Research Progress on Catalytic Pyrolysis and Reuse of Waste Plastics and Petroleum Sludge

Waste plastics (e.g., polyethylene, polyvinyl chloride, polypropylene, polystyrene) and petroleum sludge (i.e., main residual from the petroleum industry) pose a severe threat to the environment and human health. These materials are basically non-biodegradable, and it is difficult to realize the recycling of them and resources via traditional treatment methods. Catalytic pyrolysis as a new recycling treatment method has the characteristics of high efficiency, environmentally benign, no secondary pollution and high product utilization value. This paper mainly reviews the research progress of catalysts used in the catalytic pyrolysis of waste plastics and petroleum sludge. They include molecular sieves, transition metals, metal oxides, clays and activated carbons used for the recycling of plastic, and molecular sieves and M-series catalyst (M=Al, Fe, Ca, Na, K) for treating petroleum sludge. The mechanism of catalytic pyrolysis is also elucidated in this paper. In addition, the challenges faced by catalytic pyrolysis of waste polymers and the future development prospects are also presented.