The ensuing acid-base reaction forms a shell of the catalytic component on the support material. For example, the support material can be pretreated with nitric acid and then impregnated with an alkaline precursor solution such as Pd(OH) ₂ or Au(OH) ₃ . This technique can be viewed as employing a fixation step followed by a contact step.

The concentration of fixative in solution is typically in molar excess to the amount of catalytic component impregnated on the support material. The amount of fixative should be between about 1.0 to about 2.0, preferably about 1.1 to about 1.8 times the amount required to react with the catalytically active cations present in the water-soluble salt. In one embodiment using a high Au/Pd atomic or weight ratio, increasing the molar excess of hydroxide ions increases the _CO selectivity and activity of the resulting catalyst.

The fixative solution is supplied in a volume sufficient to cover the available free surface of the impregnated support material. This can be achieved by adding, for example, a volume greater than the pore volume of the contacting support material.

A combination of impregnation and immobilization steps can form a shell catalyst. However, the use of halide-free precursor solutions also allows the formation of shell catalysts with the optional elimination of the fixation step. In the absence of chloride precursors, the washing step can be avoided, as described later. Furthermore, the process may not include a step of immobilizing the catalytic components, which would otherwise require a continuation of the washing step. Since no washing steps are required, it is not necessary to immobilize the catalytic components for the continuation of the washing steps. Subsequent steps in the catalyst preparation process do not require immobilization of the catalytic components, so the remaining steps can be performed without additional preparatory steps. In summary, the use of chloride-free precursors allows catalyst or procatalyst production processes without cleaning steps, thereby reducing the number of steps required to produce catalysts and eliminating the need for disposal of chloride-containing waste.

cleaning steps

After the immobilization step, the immobilized support material may be washed to remove any halide residues on the support or otherwise treated to eliminate Potential adverse effects of pollutants. The washing step involves washing the immobilized support material in water, preferably deionized water. Cleaning can be done intermittently or continuously. Washing at room temperature should be continued until the effluent wash water has a halide ion content of less than about 1000 ppm, more preferably until the final effluent gives a negative result in the silver nitrate test. The cleaning step may be performed after or simultaneously with the reduction step (described later), but is preferably performed before. As mentioned above, the use of a halide-free precursor solution eliminates the cleaning step.

Roasting step

After contacting the at least one catalytic component with the support material, a calcining step may be employed. The firing step typically precedes the reduction step and follows the fixation step (if used), but can also be performed elsewhere in the process. In another embodiment, the calcining step follows the reducing step. The calcining step involves heating the support material in a non-reducing (ie oxidizing or inert) atmosphere. During calcination, the catalytic component on the support material is at least partially decomposed from its salt to a mixture of its oxide and free metal forms.

For example, the firing step is performed at a temperature in the range of about 100°C to about 700°C, preferably between about 200°C and about 500°C. The non-reducing gas used for firing may include one or more inert or oxidizing gases such as helium, nitrogen, argon, xenon, nitrogen oxides, oxygen, air, carbon dioxide, or a combination thereof. In one embodiment, the calcining step is performed in an atmosphere of substantially pure nitrogen, oxygen, air, or combinations thereof. The firing time can vary, but is preferably between about 1 and 5 hours. The degree of decomposition of the catalytic component salt is related to the temperature used and the length of calcination of the impregnated catalyst, which can be tracked by monitoring the volatile decomposition products.

One or more calcining steps may be employed such that calcining may be performed at any time after contacting the at least one catalytic component with the support material. Preferably the final calcination step occurs before the gold catalytic component contacts the zirconia support material. Alternatively, calcination of the gold-containing zirconia support material is performed at a temperature below about 300°C. By avoiding calcining the gold-containing zirconia support material at temperatures above about 300 °C, the risk of adversely affecting the _CO selectivity of the resulting catalyst is reduced.

Typical protocols that include a firing step include: a) palladium impregnation followed by firing followed by gold impregnation; b) palladium and rhodium co-impregnation followed by firing followed by gold impregnation; c) palladium impregnation followed by firing followed by rhodium impregnation followed by firing, impregnating with gold; or d) impregnating with palladium and rhodium, impregnating with gold, and firing.

restore steps

Another step common here is to at least partially convert any remaining catalytic components from the salt or oxide form to a catalytically active state, for example by a reduction step. This is typically accomplished by exposing the salt or oxide to a reducing agent, examples of which include ammonia, carbon monoxide, hydrogen, hydrocarbons, alkenes, aldehydes, alcohols, hydrazine, primary amines, carboxylic acids, carboxylate salts, carboxylate esters, and its combination. Hydrogen, ethylene, propylene, basic hydrazine and basic formaldehyde and combinations thereof are preferred reducing agents, with ethylene and hydrogen mixed with an inert gas being particularly preferred. Although reduction using a gaseous environment is preferred, a reduction step carried out in a liquid environment (eg, using a reducing solution) may also be used. The temperature selected for reduction may range from ambient temperature to about 550°C. Reduction times typically vary from about 1 to about 5 hours.

Since the method employed to reduce the catalytic components may affect the properties of the finished catalyst, the conditions used for reduction may vary depending on whether high activity, high selectivity, or some balance of these properties is desired.

In one embodiment, palladium is contacted with a support material, fixed and reduced, followed by contacting and reducing with gold, as described in US 6,486,093, 6,015,769 and related patents, all of which are incorporated herein by reference.

Typical protocols involving a reduction step include: a) impregnation with palladium followed by optional roasting, impregnation with gold followed by reduction; b) co-impregnation with palladium and gold followed by optional roasting followed by reduction; or c) impregnation with palladium followed by Optionally fired, then reduced, then impregnated with gold.

modification step

Usually after the reduction step and after the catalyst is used, a modification step is desired. While the catalyst can be used with a modification step, this step has several benefits, including extending the useful life of the catalyst. The modification step, sometimes referred to as the activation step, can be performed in a conventional manner. That is, the reduced support material is contacted with a modifier such as an alkali metal carboxylate and/or alkali metal hydroxide after use. The customary alkali metal carboxylates such as the sodium, potassium, lithium and cesium salts of C2-4 aliphatic carboxylic acids are used for this purpose. Preferred activators in the production of VA are alkali metal acetates, most preferably potassium acetate (KOAc).

The support material may optionally be impregnated with a solution of modifier. After drying, the catalyst may contain, for example, from about 10 to about 70, preferably from about 20 to about 60 g modifier/L catalyst.

The preparation method of alkenyl alkanoate

The present invention is useful for the production of alkenyl alkanoates from olefins, alkanoic acids and oxygen-containing gases in the presence of a catalyst. Preferred olefin feedstocks contain 2 to 4 carbon atoms (eg ethylene, propylene and n-butene). The preferred alkanoic acid starting materials used in the process of the present invention for producing alkenyl alkanoates contain 2 to 4 carbon atoms (eg, acetic acid, propionic acid and butyric acid). Preferred products of this process are VA, vinyl propionate, vinyl butyrate, and allyl acetate. The most preferred feedstocks are ethylene and acetic acid, with VA being the most preferred product. Accordingly, the present invention is applicable to the production of ethylenically unsaturated carboxylic acid esters from ethylenically unsaturated compounds, carboxylic acids and oxygen in the presence of catalysts. Although the remainder of this specification discusses only VA, it is to be understood that the catalysts, methods of preparation and production of the catalysts are equally applicable to other alkenyl alkanoates, and such description is not intended to limit the application of the invention to VA.

In producing VA with the catalyst of the present invention, a gas stream (comprising ethylene, oxygen or air, and acetic acid) is passed over the catalyst. The composition of the gas flow can be varied within wide limits taking into account the combustible zone of the outgoing gas flow. For example, the molar ratio of ethylene to oxygen can be from about 80:20 to about 98:2, and the molar ratio of acetic acid to ethylene can be from about 100:1 to about 1:100, preferably from about 10:1 to 1:10, most preferably About 1:1 to about 1:8. The gas stream may also comprise gaseous alkali metal acetates and/or inert gases such as nitrogen, carbon dioxide and/or saturated hydrocarbons. Useful reaction temperatures are elevated, preferably in the range of about 125-220°C. The pressure used may be slightly reduced, atmospheric or elevated, preferably a pressure of up to about 20 atmospheres gauge.

In addition to fixed bed reactors, the process for the production of alkenyl alkanoates and catalysts of the present invention can also be used in other types of reactions, such as fluidized bed reactors.

Example

The following examples are provided for illustration only and are not intended to be limiting. Solvent and reactant amounts are approximate. The Au/Pd atomic ratio can be converted to Au/Pd weight ratio and vice versa using the following equation: Au/Pd atomic ratio=0.54*(Au/Pd weight ratio), Au/Pd weight ratio=1.85(Au/Pd atomic ratio) . Reduction may be abbreviated as 'R' followed by the temperature (°C) at which the reduction is carried out. Similarly, calcination may be abbreviated as 'C' followed by the temperature (°C) at which calcination is performed, and the drying step may be abbreviated as "drying".

The catalysts of Examples 1-11 were prepared as described in the Examples and tested as follows, wherein the catalysts from Examples 1-7 were compared with each other and the catalysts from Examples 8-11 were compared with each other. Results are provided where available.

The catalysts of these examples were tested for activity and selectivity to various by-products in the production of vinyl acetate by the reaction of ethylene, oxygen and acetic acid. To carry out the test, about 60 ml of the catalyst prepared as described was placed in a stainless steel blue at the top and bottom of which the temperature could be measured with thermocouples. The blue was placed in a circulating Berty continuous stirred tank reactor maintained at a temperature providing about 45% oxygen conversion with an electric heating mantle. A gas mixture of about 50 standard liters (measured at NTP) of ethylene, about 10 standard liters of oxygen, about 49 standard liters of nitrogen, about 50 g of acetic acid, and about 4 mg of potassium acetate was passed through the blue at a pressure of about 12 atmospheres. , the catalyst was aged at these reaction conditions for at least 16 hours, followed by a 2-hour test, after which the reaction was terminated. On-line gas chromatographic analysis combined with off-line liquid product analysis by condensing the product stream at about 10°C was used for product analysis to obtain optimal results for the end products carbon dioxide (CO ₂ ), heavy ends (HE) and ethyl acetate (EtOAc). Analysis, the results of which can be used to calculate the percentage selectivity ( _CO Selectivity) of these substances of each embodiment. The relative activity of the reaction, expressed as an activity factor (activity), can be computed using a series of equations relating the activity factor to the catalyst temperature (during the reaction), oxygen conversion, and a series of kinetic parameters for the reaction to occur during the synthesis of VA calculate. More generally, the activity factor is typically inversely proportional to the temperature required to achieve constant oxygen conversion.

Rhodium Catalyst Example

Example 1: A support material containing palladium and rhodium metal was prepared as follows: first by incipient wetness with 82.5 ml of sodium tetrachloropalladium(II) ( _Na2PdCl4 ) sufficient to provide about 7 g of elemental palladium and about 0.29 g of elemental rhodium per liter _of catalyst ) and rhodium chloride trihydrate (RhCl ₃ ·3H ₂ O) aqueous solution impregnated 250ml carrier material, the carrier material is composed of nominal diameter 7mm, density about 0.569g/ml, absorption rate about 0.568g H ₂ O/g carrier , a surface area of about 160-175 m ² /g, and a pore volume of about 0.68 ml/g, made of Sud Chemie KA-160 silica spheres. Shake the vehicle in the solution for 5 minutes to ensure complete absorption of the solution. The treated support was then mixed with 283 ml of 120% _NaOH in the amount required to convert palladium and rhodium to their hydroxides by spin impregnation at about 5 rpm The aqueous solution was contacted for 2.5 hours to immobilize palladium and rhodium on the support in the form of palladium(II) hydroxide and rhodium(III) hydroxide. The solution was drained from the treated support, and the support was rinsed with deionized water and dried in a fluid bed dryer at 100° C. for 1.2 hours. The support material containing palladium hydroxide and rhodium hydroxide was then impregnated with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl ₄ and 2.71 g of a 50% NaOH solution (1.8 equivalents to Au) using the incipient wetness method. The NaOH-treated pellets were allowed to stand overnight to ensure precipitation of the Au salts as insoluble hydroxides. The pellets were rinsed thoroughly (-5 hours) with deionized water to remove chloride ions, then dried in a fluid bed dryer at 100°C for 1.2 hours. These supports containing palladium, rhodium and gold were then calcined at 400°C for 2 hours in air, and allowed to cool naturally to room temperature. The support was contacted with gas phase _C2H4 (1% in nitrogen) at 150°C for 5 hours to reduce palladium, rhodium and gold _. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours.

Example 2: A support material comprising palladium hydroxide and rhodium hydroxide was prepared as described in Example 1 . The support containing palladium and rhodium was then calcined at 400°C for 2 hours in air, and allowed to cool naturally to room temperature. The calcined support material containing palladium hydroxide and rhodium hydroxide was then impregnated by incipient wetness 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 to Au). The NaOH-treated pellets were allowed to stand overnight to ensure precipitation of the Au salts as insoluble hydroxides. The pellets were rinsed thoroughly (-5 hours) with deionized water to remove chloride ions, then dried in a fluid bed dryer at 100°C for 1.2 hours. The support was then contacted with gas phase _C2H4 (1% in nitrogen) at 150°C _for 5 hours to reduce palladium, rhodium and gold. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours.

Example 3: A support material comprising palladium hydroxide and rhodium hydroxide was prepared as described in Example 1 . The support containing palladium and rhodium was then calcined at 400°C for 2 hours in air, and allowed to cool naturally to room temperature. The support was then _contacted with gaseous _C2H4 (1% in nitrogen) at 150°C for 5 hours to reduce the calcined support material containing palladium hydroxide and rhodium hydroxide. The palladium and rhodium metal-containing support was then impregnated by incipient wetness with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl ₄ and 2.71 g of a 50% NaOH solution (1.8 equivalents relative to Au). The NaOH-treated pellets were allowed to stand overnight to ensure precipitation of the Au salts as insoluble hydroxides. The pellets were rinsed thoroughly (-5 hours) with deionized water to remove chloride ions, then dried in a fluid bed dryer at 100°C for 1.2 hours. The support was then contacted with gas phase _C2H4 (1% in nitrogen) at 150°C _for 5 hours to reduce palladium, rhodium and gold. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours.

Example 4: A support material comprising palladium hydroxide and rhodium hydroxide was prepared as described in Example 1 . The support containing palladium and rhodium was then calcined at 400°C for 2 hours in air, and allowed to cool naturally to room temperature. The support was then _contacted with gaseous _C2H4 (1% in nitrogen) at 150°C for 5 hours to reduce the calcined support material containing palladium hydroxide and rhodium hydroxide. The palladium and rhodium metal-containing support was then impregnated with an aqueous solution (81 ml) containing 1.1 g of Au from _KAuO2 using incipient wetness. The pellets were dried in a fluid bed dryer at 100°C for 1.2 hours. The support was then contacted with gas phase _C2H4 (1% in nitrogen) at 150°C _for 5 hours to reduce palladium, rhodium and gold. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours.

Example 5: A support material comprising palladium hydroxide and rhodium hydroxide was prepared as described in Example 1 . The support containing palladium and rhodium was then calcined at 400°C for 2 hours in air, and allowed to cool naturally to room temperature. The palladium and rhodium metal-containing support was then impregnated with an aqueous solution (81 ml) containing 1.1 g of Au from _KAuO2 using incipient wetness. The pellets were dried in a fluid bed dryer at 100°C for 1.2 hours. The support was then contacted with gas phase _C2H4 (1% in nitrogen) at 150°C _for 5 hours to reduce palladium, rhodium and gold. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours.

Example 6: A support material comprising palladium hydroxide and rhodium hydroxide was prepared as described in Example 1 . The support containing palladium and rhodium was then calcined at 400°C for 2 hours in air, and allowed to cool naturally to room temperature. The support was then _contacted with gaseous _C2H4 (1% in nitrogen) at 150°C for 5 hours to reduce the calcined support material containing palladium hydroxide and rhodium hydroxide. The palladium and rhodium metal-containing support was then impregnated with an aqueous solution (81 ml) containing 1.1 g of Au from _KAuO2 and 10 g of potassium acetate using the incipient wetness method. The pellets were dried in a fluid bed dryer at 100°C for 1.2 hours.

Example 7 (reference catalyst): A support material containing palladium metal was prepared as follows: first by the incipient wetness method with 82.5 ml of an aqueous solution of sodium tetrachloropalladium (II) (Na ₂ PdCl ₄ ) sufficient to provide about 7 g of elemental palladium per liter of catalyst Impregnate 250ml of carrier material consisting of a nominal diameter of 7 mm, a density of about 0.569 g/ml, an absorption rate of about 0.568 g H ₂ O/g carrier, a surface area of about 160-175 m ² /g, and a pore volume of about 0.68 ml/g g of Sud Chemie KA-160 silica spheres. Shake the vehicle in the solution for 5 minutes to ensure complete absorption of the solution. The treated support was then contacted by spin impregnation at about 5 rpm with 283 ml of an aqueous 110% sodium hydroxide solution prepared from 50% w/w NaOH/ _H2O in an amount required to convert palladium to its hydroxide For 2.5 hours, the palladium was immobilized on the support as palladium(II) hydroxide. The solution was drained from the treated support, and the support was rinsed with deionized water and dried in a fluid bed dryer at 100° C. for 1.2 hours. The palladium hydroxide-containing support material was then impregnated using the incipient wetness method with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl ₄ and 2.71 g of a 50% NaOH solution (1.8 equivalents relative to Au). The NaOH-treated pellets were allowed to stand overnight to ensure precipitation of the Au salts as insoluble hydroxides. The pellets were rinsed thoroughly (-5 hours) with deionized water to remove chloride ions, then dried in a fluid bed dryer at 100°C for 1.2 hours. The support was then reduced by _contacting the support with gas phase _C2H4 (1% in nitrogen) at 150°C for 5 hours to reduce the support containing palladium and gold. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours. Table 1 shows the comparison of the _CO2 selectivity and activity of the catalysts of Examples 1 and 7.

Table 1 _CO2 selectivity active Example 1 9.89 2.32 Embodiment 7 (reference catalyst) 11.13 2.36

Layered Carrier Example

Example 8: 40g of ZrO ₂ (RC-100, supplied by DKK) was calcined at 650°C for 3 hours. The BET surface area of the resulting material was 38 m ² /g. This material was ball milled with 120ml DI water for 6 hours. This sol was mixed with 22.5g of zirconium acetate binder (ZA-20) supplied by DKK and sprayed onto 55g of bentonite KA-160 balls with OD~7.5mm. The coated balls were fired at 600°C for 3 hours. Observation under a microscope showed that a uniform shell with a thickness of 250 μm had formed.

Example 9: 20 g of ZrO ₂ (XZ16075, BET surface area 55 m ² /g) was impregnated with Pd(NO ₃ ) ₂ solution (Aldrich) to a Pd loading of 39 mg/g ZrO ₂ . The impregnated material was dried and fired at 450°C for 4 hours. The material was ball milled with 60ml of DI water for 4 hours, mixed with 11g of binder (ZA-20), and sprayed onto 30g of bentonite KA-160 balls. The balls were fired at 450°C for 3 hours. This resulted in the formation of a uniform shell with a thickness of 160 μm.

Example 10: Balls from Example 8 were impregnated with a potassium acetate solution to a loading of 40 mg KOAc/ml KA-160, dried and calcined at 300° C. for 4 hours. A solution containing 9.4 mM Pd (from Pd(NH ₃ ) ₄ (OH) ₂ , supplied by Heraeus) and 4.7 mM Au (from a 1M solution, Au(OH) ₃ "Alfa" in 1.6M KOH) was then sprayed onto over these balls. The material was reduced with a 5% _H2 /95% _N2 mixture at 200°C for 4 hours. These spheres were crushed and tested in a miniature fixed bed reactor under the conditions described in the experimental section. ~6% _CO2 selectivity was achieved at 45% oxygen conversion.

Example 11 (reference catalyst): The catalyst prepared in Example 7 was used as a reference catalyst. Table 2 shows the comparison of catalyst _CO2 selectivity and activity of Examples 9-11.

Table 2 _CO2 selectivity active Example 9 9.33 2.08 Example 10 9.03 1.69 Embodiment 11 (reference catalyst) 11.13 2.36

Examples of Zirconia Support Materials and Chloride-Free Precursors

This set of embodiments employs the following general operations. Zirconia support material catalysts were prepared as follows: Catalyst supports of various shapes were crushed and sieved. Zirconia support materials were supplied by NorPro (XZ16052 and XZ16075), DKK and MEI. Silica support material was provided by Degussa and Sud Chemie. The 180-425 μm sieved sections were impregnated (simultaneously or sequentially, with an intermediate drying step at 110 °C and an optional intermediate roasting step) with Pd and Au precursor solutions to incipient wetness, optionally calcined in air, with 5 % _H2 / _N2 gas reduction, post-impregnation with KOAc solution, drying at 100 °C under _N2 , and screening in an 8 × 6 multichannel fixed-bed reactor. The KOH solution of Au(OH) ₃ was used as the Au precursor. Aqueous solutions of Pd(NH ₃ ) ₄ (OH) ₂ , Pd(NH ₃ ) ₂ (NO ₂ ) ₂ , Pd(NH ₃ ) ₄ (NO ₃ ) ₂ and Pd(NO ₃ ) ₂ were used as Pd precursors.

A silica support material catalyst reference was prepared as follows: A support material containing palladium and rhodium metal was first prepared by incipient wetness with 82.5 ml of sodium tetrachloropalladium(II) ( _Na2PdCl ) sufficient to provide about 7 g of elemental palladium per liter of catalyst. ₄ ) aqueous solution impregnated 250ml carrier material, said carrier material is composed of a nominal diameter of 7mm, a density of about 0.569g/ml, an absorption rate of about 0.568gH ₂ O/g carrier, a surface area of about 160-175m ² /g, and a pore volume of about 0.68ml/g of Sud Chemie KA-160 silica spheres. Shake the vehicle in the solution for 5 minutes to ensure complete absorption of the solution. The treated support was then contacted by spin impregnation at about 5 rpm with 283 ml of 110% aqueous sodium hydroxide solution prepared from 50% w/w NaOH/ _H2O in an amount equal to that required to convert palladium to its hydroxide for 2.5 hours, the palladium is immobilized on the support in the form of palladium(II) hydroxide. The solution was drained from the treated support, and the support was rinsed with deionized water and dried in a fluid bed dryer at 100° C. for 1.2 hours. The palladium hydroxide-containing support material was then impregnated using the incipient wetness method with an aqueous solution (81 ml) containing 1.24 g of Au from NaAuCl ₄ and 2.71 g of a 50% NaOH solution (1.8 equivalents relative to Au). The NaOH-treated pellets were allowed to stand overnight to ensure precipitation of the Au salts as insoluble hydroxides. The pellets were rinsed thoroughly (-5 hours) with deionized water to remove chloride ions, then dried in a fluid bed dryer at 100°C for 1.2 hours. The support _was then reduced by contacting the support with gas phase _C2H4 (1% in nitrogen) at 150°C for 5 hours to reduce the support containing palladium and gold. Finally the catalyst was impregnated by incipient wetness with an aqueous solution of 10 g of potassium acetate in 81 ml of H ₂ O and dried in a fluid bed dryer at 100° C. for 1.2 hours. Before testing, the catalyst was crushed and sieved. A sieve fraction with a particle size in the range of 180-425 μm was used.

A catalyst library arranged in 8 rows×6 columns in glass bottles was designed, and a rack of 36 glass bottles was installed on a vortexer (vortexer), agitated while distributing the metal precursor solution with a Cavro ^TM liquid dispenser. 0.4 ml of carrier was used per unit, per vial synthesis, and per reaction vessel.

KOAc loading is reported as g KOAc/L catalyst volume or μmol KOAc on 0.4 ml support. To normalize the Au loading, the relative atomic ratio of Au to Pd is reported as Au/Pd. The Pd loading is expressed as mg Pd/0.4 ml carrier volume (i.e. the absolute amount of Pd in the reaction vessel).

The screening protocol employed a temperature ramp from 145°C to 165°C in 5°C increments, a fixed space velocity of 175% (1.5mg Pd on 0.4ml support). 100% space velocity is defined as follows: 5.75 sccm nitrogen, 0.94 sccm oxygen, 5.94 sccm ethylene, and 5.38 μl/min acetic acid are passed through each of the 48 catalyst vessels (all having an internal diameter of about 4 mm). _CO2 selectivity was plotted against oxygen conversion, a linear fit was performed and the calculated (in most cases interpolated) _CO2 selectivity at 45% oxygen conversion is reported in the performance summary table below. The temperature at 45% oxygen conversion was calculated from the temperature rise (linear fits for _CO2 selectivity and oxygen conversion versus reaction temperature are also reported). The lower the calculated temperature, the higher the catalyst activity. The space-time yield (STY; g VA produced/ml catalyst volume/h) at 45% oxygen conversion is a measure of catalyst productivity.

Example 12: 400 μl of ZrO ₂ carriers XZ16075 (55m ² /g, when supplied) and XZ16052 (pre-calcined at 650°C/2h to reduce the surface area to 42m ² /g) were impregnated with 3 different Pd solutions to incipient wetness, Dry at 110°C for 5 hours, impregnate with KAuO ₂ (0.97M Au material solution) to incipient wetness, dry at 110°C for 5 hours, reduce in 5% H ₂ /N ₂ gas at 350°C for 4 hours, after using KOAc Dipping and drying at 110°C for 5 hours. These Pd/Au/ _ZrO2 samples (shells) were then diluted 1/9.3 with KA160 diluent (preloaded with 40 g/l KOAc), i.e. 43 μl Pd/Au/ _ZrO2 shells and 357 μl diluent (total fixed bed volume 400 μl) into the reaction vessel. The Pd loading was 14 mg Pd in a 400 μl ZrO ₂ shell (or 14*43/400=14/9.3=1.5 mg Pd in the reaction vessels of all units). The Pd precursors are: Pd(NH ₃ ) ₂ (NO ₂ ) ₂ in columns 1 and 4, Pd(NH ₃ ) ₄ (OH) ₂ in columns 2 and 5, Pd(NH ₃ ) ₄ ( NO ₃ ) ₂ . Au/Pd=0.3 in the 2nd and 5th row, Au/Pd=0.6 in the 3rd row, Au/Pd=0.9 in the 4th, 6th and 7th row. The KOAc loading was: 114 μmol for rows 2, 3 and 5 and 147 μmol for rows 4, 6 and 7. Silica reference catalyst is loaded to row 1. Screening was performed at a fixed SV using the warm-up screening protocol described. Screening results are shown in Table 3.

table 3 _CO2 selectivity temperature at STY Cl precursor on _SiO2 7.37 156.6 729 Pd(NH ₄ ) ₂ (OH) ₂ on ZrO ₂ 5.79 152.4 787 Pd(NH ₃ ) ₄ (NO ₃ ) ₂ on ZrO ₂ 5.90 152.3 783 Pd(NH ₃ ) ₂ (NO ₂ ) ₂ on ZrO ₂ 5.57 150.7 795

*The data shown are taken from the average of two Au/Pd atomic ratios (i.e. 0.3 and 0.6) and two different _ZrO2 supports.

Example 13: 400 μl of ZrO ₂ carriers XZ16075 (55m ² /g, when supplied) and XZ16052 (pre-baked at 650°C/2h to reduce the surface area to 42m ² /g) with Pd(NH ₃ ) ₄ (OH) ₂ ( 1.117M Pd liquid) impregnated to incipient wetness, baked in air at 350°C for 4 hours, impregnated with KAuO ₂ (0.97M Au liquid) to incipient wetness, dried at 110°C for 5 hours, and baked in 5% H ₂ /N ₂ Reduction at 350°C for 4 hours in generated gas, post-impregnation with KOAc, and drying at 110°C for 5 hours. These Pd/Au/ZrO ₂ samples (shells) were then diluted 1/12 with KA160 diluent (preloaded with 40 g/l KOAc), i.e. 33.3 μl Pd/Au/ZrO ₂ catalyst and 366.7 μl diluent (total fixed bed volume 400 μl) into the reaction vessel. The library design and cell composition were as follows: columns 1-3 _ZrO2XZ16075 (left half of the library) and columns 4-6 _ZrO2XZ16052 (650°C). The Pd loading is: 18 mg Pd in a 400 μl _ZrO shell in cell G2, column 3 (cell B3-G3), cell G5, column 6 (cell B6-G6) (or 18*33/400=18 in the reaction vessel 10 mg Pd in a 400 μl ZrO _shell (or 10*33/400=10/12 mgPd in the reaction vessel) in columns 1 (units A1-G1) and 4 (units A4-G4); 14mg Pd (or 14*33/400=14/12mg Pd in the reaction vessel) in a 400μl _ZrO2 shell in column 2 (units B2-F2) and column 5 (units B5-F5). Au/Pd=0.3 in rows 2 and 5, Au/Pd=0.5 in rows 3 and 6, Au/Pd=0.7 in rows 4 and 7 (except for cells A1, A4, G2, G5, where Au/Pd is 0.3) . The KOAc loading was 114 μmol (units D3, G3, D6, G6 where the KOAc loading was 147 μmol). Silica reference catalyst is loaded to row 1. Screening was performed at a fixed SV using the warm-up screening protocol described. Screening results are shown in Table 4.

Table 4 _CO2 selectivity Temperature at 45% conversion STY Au/Pd atomic ratio 0.3 0.5 0.7 0.3 0.5 0.7 0.3 0.5 0.7 Cl precursor on _SiO2 6.98 - - 154.8 - - 742.8 - - ZrO ₂ : XZ16052 6.06 5.31 5.38 153.7 152.3 154.9 776.8 806.0 803.0 ZrO ₂ : XZ16075 6.18 5.62 5.71 147.5 151.0 154.4 773.8 791.6 790.3

Example 14: ZrO ₂ carrier (provided by NorPro, XZ16075, 180-425 μm sieve fraction, density 1.15 g/ml, pore volume 475 μl/g, BET surface area 55 m ² /g) was mixed with Pd(NO ₃ ) ₂ precursor solution Immerse to incipient wetness, dry at 110°C, bake in air at 250°C (column 1-2), 350°C (column 3-4), 450°C (column 5-6), and use KAuO ₂ solution (Au (OH) ₃ was dissolved in KOH to prepare) impregnation, dried at 110°C, reduced with 5% H ₂ /N ₂ gas generation at 350°C for 4 hours, and post-impregnated with KOAc solution. The library has a gradient from 25 to 50 g/l of KOAc in rows 2 to 7. The Pd loading was 1.5 mg Pd on 0.4 ml carrier. Two different Au loadings were chosen (columns 1, 3, 5 Au/Pd = 0.5, columns 2, 4, 6 Au/Pd = 0.7). Silica reference catalyst is loaded to row 1. Screening was performed in an MCFB48 VA reactor at a fixed SV using the temperature ramp screening protocol described. Screening results are shown in Table 5.

table 5 _CO2 selectivity Temperature at 45% conversion STY Cl precursor on _SiO2 7.21 154.7 734 Pd(NO ₃ ) ₂ on ZrO ₂ 6.10 145.3 775

*The data shown are taken from the average of two Au/Pd atomic ratios (i.e. 0.5 and 0.7) at 40 g/L KOAc, calcined at 450°C and reduced at 350°C.

Example 15: Using ZrO ₂ carrier (provided by NorPro, XZ16075, 180-425 μm sieve fraction, density 1.15 g/ml, pore volume 575 μl/g, BET surface area 55 m ² /g) with Pd(NO ₃ ) ₂ precursor solution Impregnate to incipient wetness, dry at 110°C, bake in air at 450°C, impregnate with KAuO ₂ solution (prepared by dissolving Au(OH) ₃ in KOH), dry at 110°C, use 5% H ₂ /N ₂ to generate gas in Reduction at 200°C (column 1-2), 300°C (column 3-4), or 400°C (column 5-6), post impregnation with KOAc solution. The library has a gradient from 15 to 40 g/l of KOAc in rows 2 to 7. The Pd loading was 1.5 mg Pd on 0.4 ml carrier. Two different Au loadings were selected (columns 1, 3, 5 Au/Pd = 0.5, columns 2, 4, 6 Au/Pd = 0.7). Silica reference catalyst is loaded to row 1. Screening was performed at a fixed SV in an MCFB48VA reactor using the temperature ramp screening protocol described. Screening results are shown in Table 6.

Table 6 _CO2 selectivity Temperature at 45% conversion STY Cl precursor on _SiO2 7.11 154.2 738 Pd(NO ₃ ) ₂ on ZrO ₂ 5.51 145.4 797

*The data shown are taken from the average of two Au/Pd atomic ratios (i.e. 0.5 and 0.7) at 40 g/L KOAc, calcination at 450°C and reduction at 400°C.

It is obvious that the functions or structures of a plurality of components or steps may be combined into a single component or step, or that the functions or structures of one step or component may be dispersed in a plurality of steps or components. The present invention is intended to include all such combinations. Unless otherwise stated, the dimensions and geometries of the various structures described herein are not intended to limit the invention, and other dimensions or geometries are possible. Multiple structural components or steps may be provided by a single integral structure or step. Alternatively, a single overall structure or step may be divided into separate components or steps. Furthermore, while a feature of the invention may be described in only one illustrated embodiment, that feature may be used in any given application in combination with one or more other features of other embodiments. It can also be seen from the above that the fabrication of the unique structures herein and their operation also constitute the method of the invention.

The explanations and illustrations given herein are to acquaint others skilled in the art with the invention, its principles and its practical application. Those skilled in the art can adopt the present invention in its different forms, which can be best suited to the needs of practical applications. Therefore, the specific embodiments of the invention given are not intended to limit the invention. Accordingly, the scope of the invention should be determined not with reference to the above description but with that of the appended claims, along with their full scope of equivalents to which such claims are entitled. The contents of all papers and references, including patent applications and publications, are incorporated herein by reference.

Claims (60)

1. A method for the production of a catalyst or procatalyst suitable for promoting the production of alkenyl alkanoates, comprising: The first support material is layered on the second support material to produce a layered support material, wherein the layered support material comprises a catalytic component of palladium, gold, or a combination thereof in the first support material. 2. The method of claim 1, further comprising contacting said catalytic component with said first support material prior to said layering step. 3. The method of claim 1 or 2, further comprising contacting said catalytic component with said first support material after said layering step. 4. The method of any one of claims 1-3, wherein the catalytic component comprises palladium, gold, or a combination thereof. 5. The method of any one of claims 1-4, further comprising contacting palladium with said first support material prior to said layering step and contacting gold with said first support material after said layering step . 6. The method of any one of claims 1-5, further comprising contacting gold with said first support material prior to said layering step and contacting palladium with said first support material after said layering step . 7. The method of any one of claims 1-6, wherein the second support material is an inner layer and is substantially free of catalytic components. 8. The method of any one of claims 1-7, further comprising contacting at least one third component selected from the group consisting of W, Ni, Nb, Ta, Ti, Zr, Y, Re, Os, Fe, Cu, Co, Zn, In, Sn, Ce, Ge, Rh, Ga and combinations thereof. 9. The method of any one of claims 1-8, further comprising contacting said third component with said first support material after said layering step. 10. The method of any one of claims 1-9, further comprising contacting said third component with said first support material prior to said layering step. 11. The method of any one of claims 1-10, wherein the third component is a third catalytic component. 12. The method of any one of claims 1-11, further comprising a firing step prior to said layering step. 13. The method of any one of claims 1-12, further comprising a firing step after said layering step. 14. The method of any one of claims 1-13, further comprising a reducing step prior to said layering step. 15. The method of any one of claims 1-14, further comprising a reducing step after said layering step. 16. The method of any one of claims 1-15, further comprising a reducing step subsequent to the calcining step. 17. The method of any one of claims 1-16, further comprising contacting an alkali metal acetate with said support material prior to said layering step. 18. The method of any one of claims 1-17, further comprising contacting an alkali metal acetate with the support material after the layering step. 19. The method of any one of claims 1-18, further comprising impregnating the first support material with palladium, calcining the first support material, and impregnating the first support material with gold. 20. The method of any one of claims 1-19, further comprising impregnating the first support material with palladium, layering the first support material on the second support material, and layering the layered support material firing, and impregnating the first support material with gold. 21. The method of any one of claims 1-20, further comprising calcining the layered support material prior to contacting the catalytic component with the layered support material. 22. The method of any one of claims 1-21, further comprising contacting an alkali metal acetate with the layered support material prior to contacting the catalytic component with the layered support material. 23. The method of any one of claims 1-22, wherein the first and second support materials are porous. 24. The method of any one of claims 1-23, wherein the second support material is non-porous. 25. The method of any one of claims 1-24, wherein the first and second support materials comprise the same material. 26. The method of any one of claims 1-25, wherein the first and second support materials comprise different materials. 27. The method of any one of claims 1-26, wherein the first support material is selected from the group consisting of alumina, silica/alumina, zeolites, non-zeolitic molecular sieves, titania, zirconia, niobium oxide, silica, bentonite , clay, and combinations thereof. 28. The method of any one of claims 1-27, wherein the first support material comprises zirconia, silica, alumina, or combinations thereof. 29. The method of any one of claims 1-28, wherein the second support material is selected from the group consisting of alumina, silicon carbide, zirconia, titania, talc, niobium oxide, silica, bentonite, clay, metal, glass, Quartz, silicon nitride, alumina-silica, pumice, non-zeolitic molecular sieves, and combinations thereof. 30. The method of any one of claims 1-29, wherein the second support material comprises zirconia, silica, or alumina. 31. The method of any one of claims 1-36, wherein the second support material comprises pellets having a diameter of about 1 to about 10 mm. 32. The method of any one of claims 1-31, wherein the BET surface area of the first support material is between about 5 and about 300 ^m2 /g. 33. The method of any one of claims 1-32, wherein the BET surface area of the first support material is between about 5 and about 150 ^m2 /g. 34. The method of any one of claims 1-33, further comprising contacting an alkali metal acetate with the support material. 35. The method of any one of claims 1-34, further comprising a fixation step using a fixative. 36. The method of any one of claims 1-35, wherein the first support material has a thickness between about 5 and about 500 microns. 37. The method of any one of claims 1-36, wherein said layering step comprises layering said second support material on said first support material. 38. The method of any one of claims 1-37, wherein the contacting step comprises contacting the catalytic component with the first support material in the form of a substantially chloride-free precursor solution. 39. The method of any one of claims 1-38, wherein said layering step comprises contacting an adhesive with said first or second carrier material to promote adhesion between the materials. 40. The method of any one of claims 1-39, wherein the binder is selected from organic and inorganic binders. 41. The method of any one of claims 1-40, wherein the binder is a zirconia binder. 42. A composition for catalyzing the production of alkenyl alkanoate comprising: A layered support material comprising an inner layer and an outer layer on which at least palladium and gold are contacted to form a catalyst or procatalyst, wherein the inner layer is substantially free of palladium and gold. 43. The composition of claim 42, wherein said outer layer comprises a compound selected from the group consisting of alumina, silica/alumina, zeolites, non-zeolitic molecular sieves, titania, zirconia, niobium oxide, silica, bentonite, clay, and Combined materials. 44. The composition of claim 42 or 43, wherein the outer layer comprises zirconia, silica, alumina, or combinations thereof. 45. The composition of any one of claims 42-44, wherein the inner layer is selected from the group consisting of alumina, silicon carbide, zirconia, titania, talc, niobium oxide, silica, bentonite, clay, metal, glass, quartz , silicon nitride, alumina-silica, pumice, non-zeolitic molecular sieves, and combinations thereof. 46. The composition of any one of claims 42-45, wherein the inner layer comprises zirconia, silica and alumina. 47. The composition of any one of claims 42-46, wherein the palladium and gold have been calcined. 48. The composition of any one of claims 42-47, wherein the palladium and gold are reduced. 49. The composition of any one of claims 42-48, wherein the catalyst or procatalyst comprises between about 1 to about 10 grams of palladium per liter of catalyst and about 0.5 to about 10 grams of gold per liter of catalyst, the gold The amount is from about 10 to about 125 wt%, based on the weight of palladium. 50. The composition of any one of claims 42-49, wherein the atomic ratio of gold to palladium is between about 0.50 and about 1.00. 51. The composition of any one of claims 42-50, wherein palladium, gold and a third component are in contact with said outer layer, wherein said third component is selected from the group consisting of W, Ni, Nb, Ta, Ti, Zr , Y, Re, Os, Fe, Cu, Co, Zn, In, Sn, Ce, Ge, Rh, Ga and combinations thereof. 52. The composition of any one of claims 42-51, wherein the catalyst or procatalyst comprises rhodium and palladium in an atomic ratio of rhodium to palladium between about 0.01 and about 0.5. 53. The composition of any one of claims 42-52, wherein the layered carrier material comprises a granular carrier material or a powdered carrier material. 54. A process for the production of alkenyl alkanoate comprising: A feed comprising an olefin, an alkanoic acid, and an oxidizing agent is contacted with a catalyst or procatalyst comprising palladium in combination with gold or rhodium supported on a layered support material. 55. The method of claim 54, wherein the olefin is ethylene, the alkanoic acid is acetic acid, and the oxidizing agent is an oxygen-containing gas. 56. The method of claim 54 or 55, wherein the atomic ratio of gold to palladium is between about 0.50 and about 1.00. 57. The method of any one of claims 54-56, wherein the catalyst or procatalyst comprises between about 1 to about 10 grams of palladium per liter of catalyst and about 0.5 to about 10 grams of gold per liter of catalyst, the amount of gold From about 10 to about 125 wt%, based on the weight of palladium. 58. The method of any one of claims 54-56, wherein the inner layer comprises silicon oxide. 59. The method of any one of claims 54-57, wherein the outer layer comprises zirconia. 60. The method of any one of claims 54-59, wherein the catalyst or procatalyst is a shell catalyst or procatalyst, an egg yolk catalyst or procatalyst, a protein catalyst or procatalyst, or a full-through catalyst or procatalyst .