Effect of Addition of K, Rh and Fe Over Mo/HZSM-5 on Methane Dehydroaromatization Under Non-oxidative Conditions

Abstract

Methane dehydroaromatization was studied over a series of K, Rh and Fe promoted 10 wt% Mo/HZSM-5 catalysts with different promoter loadings of 0.5, 1 and 1.5 wt% at 750 °C in a recirculating batch reactor. All the catalysts were reduced in H2 at 750 °C prior to methane activation. K, Rh and Fe- promoted Mo/HZSM-5 catalysts were prepared by sequential impregnation. N-propylamine-temperature programmed desorption confirmed the significant modification in the acidity of the catalyst upon addition of K. Compared to 10 wt% Mo/HZSM-5, the conversion of CH4 remained nearly unchanged for 1 wt% K-promoted catalyst but decreased by ~ 46% for 1 wt% Rh promoted catalyst and by ~ 4.3% for Fe-promoted catalyst after 255 min of reaction. The conversion of CH4 further decreased with increase in K and Rh loading but increased with increase in Fe loading. Compared to Rh and Fe-promoted catalysts, K-promoted catalyst exhibited better selectivity for C6H6 after 255 min of reaction. The temperature programmed oxidation results revealed that K promoted catalyst significantly reduced coking. 1 wt% K added to 10 wt% Mo/HZSM-5 exhibited optimum performance, where the conversion of CH4 was ~ 28%, selectivity of C6H6 was ~ 50% while the selectivity of carbon was ~ 47% after 255 min of reaction.