Niobium rich SBA-15 materials – preparation, characterisation and catalytic activity

Hexagonally ordered mesoporous niobiosilicates of SBA-15 type were synthesised by a new synthesis route in which the use of hydrochloric acid was avoided. This route allowed the incorporation of much higher amounts of niobium into the mesoporous network (Si/Nb between 15 and 5) as compared to the conventional method of preparation. The location of niobium was determined by UV–Vis and XRD techniques. The latter combined with N2 adsorption measurements allowed the estimation of texture/structure parameters. The high niobium content in the NbSBA-15 had a significant impact on the sulphurisation of methanol leading to the formation of organic sulphur compounds. It is well correlated with the acidity of the materials measured by pyridine adsorption followed by FTIR studies. Such a relationship was not observed for oxidation of methanol and epoxidation of cyclohexene showing that the redox properties are not linear related to the amount of niobium if Si/Nb is equal or below 15 (as applied in this work).