Non-oxidative conversion of methane into higher hydrocarbons over Mo/MCM-22 catalyst

Abstract

Molybdenum impregnated zeolite catalyst has been well-known for methane conversion into higher hydrocarbons under non-oxidative condition. HZSM-5 & HMCM-22 zeolites are the effective supports for this purpose. However, the catalytic performance of HMCM-22 supported molybdenum catalyst is considered suitable than that for HZSM-5 catalyst with high aromatic selectivity due to unique pore structure and framework of MCM-22 zeolite support. Effect of Mo loading over MCM-22 zeolite has been studied for the activity test and observed that 5 wt% metal content over the support (MCM-22) is optimum for the proper tuning of acidic & metallic sites of the catalyst. Effect of silica/alumina ratio (SAR, molar) of MCM-22 zeolite has also been studied and observed that lower SAR (30) is suitable ( $$\hbox {C}_{6}\hbox {H}_{6}$$ selectivity, 37%) comparatively to higher SAR (55) ( $$\hbox {C}_{6}\hbox {H}_{6}$$ selectivity, 18%). Lower GHSV (720 mL/g.h) is effective for higher hydrocarbon production compared to higher GHSV (1200 mL/g.h) due to low residence time. Mo/MCM-22 catalysts with different Mo loading were characterized by BET surface area, XRD, Raman spectroscopy and $$\hbox {NH}_{3}$$ -TPD analysis. Unique pore systems [10 & 12 membered ring (MR)] and framework of MCM-22 zeolite support are the key factors for effective methane conversion to value added chemicals when loaded with molybdenum. Mo/MCM-22 bifunctional catalyst was studied in detail for direct methane conversion into higher hydrocarbons under non-oxidative condition. The effect of Mo loading and silica/alumina ratio of support was studied for the process. The results suggest that 5 wt% Mo loading and lower SAR (30) is effective for higher hydrocarbon formation.