Exploiting oxidative coupling of methane performed over La2(Ce1−xMgx)2O7−δ catalysts with disordered defective cubic fluorite structure

Abstract

The oxidative coupling of methane reaction to produce C₂ compounds was studied using La₂(Ce_1−xMg_x)₂O_7−δ catalysts with disordered defective cubic fluorite structures, varying the Mg content (0.0 ≤ x ≤ 1.0), CH₄/O₂ ratio, temperature, and WHSV. The partial substitution of Ce by Mg in the structure modified the morphology, adjusted the reducibility, stabilized the Ce³⁺ species, and provided different concentrations of basic sites, which allowed a 42% increase in the yield of C₂, with ethylene as the major product. The catalyst with 0.4 Mg content in the structure provided C₂ selectivity of 52%, with CH₄ conversion of 28%, even under conditions richer in O₂. The highest selectivity to C₂ (75%), with the highest selectivity to ethylene (39.1%), was achieved using a CH₄ : O₂ ratio of 8 : 1. In addition, it was possible to operate at milder temperatures (650 °C), with satisfactory CH₄ conversion (22%) and C₂ selectivity (54%). By decreasing the space velocity, the CH₄ conversion and C₂ selectivity decreased with an ethylene/ethane ratio of 3. The inhibitory effects of H₂O and CO₂ were observed at lower space velocity.