Value-Added Pyrolysis of Waste Sourced High Molecular Weight Hydrocarbon Mixtures

Abstract

In this study, Fischer-Tropsch paraffin mixture, heavy residue of waste polyethylene pyrol-ysis, shredded and crashed agricultural polyethylene waste and their combinations were pyrolysed both thermally and catalytically in a two-stage reactor system. During the experimental work, yields and compositions of pyrolysis products were studied as function of feedstock composition and catalyst placement. It was found that the average molecular weight of feedstocks and the presence of ZSM-5 catalyst also have significant effects on the product yields and the compositions. Feedstocks with high concentration of Fischer-Tropsch paraffin and real waste polyethylene resulted in deeper fragmentation in both thermal and thermo-catalytic pyrolysis. Due to the deeper fragmentation, they seemed to be suitable feedstocks for the production of C6 –C9 and C10 –C14 hydrocarbons. Meanwhile, for production of C15 –C21 hydrocarbons, the use of a higher concentration of heavy residue of waste polyethylene pyrolysis in the feedstocks is recommended. From the point of view of liquid hydrocarbon and isomer production, the placement of the catalyst into the 1st reactor proved to be more advantageous. When the catalyst was placed into the 2nd reactor, the product formation shifted to the more volatiles, isomers took part in secondary cracking reactions and aromatics formed in higher concentrations.