A New Microporous Silicate With 12-Ring Channels
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A New Microporous Silicate With 12-Ring Channels Jacques Plévert,1† Yoshihiro Kubota,2 Takahisa Honda,2 Tatsuya Okubo1 and Yoshihiro Sugi2 1 Dept of Chemical System Engineering, The University of Tokyo, Tokyo 113-8656, Japan. 2 Dept of Chemistry, Faculty of Engineering, Gifu University, Gifu 501-1193, Japan. ABSTRACT A new molecular sieve GUS-1 is synthesized under hydrothermal conditions using a new organic compound acting as structure-directing agent. The structure determination reveals a framework with one-dimensional 12-membered ring channels running parallel. The structure exhibits the same channel net as zeolite ZSM-12 and shows the same projection of the framework along the pores as mordenite. INTRODUCTION An effective way to synthesize molecular sieves with new framework topology consists of using new organic structure-directing agents (SDA). A novel crystalline microporous silicate GUS-1 is obtained using a newly designed organic compound, 1,1’-butylenedi(4-aza-1-azonia2,5-dimethylbicyclo[2.2.2]octane) dihydroxide as SDA [1]. The structure determination of the new microporous solid is described in this report. EXPERIMENTAL The synthesis of GUS-1 was performed under hydrothermal conditions in the temperature range 150-175°C for 10-20 days. The composition of the synthesis mixture is 1SiO2: 0.1R2+(OH-)2: 0.1NaOH: 50H2O, where R2+ stands for cation 1 (1 consists of 4 diastereomers). CH3
CH3 N H3C
+ N
N +
N
1
H3C
GUS-1 tends to form with another molecular sieve ZSM-12, formed of channels with 12 membered-ring aperture [2]. GUS-1 in pure form has not been obtained so far. The structure of GUS-1 has been determined from synchrotron powder diffraction data of a sample containing the two phases GUS-1 and ZSM-12, calcined at 700ºC for removing the SDA. The X-ray data were collected on the beam line X7A at the National Synchrotron Light GG6.28.1
Source at Brookhaven Laboratory. The sample was loaded in a glass capillary of diameter 1.0 mm. The powder pattern was recorded at room temperature at the wavelength λ = 1.1964 Å. STRUCTURE DETERMINATION The particular sample used for structure-solution contains the two phases GUS-1 and ZSM12 in approximate proportion 40% and 60%. Its N2 adsorption isotherm is very similar to the isotherms of pure ZSM-12 samples, suggesting that the unknown phase is a molecular sieve with 12-ring channels too. Scanning electron micrographs reveal particles of different morphologies. The largest amount of crystals shows particles of needle shape, similar to the typical morphology of crystals of ZSM-12. Overgrowth of thin needles is found and it is tempting to assign them to the phase GUS-1 (Figure 1). In addition, particles of fan-like shape can be observed in the sample, which probably correspond to zeolite SSZ-31 as the characteristic (001) reflection is found in the powder pattern, as trace, at d = 14.4 Å [3]. The powder pattern was indexed using the program TREOR [4], giving an orthorhombic cell with systematic absences consistent with the space group Cmmm and subgroups and possib
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