Multiscale modeling and simulation on oxidative dehydrogenation of ethane to ethylene

Abstract

The oxidative dehydrogenation of ethane to ethylene (ODHE) by Pt-based catalysts is a complex reaction involving endothermic dehydrogenation reactions occurring in gas and exothermic oxidation reactions occurring on the catalyst surface. It is a challenge to figure out its reaction mechanism. Kinetic Monte Carlo (kMC) method was employed to analyze 82 possible elementary reactions on Pt/Al2O3. The path of CH3-CH3 * →CH3-CH2 * →CH3-CH* →C2H4 * on the catalyst surface and the cracking of ethane in the gas phase were the main pathways for ethylene formation, which both needed heat supply. The step of C* +O* →CO* was the main oxidation path providing heat, with C* from C-C bond breaking or dehydrogenation of CHx species. The result was used to establish a particle-resolved fixed-bed computational fluid dynamics (CFD) model. The autothermal equilibrium was achieved at an inlet temperature of 773 K, a flow rate of 2 m/s, and a molar ratio (C2H6:O2) of 3:1. Besides, the oxidation reaction was enhanced by increasing the inlet molar ratio, which meant that the C* species increased. The inlet velocity strengthened the heat transfer and a higher inlet velocity resulted in a lower bed temperature. The multi-scale simulation results can provide a reference for the design of an ethylene industrial reactor.