Fischer-tropsch catalyst comprising cobalt, magnesium and precious metal

Abstract

A method is described for preparing a catalyst precursor suitable for use in the Fischer-Tropsch synthesis of hydrocarbons including 10 to 40% by weight of cobalt oxide crystallites and 0.05 to 0.5% by weight of a precious metal promoter, dispersed over the surface of a porous transition alumina wherein the surface of the transition alumina has been modified by inclusion of 0.25 to 3.5% wt magnesium, including the steps of: (a) forming a modified catalyst support by impregnating a transition alumina with a magnesium compound, drying and calcining the impregnated alumina in a first calcination at a temperature 600° C. to convert the magnesium compound into oxidic form, and (b) forming a catalyst precursor by impregnating the modified catalyst support with a cobalt compound and precious metal promoter compound, drying and calcining the impregnated catalyst support in a second calcination to convert the cobalt compound to cobalt oxide.

1 . A process for Fischer-Tropsch synthesis of hydrocarbons comprising the step of contacting in a Fischer-Tropsch reactor a synthesis gas mixture comprising hydrogen and carbon monoxide with a catalyst prepared by reducing a catalyst precursor comprising 10 to 40% by weight of cobalt oxide crystallites and 0.05 to 0.5% by weight of a precious metal promoter, dispersed over the surface of a modified catalyst support formed from a porous transition alumina the surface of which has been modified by inclusion of 0.25 to 3.5% wt magnesium. 
     
     
         2 . The process according to  claim 1  wherein the synthesis gas mixture has a hydrogen:carbon monoxide ratio in the range 1.6:1 to 3.0:1. 
     
     
         3 . The process according to  claim 1  wherein the process is operated at a pressure in the range 10 to 60 bar abs and a temperature in the range 210-260° C. 
     
     
         4 . The process according to  claim 3  wherein the process is operated at a temperature in the range 230-250° C. at a CO conversion above 40%, with a C5+ hydrocarbon selectivity ≧80% and a methane selectivity ≦15%.