High quality products from microwave catalytic pyrolysis of heavy oil and polyethylene

Abstract

Heavy hydrocarbon residue management has always been an environmental issue; thus, it is essential to find a method for upgrading heavy oils and plastic waste to high quality products as an alternative source of chemicals and fuels. In this study, the microwave catalytic pyrolysis (MCP) of heavy oil (HO) and LDPE (as plastic source) was proposed by employing a unique design of the catalyst, SiC foam@HZSM-5. This special catalyst design provided sufficient mass and heat transfer and enhanced the available catalyst surface area during the pyrolysis process. The effect of microwave power and the HO:LDPE ratio were investigated to optimize the product yield and quality. The results showed that the hazardous and unwanted elements of HO were eliminated by adding LDPE to the feedstock. More importantly, it was observed that the secondary and side reactions were accelerated due to a positive synergistic effect (ΔY), which occurred because of hydrogen donors from the LDPE degradation and the non-thermal effect of microwave heating. The HO:LDPE ratio of 1:1 with a microwave power of 800 W and 10 min heating time were the optimum conditions; the liquid yield was about 42 wt% with around 90% of aromatics (mono- and polycyclic) relative concentration. Furthermore, the proportion of BTX was about 82% of the liquid oil, while the concentration of oxygenated and nitrogenated compounds was less than 2%. Under the above conditions, the proportion of collected non-condensable gases was around 46 wt%, which comprised light olefins (C1-C6) at about 37%, and a considerable proportion of H2 as well. Additionally, adding more LDPE to the feedstock decreased solid residue by promoting the conversion of HO, which improved catalyst efficiency.