Advancements and challenges in the production of low-carbon fuels via catalytic fast pyrolysis of biomass through refinery integration and co-product generation

Abstract

The production of advanced biofuels represents a near-term opportunity to decarbonize the heavy vehicle transportation sector. However, important barriers must be overcome and successful deployment of these technologies will require (i) catalyst and process development to reduce cost and improve carbon utilization and (ii) industry-relevant validation of operability to de-risk scale-up. Herein, we seek to address these challenges for an integrated two-step process involving catalytic fast pyrolysis (CFP) followed by co-hydrotreating of bio-oil with refinery streams. Technoeconomic and lifecycle analysis based on the data presented herein reveal the potential to generate low-carbon transportation fuels and chemical co-products with a modelled selling price of $2.83 gasoline gallon equivalent (2016$) and a 78% reduction in greenhouse gas emissions compared to fossil-based pathways. The feedstock for this research was a blend of 50 wt% loblolly pine and 50 wt% waste forest residues, and the CFP step was performed using an ex situ fixed bed of Pt/TiO₂ with co-fed H₂ at atmospheric pressure. Compared to previous state-of-technology benchmarks, advancements in catalyst design and synthesis methodology enabled a four-fold reduction in Pt loading and a 400% increase in time on stream without negatively impacting upgrading performance. Additionally, a first-of-its-kind integrated assessment of waste gas adsorption showed near quantitative recovery of acetone and 2-butanone, which collectively represent approximately 5% of the biomass carbon. The valorization of these co-products opens opportunities to support decarbonization of the chemical sector while simultaneously improving the overall process carbon efficiency to >40%. After condensation, the CFP-oil was co-hydrotreated with straight run diesel (10 : 90 vol%) to achieve 95% biogenic carbon incorporation. The oxygen content of the hydrotreated oil was below detection limits, and the diesel fraction exhibited a cetane number and cloud point suitable for a finished fuel. This manuscript concludes by highlighting remaining research needs associated with improving thermal management during catalyst regeneration, mitigating catalyst deactivation due to inorganic deposition, and demonstrating the durability of biomass feeding systems when operated in hydrogen-rich environments.