Regulation of lattice oxygen reactivity of ZrO2 to promote efficient chemical looping oxidative dehydrogenation of ethane

The development of efficient catalysts for ethane dehydrogenation (EDH) to ethylene remains a challenge due to the lack of direct material property-performance relationships at the most elementary level. Here, we introduce the first application of ZrO₂-based catalysts for EDH in a chemical looping mode. Their performance in the first 1 minute, primarily via the oxidative dehydrogenation, highlights their potential for large-scale ethylene production. LaZrO_x achieves a space-time yield of 2.26 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow><mml:mstyle><mml:mtext>kg</mml:mtext></mml:mstyle> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow><mml:mstyle><mml:mtext>C</mml:mtext></mml:mstyle> </mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:msub> <mml:msub> <mml:mrow><mml:mstyle><mml:mtext>H</mml:mtext></mml:mstyle> </mml:mrow> <mml:mrow><mml:mn>4</mml:mn></mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>⋅</mml:mo> <mml:msubsup> <mml:mrow><mml:mstyle><mml:mtext>kg</mml:mtext></mml:mstyle> </mml:mrow> <mml:mrow><mml:mstyle><mml:mtext>cat</mml:mtext></mml:mstyle> </mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1</mml:mn></mml:mrow> </mml:msubsup> <mml:mo>⋅</mml:mo> <mml:msup> <mml:mrow><mml:mstyle><mml:mtext>h</mml:mtext></mml:mstyle> </mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>1</mml:mn></mml:mrow> </mml:msup> </mml:math> at about 80% ethylene selectivity and 50% ethane conversion at 700 °C. Mechanistic studies have identified the reactivity and availability of lattice oxygen as crucial descriptors for mitigating coke formation and suppressing combustion reactions. These properties can be tuned by exposing less stable ZrO₂ crystal planes or incorporating metal-oxide promoters. Strongly adsorbed oxygen species can also participate in ethane oxidation. Thus, this study establishes a catalyst system for chemical looping EDH and provides insights for designing more efficient EDH catalysts.