The Recycling of Municipal Plastic Wastes into an Alternative Hydrocarbon Fuel via Enhanced Zeolite-Based Catalytic Pyrolysis

Abstract

This study was devoted to examine the potential of recycling municipal plastic wastes composed of high and low density of polyethylene (HDPE), (LDPE), polystyrene (PS) and polypropylene (PP) into a good quality hydrocarbon oil via pyrolysis process. This process was carried out in a fixed bed reactor operated in a semi-batch operation mode, where thermal and catalytic pyrolysis were separately investigated. The pyrolysis process was conducted at heating rate of 5°C/min under 5 bar pressure and a final temperature of 470 and 437°C, respectively. Thermal pyrolysis revealed the production of hydrocarbon oil by 75.8%. However, the catalytic pyrolysis was conducted using a commercial zeolite-base catalyst, showed a higher tendency towards light gas 33.05% compared to thermal process 22.2%. Yet, oil fraction was superior at 66.55% with the dominance of longer chain hydrocarbons (C₁₂–C₂₄). Comprehensive chemical and physical characterizations were performed for the analysis of oil yield in order to consider the similarity with standard hydrocarbon fuels. A higher tendency towards the gasoline oil fraction regarding carbon number was recorded by thermal pyrolysis at 58.03% compared to catalytic pyro-oil which approached the gas oil by 65.8%. On the other hand, the PIONA (paraffin, i-paraffin, olefine, aromatic) analysis revealed a very good paraffins and aromatics content ranging from 31.63–33.69 and 39.42–40.47%, respectively, which approaches the standard fuel composition. The study has introduced a very promising recycling technique, side by side with an alternative energy source.