Hydrodealkylation of C9 + Heavy Aromatics to BTX over Zeolite-Supported Nickel Oxide and Molybdenum Oxide Catalysts

Abstract

Two series of catalysts with nickel oxide or molybdenum oxide as the active component and with different zeolites as supports were prepared by incipient wetness impregnation method, and their structural properties and acidity were characterized by means of XRD, H2-TPR, N2 adsorption and desorption, FTIR spectrum of adsorbed pyridine and NH3-TPD. The catalytic activity of the prepared materials was investigated for the hydrodealkylation of commercial C9+ heavy aromatics to BTX. The results show that the catalytic performance is greatly influenced by the specific surface area, the acidity and the interaction between zeolite and metal oxide, and little affected by the pore diameter of catalysts. For NiO catalysts, the samples with the moderate interaction between zeolite and NiO exhibit the relatively high selectivity of BTX. And for MoO3 catalysts, the presence of the molybdenum species associated with Bronsted acid site causes the remarkable reduction of selectivity. The presence of Bronsted acid sites, the growth of the strength of Lewis acid sites and the increase of acid amount and the specific surface area can all enhance the conversion of C9+ aromatics. Finally, compared with other zeolites, the HMCM-56 catalysts show the excellent overall catalytic performance with the yield of BTX more than 60 mol%, whether using NiO or MoO3 as the active component.