Advances in supported monometallic and bimetallic catalysts towards green aviation fuels: a review

Abstract

The worldwide energy crisis is triggered by the increasing exhaustion of fossil fuel supplies along with the population increase in developing nations. In addition, fossil fuels are not environmentally benign owing to their association with issues such as climate change, high toxicity, and non-biodegradability. Consequently, they are regarded as an unsustainable source of energy. Undoubtedly, green aviation fuels, also referred to as bio-jet fuels, are potential and sustainable long-term energy sources that can help decrease our reliance on fossil fuels, owing to the availability and renewability of their feedstocks. In contrast to biodiesel, which is produced through transesterification, green aviation fuel is produced via deoxygenation to eliminate oxygen and other impurities, resulting in a fuel that chemically mimics petroleum diesel. Thus, conventional homogeneous and heterogeneous catalytic systems for producing biodiesel from vegetable oil are no longer justifiable for the sustainable aviation fuel (SAF) industry in the foreseeable future. This is primarily due to the presence of oxygen-containing compounds in biodiesel (∼10–12%), which increases its susceptibility to oxidation and degradation over time, resulting in the formation of gum, clogging of filters, and decreased fuel storage stability, all of which are crucial concerns for aviation. Furthermore, jet engines are engineered to operate on drop-in fuels that closely resemble hydrocarbon-based jet fuels without requiring modifications. This review provides a detailed and systematic procedure for converting non-edible oils such as palm kernel oil (PKO) into SAFs using bimetallic nickel–cobalt onto magnetite-supported catalysts. The enhanced catalytic system can effectively convert palm kernel oil with a high yield and selectivity towards kerosene for aviation sectors via deoxygenation reactions. The use of palm kernel oil as a raw material for SAF production will help address the problem of food security that arises from using food-grade oil for SAF production while decreasing the overall manufacturing expenses for green fuel production. This article aims to highlight the use of heterogeneous bimetallic acid/base catalysts for the production of SAFs from environmentally friendly and non-edible palm kernel oil. Future research should focus on optimizing bimetallic catalysts to improve the efficiency of sustainable aviation fuel (SAF) production from non-edible oils, with the aim of reducing energy consumption and minimizing environmental impact. Additionally, it is crucial to investigate alternative sustainable feedstocks and assess their scalability to ensure the widespread adoption of green fuels in the aviation sector, addressing food security and long-term energy needs. In conclusion, this study provides insights and potential advancements for the future.