Study of oxidative coupling of methane over Mn/Na2WO4 catalyst in various forms

Abstract

In this thesis, the oxidative coupling of methane reaction over Mn-Na2WO4/SiO2 catalyst was investigated. The support silica was prepared with sol-gel, sol-gel under DC voltage and wash-coating methods, and then 2wt.% Mn and 5wt.% Na2WO4 were impregnated on silica support. The OCM performance of the catalyst was tested using quartz microreactor. Inside diameter of the quartz reactor was chosen as 10 mm and after the catalyst bed, the diameter was reduced to 2 mm to prevent by-product formation. The outlet of the reactor was analyzed using gas chromatography and CH4 conversion, C2 selectivity and yield were calculated. Catalysts, which was prepared with sol-gel method, have shown the best performance with 16.6% yield. Also, to observe the stability of the catalyst performance, an experiment was done for 10 hours and it was found that the C2 selectivity and yield did not change significantly during that time. During the sol-gel preparation, DC voltage was applied to the catalyst. However, the electricity affected neither the structure nor the performance of the catalyst. Performance of catalysts, which were prepared with this method was close to the performance of the blank reactor. In the same way, the catalysts, which were synthesized with wash-coating method, showed quite low performance.