Statistical modeling applied to the oxidative coupling of methane reaction over porous (SrxLa1-x)CeO mixed oxides for optimization of C2 yield, C2 selectivity, and C2H4 selectivity

Abstract

(SrxLa1-x)CeO mixed oxide catalysts were prepared using the sol-gel method, with a non-ionic surfactant as a soft template for a porous structure. The use of nitrogen physisorption measurements, BJH pore size distribution curves, and SEM micrographs confirmed improvement of the porous texture of the mixed oxide catalysts, compared to catalysts synthesized by a conventional method. X-ray diffraction and Raman spectroscopy analyses demonstrated that the preparation method led to different crystalline structures in the catalysts. In the oxidative coupling of methane (OCM) reaction, use of the catalyst prepared with the soft template improved C2 yield, C2 selectivity, and C2H4 selectivity by approximately 65, 101, and 130%, respectively. The addition of 0.2 Sr content in the porous catalysts also provided gains of approximately 63, 46, and 85% in C2 yield, selectivity for C2, and selectivity for C2H4, respectively, when compared to the Sr-free catalyst. The satisfactory performance of the catalyst with 0.2 Sr content was probably due to the improved textural properties that provided a surface composition with concentration of Ce3+ of 59.3%. Based on statistical modeling of variables such as temperature, CH4/O2 ratio, and WHSV, it was possible to obtain a C2 yield of 16.2%, C2 selectivity of 76.2%, and C2H4 selectivity of 50%.