Hydrogenation of CO2 conjugated with dehydrogenation of cyclohexane over an intermetallic catalyst

Abstract

Transformations of carbon dioxide catalyzed by the hydride form of [TiFe0.95Zr0.03Mo0.02]Hx, by the industrial Pt/Al2O3 catalyst, and by a mixture of the above materials were studied. Study of the thermal desorption of H2 showed the presence of two forms of absorbed hydrogen, namely, the weakly bound hydrogen, which is evolved from the intermetallic structure on heating to 430 °C under Ar, and the strongly bound hydrogen (SBH), which remains in the intermetallic compound at higher temperatures (up to 700 °C). In a carbon dioxide medium, the SBH enters into selective CO2 reduction to give CO at 350—430 °C and 10—12 atm. The selectivity of the formation of CO reaches 80—99% for conversion of CO2 between 50—70%, the SBH being consumed almost entirely for the reduction of CO2. In the presence of the mixed catalyst, conjugate reactions proceed efficiently; dehydrogenation of cyclohexane yields hydrogen, which is consumed for CO2 hydrogenation.