Catalytic upgrading of coal tar to produce value-added chemicals and fuels: A review on processes, catalytic mechanisms and catalysts

[Display omitted] •Recent advances in the catalytic upgrading of coal tar are presented.•Catalytic cracking, steam reforming, and catalytic hydrogenation are described.•The mechanisms of different processes for coal tar upgrading are analyzed.•The effects of processes and catalysts on coal tar upgrading are discussed.•Challenges and perspectives for catalyst design for tar upgrading are suggested. Coal tar is an important by-product of coal pyrolysis, carbonization and gasification processes. However, the high content of heavy fractions, complex composition and impurities of coal tar make it easy to condense, clog and contaminate equipment in industrial applications. Conversion of tar into high value-added chemicals and fuels via catalytic upgrading is an important way to achieve resource utilization, and catalysts can improve the selectivity of fuels and chemicals by enhancing or altering reaction pathways. This review describes and summarizes the progress of coal tar upgrading processes and the application of catalysts, focusing on the reaction mechanisms, process characteristics and catalyst effects on tar upgrading in catalytic cracking, steam reforming and catalytic hydrogenation. On this basis, a summary and outlook around the design and preparation of catalysts, analysis of the reaction mechanism and laboratory and industrial scale studies are presented.