Title : Ruthenium based catalyst systems for benign conversion of carbon oxides to chemicals
Abstract:
Ruthenium based catalyst systems find wide applications in catalyzing variety of chemical reactions due to versatile oxidation states of Ru, spanning from -2 to + 8, making Ru to be capable enough to manage and handle 10 electrons tuning during the reaction process. Conversion of carbon oxides via C1 gases, carbon monoxide and carbon dioxide, through environment friendly and benign route are pressingly needed due to the concern of pollution, climate change and global warming etc. and our research contributions are in line of addressing these concerns. We have developed Ru based catalyst systems and investigated them in detail for catalytic conversion of carbon oxides at laboratory scale for the hydration of carbon monoxide to formic acid, for hydrogenation of carbon dioxide to formic acid and for addition of carbon monoxide with hydrogen to olefins to produce corresponding aldehyde through hydroformylation reactions. A ruthenium-based complex, Ru-EDTA was found to be an efficient homogeneous catalyst to activate carbon monoxide as well as water molecule in hydration of CO to produce formic acid. At moderate pressures (5–20 atm) and at 10–40 0C for direct conversion of CO to formic acid in typical catalytic experiments conducted in a pressure reactor of 300 ml capacity, 75x10-3 M of formic acid was formed at 10 atm CO pressure and 40 0C. The hydrogenation of CO2 by H2 for the formation of formic acid has been investigated using ruthenium hydrotalcite (Ru-HT) catalyst. Ruthenium salt was introduced to the synthesis of HT as an active metal center to develop ruthenium based heterogeneous catalyst. Hydrotalcite here not only acted as a support for the active metal but also acted as a soft solid base avoiding the use of additional base, which is normally required under homogeneous conditions for the formation of formic acid from the hydrogenation of CO2. Reaction temperatures were in the range of 40–100?C, total pressure 10–100 bar with an ideal 1:1 ratio of pCO2:pH2. The maximum Turnover Number (TON) of 11389 was obtained for the formic acid formation under the optimized conditions at 60?C and 60 bar total pressure, using a mixture of methanol:water as a solvent (5:1, v/v). Ruthenium complexes catalyzed hydroformylation of lower and moderate alkenes for synthesizing value added corresponding aldehydes, using a mixture of carbon monoxide and hydrogen were investigated to explore the scope of ruthenium in comparison of, rhodium and cobalt based homogeneous catalyst systems, currently being practiced in industries for the production of aldehydes from alkenes. My talk will focus to address the findings of the said reactions for conversion of carbon oxides to chemicals with thorough insights in the obtained experimental results and their discussions.
