Hydrogen-free biorefinery pathway for sustainable fuel production: kinetics and thermodynamics insights

Abstract

This study explores a two-stage, hydrogen-free biorefinery process for sustainable biofuel production from Jatropha oil (JO), focusing on decarboxylation and Simultaneous Fluid Catalytic Conversion and Recovery (SFCCR) stages. Supported oxalates of bimetallic nanoparticles-Nickel-Cobalt (NiCo-Ox/AC), Nickel-Molybdenum (NiMo-Ox/AC), and activated carbon (AC)-were used as catalysts to investigate kinetic and thermodynamic parameters, optimizing reaction conditions and evaluating product yields. Optimal conditions were achieved at 360°C for decarboxylation with a 4.9g catalyst load over 64 minutes, and 390°C for SFCCR with a 5g catalyst load over 75 minutes. NiCo-Ox/AC produced the highest overall liquid hydrocarbon yield (92.87%), while NiMo-Ox/AC showed superior bioaviation fuel yield (87.5%) and selectivity, outperforming NiCo-Ox/AC (84.06%) and AC (85.0%). AC, however, favored biogasoline and biodiesel production. The biocrude oil produced exhibited n-paraffin profiles similar to conventional crude, supporting its viability as a drop-in fuel. The bioaviation fuel met ASTM D1655-18a standards, with carbon chains in the C9-C16 range. Thermodynamic analysis revealed the endothermic and spontaneous nature of decarboxylation at higher temperatures, with Gibbs free energy values ranging from-4.06 to-1.44 kJ/mol. This research confirms the feasibility of a hydrogen-free biorefinery pathway, offering an efficient alternative to hydrogen-dependent processes, and provides foundational insights for optimizing sustainable fuel production in future biorefineries.