Synergetic effect in RuxMo(1-x)S2/SBA-15 hydrodesulfurization catalysts: Comparative experimental and DFT studies

Abstract

The effect of introducing Ru impurities into the MoS2crystalline structure of the sulfided RuxMo(1-x)S2/SBA-15catalysts have been investigated using density functional theory (DFT) calculations and the catalyst character-ization by different techniques (chemical analysis (ICP-AES), temperature-programmed reduction (TPR), X-raydiffraction (XRD), N2physisorption, DRIFTS of adsorbed pyridine (DRIFTS-Py) and X-ray photoelectron spec-troscopy (XPS)). The catalyst activity was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT)reaction carried out in a batch reactor,T= 320 °C and total H2pressure of 5.5 MPa. From electronic structureDFT calculations is was concluded that the 4d orbitals of both Mo and Ru played an important role in the catalystoptimization being the processes of transport and charge transference the most important ones. It was found thatthe enrichment with Ru, promotes a greater electronic participation (DOS at the Fermi level) of the differentatoms in the RuxMo(1-x)S2phase leading to metallization of the Mo ions. The catalyst activity in HDS of DBTreaction demonstrated a similar behavior to that of theoretical density of states (DOS) calculated via DFT. Allbimetallic systems presented the synergetic effect between Ru and Mo in the HDS of DBT reaction overRuxMo(1-x)S2/SBA-15 catalysts. The highest activity observed for Ru content ofx= 0.4 was consistent with theoretical results predicting that the optimum DOS contributions should be aroundx= 0.44. The most activeRu0.4Mo0.6S2/SBA-15 exhibit the best hydrogenation properties linked with the Ru-induced metallization of Moions in the Ru0.4Mo0.6S2phase. This catalyst showed two-fold higher hydrogenation properties than CoMoS/γ-Al2O3reference catalyst. The linear dependencies of initial activity on Brønsted-to-Lewis acidities ratio (fromDRIFT-Py) and total metal surface exposure (from XPS) were observed.