CO hydrogenation into oxygenate products over Rh-based catalysts has been studied extensively.  However, the effect of surface Rh oxidation states and the role they play in the selectivity to higher alcohols is not fully understood. In this work we have prepared two Rh-based lanthanum zirconium pyrochlore (La2Zr2O7) catalysts using a sol-gel combustion method.  In the first,  Rh cations (Rh+) are fully coordinated with oxygen anions in the La2Zr2O7 lattice structure. In  the second, metallic Rh clusters ((Rh0); <2nm) were deposited on catalyst surface of La2Zr2O7. The catalysts were characterized by TPR, XPS, XRD, ICP, TEM, SEM/EDX and BET. The catalytic selectivity results show different behaviors for the substituted and supported Rh-based pyrochlores. The supported Rh pyrochlore shows a higher selectivity for higher alcohol while Rh-substituted pyrochlore favors methanol. For the supported Rh/pyrochlore,  XPS and TPR data confirm the presence of a highly stable interface between Rh species and LZ support which could plays an essential role in providing atomically close metallic and oxidized Rh species, which are thought to be necessary to maximize higher alcohol selectivity. These Rho-Rh+ pairs facilitate the associative and dissociative adsorption rate of CO molecule on the surface while the ratio (Rh+/Rho) is responsible for a balanced rate for these two adsorption processes.

CO hydrogenation over Rh-based pyrochlore catalysts for higher alcohols synthesis

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.