Synthesis of higher carboxylic acids via reaction of polyols with CO2 and H2

Abstract

Synthesis of value-added chemicals from biomass-derived polyols and CO 2 is of great importance. Herein we report a strategy to produce higher carboxylic acids by the reaction of polyol, CO 2 , and H 2 . The reaction can be efficiently accelerated by Rh catalyst in a binary solvent of ionic liquid (1-butyl-3-methylimidazolium iodide) and water, where cheap and nontoxic I 2 was used as a promoter. The reaction can occur at above 100°C. At optimal conditions, the yield of the carboxylic acids was as high as 86.4%. The catalytic mechanism is proposed based on a series of control experiments. Interestingly, the polyol could be effectively transformed into olefin intermediate at metal-free and mild conditions, which was the key to the success of this strategy. The peculiar solvent effect was also favorable to the reaction. In addition, the catalytic system was adaptable to various polyol substrates. • Higher carboxylic acids are effectively produced from polyol, CO 2 , and H 2 • The Rh/I 2 catalyst may accelerate the reaction in the ionic liquid/water solvent • The polyol is transformed into the olefin intermediate at metal-free condition • Various polyols and simulated crude glycerol could be applied as substrates The accumulation of CO 2 in the environment and the over-reliance on dwindling fossil fuel may cause disastrous consequences. In mitigating these challenges, chemical utilization of CO 2 and biomass-derived polyols have aroused extensive interest among scientists all over the world. As a clean reductant, H 2 can be produced from water by renewable energy, such as wind, hydro, and solar energy. Higher carboxylic acids are basic and very useful chemicals. Synthesis of higher carboxylic acids from CO 2 usually needs expensive or air/water-sensitive substrates, such as organometallic reagents, organic halides, and/or unsaturated hydrocarbons. In addition, metallic reducing agents and/or silanes are often needed to drive the reactions. In this report, we developed a method to efficiently produce higher carboxylic acids via reaction of CO 2 , biomass-derived polyols, and H 2 . The catalytic system was recyclable and may apply to various polyols and simulated crude glycerol. Higher carboxylic acids are efficiently synthesized by the reaction of biomass-derived polyols, CO 2 , and H 2 accelerated by a Rh catalyst with cheap and nontoxic I 2 promoter in a binary solvent of 1-butyl-3-methylimidazolium iodide and water. The catalytic system may apply to various polyol substrates and simulated crude glycerol.