Catalyst-Green Solvent System for Highly Efficient Production of Carboxylic Acids from Light Oxygenates, CO₂ and H₂

Catalytic hydrogenation of carbon dioxide (CO2) for the preparation of higher carboxylic acids is attractive and promising. Herein, we demonstrate a general strategy for producing higher carboxylic acids via reaction of CO2 and H-2 with light (C-2 similar to C-4) oxygenates such as ketones, alcohols, polyols, ethers and epoxides. In a green solvent consisting of ionic liquid (1-ethyl-3-methylimidazolium iodide) and water, the reaction can be efficiently accelerated by RhI3 catalyst and I-2 promoter at 170 degrees C. Very high or remarkable yields of higher carboxylic acids were synthesized via C-C bond formation between the intermediates generated from the oxygenates and CO2. Detailed study indicated that the catalyst and the solvent had excellent synergistic effect for promoting the reaction. The strategy can effectively convert the bulk and inexpensive feedstocks to value-added carboxylic acids, and therefore is promising for commercial application.