Thermal degradation of polyethylene in the presence of a non-acidic porous solid by a continuous flow reactor

Abstract

Thermal degradation of polyethylene (PE) in the presence of a non-acidic porous solid (silicalite) was performed under atmospheric pressure in a continuous flow reactor, at 420 °C and feeding rate of 0–1.5 kg h−1. Conducting pyrolysis at steady state allowed observations on the behavior of polymers during thermal degradation. Based on collected information about reaction rates and the composition of pyrolysis products as well as of reactor content we could distinguish between the random and the chain-end scissions of polymer macromolecules and we showed that porous silicalite favored the later ones. Although silicalite had no acid reactive centers, it influenced the equilibrium attained at steady state and changed the composition of pyrolysis products. As a result, the rate of double bonds formation strongly increased with the silicalite amount; however the mass rate of pyrolysis was not significantly affected. The macroscopic mechanism for the thermal degradation of polymer explained why the amount of silicalite does not contribute to the improvement of the mass rate of volatilization.