Selective propane dehydrogenation with single-site CoII on SiO2 by a non-redox mechanism

• Single-site Co2+/SiO2 is a highly selective (>95%) catalyst for propane dehydrogenation to propene and H2.
• The catalyst exhibits stable activity over 24 h.
• Single-site nature elucidated with surface Co chemistry, spectroscopic measurements, and theoretical calculations.
• In situ XAS and computational studies are consistent with a non-redox, Lewis acid mechanism for the observed catalysis.

We report the synthesis, characterization, and catalytic performance for gas phase propane dehydrogenation of single-site Co2+ ions supported on silica. Spectroscopic characterization by resonance Raman, electron paramagnetic resonance, and X-ray near-edge and extended absorption fine structure revealed that tetrahedrally coordinated Co2+ ions are chemisorbed into the trisiloxane rings on the surface of amorphous silica. In situ XAS shows that Co is not oxidized by air nor reduced by hydrogen even at 650 °C. For catalytic propane dehydrogenation, single-site Co2+/SiO2 exhibits selectivities >95% at 550 °C and >90% at 650 °C with stable activity over 24 h. Calculations with hybrid density functional theory support a non-redox mechanism for activation of C–H and H–H bonds by Co2+ similar to that previously reported for single-site Zn2+/SiO2.

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