Identification of the coke accumulation and deactivation sites of Mo2C/HZSM-5 catalyst in CH4 dehydroaromatization

Identifying the preferentially coking sites of Mo2C/HZSM-5 catalyst in the CH4 dehydroaromatization at non-oxidative conditions was attempted by employing a physically separable Mo2C/alpha-Al2O3 + HZSM-5 mixture instead of Mo2C/HZSM-5 as catalyst. Photographic observation on the spent Mo2C/alpha-Al2O3 and HZSM-5 components separated from the deactivated mixture and their thermogravimetric analysis clearly revealed that coke accumulation occurred predominantly on the HZSM-5. Then, the comparative activity tests with the physical blends of the deactivated Mo2C/alpha-Al2O3 + HZSM-5 mixture sample with fresh Mo2C/alpha-Al2O3 or HZSM-5 further confirmed that the coked HZSM-5 component in the deactivated mixture definitely deactivated while that uncoked Mo2C constituent remained highly active. (C) 2004 Elsevier B.V. All rights reserved.