Optimized Distillation design for CCU-Based Formic Acid Process: A Combined Experimental and Modeling Approach

The global effort to mitigate carbon dioxide (CO 2) emissions has spurred the development of Carbon Capture and Utilization (CCU) technologies, which transform CO2 into valuable products. This study investigates a formic acid (FA) production process through CO2 hydrogenation, mediated by amines. Appropriate selection of the mediating amines is a crucial factor that determines the economic feasibility of the system, since the amount of steam energy required in the purification process of FA depends significantly on the FA-amine interactions. In this study, a systematic screening process for identifying the optimal amine which enhances FA production while minimizing energy consumption, is proposed. The four-step screening process comprises the following: 1) a preliminary screening step based on boiling points and pKa values, 2) COSMO-RS simulations for examining the azeotropic points, 3) rigorous VLE experiments to model the FA-amine relationships, and 4) process modeling to determine the FA production efficiency of candidate amine systems. Experimental VLE data confirmed the presence of azeotropes in most FA-amine systems, highlighting the need of exploration for efficient separation techniques, including pressure-swing distillation (PSD). 1-butylimidazole emerged as the most promising SA for recovering only the light component, while 1-ethylimidazole was optimal for recovering both light and heavy components, providing a cost-effective solution due to the azeotrope's pressure sensitivity in a binary system with FA. The study concludes with single-column and PSD designs that achieve high-purity FA production, supporting the commercial viability of this CCU-based process.