The Role of Ir in Ternary Rh-Based Catalysts for Syngas Conversion to C Oxygenates.

Transition metal modified Rh-catalysts can be used for converting syngas (CO + H) into C oxygenates. It has been found that Mn has a favorable effect in the selectivity towards oxygenates, while addition of Ir to the binary Rh-Mn catalysts significantly increases the space-time-yield (STY) of C oxygenates, mainly by formyl formation at the early stages of conversion. Quantum mechanical calculations used to investigate the distribution of promoter sites in Rh-rich nanoparticles show that moderately high Mn/Ir ratios result in particles with all 3 metals on the surface, and that Ir atoms act as co-adsorption sinks of CO and H leading to HCO in the initial stages. [ABSTRACT FROM AUTHOR]