Characterisation of modified Cr—silica catalysts

Abstract

The Cr—silica catalyst system is commercially important in the polymerisation of ethene. This catalyst is made much more active by the inclusion of small quantities of titanium. This study attempts to identify the nature of any new species which may be formed by investigation of a series of titanium and magnesium modified Cr—silica catalysts. TPR experiments of the modified catalysts showed evidence for two new surface species. These species exhibited increased thermal stability with respect to the surface chromate and dichromate-like species already present and approximated to aggregates of titanium or magnesium chromate and dichromate.