Synthetic strategies and performance of catalysts for pyrolytic production of alternative aviation fuels using non-edible lipids: A critical review

Non-edible lipids are an alternative source of liquid hydrocarbon fuels, particularly aviation fuels. As a transformation pathway, the catalytic pyrolysis of lipids can remove oxygen atoms and modify molecular structures via carbon chain cracking and aromatisation. However, this pathway has not yet been certified for the production of alternative aviation fuels. Therefore, a detailed review of various heterogeneous catalysts for the conversion of lipids into hydrocarbon fuels with molecular weights and structures suitable for use in aviation is presented herein, with a focus on aspects such as their physical and chemical properties, pore distributions and structures, active sites, key functions, catalytic performance, and pyrolysis mechanisms. Metal oxides can effectively remove oxygen atoms, whereas zeolites can achieve long-carbon-chain cracking to yield desirable gasoline-, kerosene-, or diesel-range fuels. Moreover, zeolites typically permit aromatisation, which yields the aromatic hydrocarbons required for liquid fuels. Modification of the pore structures of zeolites to yield hierarchical pores can improve the production of C8–C16-range liquid fuels to maximise the bio-kerosene yield. Therefore, composite catalysts (metal oxides supported on zeolites with hierarchical pores) can be effective for molecular-level structural modification in the pyrolytic production of alternative aviation fuels using lipids. However, rapid deactivation due to coking, poisoning, and sintering hinder the operation of these catalysts. Coking, which is predominantly responsible for pyrolysis catalyst deactivation, should be targeted in future research on novel catalysts. The synthetic strategy of catalysts and the mitigation of their issues are critical to the design of novel catalytic pyrolysis systems for the efficient cracking of triglyceride-rich feedstock to yield alternative aviation fuels. [Display omitted] •Synthetic strategy of catalysts used in catalytic pyrolysis of lipid was reviewed.•Metal oxides supported in zeolites remove oxygen and crack carbon chain.•Aromatization is realized by porous zeolites to produce aromatic hydrocarbons.•Carbon chain length can be modified by ratio of micropores and mesopores.•Microalgal lipid is an alternative feedstock for aviation fuel production.