Brønsted-Acid-Guided Esterification: Mechanistic and Kinetic Insights for Long-Chain Fatty Acid to Alkyl Ester Conversion on a Heterogenized Porous Acid Platform

• Richa Singh

  Author

This comprehensive study investigates the acid-catalyzed esterification of sterically demanding carboxylic acids with lower alcohols using a heterogenized Brønsted acid system embedded within a bimetallic metal-organic framework. The research emphasizes mechanistic pathways, kinetic behavior, and substituent effects fundamental to organic synthesis. The developed HPMo@Bi/Ce-BTC catalyst demonstrates exceptional catalytic performance through optimized site density and acid strength, achieving 92.7\% conversion of oleic acid under moderate conditions (150°C, 5 h, methanol: oleic acid = 20:1) while maintaining excellent recyclability over six cycles. Kinetic analysis reveals pseudo-first-order behavior with an apparent activation energy of 60.9 kJ mol$^{-1}$, consistent with chemically controlled reaction pathways. A classical stepwise mechanism is substantiated, involving carbonyl activation through protonation, nucleophilic addition forming tetrahedral intermediates, water elimination, and product liberation. Substrate scope investigations across C12–C18 saturated and unsaturated fatty acids with various primary alcohols demonstrate steric modulation of transition-state accessibility, with reduced rates observed for bulkier nucleophiles aligning with established nucleophilic acyl substitution principles. Operational stability assessments through reuse experiments, hot-filtration tests, and post-reaction characterization confirm authentic heterogeneous behavior with minimal leaching, highlighting the practical utility of immobilized strong acid systems for scalable esterification of complex organic feedstocks in sustainable biodiesel production.

• PDF

Copyright (c) 2026 International Journal of Clinical Research and Medical Sciences

This work is licensed under a Creative Commons Attribution 4.0 International License.