Isomerization catalysts and technologies for biorefining: Opportunities for producing sustainable aviation fuels

An overview of the recent advances in the field of catalytic hydroisomerization of hydrocarbons is presented in this article, with a particular focus on promising technologies for the production of sustainable aviation fuels or biojet fuels. Processing of biogenic feedstocks, such as waste vegetable oils and animal fats, to produce biofuels yields hydrocarbons containing linear paraffins. Abundance of these linear paraffins leads to poor cold flow properties in the resultant fuels, requiring further refining in order to meet the jet fuel specifications. Catalytic hydroisomerization is an effective approach that transforms linear paraffins into branched ones or isoparaffins, thereby improving cold flow properties. Adapting this technology from its conventional use in petroleum refineries to biorefining requires technological improvements. In principle, this technology could be modified for use in aviation biofuel refining by adjusting the catalyst’s formulation based on the chemical characteristics of the unrefined biofuel and finding the optimum working conditions for such new catalysts. A major challenge in this area is the development of an efficient catalyst capable of selectively isomerizing long-chain linear paraffins without much cracking and with tolerance to impurities in the biofuel. The review presented here ultimately aims at identifying suitable catalyst candidates that can be adapted for refining a range of biogenic feedstocks into jet fuels. The desirable catalyst attributes, such as resistance to contaminants, balanced acidity to minimize cracking, and selectivity towards reactions that lead to cold flow property improvement, are examined.