A multistep surface mechanism for ethane oxidative dehydrogenation on Pt- and Pt/Sn-coated monoliths

A computational study of ethane oxidative dehydrogenation to ethylene on Pt- and Pt/Sn-coated monoliths is presented as an improvement to previous kinetic models in reproducing experimental findings over a wide range of feed conditions. The multistep surface mechanism containing 20 reversible reactions among 11 surface species is based on published reaction steps for hydrogen and methane oxidation combined with lumped steps for ethane surface chemistry and coupled with an established homogeneous mechanism to form the detailed chemistry model. Simulation results at 1 atm are in good agreement with experimental data obtained on Pt at variable C2H6/O-2 and C2H6/O-2/H-2 ratios and predict experimentally observed phenomena such as ignition temperatures and homogeneous ethylene formation. The model is also used to predict Pt monolith performance over an industrially relevant range of space velocities (0.7-3.4 x 10(5) h(-1)) and pressures (1-10 atm). Furthermore, the Pt mechanism is extended to a Pt/Sn catalyst by changing two parameters in the H and CO oxidation steps, and agreement with experiments is obtained with and without H-2 addition.