Efficient CH4 oxidation to C1/C2 oxygenates over cluster-dispersing Rh decorated ZSM-5

Abstract

Crafting highly dispersed active metal sites on catalysts is an optimal method for improving the catalytic reactivity and stability, as it would improve atomic utilization efficiency, enhance reactant adsorption and activation ability through unique geometric and electronic properties. In this study, two synthesis methods were employed (ammonia evaporation (AE) and the impregnation method (IM)) to load Rh species onto the ZSM-5 support in order to attain tunable dispersivity, during which a 1.25-fold increase in the total yield of liquid oxygenated products (32 433.33 μmol g_cat⁻¹ h⁻¹) was achieved specifically over a Rh–ZSM-5-AE sample when the reaction was carried out at a loading level of 0.3 wt% and at 240 °C for half an hour. The results of the study revealed that this elevated productivity originated from the smaller size and higher degree of dispersion of Rh clusters on AE samples. It was demonstrated that the ammonia evaporation method would cause Si leaching and introduce a substantial number of –OH groups during the preparation process, which worked in coordination in altering the electronic structure of Rh species. Consequently, these modifications modified the disordered Rh precursor adsorption, which resulted in a more homogeneous distribution of Rh species, hence facilitating the activation of methane. This study offers a practical and constructive approach for improving the dispersion of Rh nanoclusters and designing strong metal–support interactions (SMSI).