Catalytic Degradation of Polymers

Abstract

The effect of various catalysts such as TiO?, cobalt Fischer–Tropsch catalyst, and AlCl? was studied on the thermal degradation of various polymers including poly(vinyl chloride) (PVC), polystyrene, and polybutadiene, both in pyrolysis and in solution.

The molecular weight distribution of the polymers was obtained by analyzing the samples using gel permeation chromatography (GPC). Continuous distribution kinetics was employed to evaluate the degradation rate coefficients for both thermal and catalytic degradation of polymers in solution.

TiO? reduced the thermal degradation rate of polystyrene during pyrolysis and had no effect on PVC and polybutadiene. No significant effect of the cobalt Fischer–Tropsch catalyst or AlCl? was observed on the thermal degradation of the polymers under pyrolysis conditions.

In solution, the degradation temperatures and activation energies were found to be lower compared to those in pyrolysis. TiO? enhanced the thermal degradation rate of PVC, decreased the degradation rate of polystyrene, and had no effect on the degradation of polybutadiene. AlCl? enhanced the degradation rate of PVC and reduced the degradation rate of polybutadiene. The cobalt Fischer–Tropsch catalyst enhanced the thermal degradation rate of polybutadiene but had no effect on the degradation of the other polymers.

The activation energies calculated from the temperature dependence of the rate coefficients were 26.5, 12.06, and 31 kcal/mol for the thermal degradation of PVC, polystyrene, and polybutadiene, respectively.

In the presence of TiO? and Pt/TiO?, the activation energy for the degradation of PVC increased compared to thermal degradation alone, suggesting a complex degradation mechanism involving different rate-controlling steps.

A continuous flow reactor packed with catalyst was designed to study the degradation of polybutadiene using two catalysts: cobalt Fischer–Tropsch catalyst and HZSM-5