(415i) Numerical Modeling of Chemical Looping Oxidative Dehydrogenation of Ethane in a Packed Bed Reactor

Chemical looping oxidative dehydrogenation (CL-ODH) of ethane is a promising alternative to steam cracking for ethylene production. Accurate reactor modeling is of critical importance in order to efficiently scale up and implement this new technology. In this study, a one-dimensional, heterogeneous packed bed model was developed to simulate the CL-ODH of ethane to ethylene with Na₂MoO₄ promoted CaTi_0.1Mn_0.9O₃ redox catalysts. The reaction kinetics was described by coupling the widely accepted reaction scheme for steam cracking of ethane with oxidation kinetics of H₂ and C₂H₄. The competition between H₂ and C₂H₄ for active oxygen species on the surface of the redox catalyst was also determined and implemented in the reactor model. The temperature variation in the different CL-ODH steps and the temperature distribution along the bed were also carefully considered. The feasibility and accuracy of this model were validated by experiments conducted in a relatively large packed bed reactor with 200 g catalysts. The results showed that C₂H₆ conversion, C₂H₄ yield, CO₂ selectivity, and CH₄ yield all increased with the bed height and the reaction temperature but decreased with the total flow rate. The existence of H₂ significantly suppressed the oxidation rates of C₂H₄, and 2%H₂ decreased CO₂ selectivity by 30%-50%. The released heat during the regeneration step substantially increased the bed temperature, leading to a much higher initial temperature during the reduction step. The model is subsequently used to optimize the operating parameters and reactor design for the CL-ODH process.