Modelling of formic acid production using solventless trialkylamine reduction strategies

Solventless fed-batch experiments at elevated pressures were performed to gain insights into the performance of triethylamine as an extraction base during the direct hydrogenation of CO₂ to formic acid. No formic acid was observed in the bulk liquid after several hours of reaction using an Au/TiO₂ catalyst. Analysis on the spent catalyst revealed significant formic acid build-up within the catalyst pores. A fundamental, continuum model based on Cahn-Hilliard spinodal decomposition was developed and validated to study the influence of the biphasic nature of formic acid - trialkylamine structures during reaction at pore level. The biphasic nature of the tertiary alkylamine - formic acid system was found to have significant implications for the reaction performance of the proposed system, demonstrating the requirement of additional solvents besides tertiary amines to ensure solubility of the complete system.