Carbon Dioxide Hydrogenation under Subcritical and Supercritical Conditions in the Presence of 15% Fe/SiO2 Catalyst
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Results are presented from a comparative study of CO2 hydrogenation under gas-phase and supercritical conditions for CO2 in the presence of 15% Fe/SiO2 catalyst. The reaction is studied in the temperature range of 300–500°C at atmospheric pressure under gas-phase conditions and at a pressure of 95 atm under supercritical conditions at an Н2 : СО2 molar ratio of 2 : 1. It is found that the process proceeding under supercritical conditions lowers CO selectivity from 90–95 to 30–50% over the range of temperatures and raises (up to 60%) the hydrocarbon selectivity. In contrast to gas-phase hydrogenation, the formation of alcohols is observed in the reaction under supercritical conditions. Using a combination of thermogravimetry, differential thermogravimetry, and differential thermal analysis (TG–DTG–DTA), it is shown that the process proceeding under supercritical conditions results in a 2.2-fold drop in the amount of carbon-like deposits on the catalyst surface. X-ray diffraction analysis shows that under gas-phase process conditions, graphite-like structures form on the catalyst surface; this effect is not observed under supercritical conditions. The developed catalyst and the process for CO2 hydrogenation can be recommended for the further modification and improvement of the properties of a catalyst based on iron nanoparticles that is much (10–100 times) cheaper than the previously reported CO2 hydrogenation catalysts.
Keywords:supercritical fluid hydrogenation carbon dioxide supercritical conditions catalysis iron catalyst
The authors thank I.V. Mishin (Zelinsky Institute of Organic Chemistry) for her assistance in our XRD studies of the catalyst samples and V.D. Nissenbaum (Zelinsky Institute of Organic Chemistry) for performing our TG–DTG–DTA studies of the samples. This work was supported by the RF Ministry of Education and Science, project identifier RFMEFI61615X0041.
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