Synthesis of micro-mesoporous aluminosilicates on the basis of ZSM-5 zeolite using dual-functional templates at presence of micellar and molecular templates

Micro-mesoporous aluminosilicates consisting of agglomerates of the ZSM-5 nanoparticles were obtained using dual-functional templates [C6H13-N+CH3)(2)-C6H12-N+(CH3)(2)-C6?H13](Br-)(2) (C6-6-6Br2), [C8H17-N+(CH3)(2)-C6H12-N+(CH3)(2)-C8H17](Br-)(2) (C8-6-8Br2). Aluminosilicates with randomly oriented flake-like particles built from ZSM-5 layers were obtained using [C16H33-N+CH3)(2)-C6H12-N+(CH3)(2) -C6H13](Br-)(2) (C16-6-6Br2). Use of C8-6-8Br2 and additive of cetyltrimethylammonium bromide CTAB (CTAB concentration is lower than the first critical micelle concentration, CMC1) leads to an increase of the total specific surface area, mesopore surface area and the mesopore size uniformity in the product, as well as the concentration of Bronsted acid sites accessible for bulk molecules. It is assumed that CTAB role is to limit the zeolite crystals growth. Addition of CTAB to C16-6-6Br2 (CTAB concentration is also lower than CMC1) promotes the formation of micro-mesoporous aluminosilicate possessing disordered lamellar mesostructure stable upon calcination which is characterized by a higher total specific surface area and better mesopores uniformity than ZSM-5 obtained in the presence of C16-6-6Br2. The additive of a molecular template tetrapropylammonium hydroxide (TPAOH) shifts the structure formation toward zeolite and leads to an increase in the ratio of concentrations of Bronsted and Lewis acid sites for the obtained aluminosilicates. The addition of small amounts of TPAOH into the reaction mixture (TPAOH/C16-6-6Br2 = 6.5.10(-3)) leads to formation of self-pillared aluminosilicate. In this material the nanoparticles act as pillars between the layers of ZSM-5 and thus contribute to retention of low-ordered lamellar mesostructure after calcination, leading to increase of the total specific surface area and improving mesopores uniformity. (C) 2016 Elsevier Inc. All rights reserved.