Oxidative coupling of methane (OCM) in a catalytic membrane reactor and comparison of its performance with other catalytic reactors

Abstract

The oxidative coupling of methane (OCM) was studied in a catalytic membrane reactor (CMR), catalyst packed bed reactor (PBR) and catalyst packed bed membrane reactor (PBMR) respectively. The CMR consists of a mixed ionic-electronic conducting membrane (MIECM) Ba0.5Ce0.4Gd0.1Co0.8Fe0.2O3−δ (BCGCF) coating on the outer surface of ceramic tubular support using sol–gel method. The inner surface of the membrane tube was coated with 3 components (Na-W-Mn) catalyst using mixture slurry dip coating method. Prior to the OCM reaction, separation of oxygen from the mixture of nitrogen and oxygen similar to air composition was performed in the membrane reactor. In the absence of chemical reaction, the oxygen permeation flux was 0.6 cm3/min cm2 at 900 °C with sweep gas flow rate 100 cm3/min. The oxygen permeation flux increased significantly during the oxidative coupling of methane reaction. 67.4% of C2+ selectivity and methane conversion of 51.6% with oxygen permeation flux 1.4 cm3/min cm2 was obtained at 850 °C with sweep gas flow rate of 100 cm3/min. The performances of PBR and PBMR using Na-W-Mn/SiO2 were compared with the performance of CMR. The catalytic membrane reactor performed best among three reactors with C2+ yield of 34.7%. The deterioration of the catalytic membrane performance after reaction was investigated by SEM and XRD analyses.