Carbon Oxide Hydrogenation over GdBO 3 (B = Fe, Mn, Co) Complex Oxides: Effect of Carbon Dioxide on Product Composition

The catalytic properties of GdFeO 3 , GdСоO 3 , and GdMnO 3 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: GdFeO 3 < GdMnO 3 ≤ GdСоO 3 ; carbon dioxide conversion increases in the reverse order. Differences in the catalytic characteristics of GdFeO 3 , GdMnO 3 , and GdCoO 3 are attributed to different forms of chemisorbed CO, CO 2 , and H 2 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, GdCoO 3 is partially decomposed into Gd 2 O 3 , Co, and Gd 2 O 2 CO 3 . It is assumed that carbon oxides are adsorbed by Gd 3+ 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.