Systematic approaches towards template-free synthesis of EMT-type zeolites

•Successful synthesis of EMT-type zeolite using a lower amount of 18-crown-6 ether than previously reported.•Extended hydrothermal synthesis duration can be used to compensate for the decreased crystallinity at low amounts of 18-crown-6 ether.•Lowering the amount of 18-crown-6 ether in the hydrogel promotes growth along c axis of the hexagonal platelet crystals.

Presently it is understood that 18-crown-6 ether is necessary as an organic template to synthesise pure and well crystalline EMT-type zeolites. This is problematic for optimisation of organic-free synthesis of zeolites. We report a new method to synthesise pure zeolite EMC-2 using a lower amount of 18-crown-6 ether than previously reported. At these low 18-crown-6 ether concentrations, FAU-type zeolites were not seen to co-crystallise. We observe that the crystallinity of the EMT-type zeolite is proportional to the amount of 18-crown-6 ether added in the synthesis. The as-synthesised zeolites were characterised using X-ray powder diffraction, scanning electron microscopy and solid state nuclear magnetic resonance. These findings are a crucial step towards understanding template roles and designing syntheses for zeolites without the use of toxic organic templates.

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