Two-Dimensional Modeling of the Oxidative Coupling of Methane in a Fixed Bed Reactor: A Comparison among Different Catalysts
A proposed two-dimensional model of the oxidative coupling of methane (OCM) to C2 hydrocarbons (e.g., C2H4 and C2H6) in a fixed bed reactor operated under isothermal and non-isothermal conditions is described which can provide more accurate predictions of experimental data than the simplified one-dimensional model. The model includes a set of partial differential equations of the continuity, mass transfer and energy balance equations. The performance of the OCM using different catalysts was assessed in terms of CH4 conversion, C2 selectivity and C2 yield with respect to key operating parameters, such as feed temperature (973 - 1173 K), CH4/O2 ratio (3.4 – 7.5) and gas hour space velocity (GHSV) (18000 - 30000 h-1). The simulation results indicated that the Na-W-Mn/SiO2 catalyst exhibits the best performance among all of the catalysts. The C2 yield were 20.16% and 20.00% for non-isothermal and isothermal modes respectively which the OCM reactor is operated at a CH4/O2 ratio of 3.4, a feed temperature of 1073 K and a GHSV of 9720 h-1. An increase in the operating temperature increases the CH4 conversion but decreases the C2 selectivity. However, the effects of the CH4/O2 ratio and the GHSV exhibit an opposite trend to that of the operating temperature.