Development of Mn-Na₂WO₄ catalyst on La₂O₃, Y₂O₃ and YSZ supports for oxidative coupling of methane reaction in fixed bed and solid oxide fuel cell reactors

Abstract

This research studies the development of Mn-Na₂WO₄ catalysts on La₂O₃, Y₂O₃ and YSZ supports 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 supports La₂O₃, Y₂O₃ and YSZ were 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%. S-Mn-Na₂WO₄/YSZ, P-Mn-Mn-Na₂WO₄/YSZ and Mn-Na2WO4/YSZ catalysts part I were selected as anode catalysts for further study in the SOFC reactor. The experiments were carried out using La[subscript 0.8]Sr[subscript 0.2]MnO₃ (LSM) as the cathode catalyst, 8mol% 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 electrical power density of 13.2 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 twenty nine hours.