A DFT study of the effect of K and SiO2 on syngas conversion to methane and methanol over an Mo6P3 cluster

Abstract

Synthesis gas (CO+H2) conversion to CH4 and CH3OH over an Mo6P3 cluster, an Mo6P3–Si3O9 and a K–Mo6P3–Si3O9 cluster has been studied using density functional theory (DFT). The study focused on the reaction between the intermediate species CH2OHad+Had, comparing methanol formation to C–O bond scission that yields CH2.ad+H2Oad species. The activation energies of both the reactions decreased on the Mo6P3–Si3O9 and the K–Mo6P3–Si3O9 clusters compared to the Mo6P3 cluster. However, on the K–Mo6P3–Si3O9 cluster, the activation energy for methanol formation (12.1 kcal/mol) was higher than the C–O bond-breaking activation energy (9.9 kcal/mol). Although the DFT study predicted preferential formation of CH4 versus CH3OH on all the Mo6P3 clusters, the study also predicted an increased formation of CH3OH with the addition of K and experimental measurements are in agreement with this prediction.