Due to the complexity of heterogeneous catalysts, identification of active sites and the ways for their experimental design are not inherently straightforward but important for tailored catalyst preparation. The present study reveals the active sites for efficient C–H bond activation in C1–C4 alkanes over ZrO2 free of any metals or metal oxides usually catalysing this reaction. Quantum chemical calculations suggest that two Zr cations located at an oxygen vacancy are responsible for the homolytic C–H bond dissociation. This pathway differs from that reported for other metal oxides used for alkane activation, where metal cation and neighbouring lattice oxygen form the active site. The concentration of anion vacancies in ZrO2 can be controlled through adjusting the crystallite size. Accordingly designed ZrO2 shows industrially relevant activity and durability in non-oxidative propane dehydrogenation and performs superior to state-of-the-art catalysts possessing Pt, CrOx, GaOx or VOx species.
Conversion of propane or isobutane from natural/shale gas into propene or isobutene, which are indispensable for the synthesis of commodity chemicals, is an important environmentally friendly alternative to oil-based cracking processes.
Environmentally friendly and low-cost catalysts are required for large-scale non-oxidative dehydrogenation of propane to propene (PDH) to replace currently used CrO x -or Pt-based catalysts. This work introduces ZnO-containing ZrO 2 -or MZrO x -supported (M=Ce, La, Ti or Y) catalysts. The most active materials outperformed the state-of-the-art catalysts with supported CrO x , GaO x , ZnO x or VO x species as well as bulk ZrO 2 -based catalysts without ZnO. The spacetime yield of propene of 1.25 kg C3H6 •kg -1 cat •h -1 at a propane conversion of about 30% with propene selectivity of 95% was obtained over Zn(4 wt%)/TiZrO x at 550°C.For deriving key insights into the structure of active sites, reactivity, selectivity and onstream stability, the catalysts were characterized by XRD, HRTEM, EDX mapping, XPS, X-ray absorption, CO-TPR, CO 2 -TPD, NH 3 -TPD, Pyridine-FTIR, operando UV-Vis spectroscopy, Raman spectroscopy, TPO and temporal analysis of products. In contrast with previous reports used bulk ZrO 2 -based catalysts without ZnO, coordinatively unsaturated Zr cations are not the main active sites in the ZnO-containing catalysts.Supported ZnO x species were concluded to participate in the PDH reaction. The current X-ray absorption analysis proved that their structure is affected by the type of metal oxide used as dopant for ZrO 2 and on crystallinity of ZrO 2 . Isolated tricoordinated Zn 2+ species
Non-oxidative dehydrogenation (DH) of propane, n-butane, and isobutane was investigated over bare ZrO2 and binary MZrOx (M = Li, Ca, Mg, Y, Sm or La) materials.
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