Method of preparing a molecular catalyst
Method of preparing a molecular catalyst from a mixture comprising a (C 5 -C 7 )alkane, a spray-dried alkylaluminoxane, and a molecular procatalyst. Molecular catalysts prepared by the method may be screened.
1. A method of preparing a molecular catalyst, the method comprising mixing under activating conditions a molecular procatalyst, a spray-dried alkylaluminoxane on hydrophobic fumed silica (sdAAO/HFS), and a (C 5 -C 7 )alkane to give a catalyst system comprising a molecular catalyst in the (C 5 -C 7 )alkane; and replacing the (C 5 -C 7 )alkane of a mixture of a molecular catalyst and the (C 5 -C 7 )alkane with a mineral oil to give a mixture of the molecular catalyst and the mineral oil that is free of the (C 5 -C 7 )alkane.
2. The method of claim 1 wherein the (C 5 -C 7 )alkane is a (C 5 )alkane, a (C 6 )alkane, or a mixture of a (C 5 )alkane and a (C 6 )alkane.
3. The method of claim 1 wherein the (C 5 -C 7 )alkane is hexane, pentane, or a mixture of hexane and pentane.
4. The method of claim 1 wherein (i) the alkylaluminoxane is methylaluminoxane (MAO); (ii) the hydrophobic fumed silica is a treated fumed silica prepared by treating an untreated fumed silica with a treating effective amount of a treating agent reactive with silicon-bonded hydroxyl groups; or (iii) both (i) and (ii).
5. The method of claim 4 wherein the treating agent reactive with silicon-bonded hydroxyl groups is hexamethyldisilazane; a cyclic silazane; a combination of hexamethyldisilazane and a cyclic silazane; a combination of hexamethyldisilazane in a silicone oil; a (C 5 -C 10 )alkyltrialkoxysilane; an alkylchlorosilane of formula R x SiCl (4-x) , wherein subscript x is an integer of 0, 1, 2, or 3; and each R is independently a (C 1 -C 10 )alkyl; an alkylhydridosilane of formula R y SiH (4-y) , wherein subscript y is an integer of 0, 1, 2, or 3; and each R is independently a (C 1 -C 10 )alkyl; or a combination of any two or more thereof.
6. The method of claim 5 wherein the treating agent reactive with silicon-bonded hydroxyl groups is hexamethyldisilazane; a combination of hexamethyldisilazane and octamethylcyclotetrasilazane; a combination of hexamethyldisilazane in a bis[trimethylsilyl-endcapped] polydimethylsiloxane liquid; octyltrimethoxysilane; octyltriethoxysilane; dimethyldichlorosilane; or octylsilane.
7. The method of claim 1 wherein the molecular procatalyst is a (i) a cyclopentadienyl ligand-metal complex procatalyst or (ii) a cyclopentadienyl-free ligand-metal complex procatalyst; and the molecular catalyst is a product of an activation reaction of (i) or (ii) with the sdAAO/HFS.
8. The method of claim 1 further comprising contacting a catalytic amount of the molecular catalyst with at least one polymerizable olefin under polymerization conditions to give a polyolefin product.
9. The method of claim 8 wherein the at least one polymerizable olefin is 1-octene or a mixture of ethylene and 1-hexene, the method further comprising replicating the contacting step in at least 1 additional polymerization run under identical polymerization conditions and with identical polymerizable olefin(s) and determining a catalyst productivity value for each polymerization run.