| 摘要 |
A new catalyst useful in the polymerization of at least one olefin is disclosed. The catalyst comprises the product obtained by contacting silica, in random order, with (1) at least one hydrocarbon soluble magnesium-containing compound; and (2) a first modifying compound selected from the group consisting of silicon halides, boron halides, aluminum halides and mixtures thereof followed by a second modifying compound selected from the group consisting of halides having the structural formula SiHrX2s, where X2 is halogen; r is an integer of 1 to 3; and s is an integer of 1 to 3 with the proviso that the sum of r and s is 4, a hydrogen halide and mixtures thereof. The product of this step is contacted with a first titanium-containing compound having the structural formula Ti(OR)mXn, where R is hydrocarbyl or cresyl; X is halogen; m is an integer of 1 to 4; and n is 0 or an integer of 1 to 3, with the proviso that the sum of m and n is 4. Finally, the product of this latter step is, in turn, contacted with a second titanium-containing compound, different from the first titanium-containing compound, having the structural formula TiX1p(OR)1)q, where X1 is halogen; R1 is hydrocarbyl; p is an integer of 1 to 4; and q is 0 or an integer of 1 to 3, with the proviso that the sum of p and q is 4. A catalyst system comprising the above catalyst, an aluminum-containing first cocatalyst and at least one silane second cocatalyst is also set forth. Finally, a process for polymerizing at least one olefin utilizing the catalyst system of this disclosure is taught.
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