Experimental Study on Dehydration of Propane Oxidation Catalysts Based on Molybdenum over Ti-based Nanostructures

Propylene is one of the most important building blocks in petrochemical and polymer processes. The demand for propylene is growing faster than that for ethylene; therefore the current production is not in line with the forecast market demand for olefins. In this paper, oxidative dehydrogenation has been used in order to obtain propylene from propane, and oxygen was used as the oxidant. Molybdena-containing catalysts with nominal loading 5, 10, and 15 wt% were supported on titanate Nanotubes. Also, for the sake of comparison, Degussa TiO2 P25 supported molybdena catalyst (5 wt%) was elaborated. All catalysts were prepared by incipient wetness impregnation method and were calcined at 500°C. Analysis by FT-IR, XRD, Raman, BET, TEM, and TPR was done. The results show that the main characteristics of the titanate nanotube were confirmed by FT-IR, and the presence of H2Ti5O11.H2O was confirmed by XRD technique. Moreover, no evidence of the existence of Na-O-Ti bond was observed, and an important bond for the existence of the stable phase of the titanate nanotubes, Ti-O-H, was detected by Raman spectroscopy. TEM micrographs exhibited the layered structure of the prepared sample. The phase of the titanate nanotubes supported molybdena catalysts altered during calcination, in order to do that anatase phase was observed in all the samples. However, the rutile phase was detected along with the anatase phase in Degussa TiO2 P25 and 15 wt% supported molybdena catalyst. Calcination led to BET-specific surface area loss. The crystalline phase of molybdenum oxide of higher loading shows a higher maximum reduction peak by H2-TPR profile. As compared to titanate nanotubes, in the identical molybdena loading lower specific surface area as well as inferior catalytic activity and lesser lifetime was observed for TiO2 P25 support. However, increasing molybdena loading on the titanate nanotubes led to catalytic performance deterioration. The highest yield is for MoTNT-10 with a selectivity 31% and conversion 21.4%.