Abstract
The stationary rate of propylene polymerization with titanium trichloride-triethyl-aluminum catalyst has been expressed byr=Ae-10kcal/RTwhere P is the pressure of propylene, G the weight of titanium trichloride and A the frequency factor, of which A has been discussed here. From the experimental values of the rate and the specific surface area of the commercial titanium trichloride catalysts measured by BET method, we have 1022-1028 molecules/cm2 sec for the values of A. That is close to the surface collision number of propylene, Z=1.4×1022 molecules/cm2 sec, at P=1 atm and T=300°C K, which is given by Herz-Knudsen equation. Then the above rate equation may be apparently represented byr=ZSe-10kcal/RTwhere S is the total area of the solid catalyst used. Applying the absolute rate theory of heterogeneous reaction to the latter equation, the reaction mechanism has been discussed. The most appropriating model of the polymerization is a Twigg-Rideal type, i. e., the simple collision of a propylene monomer to one of the polymerization center which covers the whole surface. Here, “the simple collision” means that the proplene in the activated complex has the same internal motions as that of gaseous propylene. Excepting some special model, the usual Langmuir-Hinshelwood type, i. e., the reaction between adsorbed propylene and polymerization center, can not explain the experimental result.
