Researchers from the University of Cambridge (UK) have developed a new high-yield process for recycling waste crankcase oil into gasoline-like fuel based on microwave pyrolysis—i.e., using microwave energy as the heat source.
The recovered pyrolysis oils contain substantial concentrations of paraffinic hydrocarbons with low sulphur and oxygen content, and a density and calorific value comparable to traditional liquid fuels derived from fossil fuel. The researchers attributed the high yield of pyrolysis oil to the unique heating mode and chemical environment present during microwave-heated pyrolysis. They presented their results during the 241st national meeting of the American Chemical Society in Anaheim.
Transforming used motor oil into gasoline can help solve two problems at once. It provides a new use for a waste material that’s too-often disposed of improperly, with harm to the environment. In addition, it provides a supplemental fuel source for an energy-hungry world—study leader Howard Chase, Professor of Biochemical Engineering at the University of Cambridge
Estimates suggest that changing the oil in cars and trucks produces about 8 billion gallons of used motor oil each year around the world. In the United States and some other countries, some of that dirty oil is collected and re-refined into new lubricating oil or processed and burned in special furnaces to heat buildings. In many other countries, used automotive waste oil is discarded or burned in ways that can pollute the environment.
Current pyrolysis processes heat the oil unevenly, producing gases and liquids not easily converted into fuel. Chase and his research team say the new method overcomes this problem and uses their new pyrolysis technology. In lab studies, his doctoral students, Su Shiung Lam and Alan Russell, mixed samples of waste oil with a highly microwave-absorbent material and then heated the mixture with microwaves. The pyrolysis process appears to be highly efficient, converting nearly 90% of a waste oil sample into fuel. So far, the scientists have used the process to produce a mixture of conventional gasoline and diesel.
Microwave-heated pyrolysis of waste automotive engine oils produces significant amounts of liquid hydrocarbon oils containing BTX and benzene derivatives; these products can be treated and used as either an energy source or industrial feedstock. It is evident that microwave-induced pyrolysis has huge potential as a means of recovering commercially valuable products from problematic waste oil, in addition to diverting waste streams from current yet environmentally-harmful disposal techniques such as landfilling and incineration.—Lam et al.