Modified Catalyst Supports

A process for preparing a polyolefin comprising polymerizing an olefin in the presence of a supported catalyst system to form a polyolefin having an atomic molar ratio of Ti/M of from 0.13 to 500, wherein M is a transition metal selected from one or more of zirconium, hafnium and vanadium, and an atomic molar ratio of Cl/Ti of less than 2.5, wherein the supported catalyst system is prepared by a process comprising:

• impregnating a silica-containing catalyst support having a specific surface area of from 150 m2/g to 800 m2/g, with a mixture of titanium compounds of the general formula RnTi(OR′)m or (RO)nTi(OR′)m, wherein R and R′ are the same or different and are selected from hydrocarbyl groups containing from 1 to 12 carbon and halogens, and wherein n is 0 to 4, m is 0 to 4 and m+n equals 4, to form a titanated silica-containing catalyst support having a Ti content of at least 0.1 wt % based on the weight of the Ti-impregnated catalyst support;
• wherein the supported catalyst system further comprises an alumoxane and a metallocene, and wherein the metallocene comprises a transition metal;
• ii). drying the Ti-impregnated catalyst support prior to the addition of alumoxane and metallocene on the Ti-impregnated catalyst support;
• iii). adding the alumoxane on the Ti-impregnated catalyst support prior to or during the addition of metallocene;
• wherein the ratio of aluminum from the alumoxane to transition metal of the supported catalyst system is between 30 and 100;
• and
• wherein the silica-containing catalyst support is not contacted with a halogenated compound other than the metallocene