Synthesis, Characterizations And Catalysis Of Al-SBA-15 And Fe-SBA-15 Mesoporous Materials

The introduction of metal ions in the framework of mesoporous materials SBA-15 is one of the important approaches for its catalytic applications. Nevertheless, it is very difficult to directly incorporate metal atom into the framework of SBA-15 material because it is synthesized under strong acidic conditions. It is a big challenge to synthesize metal-substituted SBA-15 materials with high metal contents under acidic conditions.In this work, highly ordered Al-SBA-15 mesoporous materials with Si/Al ratios of 1 to 100 were synthesized via a hydrolysis-controlled and a two-steps pH adjusted approaches. It was found that the matched hydrolysis and condensation rate of silicon and metal precursors is most important to achieve highly ordered mesoporous materials. The acidity of the solution is decisive for the successful incorporation of metal atoms into the mesoporous materials. Aluminum atoms can be stoichiometrically incorporated into the SBA-15 material by using a single molecular precursor with Al-O-Si bonds.The acidity of the mesoporous aluminosilicates with high aluminum content was investigated by NH3-TPD and IR spectra of adsorbed pyridine. It was found that the mesoporous aluminosilicates can only generate medium acidity due to the coordinated environment of aluminum in mesoporous materials is not as rigid as that in zeolite. The amount of acidic sites of mesoporous materials increased with aluminum content. The amount of Br?nsted acidic sites and total amount acidic sites don't increase with the content of aluminum when the Si/Al ratios lower than 10. The Al-SBA-15 materials show high activity and stability in the alkylation of 2, 4-di-tert-butylphenol with cinnamyl alcohol because of its medium acidity and the large pore size.