Patent ID: 6538077
Filing Date: 2003-03-25
Classification: B01J,C08F,Y02P

Abstract:
A process for producing a polyethylene comprising contacting ethylene under suitable polymerization conditions with a catalyst system comprising a chromium-containing catalyst prepared by contacting a silica-containing inorganic oxide with a magnesium compound, contacting the resulting combination with a base to form a magnesium hydroxide, drying the resulting combination, and then calcining the dried product in the presence of oxygen, wherein the amount of magnesium compound is such that the resulting catalyst has a higher surface area than the silica-containing inorgranic oxide starting material, wherein the chromium in the catalyst is provided by (a) employing as the silica-containing inorganic oxide a silica/chromium cogel, (b) adding a chromium compound with the magnesium compound, (c) adding a chromium compound to the dried magnesium silica combination prior to the calcinations, (d) adding a chromium compound after the support has been calcined, or (e) adding a chromium compound after the drying step by combining additional magnesium compound with a solution of a chromium compound.