CO2 Hydrogenation on Carbides Formed in situ on Carbon-Supported Iron-Based Catalysts in High-Density Supercritical Medium.

CO2 conversion via hydrogenation on iron-based catalysts on non-carbon supports produces mainly CO or methane by the Sabatier reaction, while the formation of C2+ hydrocarbons is of greatest interest. CxHy production from CO2 may be considered as a two-step process with the initial formation of carbon monoxide by the reverse water gas shift reaction followed by the Fischer-Tropsch synthesis (FTS). In the present work CO2 hydrogenation over iron-based catalysts (Fe, FeCr, FeK) deposited on a carbon carrier has been studied. The catalyst structure has been investigated by XRD, TEM, XPS, Mössbauer spectroscopy and in situ magnetometry. Spinel-type oxide phases (magnetite Fe3O4; maggemite γ-Fe2O3, and, in the case of FeCr/C catalyst, iron chromite Fe1+xCr2-xO4) are formed on the catalysts, and they contribute exclusively to the CO production. Iron carbides, active in FTS, are formed on Fe- and FeK-catalysts during pre-activation in reducing environment and then during the reaction. The reaction over the 20Fe1K/C catalyst in supercritical high-density CO2/H2 substrate (400°C, 8.5 MPa) leads to 72% selectivity for C1-C12+ hydrocarbons (alkanes and alkenes). Under the same conditions, iron carbides do not form on the FeCr/C catalysts, and CO2 hydrogenation results in the CO formation with the selectivity of 90-100%.

Conversion of Phenol and Lignin as Components of Renewable Raw Materials on Pt and Ru-Supported Catalysts.

Hydrogenation of phenol in aqueous solutions on Pt-Ni/SiO2, Pt-Ni-Cr/Al2O3, Pt/C, and Ru/C catalysts was studied at temperatures of 150-250 °C and pressures of 40-80 bar. The possibility of hydrogenation of hydrolysis lignin in an aqueous medium in the presence of a Ru/C catalyst is shown. The conversion of hydrolysis lignin and water-soluble sodium lignosulfonate occurs with the formation of a complex mixture of monomeric products: a number of phenols, products of their catalytic hydrogenation (cyclohexanol and cyclohexanone), and hydrogenolysis products (cyclic and aliphatic C2-C7 hydrocarbons).

Carbon Dioxide Reduction with Hydrogen on Fe, Co Supported Alumina and Carbon Catalysts under Supercritical Conditions.

Reduction of CO2 with hydrogen into CO was studied for the first time on alumina-supported Co and Fe catalysts under supercritical conditions with the goal to produce either CO or CH4 as the target products. The extremely high selectivity towards methanation close to 100% was found for the Co/Al2O3 catalyst, whereas the Fe/Al2O3 system demonstrates a predominance of hydrogenation to CO with noticeable formation of ethane (up to 15%). The space-time yield can be increased by an order of magnitude by using the supercritical conditions as compared to the gas-phase reactions. Differences in the crystallographic phase features of Fe-containing catalysts cause the reverse water gas shift reaction to form carbon monoxide, whereas the reduced iron phases initiate the Fischer-Tropsch reaction to produce a mixture of hydrocarbons. Direct methanation occurs selectively on Co catalysts. No methanol formation was observed on the studied Fe- and Co-containing catalysts.