Temperature‐programmed surface reaction study on C 2 ‐oxygenate synthesis over SiO 2 and nanoporous zeolitic material supported Rh–Mn catalysts

Temperature‐programmed surface reaction (TPSR), temperature‐programmed reaction (TPR) and temperature‐programmed desorption (TPD) were used to study the synthesis of C 2 ‐oxygenates from syngas over Rh–Mn‐based catalysts supported on amorphous silica and mesoporous MCM‐41 supports. Both TPD and TPSR reveal the existence of several different kinds of CO species on the catalyst surface in the course of the catalytic reaction (linear, geminal, bridged and tilt‐adsorbed CO species) but only the bridged form and tilt‐adsorbed CO species are the precursors for CO dissociation and the formation of C 2 ‐oxygenates. The formation temperature of acetaldehyde is higher than that of ethanol, which suggests that they may be formed via different mechanisms. The ethanol formation activity over the Rh–Mn/MCM‐41 catalyst is lower than that over the Rh–Mn/SiO 2 , which suggests that the number of active sites for ethanol formation are fewer on the surface of Rh–Mn/MCM‐41. However, the acetaldehyde formation activities are almost identical for the Rh–Mn catalysts supported on amorphous SiO 2 and MCM‐41, meaning that acetaldehyde and ethanol might be formed on different active sites.