Influence of the drying treatment on the performance of V–Nb mixed oxides catalysts synthesised via sol–gel

• Sol–gel synthesis of NbVO5 amorphous catalysts using different V/H2O ratios
• Study of the microwave drying influences on properties of synthesised catalysts.
• Crystallinity, reducibility and surface acidity were investigated by DTA, XRD, TPR, TPD.
• Catalytic performances in the oxidative dehydrogenation of ethane were investigated.
• Microwave drying and low V/H2O ratio were provided the best catalytic performances.

Mixed oxides NbVO5 amorphous catalysts have been synthesised by means of the sol–gel technique using different vanadium oxide to water ratios and gel drying treatments: in particular air-drying at room temperature and microwave heating have been adopted. Successively, the dried materials were calcinated up to 550 °C in flowing air. Brunauer–Emmett–Teller (BET) surface area analysis showed that this parameter depends on drying method and on the thermal treatment. Differential thermal analysis (DTA) proved that the crystallisation process of the NbVO5 powders occurred at lower temperature when microwave drying was used. An increase of crystallinity was also recorded by X-ray diffraction (XRD) analysis for samples prepared using a high V/H2O ratio and dried by microwave heating. These samples also show high reducibility and surface acidity, as demonstrated by temperature programmed reduction (TPR) and temperature programmed desorption (TPD) techniques respectively.An improvement of the catalytic performances for the gel dried by microwave heating in the oxidative dehydrogenation of ethane at 550 °C has been observed.