Pyrolysis Using Microwave Heating: A Sustainable Process for Recycling Used Car Engine Oil

Abstract

We demonstrate the applicability of pyrolysis using microwave heating to recycle used car engine oil. Waste oil was thermally cracked in an inert microwave-heated bed of particulate carbon from which oxygen was excluded, and the relationship between temperature, the chemical composition of the hydrocarbons, and the metal fraction produced was determined. A reaction temperature of 600 °C provided the greatest yield of commercially valuable products: the recovered liquid oils were composed of light paraffins and aromatic hydrocarbons that could be used as industrial feedstock; the remaining incondensable gases comprised light hydrocarbons that could potentially be used as a fuel source to power the process. In addition, the recovered liquid oils showed a significant reduction in the metal contaminants accumulated throughout their use cycle: a 93−97% reduction in Cu, Ni, Pb, Zn, Fe; a 46% reduction in Cd; and a 32% reduction in Cr. Our results indicate that microwave pyrolysis shows exceptional promise as a means for recycling and treating problematic waste oil.