51464-74-5Relevant articles and documents
Fractal MTW Zeolite Crystals: Hidden Dimensions in Nanoporous Materials
Wang, Lei,Zhu, Sheng-Cai,Shen, Mei-Kun,Tian, Hai-Wen,Xie, Song-Hai,Zhang, Hong-Bin,Zhang, Ya-Hong,Tang, Yi
, p. 11764 - 11768 (2017)
Screw dislocation structures in crystals are an origin of symmetry breaking in a wide range of dense-phase crystals. Preparation of such analogous structures in framework-phase crystals is of great importance in zeolites but is still a challenge. On the basis of crystal-structure solving and model building, it was found that the two specific intergrowths in MTW zeolite produce this complex fractal and spiral structure. With the structurally determined parameters (spiral pitch h, screw angle θ, and spatial angle ψ) of Burgers circuit, the screw dislocation structure can be constructed by two different dimensional intergrowth sections. Thus the reported complexity of various dimensions in diverse crystals can be unified.
Germanate with three-dimensional 12 × 12 × 11-ring channels solved by X-ray powder diffraction with charge-flipping algorithm
Xu, Yan,Liu, Leifeng,Chevrier, Daniel M.,Sun, Junliang,Zhang, Peng,Yu, Jihong
, p. 10238 - 10244 (2013)
A new open-framework germanate, denoted as GeO-JU90, was prepared by the hydrothermal synthesis method using 1,5-bis(methylpyrrolidinium)pentane dihydroxide as the organic structure-directing agent (SDA). The structure of GeO-JU90 was determined from synchrotron X-ray powder diffraction (XRPD) data using the charge-flipping algorithm. It revealed a complicated framework structure containing 11 Ge atoms in the asymmetric unit. The framework is built of 7-connected Ge7 clusters and additional tetrahedral GeO 3(OH) units forming a new three-dimensional interrupted framework with interesting 12 × 12 × 11-ring intersecting channels. The Ge K-edge extended X-ray absorption fine structure (EXAFS) analysis was performed to provide the local structural information around Ge atoms, giving rise to a first-shell contribution from about 4.2(2) O atoms at the average distance of 1.750(8) A. The guest species in the channels were subsequently determined by the simulated annealing method from XRPD data combining with other characterization techniques, e.g., 13C NMR spectroscopy, infrared spectroscopy (FTIR), compositional analyses, and thermogravimetric analysis (TGA). Crystallographic data |(C15N2H32) (NH4)|[Ge11O21.5(OH)4], orthorhombic Ama2 (No. 40), a = 37.82959 A, b = 15.24373 A, c = 12.83659 A, and Z = 8.
Synthesis and characterisation of aluminophosphate-based zeotype materials prepared with α,ω-bis(N-methylpyrrolidinium)alkane cations as structure-directing agents
Maple, Martin J.,Williams, Craig D.
, p. 4175 - 4181 (2007)
New routes to the preparation of two families of small pore microporous solids are described. Flexible diquaternary alkyl ammonium cations (C 4H8)CH3N+(CH2) nN+CH3(C2H8), n = 3-5, have been found to act as structure directing agents in the synthesis of aluminophosphate-based materials of the ABC-6 group. The templates exhibit considerable selectivity in crystallising phases of the ERI or AFX-type (MeAPO-17 or MeAPO-56, respectively) from a wide variety of metalloaluminophosphate gels (Me = Mg2+, Co2+ or Si 4+). For example, from gels containing Mg/P = 0-0.25, 1,4-bis(N-methylpyrrolidinium)butane cations gave MgAPO-17, and 1,5-bis(N-methylpyrrolidinium)pentane cations gave MgAPO-56. Notably, materials could be prepared with levels of metal-substitution tailored to a high degree and distributed non-randomly within the framework. As-prepared solids have been characterised by powder XRD, multinuclear solid state NMR, FT-IR, SEM, and thermal and elemental analysis. The Royal Society of Chemistry.
Three-dimensional 10-ring zeolites: The activities in toluene alkylation and disproportionation
Kub?, Martin,?ilková, Nadě?da,Zones, Stacey I.,Chen, Cong-Yan,Al-Khattaf, Sulaiman,?ejka, Ji?í
, p. 97 - 106 (2015/10/29)
Three-dimensional 10-ring zeolites TUN, IMF, -SVR, MFI and MEL were investigated as for their acid properties, adsorption of 2,2-dimethylbutane and in toluene disproportionation and its alkylation with isopropyl alcohol. The results were compared against zeolite?SFV, the structure of which consists mainly of MEL zeolite with some additional 12-ring channel system. With exception of -SVR synthesized with high Si/Al ratio, all other zeolites provided Si/Al ratios in a narrow region. Novel zeolites TUN, IMF, and -SVR exhibited higher conversions than MFI and MEL in toluene alkylation. TUN and IMF were substantially more active in toluene disproportionation indicating less diffusion restrictions of channel structure on the disproportionation reaction.?SFV showed a similar catalytic behavior to MEL with much lower selectivity to p-xylene and p-cymene. This could indicate that both toluene disproportionation and alkylation proceed in reaction space of?SFV being similar to those of MFI and MEL.?SFV and TUN exhibited much faster adsorption of 2,2-dimethylbutane than MFI, MEL, IMF, and -SVR. It was concluded that the presence of some larger transport pores in?SFV than in other zeolites is responsible for fast adsorption of 2,2-dimethylbutane and transport of products resulting in a low selectivity to p-xylene and p-cymene.
Synthesis, characterization, and catalytic properties of zeolites IM-5 and NU-88
Lee, Song-Ho,Lee, Dong-Koo,Shin, Chae-Ho,Park, Yong-Ki,Wright, Paul A.,Lee, Won Mook,Hong, Suk Bong
, p. 151 - 170 (2007/10/03)
The synthesis, characterization, and catalytic properties of two high-silica zeolites IM-5 and NU-88, whose structures still remain unresolved, were presented. The strength of both Bronsted and Lewis acid sites was stronger in H-IM-5 than in H-NU-88. However, despite its nanocrystallinity, NU-88 exhibited a very high thermal stability. The catalytic properties of these two zeolites were evaluated for the skeletal isomerization of 1-butene to isobutene and the cracking of n-octane and compared to those from various zeolites with known structures. H-IM-5 and H-NU-88 both exhibited a very high 1-butene conversion compared to H-ZSM-35 over the period of time studied, whereas the opposite holds for the formation of isobutene. Their pore topologies were large enough to allow undesired side reactions, e.g., 1-butene dimerization followed by cracking to light olefins. They also showed the initial n-octane cracking activity comparable to that on H-ZSM-5. However, a notable decrease in n-octane conversion on these two zeolites with increasing lime on stream was observed. When the isomerization and cracking activities of all zeolites employed were correlated with their coke-forming propensities, both materials presented a shape-selective character falling within the category of multidimensional, large-pore zeolites.
