Oxidative Dehydrogenation of Cyclohexane Over Halogen-Decorated Ceria Nanorods with Tuned Electronic Structure and Surface Oxygen Species

Abstract

Doping of non-metallic elements is considered a promising strategy for metal oxide catalysts modification in alkane oxidative dehydrogenation (ODH). It can avoid over-oxidation of alkane and improve product selectivity. Regulating electronic properties of oxygen species on cerium oxide (CeO₂) surface is effective for cyclohexane ODH to cyclohexene. In this work, the catalytic performance of CeO₂ in cyclohexane ODH is regulated by halogens (F, Cl, and I). Halide solution-etched of CeO₂ nanorods effectively inhibits cyclohexane over-oxidation while promoting cyclohexene generation. At 350 °C, optimal catalysts have good cyclohexene yields of 11.7%. Halogen modification changes reactive oxygen species distribution and oxygen nucleophilicity over catalysts. Pulsed oxygen isotope exchange experiments show halogen modification limits oxygen doping rate. Active O₂⁻ and O²⁻ help convert cyclohexane to cyclohexene, while O₂²⁻ and O⁻ cause over-oxidation. Halogen modification is valuable for alkane ODH and helps optimize CeO₂-based catalysts.