Novel Self-Solidifying Polymeric Ionic Liquid via Phenolic Condensation as Efficient and Reusable Catalyst for Biodiesel Production

A novel self-solidifying polymeric ionic liquid (P-[DMT-PS][PHSA]) was synthesized via phenolic condensation and applied as a recyclable acidic catalyst for biodiesel production. The catalyst demonstrated high acidity (4.68 mmol/g), excellent thermal stability, and effective catalytic performance, achieving 98.19% oleic acid conversion under optimized conditions. Notably, P-[DMT-PS][PHSA] is soluble during the esterification, allowing it to act as a homogeneous catalyst, and re-precipitates upon methanol evaporation for easy recovery. Even after 10 cycles, the catalyst maintained 97.0% oleic acid conversion, highlighting its stability and reusability. Additionally, P-[DMT-PS][PHSA] exhibits remarkable substrate adaptability, effectively catalyzing the esterification of a range of substrates. This study presents a simple and mild synthesis method for polymeric ionic liquids and showcases P-[DMT-PS][PHSA] as a promising alternative to conventional catalysts for biodiesel production.