Structure and acidity of Mo/H-MCM-22 catalysts studied by NMR spectroscopy

摘要: A comprehensive study on physical and chemical properties of Mo/MCM-22 bifunctional catalysts has been made by using combined analytic spectroscopic techniques, such as adsorption, elemental analysis, 129 Xe 31 P NMR adsorbed trialkylphosphine oxide probe molecules. Samples prepared the impregnation method with Mo loadings ranging from 2–10 wt.% have examined results are compared that obtained samples mechanical mixing MoO3 or Mo2C agents. Sample calcination treatment is essential in achieving a well-dispersed metal species Mo/MCM-22. It was found that, upon initial incorporation, tend to inactivate both Bronsted Lewis sites locate predominantly supercages rather than 10-membered ring channels MCM22. However, loading exceeds 6 wt.%, excessive migrate toward extracrystalline surfaces catalyst. consistent decrease concentrations acid increasing further decreases acidities were observed. These provide crucial supports for interpreting peculiar behaviors previously observed during conversion methane benzene over catalyst under non-oxidative conditions, which an optimal performance achieved wt.%. The effects incorporation porosity acidity features discussed. # 2004 Published Elsevier B.V.