Abstract
Synthesis gas (CO + H-2) 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 + H-ad, 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.