Oxidative coupling of methane over Mn-Na2WO4 catalyst supported by monolithic SiO2

In this work, oxidative coupling of methane was studied over monolithic Mn/Na2WO4/SiO2 catalysts. The monolithic catalysts were prepared by three different ways as (1) preparation of monolithic silica (monosil) followed by impregnation of Mn and Na2WO4, (2) preparation of monolithic silica with Mn addition during gelation (Mn-monosil) followed by impregnation of Na2WO4 and (3) preparation of monolithic silica as MCM-41 structure (MCM-monosil) followed by impregnation of Mn and Na2WO4. The catalysts were tested in a microflow reactor and the results were compared with those obtained over particulate catalysts. It was found that Mn-monosil performed best and produced C-2 yield of 16.2%, which is close to the values obtained over particulate catalyst (19.3%). Mn-monosil was also passed the 10 h stability and hysteresis tests successfully. SEM characterization revealed that monolithic catalysts prepared by three different methods had different pore structure; it was also seen from SEM images that Mn-monosil preserved its original form better, and this was also verified by XRD analysis.