Promoted molybdena‐alumina catalysts in ethylene polymerization: Kinetic considerations

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Abstract
Preformed transition‐metal oxides on high‐surface supports and precipitated catalysts from transition‐metal salts and aluminum alkyls produce linear polyethylene and stereoregular polyolefins. An introductory study of the kinetics of ethylene polymerization with a specially prepared preformed solid catalyst was undertaken as an aid in understanding the catalytic action. At constant pressure, ethylene uptake is linear. The rate depends on amount of catalyst and on ethylene concentration at various temperatures and pressures. The molecular weight of the product is primarily a function of temperature. The observed rate and its dependence on ethylene concentration and temperature are consistent with bound‐ion‐radical polymerization in a chemisorbed ethylene layer. The equations are similar in form to those based on a coordinate‐anion Polymerization mechanism. Further study will be needed to distinguish between these mechanisms, because they differ essentially only in the electronic environment of the growing chain end and in the movement of the growing reaction center during polymerization.