EFFECT OF THE B-SITE CATION IN GdBO3 (B = Fe, Mn, Co) PEROVSKITE-TYPE OXIDES ON CATALYTIC PERFORMANCES FOR SYNGAS PRODUCTION

Perovskite-type compounds are an important class of materials and there are extensively studied in high-temperature catalytic processes. Dry (carbon dioxide) reforming of methane (DRM) to synthesis gas is one of the most important reactions using such materials as catalysts. In this study, perovskite-type complex oxides GdBO3 (B = Fe, Mn, Co) applied as catalysts for syngas production via dry reforming of methane. These samples were obtained by ceramic technology and were investigated by means of X-ray diffraction, scanning electron microscopy, Mossbauer microscopy, and X-ray photoelectron spectroscopy. Catalytic activities were evaluated at atmospheric pressure in the temperature raised from 773 to 1223 K under continuous flow of reactant gases with a CH4:CO2 = 1:1 ratio. The test samples catalytic activity depends on the oxygen stoichiometry in the complex oxide. Thus, the presence of oxygen vacancies in the perovskite containing cobalt cation in the B-site of the perovskite structure proved to be favorable for DRM. It was on this sample that conversions of CH4 and CO2 were the maximum values of 99 and 97% at 1223 K, respectively, while syngas was obtained with H-2/CO molar ratio close to unity. Besides, GdCoO3 showed the high stability in the DRM process: the catalytic performances retained more than 110 h time. The presence of oxygen vacancies is probably due to the crystallographic radius size of the cation introduced into the B-site of the complex oxide. Therefore, the catalytic activities of the investigated samples increased in the order: GdMnO3 < GdFeO3 < GdCoO3.