Frequency Factor of Natta's Propylene Polymerization

Abstract

ACCORDING to Natta and Pasquon¹, the stationary rate, r_∞, of propylene polymerization with titanium trichloride-triethyl aluminium catalyst is expressed by: where P is the propylene pressure, G the weight of the solid catalyst and A the frequency factor. The observed values of r_∞ at room temperature and atmospheric pressure are usually 5–35 g-propylene/h atm. g-titanium trichloride^1,2. The surface areas of the commercial titanium trichloride catalysts (prepared from titanium tetrachloride by reduction with hydrogen, aluminium or titanium and activated by grinding) have been measured as 10–30 m²/g by the Brunauer–Emmett—Teller method with nitrogen adsorption³. From these values and (1) we have 10²²–10²³ molecules/sec cm² for the order of magnitude of A. This value is almost the same as that of the surface collision number, Z, of gas molecule per unit area at the same temperature and pressure. Then the rate per g-titanium trichloride may be represented, denoting the surface area by S: To note this may be valuable for discussing the reaction mechanism of this polymerization.