CO2 hydrogenation to methanol over supported copper and gallium based catalysts at the atmospheric pressure

2022-8
Osmanağa, Sezer
The continuous increase of the CO2 concentration in the atmosphere has been negatively impacting the environment, due to its contribution in the global warming. Hence, it is necessary for the current CO2 valorization techniques to advance in order to make use of CO2. A possible technique is the CO2 hydrogenation to methanol and DME. The process of CO2 hydrogenation to methanol has been taking place in industry for about a century. However, due to the thermodynamic limitation imposed by the reaction stoichiometry, it has been carried out at elevated pressures of about 50100 bar to achieve high yield. Due to the high cost of supplying high pressure, it is desired to run the process at low pressures. Furthermore, it is known that dehydrating methanol into dimethyl ether (DME) via a solid acid catalyst improves the methanol and DME selectivity by suppressing the formation of the side product, CO. Catalysts that can achieve both methanol and DME production are bifunctional catalyst such as Cu catalysts supported on solid acid catalysts, such as zeolites or γ-Al2O3. In this study, the CO2 hydrogenation to methanol is carried out at atmospheric pressure, using Cu based catalysts. Different supports, including γ-Al2O3, H+-ZSM5, and CeO2, and different promoters, including Ga, Ho and La are used to prepare different catalysts with different promoter concentrations. Results showed that Cu containing and 5 wt. % Ga promoted γ-Al2O3 catalyst (10Cu-5Ga/γ-Al2O3) had the highest combined methanol and DME activity and selectivity, showing methanol and DME formation rates of 52.5 and 96.5 μmol gcat-1 h-1, respectively, and a combined selectivity of 20.5%. Those results were recorded at the optimized reaction conditions, at a temperature of 220 ℃, feed ratio of 9H2/1CO2, and gas hourly space velocity (GHSV) of 25,000 h-1.

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Citation Formats
S. Osmanağa, “CO2 hydrogenation to methanol over supported copper and gallium based catalysts at the atmospheric pressure,” M.S. - Master of Science, Middle East Technical University, 2022.