A Review on Catalytic Co-Pyrolysis of Biomass and Plastics Waste as a Thermochemical Conversion to Produce Valuable Products

In order to satisfy the increasing need for renewable chemicals and fuels, it is important to replace petroleum-based products with alternative feedstocks. Lignocellulosic biomass is considered to be the most capable alternative source for producing sustainable biofuels. Catalytic co-pyrolysis (CCP) is a process that involves simultaneously pyrolyzing biomass and plastics to produce a combination of liquid and gaseous products, such as bio-oil and syngas. Catalysts are used to raise the reaction degree and the selectivity of the co-pyrolysis process, with the choice of catalyst dependent on the physico-chemical features of the feedstock. Catalytic pyrolysis is a useful method for producing high-quality biofuels directly from biomass, although it typically yields a modest amount of aromatic hydrocarbons (HCs) and a large amount of coke, even with highly effective catalysts. Adding a co-reactant high in hydrogen to the CCP process can significantly increase the yield of aromatics while reducing coke formation. The use of CCP can help to address the environmental issues related to waste plastic disposal and improve energy security. This review article thoroughly discusses the process and mechanism of catalytic co-pyrolysis, the influence of plastics on the process, and how the addition of plastics can improve the quality and output of bio-oil while reducing the production of oxygenated compounds and coke. The importance of various catalysts (such as biochar, activated carbon, and acid and base catalysts) in improving the production and quality of obtained products is also compared and discussed.