From Bio-Based Solvents to a Phosphonium Salt on a Biorefinery Concept: Multiobjective Optimization-Extended Techno-Economic Assessment

Biobased solvents in biorefineries are pivotal for advancing sustainable chemical manufacturing, especially for the production of ethyltriphenylphosphonium bromide (ETPB), which is essential for various applications. In this study, optimizing the solvent and temperature conditions for the synthesis of ETPB significantly enhances the yield and process sustainability. Screening of 12 solvents revealed that isopropanol was the most efficient solvent, owing to its effective solvation of the ionic transition states. Optimal conditions included a temperature range of 132–146 °C. Multiobjective optimization utilizing a genetic algorithm identified a balanced solvent-to-triphenylphosphine ratio of 46.2 mol/mol and a temperature of 135.7 °C as optimal for maximizing yield (76.1%) while minimizing health and environmental risks. Breeding material factor peaked at 0.9 kg/kg under optimal conditions, while environmental impact assessments showed that the recycling potential of isopropanol reduced solvent costs to 7–10% of the total expenses. Thus, isopropanol has emerged as a viable solvent, offering high yield, cost-effective recycling, and minimal environmental impact.