Hydrogenation of Carbon Dioxide on Iron Manganese Catalysts

Abstract

The synthesis of hydrocarbons from hydrogenation of carbon dioxide bas been studied on a series of coprecipitated iron-manganese catalysts. Kinetic measurements, X-ray diffraction, Mossbauer spectroscopy, and temperature-programmed reaction of adsorbed species were used for activity tests and catalyst characterizations. The results showed that the yields of low-carbon oletins decrease, whereas the amount of methane increases with increasing manganese content in catalysts. The conversion to hydrocarbons is suppressed by the reverse water-gas shift (RWGS) reaction equilibrium. Mossbauer spectra and XRD patterns of catalysts after reaction indicate that catalysts are severely oxidized; it is speculated that the olefin producing surface structure in CO hydrogenation may be destroyed by this oxidation. A pulse-reactor study of the Boudouard reaction showed that manganese has the effect ofsuppressing CO dissociation and thus decreasing carbon content on catalysts. For CO 2 hydrogenation, the affinityto carbon on catalysts is important; therefore manganese is not a good promoter. Among all catalysts tested, pure iron has the best selectivity to olefinicand long-chain hydrocarbons.

Hydrogenation of CO2 to Olefins over Iron-Based Catalysts: A Review

“…Kinetic studies further demonstrated the effect of MnO x on promoting CO dissociation and monomer formation, reducing the effective sites of H 2 dissociation, olefin reabsorption and secondary hydrogenation [102], which promoted the generation of low-carbon olefins. Unlike CO hydrogenation, Kuei et al [103] concluded that manganese showed little promotion effect on the selectivity of olefinic hydrocarbons in CO 2 hydrogenation. Generally, manganese decreased CO dissociation ability and the carbon content on catalysts, creating the proper oxide-carbide surface structure to produce olefins in CO hydrogenation.…”