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CO2 conversion via hydrogenation over 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 %. [ABSTRACT FROM AUTHOR]

The fundamental role of the carbon carrier Sibunit® in the formation of active and selective phases in low-percentage Pt-containing catalysts Pt/C, Pt/Ni/C, Pt/Ni-Cr/C for the complete dehydrogenation of bicyclohexyl into biphenyl (320 °C, 1 atm) is shown. The Pt/Ni-Cr/C catalyst showed the greatest activity and selectivity in the complete dehydrogenation of bicyclohexyl into biphenyl. Detailed analysis of the catalyst surface by XPS, TEM-HR and EDX methods revealed two main processes associated with the high activity and successful course of the reaction of bicyclohexyl dehydrogenation: the formation of an active carbide Pt 1- x C x phase and graphitization of the carbon carrier. Both these processes are realized equally in the Pt/Ni-Cr/C catalyst demonstrating the highest activity. The formation of the Pt 1- x C x carbide phase at a low extent of graphitization of the catalyst surface is predominant for the Pt/C catalyst. Graphitization of the carbon carrier is most pronounced for Pt/Ni/C, where the yield of biphenyl is significantly reduced. The formation of graphite for the Pt/Ni/C catalyst at the metal-carrier interface leads to the encapsulation of a metal particle in a graphite shell, which apparently determines its low activity in the conversion of bicyclohexyl.