Carbon Oxide Hydrogenation over GdBO3 (B = Fe, Mn, Co) Complex Oxides: Effect of Carbon Dioxide on Product Composition

The catalytic properties of GdFeO3, GdСоO3, and GdMnO3 perovskite-type complex oxides in carbon oxide hydrogenation are studied. A correlation between the composition and catalytic properties of the oxide is found. It is shown that carbon monoxide conversion increases in the following order: GdFeO3 < GdMnO3 ≤ GdСоO3; carbon dioxide conversion increases in the reverse order. Differences in the catalytic characteristics of GdFeO3, GdMnO3, and GdCoO3 are attributed to different forms of chemisorbed CO, CO2, and H2 and the hydrogen mobility across the catalyst surface. The introduction of carbon dioxide into the reaction mixture suppresses the formation of olefins and causes an increase in methane yield. In the catalytic process, GdCoO3 is partially decomposed into Gd2O3, Co, and Gd2O2CO3. It is assumed that carbon oxides are adsorbed by Gd3+ ions (A site), while transition metal ions (B site) are responsible for the formation of atomic hydrogen. It is presumed that carbon sites formed on the surface differ in catalytic activity: some of them are responsible for the formation of unsaturated hydrocarbons, and the others are responsible for the formation of paraffins.