Mechanochemistry: Fundamentals, applications and future

Solventless and template-free synthesis of SOD zeolite Haochen Wu and Stuart L. James School of Chemistry and Chemical Engineering, Queen’s University Belfast, UK

Zeolites are microporous crystalline aluminosilicate compounds, composed of TO 4 tetrahedra (T=Si, Al) with oxygen atoms connecting adjacent tetrahedra. 1 Although these materials are required on very large scales, the conventional hydrothermal synthetic method used is not sustainable on account of the toxicity, low efficiency ( e.g. , long reaction times), and high cost of both the template and solvent. Consequently, a solventless, template-free synthetic route would be advantageous. 2 Various zeolites such as Zeolite Socony Mobil-5 (ZSM- 5), mordenite (MOR), sodalite (SOD) and beta zeolite (BEA) have been prepared by Ren et al. 3 under solvent- free, batch conditions. As mechanochemistry often provides a facile route for achieving solvent-free chemistry, this work was built upon by Nada et al . 4,5 who investigated the solvent and template-free ball mill synthesis of ZSM-5. Problematically, the resultant zeolite from Ren et al. 3 displayed a high level of amorphization, which is not favourable for optimal properties. Herein we report the solvent and template-free synthesis of SOD, using tetraethyl orthosilicate (TEOS), SiO 2 gel and basic aluminum acetate, which gives products with high crystallinity. These results form an excellent starting point for mechanochemical scale-up by Twin-Screw Extrusion (TSE), as applied to MOF-type materials previously. 6 References 1. Auerbach et al ., Handbook of Zeolite Science and Technology, 2003 , 1-9. 2. Meng et al., Chem. Rev ., 2014 , 114, 2, 1521–1543. 3. Ren et al ., J. Am. Chem. Soc. 2012 , 134, 37, 15173–15176 . 4. Nada et al., Microporous and Mesoporous Materials , 2019 , 276, 23-28.

5. Nada et al., Nanoscale Adv ., 2019 , 1, 3918 -3928. 6. Crawford et al., Chem. Sci. , 2015 , 6, 1645-1649.

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