Epoxidation of propane with oxygen and/or nitrous oxide over silica-supported vanadium oxide

Abstract Propane to propene oxide (PO) oxidation over V-containing mesoporous silica of SBA-3 structure, has been studied using different oxidants (nitrous oxide, oxygen, and their mixture) in the temperature range of 673 – 773 K. Electron spin resonance spectroscopy (ESR), ultraviolet–visible (UV-vis), and X-ray photoelectron (XPS) spectroscopies as well as X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (H2-TPR), and low temperature N2 adsorption/desorption were applied for characterization of fresh and spent catalysts. XPS spectra and H2-TPR profiles revealed a significant reduction of V-species as a result of propane oxidation with only N2O which leads to a decrease in both propane conversion and the space-time yield (STY) of PO. The use of N2O and oxygen mixture as an oxidant of propane allows the vanadium valence to be stabilized at a level similar to the initial sample, which results in stable activity noted with time on stream. Propane conversion of 40%, propylene selectivity of 45%, and propylene oxide selectivity of 11%, corresponding to a STY of propylene oxide of about 15 g kgcat-1 h-1 have been obtained which makes these results very promising compared to the data reported in the literature. Vanadium catalyst used with only oxygen results in stable propane conversion with high total oxidation and stable propene selectivity, although, the STY of PO is ten times lower. N2O applied as the only oxidant results in rapid catalyst deactivation and after 2 h on stream STY of PO is only 2.5 g kgcat-1 h-1.