Comparative study of oxidative coupling of methane modeling in various types of reactor

Abstract

Oxidative coupling of methane (OCM) was simulated using plug flow reactor models. Performances of several membrane reactors; i.e. porous membrane reactor (PMR), mixed ionic and electronic conducting membrane reactor (MIEMR) and solid oxide fuel cell reactor (SOFCR) were compared with those of a conventional fixed-bed reactor (FBR). For SOFCR, La 0.85 Sr 0.15 MnO 3 /8 mol%Y 2 O 3 –ZrO 2 /La 1.8 Al 0.2 O 3 (abbreviated as LSM/YSZ/LaAlO) were the components of cathode, electrolyte and anode, respectively. The membranes for PMR and MIEMR were γ-alumina and La 0.40 Sr 0.60 Ga 0.40 Fe 0.60 O 3− δ , respectively. The kinetic expressions of Li/MgO catalyst were employed in the FBR, PMR and MIEMR models. All types of membrane reactors obviously improved C2 selectivity compared to FBR. However, only SOFCR was inferior to FBR in term of C2 yield due to much lower methane conversion when operating at the same temperature. PMR was superior to the other membrane reactors at low temperature (<1150 K) while MIEMR was attractive at high temperature (>1150 K). However, PMR might not be suitable for use, especially, in the case with inerts or impurities in the oxygen feed. Operation at high pressure was obviously beneficial only to MIEMR and SOFCR. The drawback of PMR was methane loss through the non-selective porous membrane while that of SOFCR was the requirement of higher operating temperature of approximately 200 K compared to the others. However, the electricity simultaneously generated as a by-product might make SOFCR still attractive.