With ever growing concerns over increased anthropogenic carbon dioxide concentrations, we have developed a catalytic system to convert carbon dioxide to methanol. In this system, carbon dioxide, a greenhouse gas, is converted into methanol, an important building block for the generation of commodity and fine chemicals. This system exploits metal-ligand cooperativity via use of a PNP-based ruthenium hydrogenation catalyst. The catalyst first hydrogenates carbon dioxide to formic acid, which then undergoes an amidation reaction with cocatalytic amine to form the corresponding amide. The amide can finally be hydrogenated by the same ruthenium catalyst to generate methanol and regenerate the amine. Recent research aims to explore different PNP-catalysts to discover both more reactive and more stable complexes by investigating electronically and sterically different substituents on the phosphorous atoms. In order to better understand and compare these catalysts, high pressure in-situ Raman monitoring was utilized to elucidate kinetic data for dimethylformamide hydrogenation, the amide generated in the current system. Carbon dioxide hydrogenation was also studied in detail. Five catalysts were identified as having distinctly different propensities to hydrogenate carbon dioxide and dimethylformamide. Three main catalysts were selected due to their high reactivity and stability, and applied to the full cascade system converting carbon dioxide to methanol. Most notably, by combining the best carbon dioxide hydrogenation catalyst and the best dimethylformamide hydrogenation catalyst, a synergistic effect is apparent due to the increased production of methanol compared to the catalysts alone. Further experimentation is ongoing to gain a more detailed understanding of the mechanistic pathway operable, as well as the differences in reactivity.

Ruthenium-PNP catalyzed cascade conversion of carbon dioxide to methanol

254th National Meeting (2017)

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