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ABSTRACT
Substitution of Al atoms in a zeolite framework by catalytic metal atoms has attracted considerable attention because the catalytic behavior can be tuned by the substituted atoms. In the present study, Sn-substituted MFI-type silicates were synthesized using a hydrothermal reaction of an amorphous Si-O-Sn precursor prepared by mechanochemical grinding of SiO2 and Sn(OH)4. The mechanochemical treatment was found to be a key technique for obtaining the amorphous Si-O-Sn precursor, where tetrahedral Sn4+ species were incorporated into the amorphous matrix. The Sn content in the framework of the MFI-type silicates was successfully controlled by the initial HCl/Si molar ratio of the hydrothermal procedures. Optical reflectance measurements revealed that the Sn4+ ions were dispersedly incorporated into the silicate framework while preserving the initial tetrahedrally coordinated species. Infrared results imply that the resulting Sn-substituted MFI-type silicate has Brønsted acid character. Precise control of the Brønsted and Lewis acid properties by Sn doping is a promising approach to the development of novel types of zeolite-based catalytic materials.
GRAPHICAL ABSTRACT
Acknowledgments
This project was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan for the Management Expenses Grants for National Universities Corporations. The authors also thank JSPS [Grant-in-aid for scientific research (B) No. 15H04181] for funding this study. This work is also supported by JST CREST. We also appreciate the STAM joint program for publishing the present work.
Disclosure statement
No potential conflict of interest was reported by the authors.