The present disclosure generally relates to a silver-based epoxidation catalyst. In certain embodiments, a method is provided for modulating the reactivity of the silver-based epoxidation catalyst, comprising the catalyst being post-treated with at least two different salt solutions. In some embodiments, the treatment results in the deposition of one or more metals onto the surface of the catalyst. In further embodiments, method is also provided of using the silver catalyst to generate an epoxide from an olefin.

A silver-based ethylene epoxidation catalyst is provided that exhibits improved performance, i.e., selectivity and activity decline. The catalyst that exhibits the improved performance includes greater than about 20% by weight of silver disposed on an alpha-alumina carrier, and a promoting amount of one or more promoters disposed on the alpha-alumina carrier. The silver is present on the alpha-alumina carrier as silver particles having a diameter of greater than about 150 nm and a distribution density of about 20 particles per 1 square micron or less.

A shaped catalyst body for producing ethylene oxide by gas-phase oxidation of ethylene, comprising silver deposited on a porous refractory support, the shaped catalyst body having a first face side surface, a second face side surface and a circumferential surface, characterized by a content of at least 20 wt.-% of silver, relative to the total weight of the shaped catalyst body; a multilobe structure; a plurality of passageways extending from the first face side surface to the second face side surface, outer passageways being arranged around a central passageway with one outer passageway being assigned to each lobe, wherein neighboring outer passageways are arranged essentially equidistantly to each other and the outer passageways are arranged essentially equidistantly to the central passageway; a minimum wall thickness A between two neighboring passageways in the range of 0.6 to 1.3 mm; a minimum wall thickness B between each outer passageway and the circumferential surface in the range of 1.1 to 1.8 mm; and a BET surface area in the range of 1.6 to 3.0 m.sup.2/g. The shaped catalyst bodies allow for a favorable balance between mechanical stability, pressure drop and selectivity. The invention also relates to a process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of a shaped catalyst body as defined above. The invention further relates to a process for preparing a shaped catalyst body as above, comprising i) impregnating a refractory support having a BET surface area in the range of 1.4 to 2.5 m.sup.2/g with a silver impregnation solution; and ii) subjecting the impregnated refractory support to a calcination process; wherein steps i) and ii) are optionally repeated.

A carrier for an ethylene epoxidation catalyst, the carrier comprising a porous alumina body formed of sintered particles of alumina in a substantial absence of inorganic binder species other than alumina, wherein the substantial absence of inorganic binder species corresponds to an amount of less than 0.6 wt % inorganic binder species other than alumina and comprises at least a substantial absence of silicon-containing species.

An ethylene epoxidation catalyst is disclosed that comprises a fluoride-mineralized carrier having silver and a rhenium promoter deposited thereon, wherein the fluoride-mineralized carrier has: a total fluorine (TF) content less than 5000 ppm as measured by XRF, a water extractable fluorine (WEF) content greater than 45 ppm as measured by microwave extraction and ion specific electrode, and wherein the ratio of TF:WEF is between 10 and 110. Associated methods of manufacturing such catalysts and epoxidation methods using such catalysts are similarly provided.

A carrier having at least three lobes, a first end, a second end, a wall between the ends and a non-uniform radius of transition at the intersection of an end and the wall is disclosed. A catalyst comprising the carrier, silver and promoters deposited on the carrier and useful for the epoxidation of olefins is also disclosed. A method for making the carrier, a method for making the catalyst and a process for epoxidation of an olefin with the catalyst are also disclosed.

The present invention relates to a high-performance polyoxometalate catalyst and a method of preparing the same. More particularly, the present invention provides a high-performance polyoxometalate catalyst, the activity and selectivity of which may be improved by controlling the content of vanadium and the like and which has superior reproducibility and may unsaturated carboxylic acid from unsaturated aldehyde in a high yield for a long time, a method of preparing the same, and the like.

An oxidation catalyst for treating an exhaust gas from a diesel engine and an exhaust system comprising the oxidation catalyst are described. The oxidation catalyst comprises a washcoat region disposed on a substrate, wherein the washcoat region comprises: palladium (Pd), gold (Au) and a support material, wherein the palladium (Pd) and gold (Au) are supported on the support material; and a molecular sieve catalyst, wherein the molecular sieve catalyst comprises a noble metal and a molecular sieve.

Methods of preparing a second high-efficiency, rhenium-promoted silver catalyst for producing alkylene oxide from an alkylene based on a first catalyst are disclosed and described. In accordance with the disclosed methods, the first and second catalysts include at least one promoter that includes a rhenium promoter. The target catalyst concentrations of one or more promoters of the at least one promoter on the second catalyst are determined based on the values of a catalyst reference property for the two catalysts and the concentration of the one or more promoters of the at least one promoter on the first catalyst. Suitable catalyst reference properties include carrier specific surface area and silver specific surface area. Reaction systems utilizing the first and second catalysts are also described.

An epoxidation catalyst comprising silver, cesium, rhenium and tungsten deposited on an alumina support, wherein the catalyst comprises 20 to 50 wt.-% of silver, relative to the weight of the catalyst, an amount of cesium C.sub.cs of at least 7.5 mmol per kg of catalyst, and an amount of rhenium CR6 and an amount of tungsten Cw so as to meet the following requirements: C.sub.Re6.7 mmol per kg of catalyst; and C.sub.Re+(2c.sub.w)13.2 mmol per kg of catalyst. The epoxidation catalyst allows for a more efficient conversion of ethylene oxide by gas-phase oxidation of ethylene, particularly displaying high selectivity and high activity. The invention also relates to a process for preparing an epoxidation catalyst as defined in above, comprising i) impregnating an alumina support with a silver impregnation solution; and ii) subjecting the impregnated refractory support to a calcination process; wherein steps i) and ii) are optionally repeated, and at least one silver impregnation solution comprises rhenium, tungsten and cesium. The invention moreover relates to a process for producing ethylene oxide by gas-phase oxidation of ethylene, comprising reacting ethylene and oxygen in the presence of an epoxidation catalyst according to any one of the preceding claims.