THERMODYNAMICS OF THE CATALYTIC POLYMERIZATION OF ALKENES IN THE GAS-PHASE

The polymerization of alkenes is catalyzed by zeolite catalysts in the temperature range 450-800 K. As expected from thermodynamics the degree of polymerization is higher at lower temperatures and higher pressures. Equilibrium distributions of alkene isomer groups in the ideal gas phase have been calculated over a range of temperatures and pressures. The use of isomer groups greatly reduces the number of species that have to be considered in an equilibrium calculation and provides a means for extrapolating to higher carbon numbers. Since ZSM-5 is selective, equilibrium distributions have also been calculated for three restricted isomer groups from which certain bulky isomers have been excluded. Comparison of theory and experiment provides a means for learning about the nature of isomers excluded by the catalyst.