Minimizing decomposition of formic acid in microchannel reactors for efficient biomass-to-formic acid conversion

Abstract

The conversion of biomass glucose to formic acid (FA) has been demonstrated as a promising sustainable manufacturing process, further enhanced by the application of the microchannel reactor technology. However, FA decomposition remains a challenge, limiting FA yield in the catalytic oxidation process. To gain insights into the reaction kinetics of FA decomposition, the effects of reaction temperature, O₂ pressure, residence time, catalyst content (H₅PV₂Mo₁₀O₄₀), and pH value on FA decomposition were systematically investigated. The results showed that FA decomposition involved hydrothermal decomposition, acid decomposition, and catalytic oxidative decomposition. When the reaction temperature exceeded 160 °C, the degree of FA decomposition increased significantly. High oxygen partial pressure, long residence time, and high catalyst content all had a significant positive impact on the FA decomposition. The decomposition of FA in this process was found to follow second-order kinetics, with an apparent activation energy of 154.1 kJ/mol. Based on these findings, a novel strategy was proposed and evaluated by coupling reaction and extraction processes facilitated by a gas–liquid-liquid three-phase flow configuration in a microchannel reactor, enabling the in-situ extraction of FA from the strong oxidative environment using isoamyl alcohol. By minimizing the oxidative decomposition of FA during FA production, this development provides an effective means to enhance the process efficiency of biomass-to-FA production.