EU-12: A Small-Pore High-Silica Zeolite Containing Sinusoidal Eight-Ring Channels

Abstract

Zeolite EU-12, the framework structure of which has remained unsolved during the past 30 years, is synthesized at a specific SiO2/Al2O3 ratio using choline as an organic structure-directing agent, with both Na+ and Rb+ ions present. Synchrotron powder X-ray diffraction and Rietveld analyses reveal that the EU-12 structure has a two-dimensional 8-ring channel system. Among the two distinct 8-ring (4.6 x 2.8 and 5.0 x 2.7 angstrom) channels along c axis, the smaller one interconnects with the sinusoidal 8-ring (4.8 x 3.3 angstrom) channel along a axis. The other large one is simply linked up with the sinusoidal channel by sharing 8-rings (4.8 x 2.6 angstrom) in the ac plane. The proton form of EU-12 was found to show a considerably higher ethene selectivity in the low-temperature dehydration of ethanol than H-mordenite, the best catalyst for this reaction.