Abstract:
A supported chromium oxide polymerization catalyst is prepared by a process which includes the steps of heating silica-supported chromium oxide or a substance oxidizable to chromium oxide in a nonoxidizing atmosphere in the presence of formaldehyde or a compound thermally decomposable to formaldehyde, and then heating the thus-treated catalyst in an oxygen-containing atmosphere. The temperatures of the respective heating steps can vary depending upon the properties desired in the polymer to be produced with the invention catalyst; however, the invention catalyst preparation method enables the production of a catalyst having a high melt index potential at relatively low treatment temperatures, e. g. no higher than about 600. degree. C.