The invention concerns a catalyst for hydrogenation of unsaturated hydrocarbons.
A method for catalytic hydrogenation of acetylenic compounds with 2 or 3 carbon atoms to the corresponding olefin compounds is known from EP-A-0 686 615, in which a supported catalyst in the form of spheres or extrudate is used, containing palladium and silver. At least 80% of the palladium and at least 60% of the silver are located close to the surface of the catalyst. The catalyst preferably contains aluminum oxide as a support and 0.01 to 0.5 wt. % palladium and 0.001 to 0.002 wt. % silver. Because of the form of the support, the activity and selectivity, in relation to the weight, are relatively low. Only a relatively low space velocity can be used with this catalyst and the pressure drop is relatively high.
A catalyst, containing Pd and Ag for selective hydrogenation of acetylene, is known from EP-A-0 689 872. The catalyst is produced by treating a support material (preferably aluminum oxide) in the form of spheres or cylindrical pellets, with an alkaline solution of reducing agent for Pd and Ag.
A supported catalyst for diolefin hydrogenation, containing palladium, silver and an alkali fluoride is known from EP-A-0 693 315. Spherical pellets or cylindrical extrudates are preferably used as support.
A catalyst for hydrogenation of C2 to C10 alkynes, preferably acetylene, to the corresponding alkenes in the presence of sulfur compounds is known from EP-A-0 738 540, which contains palladium, silver, at least one chemically bonded alkali metal (preferably K), chemically bonded fluorine and an inorganic support (preferably aluminum oxide) in the form of pellets.
EP-A-0 732 146 describes catalysts, whose supports represent molded bodies with a trilobal cross section and through openings. The catalysts contain iron oxide-molybdenum. oxide compounds as catalytically active components. The catalysts are used specifically for oxidation of methanol to formaldehyde, although some other applications not demonstrated by examples are stated (for example, hydrogenation of acetylene and olefins).
EP-A-464 633 describes catalysts, whose support represents molded bodies with a trilobal cross section and continuous openings (cf. FIG. 5). The catalysts contain a mixture of elements of groups VIII and 1B of the Periodic Table, especially palladium and gold, as the catalytically active components. They are used for conversion of olefins with organic carboxylic acids and oxygen to unsaturated esters, especially for production of vinyl acetate from ethylene and acetic acid.
EP-B-591 572 describes a catalytic material in the form of particles with a trilobal cross section and at least three continuous pore openings, as well as a specific ratio between height of the particles and spacing between the axes of the holes. This material is used for oxidative dehydrogenation of methanol to produce formaldehyde.
Catalysts for selective hydrogenation of diolefins and alkynes to mono-olefins and alkenes are also marketed by the applicant under the names G-58 and G-83, which contain palladium and silver on a spherical support or on a support in the form of solid pellets or extrudates (cf. data sheets “Girdler Catalysts G-58 C, G-58 D, G-58 H, G-58 I and G-83 for Selective Hydrogenation”, from January 1998).
Catalysts on such supports generally have the drawback that their activities and selectivities are relatively low and hydrogenation reactions can only be run at relatively low space velocities. These catalysts also have relatively high flow resistance.
The task underlying the present invention is to eliminate these shortcomings. It was surprisingly found that these shortcomings could be eliminated by using a catalyst whose support has a specific shape.
The object of the invention is therefore a catalyst for hydrogenation of unsaturated hydrocarbons, containing catalytically effective amounts of Pd and optionally Ag on a support. The catalyst is characterized by the fact that the support represents a shaped body with a trilobal cross section, in which the lobes are provided with through openings.