Modeling the partial oxidation of methane in a short-contact-time reactor

Partial oxidation of methane in monolithic catalysts at very short contact times offers a promising route to convert natural gas into syngas (H-2 and CO), which can than be converted to higher alkanes or methanol. Detailed modeling is needed to understand their complex interaction of transport and kinetics in these systems and for their industrial application. In this work, the partial oxidation of methane in noble-metal (Rh and Pt)-coated monoliths was studied numerically as an example of short-contact-time reactor modeling. A tube wall catalytic reactor was simulated as a model for a single pore of the monolithic catalyst using a 2-D flow field description coupled with detailed reaction mechanisms for surface and gas-phase chemistry. The catalytic surface coverages of adsorbed species are calculated vs. position. The reactor is characterized by competition between complete and partial oxidation of methane. At atmospheric pressure, CO2 and H2O are formed on the catalytic surface at the entrance of the catalytic reactor. At higher pressure, gas-phase chemistry becomes important, forming more complete oxidation products downstream and decreasing syngas selectivity by about 2% at 10 bar. Temperature (from 300 to similar to 1,200 K), velocity, and transport coefficients change very rapidly at the catalyst entrance. The dependence of conversion and selectivity on reactor conditions was examined.