Structural characterisation of thermally treated molybdena-silica catalysts

Abstract

Various Mo-Si mixed oxides of different compositions. have been prepared by impregnation method and characterised by X-ray diffraction and DTA techniques. The results show that at low molybdenum concentration an interaction species, possibly resulting from the reaction of molybdic acid with surface hydroxyl groups is formed and at higher molybdenum concentration, bulk MoO₃ is formed. Nitrogen physisorption isotherms, analysed by the α_s, method, have been used to determine the physical structure of the molybdena-silica catalysts. Surface area <i>S</i>_BET,<i>S</i>_s and the pore structure have been calculated. The effect of both molybdenum content and calcination temperature on the textural properties has also been studied. Sintering of the mixed oxide starts at about 700°C and becomes more pronounced at 900°C.