Oxidative Coupling of Methane over YSZ Support Catalysts for Application in C2 Hydrocarbon Production

Abstract

This paper studies the development of Mn-Na2WO4 catalysts on YSZ support for oxidative coupling of methane reaction. It can be divided into two parts; (1) study in fixed bed reactor (FBR), and (2) study in solid oxide fuel cell reactor (SOFC). In part I, the experiments were performed using co-feeds of methane, oxygen and nitrogen inert gas at a ratio of 4:1:5 for different temperatures (973 - 1173 K). Mn-Na₂WO₄ catalyst on YSZ support was doped with sulfur, phosphorous, and cerium in order to improve its catalytic reactivity. The results indicated that sulfur and phosphorous showed the good improvement for Mn-Na2WO4 catalyst on YSZ support. At 1073 K, S-Mn-Na₂WO₄/YSZ provided C₂ selectivity of 60.3% and methane conversion of 31.1%, while P-Mn- Na₂WO₄/YSZ offered C₂ selectivity of 59.8% and methane conversion of 34.1%. P-Mn-Na₂WO₄/YSZ catalyst was selected as anode catalysts for further study in the SOFC reactor. The experiments were carried out using La_0.8Sr_0.2MnO₃ (LSM) as the cathode catalyst, 8 mol% yttria-stabilized zirconia (YSZ) as the electrolyte. P-Mn-Na₂WO₄/YSZ exhibited the best performance, providing C₂H₄ selectivity of 89.0%, methane conversion of 10.5% and maximum power density of 7.2 W/m² at 1123 K. In addition, the stability of the P-Mn-Na₂WO₄/YSZ catalyst was tested at 1123 K. Good stability of the reaction system could be observed at least for 29 hours.