Characterisation of Cr/silica catalysts. Part 2.—Ti- and Mg-modified catalysts

Abstract

The Cr/silica catalyst system, which is commercially important in the polymerisation of ethane, is made much more active by the inclusion of small quantities of titanium. The nature of any new surface species which may be formed has been studied by investigation of a series of titanium- and magnesium-modified Cr/silica catalysts.

Temperature-programmed reduction (TPR) experiments on 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 may approximate to aggregates of titanium or magnesium chromate and dichromate.