Mechanochemically-assisted solvent-free and template-free synthesis of zeolites ZSM-5 and mordenite. Issue 10 (3rd September 2019) - Nada, Majid H.
Abstract : Solvent-free and template-free synthesis of crystalline zeolites using mechanochemical pre-reactions between Na2 SiO3 and Al2 (SO4 )3 forming Na2 SO4 and well-mixed aluminosilicate intermediates. Abstract : Aluminosilicate-based zeolite materials, such as ZSM-5 and mordenite, are well-studied as catalysts. Typical approaches to synthesize these zeolites require either templates or seeds to direct ordered crystal growth and both of these are expensive and add to the complexity of zeolite synthesis. In this paper, we describe a solvent-free and template-free method to synthesize crystalline ZSM-5 and mordenite zeolites without any added seed crystals. Key to the success of this approach is a mechanochemical precursor pre-reaction step. High-energy ball-milling is used to initiate a solid-state metathesis (exchange) reaction between Na2 SiO3 and Al2 (SO4 )3 reagents, forming crystalline Na2 SO4 and well-mixed aluminosilicate precursor. The solid precursor mixture is thermally converted to crystalline ZSM-5 or mordenite at moderate 180 °C temperatures without solvents or an organic amine structure directing template. Variations in Si/Al ratios in the precursor mixture and additions of solid NaOH to the mechanochemical reaction were found to influence the subsequent growth of either crystalline ZSM-5 or mordenite zeolites. The crystalline zeolites from this solvent-free and template free method have high ∼300 m 2 g −1 surface areas directly from the synthesis without requiring high-temperature calcination. These materials are also comparably active to their commercial counterparts in cellulose and glucose biomass catalytic conversion to hydroxymethylfurfural.