Non-oxidative dehydrogenation of isobutane over supported vanadium oxide: Nature of the active sites and coke formation

Abstract
We combine Raman spectroscopy, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), X-ray diffraction (XRD), high-field 51V-solid-state magic angle spinning NMR spectroscopy (ssNMR), transmission electron microscopy (TEM) and N2-physisorption to unravel structure-activity relationships during the non-oxidative dehydrogenation of isobutane over a V-based catalyst. The use of SBA-15 as a support favours the formation of oligomeric tetrahedral VOx species along with a smaller amount of V2O5 clusters. EPR, 51V-ssNMR and XPS suggest the formation of mostly V4+ species under reaction conditions. Investigation of "coke"species by dynamic nuclear polarization surface enhanced solid-state NMR (DNP SENS) reveals the co-existence of aliphatic, olefinic/aromatic, acetal/alkoxy and carbonyl-based organic moieties in the post-reacted catalyst. Together with TPR and XRD results, we postulate that oxygenated coke species are the main components responsible for vanadium clustering, which results in the irreversible deactivation of the catalyst.

Citation
Rodriguez-Gomez, A., Chowdhury, A. D., Caglayan, M., Bau, J. A., Abou-Hamad, E., & Gascon, J. (2020). Non-oxidative dehydrogenation of isobutane over supported vanadium oxide: nature of the active sites and coke formation. Catalysis Science & Technology, 10(18), 6139–6151. doi:10.1039/d0cy01174f

Acknowledgements
This work is funded by King Abdullah University of Science and Technology (KAUST). We also thank Sandra Ramirez Cherbuy for TOC art.

Publisher
Royal Society of Chemistry (RSC)

Journal
Catalysis Science & Technology

DOI
10.1039/d0cy01174f

Additional Links
http://xlink.rsc.org/?DOI=D0CY01174F

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