Studies on molybdenum carbide supported HZSM-5 (Si/Al = 23, 30, 50 and 80) catalysts for aromatization of methane

Abstract

Here in, for the first time we are reporting molybdenum carbide reduction into metallic molybdenum during methane aromatization on HZSM-5 (Si/Al ratio = 23, 30, 50 and 80) at methane space velocity of 1800 mL.gcat−.h−. Benzene yield was influenced by the surface metallic molybdenum through the non-aromatic carbon deposits formation via linear hydrocarbons degradation on HZSM-5 with fewer acidity (Si/Al ratio = 30, 50 and 80). Our XPS analysis results demonstrated improved surface metallic molybdenum in spent Mo2C/HZSM-5 = 80 (0.71 atom. %) and 50 (0.54 atom. %) samples over Mo2C/HZSM-5 = 30 (0.33 atom. %) and 23 (0.20 atom. %) samples. Furthermore, HR-TEM and FFT analysis images clearly established fine distribution of distorted spherical shaped Mo2C particles with 6–14 nm size in spent Mo2C/HZSM-5 = 23. On the other hand, Mo2C particle size was increased upto 22 nm in Mo2C/HZSM-5 = 80. The ease reduction of Mo2C into metallic molybdenum and aggregation of Mo2C particles in spent higher Si to Al ratio (50 and 80) samples was associated with weak interactions between Mo2C and the HZSM-5 with fewer acidity. At 700 °C, the order of benzene yield as follows: Mo2C/HZSM-5 = 80 (2.2%) < Mo2C/HZSM-5 = 50 (3.25%) < Mo2C/HZSM-5 = 30 (5.2%) < Mo2C/HZSM-5 = 23 (8.0%).