Hanieh Habibpoor, M. Taghizadeh
The oxidative dehydrogenation (ODH) of propane using CO 2 as a soft oxidant represents a promising strategy for selective propylene production alongside effective CO₂ valorization, emphasizing the critical need for highly active and stable catalysts. In this work, a series of Cr-based catalysts with chromium loadings ranging from 3 to 10 wt% were synthesized via the incipient-wetness impregnation method, employing three-dimensional mesoporous silica KIT-6 as the support. The catalysts were further modified by zinc promotion to enhance catalytic performance in the CO 2 -ODP. Comprehensive physicochemical characterization-including XRD, FT-IR, SEM, EDX elemental mapping, HRTEM, N 2 physisorption, H 2 -TPR, NH 3 -TPD, CO 2 -TPD, XPS, Raman and TGA-confirmed that the ordered 3D mesoporous structure of KIT-6 was retained post-metal impregnation, facilitating superior dispersion of chromium oxide species. Among the prepared catalysts, 7 %Cr/KIT-6 exhibited optimal propane conversion and propylene selectivity. Zinc promotion significantly enhanced the chromium-support interaction and increased the surface concentration of highly oxidizing Cr 6 + species, which plays a crucial role in improving catalytic activity for the propane dehydrogenation reaction. The 1.5 %Zn-7 %Cr/KIT-6 catalyst exhibited initially superior performance at 550 °C, achieving 50.7 % propane conversion, with propylene selectivity and yield of 79.9 % and 40.5 %, respectively. Kinetic studies based on the Langmuir-Hinshelwood model effectively described the reaction mechanism over the promoted catalyst. The estimated apparent activation energy ( E a p p c a t = 83.98 kJ·mol −1 ) indicates that the dehydrogenation proceeds rapidly and more easily in the presence of this catalyst.