CO₂-mediated oxidative dehydrogenation of propane to propylene and syngas: Reaction and energy performance matrices

The performance of CO₂-assisted oxidative dehydrogenation of propane to propylene is investigated. The energy performance matrices are defined as energy efficiency and exergy efficiency at both the reactor level and the overall system level. Oxidants are the main factor that dictates the performance of the dehydrogenation of propane. Oxygen is a strong oxidant which helps in promoting the endothermic dehydrogenation of propane. CO₂ is considered a mild oxidant that hinders the over-oxidation of propane. The addition of CO₂ promotes propane conversion but sacrifices the other performance matrices including propylene selectivity and the H₂/CO ratio of the syngas. Consequently, the energy and exergy efficiencies of the reactor as well as the DHP system decrease with increasing CO₂ supply. The addition of O₂ has positive impacts on the energy performance matrices at a certain temperature range (from 863 K to 1273 K). However, the addition of O₂ leads to an adverse impact on the propylene selectivity and H₂/CO ratio of the syngas. Under the absence of O₂, the DHP exhibits a propane conversion of 91% with the propylene selectivity and system exergy efficiency of 90% and 86%, respectively when the CO₂/C₃H₈ ratio of 0.25 at 973.15 K. This work provides strong evidence that the reaction performance matrices have a strong relation to the energy performance matrices and offers a baseline for future research and optimization in the presence of O₂ and CO₂.