Organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite

A series of ZSM-5/ZSM-11 co-crystalline zeolites with various compositions and morphologies were successfully synthesized via an organic template-free hydrothermal route and characterized by XRD, XRF, SEM, NMR and N2 adsorption/desorption technologies. The effects of raw materials and batch composition were investigated systematically. Various silicon sources can be employed in the organic template-free synthesis of ZSM-5/ZSM-11 co-crystalline zeolite, however only a few types of aluminum sources are available. This organic template-free system is favorable to the aluminum-rich zeolite. With the increase of initial SiO2/Al2O3 ratio, the ZSM-5 percentage in the ZSM-5/ZSM-11 co-crystalline zeolite increases as well as the crystal size, and especially the morphology of ZSM-5/ZSM-11 co-crystalline zeolite prepared from the colloidal silica–NaAlO2 solution system changes gradually from nano-rod aggregation, micro-spindle to single hexagon and then to twinned hexagon crystals. Moreover, Na+ and OH− in the initial materials can promote the nucleation of the ZSM-5/ZSM-11 co-crystalline zeolite significantly and are beneficial to the formation of crystals with relatively low length/width ratio, while K+ postpones the crystallization process seriously.

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► ZSM-5/ZSM-11 co-crystalline zeolite was organic template-free synthesized.
► The crystal phase was more sensitive to the aluminum source than the silicon source.
► The ZSM-5 percentage and crystal size increased with the initial SiO2/Al2O3 ratio.
► Na+ and OH− promoted the nucleation of ZSM-5/ZSM-11 co-crystalline zeolite.
► K+ postponed the crystallization process of ZSM-5/ZSM-11 co-crystalline zeolite.