(212g) Bulk and Surface Characteristics of Mo-V-Te-(Ta, Nb)-O Catalyst Prepared by Dry-up, Hydrothermal, and Microwave-Assisted Hydrothermal Methods

Abstract There has been a growing interest in developing a highly active and selective catalyst for direct propane (amm)oxidation to acrylonitrile (ACN) in order to replace the current industrial technology that relies on conversion of olefins and aromatics. The (amm)oxidation of propane to ACN has been receiving great interest over the last few decades as a possible alternative to the current industrial process of propylene (amm)oxidation providing a high-volume valuable intermediate for manufacture of synthetic fibers, resins and rubber. Among the different systems being investigated by academic and industrial research groups for one-step propane (amm)oxidation, the most promising one is Mo-V-Te-Nb-O based mixed metal oxide catalyst consisting of ?M1? and ?M2? phases. Previous studies have demonstrated that propane activation occurs over surface V sites and that synthesis methods impact the distribution of V in a multi-metallic active center located in the surface ab planes of the M1 phase. However, the strong evidence supporting the correlations between catalytic activity/selectivity and the distribution of V at the active center is lacking now. In this study, the phase pure M1 Mo-V-(Ta, Nb)-Te-O catalyst was prepared by three different methods, dry-up, hydrothermal, and microwave-assisted hydrothermal synthesis. The distribution of Mo/V cations, V-O-(Ta, Nb) bonds, and location of Nb and Ta at the active centers designated by Ta amount were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and low energy ion scattering (LEIS). The catalytic behavior of the Ta catalyst was tested in propane (amm)oxidation using a fixed bed micro-reaction at atmospheric pressure at 300 ? 400 C°. The results of this study provide the location and solubility of Nb and Ta in the M1 phase as well as its impact on the Mo/V distribution at the ab planes to establish the model for optimized catalyst in propane (amm)oxidation.