Patent ID: 7271122
Filing Date: 2007-09-18
Classification: C08F

Abstract:
1. A method for making a catalyst suitable for the production of high density polyethylene comprising: (a) selecting a particulate silica support comprising silica grains having a specific surface area larger than 300 m (b) providing an initial treating agent comprising a titanium compound and a second treating agent comprising an aluminum compound in the form of a polymeric aluminum oxyalkyl. (c) initially treating said silica grains with said initial treating agent in order to coat said silica grains with an initial thin external shell of said initial treating agent; (d) thereafter treating said silica grains with said second treating agent in order to coat said silica grains with a second thin external shell of said second treating agent; (e) depositing a chromium compound on the titanated and aluminated silica grains to form a catalyst; and (f) thereafter activating said catalyst by heating said catalyst under air at a temperature within the range of 600-800° C.