Catalytic Activities of Noble Metals Supported on Zeolites and Related Materials for the Hydrodesulfurization of Thiophenes.

Abstract

The catalytic performance of noble metals supported on zeolites and related materials such as Al-pillared clays (Al-PILCs) and mesoporous silica (MCM-41) for the hydrodesulfurization (HDS) of thiophene and benzothiophene as a model HDS reaction were investigated to develop highly active new HDS catalysts.Pt/HZSM-5, Rh/Al-PILM (montmorillonite), sulfided Rh/Al-PILH (hectorite) and Pt/MCM-41 catalysts showed high and stable activities for the HDS of thiophene which were higher than that of commercial CoMo/Al2O3 HDS catalyst. Pt/HZSM-5, Pt/Al-PILH and Pt/MCM-41 catalysts showed higher activity for the HDS of benzothiophene than CoMo/Al2O3 catalyst, indicating that these catalysts have high activity for the HDS of large organic sulfur molecules in petroleum feedstocks. Therefore, noble metals supported on zeolites and related materials might provide promising new catalysts for the HDS of petroleum feedstocks.Furthermore, noble metals supported on zeolites and related materials act as bifunctional catalysts for the HDS reactions, in which the noble metal acts as the active site for the activation of hydrogen to form spillover hydrogen and the acid sites of the support acts as the active site for activation of thiophenes. As the spillover hydrogen formed on the noble metals attacks the activated thiophenes formed on the acid sites of the support, the HDS reaction proceeds smoothly to form hydrogen sulfide and hydrocarbons. Therefore, the hydrogen activation of the noble metal and the acidity of the support must be complementary to develop much more active noble metals HDS catalysts supported on zeolites and related materials.