Gas-Phase Oxidative Dehydrogenation of Ethane via NO/O2 Mixtures

A kinetic and thermodynamic tubular reactor model for the oxidative dehydrogenation of ethane using homogeneous NO/O2 mixtures is developed to investigate the factors controlling the ethylene selectivity. Two primary mechanisms for ethane oxidative dehydrogenation are identified from the model: the reaction between NO and NO2 to form OH radicals drives ethane dehydrogenation at large NO volume fractions (≥5%), and H2O2 homolysis drives the reaction at low NO volume fractions (<5%). The reaction conditions were optimized for C2H6 conversion; a near three-fold increase in conversion was achieved with a final 53% ethane conversion and a 90% ethylene selectivity. CO, CO2, H2O, He, and N2 were explored to control the selectivity and reaction kinetics but had little impact. Under optimal conditions, most initial NO radicals were converted into NO2; replacement of NO with NO2 was investigated. NO2/O2 mixtures achieved a maximum of 38% ethane conversion at a 90% ethylene selectivity with a 5% NO2 conversion.