Deoxygenation Pathways for Sustainable Aviation Fuel from Used Cooking Oil: A Review on Catalyst and Operating Parameters
Rahul Kumar Singh, Devdutt Panda, Saurabh Singh
Abstract
The aviation industry stands at the crossroads of a climate crisis, which significantly contributes to worldwide carbon (C) emissions. To combat this issue and embrace environmental sustainability, the production of sustainable aviation fuel (SAF) from triglyceride-based bio-oils has emerged as a pivotal research and industry pursuit. Traditional aviation fuels that are derived from fossil sources are a major contributor to carbon dioxide (CO2) emissions. However, SAF presents a sustainable and environmentally friendly alternative by harnessing the potential of a used cooking oil (UCO) (triglyceride source), an often-neglected waste stream with significant environmental implications when improperly managed. Among the various conversion methods, the deoxygenation (DO) reaction pathway has emerged as a promising method for converting triglycerides into SAF. However, this emerging technology has significant challenges, which primarily revolve around the selection of feedstocks, catalysts, reaction pathways, and operational parameters. Therefore, this study provides a holistic overview of the DO of a triglyceride-based UCO feedstock as a promising avenue for SAF production by navigating diverse SAF feedstocks, tailoring the DO to enhance versatility, exploring catalyst nuances that impact the DO, and unraveling the optimal operating conditions for superior SAF yields and selectivity. This study concludes that the optimal conditions for SAF production involve utilizing feedstocks with a low free fatty acid (FFA) content, such as canola or high oleic sunflower oils. Employing catalysts with a high surface area and abundant acid sites, such as Zeolite Socony Mobil–5 (ZSM–5), along with metal impregnators such as carbon monoxide (CO) and nickel (Ni) as active metal and promoters, in a down-trickle bed reactor within 300°C–380°C and pressure range of 10–50 bar, proves to be the most effective approach.