Hydrogenation of CO2 over 15% Fe/SiO2 Catalyst under Sub- and Supercritical Conditions

The results of comparative studies of CO 2 hydrogenation over 15% Fe/SiO 2 catalyst under sub- and supercritical conditions are presented for the first time. The reaction was studied at 300–500 °C and atmospheric pressure in gas phase and at 95 atm under supercritical conditions. The molar H 2 : CO 2 ratio was 2 : 1. Under supercritical conditions, the selectivity to CO 2 decreased from 90–95 to 30–50 % at all temperatures, while the selectivity to hydrocarbons increased up to 60 %. The reaction under supercritical conditions, unlike gas-phase hydrogenation, produced alcohols. TG-DTG-DTA techniques were used to demonstrate 2.2-fold decrease in the quantity of carbon-like deposits in comparison to that in the gas-phase reaction. XRD studies revealed the formation of graphite-like species on the catalyst surface under gas-phase but not supercritical conditions. The developed process and catalyst for hydrogenation of CO 2 can be recommended to be further modified in order to improve the catalyst based on iron nanoparticles that is as expensive as 0.1–0.01 of the known catalysts for CO 2 hydrogenation.