KINETIC TRANSPORT MODELS AND THE DESIGN OF CATALYSTS AND REACTORS FOR THE OXIDATIVE COUPLING OF METHANE

The design of catalytic pellets and reactors using detailed kinetic-transport models is illustrated for the oxidative coupling of methane to form ethane and ethylene. Oxygen sieving within diffusion-limited pellets and staged oxygen injection reactors increase C2 selectivity by inhibiting full oxidation homogeneous pathways that lead to CO and CO2 products. Our simulations suggest that high densities of surface sites with kinetics that depend weakly on oxygen concentration are required to benefit from oxygen-sieving catalyst and reactor schemes. These sites favor beneficial surface activation processes even at the low oxygen concentrations present within staged injection reactors and diffusion-limited pellets. Controlled introduction of stoichiometric oxygen reactants leads to C2 yields as high as 50%; the reactions, however, occur at much slower rates and require much greater reactor volumes than in conventional cofeed reactors.