Preparation and characterization of vanadia catalysts supported on non-porous, microporous and mesoporous silicates for oxidative dehydrogenation of propane (ODP)

The present study focuses on the synthesis and characterization of vanadia catalysts supported on non-porous (SiO2), microporous (silicalite), mesoporous (MCM-41, HMS, SBA-15) and ultra-large mesoporous (MCF) silicate materials. The structure and porosity characteristics of the above mesoporous supports were verified by means of XRD, N2 porosimetry and HR-TEM studies. Vanadium was introduced in the porous materials via wet impregnation of vanadium oxalate complex in strongly acidic aqueous media. No crystalline V2O5 phases were found on the surface of all the above mesoporous supports for V loadings as high as 8 wt.%, in contrast to microporous zeolite silicalite and non-porous SiO2 on which V2O5 crystals were formed as evidenced by XRD. Increasing addition of vanadium under the strongly acidic impregnation conditions followed by typical calcination of the catalyst, resulted in partial structure breakdown and loss of surface area of the mesoporous supports which was more pronounced in the case of SBA-15 and MCF materials. The most active catalysts for the formation of propene in the oxidative dehydrogenation of propane (ODP) at reaction temperatures 500–600 °C were those supported on HMS and MCM-41 mesoporous materials showing high propene yields up to 19% at about 600 °C. The vanadia catalysts based on SBA-15 and MCF were less active in the production of propene (yields up to 13%) compared to the MCM-41 and HMS based catalysts. The SiO2 and silicalite based catalysts showed much lower yields of propene (<7%).