A review on current trends and prospects in the pyrolysis of heavy oils

Abstract

AbstractIncreasing global demand for energy is an aftermath of an upsurge in world population and industrialization. The exploration of heavy oils such as oil sands, tight oils, and heavy oils, is thus becoming a necessity in a bid to alleviating the energy crisis. The processing of fossil fuels using conventional methods is known to have devastating effects on global warming and ocean acidification. This has brought about innovation and development of environmental-friendly processing technologies. Of these processing technologies available to date, pyrolysis is the most widely employed due to low operating complexity and economic cost. As revealed by the reviewed studies, the distribution of products formed during pyrolytic processes is a function of residence time, heating rate, the temperature of reaction, and reactor design. The latter significantly influenced the qualitative and quantitative yield of products formed during pyrolysis. Operating conditions of temperature, pressure, and catalyst are also influential factors in determining the product yields. Most research efforts in the last 30 years have identified that optimum production of pyrolytic oils occurred between thermal cracking temperature of 350 °C and 500 °C. The plausible mechanisms of pyrolysis are the free radical chain mechanism involving the homolytic cleavage of the C–C bond, and the electron transfer mechanism. This review pointed out the current status of the adoption of pyrolysis by petroleum and petrochemical industries as a processing technology for low-value heavy oils into high-value light fractions. The findings of the studies reviewed can help for better understanding of the optimum pyrolysis conditions required for maximum production of oils and gases. It will also help in carefully choosing the most sustainable approach in a bid to averting economic and environmental risks.