Porous catalyst-support shaped body

Abstract

A porous shaped catalyst support body comprising at least 85% by weight of alpha-alumina, wherein the support has a total pore volume in the range from 0.5 to 2.0 mL/g as determined by mercury porosimetry, and a pore structure characterized by a geometric tortuosity τ in the range from 1.0 to 2.0; and an effective diffusion parameter η in the range from 0.060 to 1.0; wherein geometric tortuosity τ and effective diffusion parameter η are determined by image analysis algorithms from computer-assisted 3D reconstructions of focused ion beam scanning electron microscope analyses. The structure of the support has a high total pore volume, such that impregnation with a large amount of silver is possible, while the surface area is kept sufficiently high in order to assure optimal dispersion of the catalytically active species, especially metal species. The support has a pore structure that leads to a maximum rate of mass transfer within the support. The invention also relates to a shaped catalyst body for preparation of ethylene oxide by gas phase oxidation of ethylene, comprising at least 15% by weight of silver, based on the total weight of the catalyst, deposited on a porous shaped catalyst support body as described above. The invention further relates to a process for producing the shaped catalyst body, in which a) a porous shaped catalyst support body as described above is impregnated with a silver impregnation solution, preferably under reduced pressure; and the impregnated porous shaped catalyst support body is optionally subjected to drying; and b) the impregnated porous shaped catalyst support body is subjected to a heat treatment; wherein steps a) and b) are optionally repeated. The invention also relates to a process for preparing ethylene oxide by gas phase oxidation of ethylene, comprising the reaction of ethylene and oxygen in the presence of a shaped catalyst body according to claim 11.

1 - 13 . (canceled) 
     
     
         14 . A porous shaped catalyst support body comprising at least 85% by weight of alpha-alumina, wherein the support has a total pore volume in the range from 0.5 to 2.0 mL/g as determined by mercury porosimetry, and a pore structure characterized by
 - a geometric tortuosity τ in the range from 1.0 to 2.0; and   - an effective diffusion parameter η in the range from 0.060 to 1.0;   wherein geometric tortuosity τ and effective diffusion parameter η are determined by image analysis algorithms from computer-assisted 3D reconstructions of focused ion beam scanning electron microscope analyses.   
     
     
         15 . The porous shaped catalyst support body according to  claim 14 , having a density in the packed tube of more than 450 g/L. 
     
     
         16 . The porous shaped catalyst support body according to  claim 14 , having a BET surface area in the range from 0.5 to 5.0 m 2 /g. 
     
     
         17 . The porous shaped catalyst support body according to  claim 14 , obtained by
 i) providing a precursor material comprising, based on the content of inorganic solids,
 - at least 50% by weight of a transition alumina having a loose bulk density of not more than 600 g/L, a pore volume of at least 0.6 mL/g and a median pore diameter value of at least 15 nm; and 
 - not more than 30% by weight of an alumina hydrate; 
   ii) shaping the precursor material to shaped bodies; and   iii) calcining the shaped bodies in order to obtain the porous shaped catalyst support body.   
     
     
         18 . The porous shaped catalyst support body according to  claim 17 , wherein the transition alumina has a loose bulk density in the range from 50 to 600 g/L and a pore volume of 0.6 to 2.0 mL/g. 
     
     
         19 . The porous shaped catalyst support body according to  claim 17 , wherein the transition alumina comprises a phase selected from gamma-alumina, delta-alumina and theta-alumina. 
     
     
         20 . The porous shaped catalyst support body according to  claim 17 , wherein the alumina hydrate comprises boehmite and/or pseudoboehmite. 
     
     
         21 . The porous shaped catalyst support body according to  claim 17 , wherein the precursor material also comprises pore-forming materials, lubricants, organic binders and/or inorganic binders. 
     
     
         22 . The porous shaped catalyst support body according to  claim 17 , wherein the precursor material is shaped to shaped bodies by extrusion, tableting, pelletization, casting, forming or microextrusion. 
     
     
         23 . The porous shaped catalyst support body according to  claim 17 , wherein the calcining is performed at a temperature of at least 1100° C. 
     
     
         24 . A shaped catalyst body for preparation of ethylene oxide by gas phase oxidation of ethylene, comprising at least 15% by weight of silver, based on the total weight of the catalyst, deposited on a porous shaped catalyst support body according to  claim 14 . 
     
     
         25 . A process for producing a shaped catalyst body according to  claim 24 , in which
 a) the porous shaped catalyst support body is impregnated with a silver impregnation solution; and the impregnated porous shaped catalyst support body is optionally subjected to drying; and   b) the impregnated porous shaped catalyst support body is subjected to a heat treatment;   wherein steps a) and b) are optionally repeated.   
     
     
         26 . A process for preparing ethylene oxide by gas phase oxidation of ethylene, comprising the reaction of ethylene and oxygen in the presence of a shaped catalyst body according to  claim 24 .