Ruthenium catalysts

Abstract

Sugar alcohols are prepared by catalytically hydrogenating the corresponding monosaccharides and oligosaccharides in the liquid phase over a heterogeneous ruthenium catalyst, with the exception of the preparation of sorbitol, wherein the heterogeneous ruthenium catalyst is prepared by: i) treating a support material based on amorphous silicon dioxide comprising at least 95% by weight of silicon dioxide and less than 1% by weight aluminum oxide, calculated as Al 2 O 3 , one or more times with a halogen-free aqueous solution of a low molecular weight ruthenium compound which is a ruthenium (III) salt or a metal ruthenate and subsequently drying the treated support material at a temperature below 200° C., and ii) reducing the solid obtained in i) by means of hydrogen at a temperature ranging from 100 to 350° C., wherein step ii) is carried out directly after step i), and wherein the ruthenium content in the catalyst ranges from 0.1 to 5% by weight, based on the support material.

1 . A process for preparing sugar alcohols, comprising:
 catalytically hydrogenating the corresponding monosaccharides and oligosaccharides in the liquid phase over a heterogeneous ruthenium catalyst, with the exception of the preparation of sorbitol, wherein the heterogeneous ruthenium catalyst is prepared by:   i) treating a support material based on amorphous silicon dioxide comprising at least 95% by weight of silicon dioxide and less than 1% by weight aluminum oxide, calculated as Al 2 O 3 , one or more times with a halogen-free aqueous solution of a low molecular weight ruthenium compound which is a ruthenium (III) salt or a metal ruthenate and subsequently drying the treated support material at a temperature below 200° C., and   ii) reducing the solid obtained in i) by means of hydrogen at a temperature ranging from 100 to 350° C.,   wherein step ii) is carried out directly after step i), and wherein the ruthenium content in the catalyst ranges from 0.1 to 5% by weight, based on the support material.   
     
     
         2 . The process as claimed in  claim 1 , wherein the monosaccharide or oligosaccharide is in the form of an aqueous solution having a pH in the range of 4 to 10. 
     
     
         3 . The process as claimed in  claim 1 , wherein the hydrogenation is conducted at a hydrogen partial pressure in the range of 10 to 500 bar. 
     
     
         4 . The process as claimed in  claim 1 , wherein the hydrogenation is conducted at a temperature ranging from 40 to 250° C. 
     
     
         5 . The process as claimed in  claim 1 , wherein the hydrogenation is conducted over a fixed catalyst bed. 
     
     
         6 . The process as claimed in  claim 1 , wherein the hydrogenation is conducted in a liquid phase in which the catalyst is present in the form of a suspension.