synopsisA study of the nature of polymerization catalysis over CrOl-silica and of the nature of the polyethylene obtained is presented. A fixed surface chromate (or possibly dichromate) species was shown to be activated for polymerization by an oxidationreduction reaction with the monomer or with other reactive compounds such as CO. A change in catalyst color from orange to blue occurred simultaneously, and an indigoblue color was present only during ethylene addition, indicating involvement of Cr d orbitals. A spectacular chemiluminescence, due to excitation of oxygen, occurred when CO-treated catalyst was exposed to air. Active site population and the rate at which each site produced polymer molecules were calculated. A reaction mechanism compatible with the experimental data is depicted. 2631 93 94 94 57 81 33 85 87 65 8 Silica catalysts activated 5 hr at temperature in air as shown. b Determined independently by solubility and by reaction with Fe++. Saturated with water vapor at 38°C.
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