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

Zeolite EU-12, the framework structure of which has remained unsolved during the past 30 years, is synthesized at a specific SiO2 /Al2 O3 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 (4.6×2.8 and 5.0×2.7 Å) channels along c axis, the smaller one interconnects with the sinusoidal 8-ring (4.8×3.3 Å) channel along a axis. The other large one is simply linked up with the sinusoidal channel by sharing 8-rings (4.8×2.6 Å) 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.