Studies On VTeO/SiO₂ Catalysts For Selective Oxidation Of Propane To Acrolein

The selective oxidation of propane to acrolein has been attracting a lot of attention in both academia and industry. This process, however, is usually accompanied by such a difficulty that propane is quite inactive and acrolein is easily further oxidized under the reaction condition. Therefore, how to get the catalysts with high activity and high selectivity in oxidation of propane to acrolein is challenging. In order to shorten the path to discovery of the appropriate catalysts, the understanding of the roles of the constituent elements in the reaction is very important. So far, most catalysts reported for the reaction have been multi-component oxides, containing Mo, V, Te (Bi) and/or other transition metals. Since the complexity of the catalyst composition, it is indeed difficult to clarify how the active centers function.In the present work, a relatively simple SiO₂-supported VTeO catalyst system has been prepared and studied for selective oxidation of propane to acrolein. The effects of composition, catalyst preparation and reaction conditions on the catalytic performance were investigated. In order to reveal the relationship of the catalytic performance with the chemical and physical properties of the catalysts, VO_x/SiO₂, TeOx/SiO₂ and VTeO/SiO₂ catalysts have been comparatively characterized by BET, XRD, TPR, XPS, Raman techniques. Furthermore, for the VTeO/SiO₂ catalysts the roles of their catalytically active sites in the reaction have been identified by pulse reaction using allyl bromide and propene as molecular probes. The main results of the study are summarized as follows:1) The VO_x/SiO₂ catalyst showed a high activity for propane conversion but producing mainly C₃H₆, CO and CO₂, and its selectivity was closely related to dispersion of V species. It was found that the isolated and highly...