Renewable jet fuel processes currently certified for use in commercial aviation include fuel produced from triglycerides using the Hydro-processed Esters and Fatty Acids (HEFA) process. This hydro-processing route uses large amounts of hydrogen to remove oxygen from the triglycerides and the fatty acids. Due to the severity of catalyst and reaction conditions a number of carbon compounds of smaller lengths are formed due to cracking. The biggest hurdle in the conversion of renewable feedstock to jet fuels is this loss of raw material through cracking and decarbonylation reactions. To make such technologies commercially viable, it is therefore imperative to maintain high selectivity by minimizing the loss of carbon content while minimizing hydrogen consumption.
The Exelus approach for converting triglycerides to jet fuels involves a combined approach of novel reaction chemistry and innovative catalyst and reactor design. In this process water (rather than hydrogen) is used to break-down triglycerides into free fatty acids and glycerol. In the next step, glycerol is reformed to generate 7 moles of hydrogen which are then used in the final step, to convert free fatty acids directly into jet-fuel range iso-paraffins which meet standard jet fuel specifications (Jet A-1 or JP-8) using a multifunctional catalyst and low hydrogen partial pressures. Due to the high efficiency of this process and minimal wastage of the carbon content of the feedstock, the amount of oil required to produce a given amount of jet fuel is lower than the conventional hydro-processing route. Due to the in situ generation of hydrogen from glycerol, there is a steep reduction in the hydrogen consumption related which contributes to a significant reduction of – roughly $1/gallon of jet-fuel production cost
Most technologies being researched today for producing bio-jet fuel rely on decade old processes with some minor variations. Hydrotreating processes or gasification of biomass were developed during the second world war. Acid pretreatment to breakdown cellulose to sugars are almost 100-years old. The Exelus route uses innovative, new chemistry which allows for two major advantages over all other conventional processes a) significant reduction in hydrogen use by using a by-product as the hydrogen source and b) maintaining high carbon efficiency to jet fuels by using process intensification – by a combined approach of novel reaction chemistry and innovative catalyst and reactor design. Plant size is reduced by replacing large, expensive and energy-intensive equipment with ones that are smaller, less costly and more efficient ones.
Research on this breakthrough technology is focused on catalyst hydro-thermal stability