Spatial distribution and catalytic performance of metal-acid sites in Mo/MFI catalysts with tunable meso-/microporous lamellar zeolite structures

The lamellar MFI zeolite with tunable meso-/microporosity was prepared by a dual template synthesis method. Implications of the tunable meso-/microporosity on the spatial distribution and catalytic performance of metal-acid sites in Mo/lamellar MFI catalysts were studied. The number of free Bronsted acid sites increases linearly, accompanied by a linear decrease in Mo dispersion, with decreasing external surface areas in catalysts. The Mo-acid active sites coexisted on the external surface or mesopores of the catalysts linearly depends on the hierarchy factor, being the product of relative micropore volume and relative external surface area. The reaction rate and product selectivity of Mo/lamellar MFI in direct methane aromatization reactions are consistent with the trends of changes in zeolite porosities. These results imply that a balance between the meso- and microporosity in zeolite and the resultant active site distribution can be realized for desirable catalysis by simple one-step dual template synthesis of zeolites. (C) 2015 Elsevier Inc. All rights reserved.