Effect of Co additive on the formation of carbon deposit on Mo/MCM-22 catalyst for methane dehydro-aromatization

Methane dehydro-aromatization (MDA) under non-oxidative conditions was carried out over the Mo/ MCM-22 catalyst modified by Co additive, and the results suggested that the addition of Co dramatically improved the activity and stability of Mo/MCM-22. Moreover, the chemical nature and physical properties of the carbon deposit formed on Mo/MCM-22 and Co-Mo/MCM-22 catalysts were studied by temperature-programmed reaction with hydrogen (TPH) and temperature-programmed reaction with CO2 (TPCO2) combining with thermal gravimetric analysis (TGA). The results showed that there were two kinds of carbon deposit formed on the surface of the catalysts during MDA. TPH experiment only had effect on the carbon deposit burnt-off at high temperature. However, TPCO2 experiment could result in diminishing of the carbon deposit burnt-off at both low temperature and high temperature. The formation of the two kinds of carbon deposit was distinctly suppressed on the Co-modified Mo/MCM-22 catalyst, which directly led to the obvious increase of the stability of the Mo/MCM-22 catalyst in MDA.