Our group synthesized mordenite nanosheets with shortened channel lengths along its 12-member ring channel. The finding was published in J. Mater. Chem. A.
Microporous zeolites are widely used as catalysts in the petrochemical industry. However, the rather long micropore up to several micrometers heavily hampered the diffusion of molecules into and out of the pores and caused rapid deactivation due to coke deposition through secondary reactions. To avoid diffusion limitations of microporous zeolites, the researchers synthesized mordenite nanosheets of 20–40 nm thickness in its 12-membered ring using a monovalent quaternary ammonium salt C16H33-N+(CH3)2-C2H4-N(CH3)2Br (C16-2-0) as the structure directing agent. Further investigation indicated that the formation of MOR nanosheets might be a process of rapid heterogeneous transformation of the initial gel into MOR crystals, followed by a slow and oriented growth through homogeneous liquid-phase transformation due to the strong interaction between the cations of C16-2-0 with silicon and aluminum species. The strong hydrophobic tails of the C16-2-0 precluded the growth along [001] plane and directed the formation of the sheet-like structure. The synthesized mordenite nanosheets remarkably enhanced the catalytic activity for the carbonylation of dimethyl ether due to the shortened lengths of its 12-member ring channels, which greatly facilitated the diffusion of molecules inside the micropores and increased the accessible active sites in the parallel 8-membered ring channels.
The research was supported by National Natural Science Foundation of China and Ministry of Science and Technology of China.(Text by Xiumin Huang)
