Modulating selectivity in CO2 Methanation through Rhodium catalysts supported on Zirconia-Chemically grafted SBA-15

Abstract

This study presents the impact of ZrO2 incorporation on Rh-supported SBA-15 catalysts for CO2 hydrogenation. ZrO2 was chemically grafted onto the SBA-15 surface, varying concentrations of ZrO2 from 5 to 20 wt.%. The ZrO2-free catalyst favored CO production, leaning towards the reverse water gas shift reaction. The addition of ZrO2 notably enhanced catalytic activity and led to a significant shift in selectivity towards methane production. The selectivity modulation is linked with the modified surface of SBA-15, covered with a ZrO2 phase. The FTIR characterization under reaction conditions evidenced Rh-carbonyls formation in all samples. However, in catalysts materials with ZrO2, formate species are also formed, probably promoted by the Zr-OH groups. A linear relation between formate species and the CH4 selectivity suggests that the methane formation could be associated with the hydrogenation of formate species, while the desorption of carbonyls on Rh can explain the CO generation.