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

• Published in: Journal of catalysis 2021-12, Vol.404, p.231-243
• Main Authors: Held, A., Kowalska-Kuś, J., Janiszewska, E., Jankowska, A., Nowińska, K.
• Format: Article
• Language: English
• Subjects: adsorption; catalysts; catalytic activity; desorption; electron paramagnetic resonance spectroscopy; epoxidation reactions; hydrogen; N2O; nitrous oxide; oxidants; oxidation; oxygen; porous media; propane; Propane epoxidation; propylene; Propylene oxide; SBA-3; silica; space and time; streams; temperature; ultraviolet-visible spectroscopy; V-containing molecular sieves; vanadium; X-ray diffraction; X-ray photoelectron spectroscopy
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2021.09.022

[Display omitted] •Direct propane epoxidation was performed over V-containing mesoporous silica.•N2O or O2 separately and their mixture were used as oxidants.•Mixed oxidants provide stable conditions of propane epoxidation over 5V-SBA-3.•Reaction pathways for propane epoxidation with N2O/O2 have been proposed. 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 673–773 K. Electron spin resonance spectroscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy (XPS), as well as X-ray diffraction, 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 N2O alone, which leads to a decrease in both propane conversion and the space–time yield (STY) of PO. The use of an N2O–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 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-1h−1, have been obtained, which makes these results very promising compared with 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 10 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-1h−1.