Continuous Homogeneously Catalyzed Hydrogenation of CO 2 to Formic Acid in Miniplant Scale

A homogeneously catalyzed, high‐pressure hydrogenation reaction to convert carbon dioxide to formic acid was investigated in a continuous miniplant. In the multiphase reaction system, the ruthenium‐based catalyst was retained in a nonpolar phase, and the produced formic acid was reactively extracted in a polar phase. The feasibility of catalyst recycling by phase separation at reaction conditions and recirculation into the reactor was demonstrated. Although the produced formic acid was stable at ambient conditions, an increase in temperature to 333 K partly caused its decomposition due to catalyst traces in the polar phase. Phase equilibrium experiments revealed that decreasing the temperature lowers the catalyst concentration in the polar phase, thereby mitigating formic acid decomposition.