Electrochemical Synthesis of Ortho- and Para-Hydroxybenzoic Acids Using CO₂: Experimental and Simulation-Based Optimization

The electrochemical synthesis of ortho- and para-hydroxybenzoic acids (o-HBA and p-HBA) utilizing CO₂ as a carbon source represents a sustainable and energy-efficient alternative to traditional high-temperature synthetic methods, such as the Kolbe–Schmitt reaction. These hydroxybenzoic acid isomers are valuable intermediates in pharmaceuticals, polymers, and cosmetics. This study presents an integrated approach combining experimental electrochemical analysis with process modeling using Aspen Plus to optimize key parameters affecting product yield and selectivity. Laboratory experiments identified the optimal reaction conditions at an applied potential of −1.2 V (vs. Ag/AgCl), 3 atm CO₂ pressure, and 50 °C, yielding 55.6% o-HBA and 38.2% p-HBA. Electrochemical behavior was further supported by simulations incorporating electrolyte thermodynamics (ELECNRTL) and yield-based reaction blocks (RYield), which accurately reflected observed trends. The model also included a recycle loop that improved the effective CO₂ utilization to over 76.8%, demonstrating process efficiency and resource recovery. Despite slight discrepancies between experimental and simulated yields due to modeling simplifications, the framework proved effective for evaluating process scalability. The study underscores the potential of CO₂-based electrochemical methods as green pathways for producing high-value chemicals while contributing to carbon mitigation strategies. This work lays a foundation for future advancements in reactor design, catalyst development, and industrial integration of CO₂ valorization technologies, aligning with global sustainability goals and the circular carbon economy.