Chabazite

Zeolites are tire product of a hydrotliennal conversion process [28]. As such tliey can be found in sedimentary deposits especially in areas tliat show signs of fonner volcanic activity. There are about 40 naturally occurring zeolite types. Types such as chabazite, clinoptilolite, mordenite and phillipsite occur witli up to 80% phase purity in quite large... 

Adsorbents Table 16-3 classifies common adsorbents by structure type and water adsorption characteristics. Structured adsorbents take advantage of their crystalline structure (zeolites and sllicalite) and/or their molecular sieving properties. The hydrophobic (nonpolar surface) or hydrophihc (polar surface) character may vary depending on the competing adsorbate. A large number of zeolites have been identified, and these include both synthetic and naturally occurring (e.g., mordenite and chabazite) varieties. 

Reaction Conditions Temperaturc=603 W/F=200 g h mol, NHa/EAsSO EDA ethylenediamine, El ethyleneimine, PA piperazine derivatives CHA chabazite, FAU faujasite 00, LTL Linde type L, MOR mordenite, EDTA-MOR Na-mordenite was treated with EDTA and then ion-exchanged to H-form, MFl ZSM5. 

Haase, F., Sauer, J., Hutter, J., 1997, Ab Initio Molecular Dynamics Simulation of Methanol Adsorbed in Chabazite , Chem. Phys. Lett., 266, 397. 

One of the most promising techniques for studying transition metal ions involves the use of zeolite single crystals. Such crystals offer a unique opportunity to carry out single crystal measurements on a large surface area material. Suitable crystals of the natural large pore zeolites are available, and fairly small crystals of the synthetic zeolites can be obtained. The spectra in the faujasite-type crystals will not be simple because of the magnetically inequivalent sites however, the lines should be sharp and symmetric. Work on Mn2+ in hydrated chabazite has indicated that there is only one symmetry axis in that material 173), and a current study in the author s laboratory on Cu2+ in partially dehydrated chabazite tends to confirm this observation. 

Structural study by solid state NMR and powder X-ray diffraction of the pure silica chabazite through water intrusion-extrusion processes... 

Water intrusion-extrusion isotherms performed at room temperature on hydrophobic pure silica chabazite show that the water-Si-CHA system displays a real spring behavior. However, Pressure/Volume differences are observed between the first and the second cycle indicating that some water molecules interact with the inorganic framework after the first intrusion. 29Si and especially H solid state NMR and powder X-ray diffraction demonstrated the creation of new defect sites upon the intrusion-extrusion of water and the existence of two kinds of water molecules trapped in the super-cage of the Si-CHA a first layer of water strongly hydrogen bonded with the silanols of the framework and a subsequent layer of liquid-like physisorbed water molecules in interaction with the first water layer. 

Keywords Chabazite, water condensation, solid-state NMR, Rieveld refinement. 

CAL-4, a structural study of a dual templated chabazite-type silicoaluminophosphate... 

X-ray structure analysis showed that each of the cavities in the chabazite-type host structure contains two disordered SDA molecules. The lack of a superstructure suggests a random layered arrangement of the template molecules (Figure 2) similar to the crystal structure of the related compound CAL-1 [5],... 

Figure 2 (i) Layered organization. ..abc... stacking) of the organic molecules within the chabazite-type host framework, (ii) schematic representation of the SDA s random distribution within the cages. 

The crystal structure of the novel chabazite-type material CAL-4 displays a layered organization of the SDAs, which may be responsible for an unusual plate-like particle shape. It is predicted that the morphology of the crystallites can be designed by choosing suitable SDAs. 

Size limit for Ca-rich chabazite, Linde sieve 5 A, Ba-zeolite and gmelinite about here ( 0.49 nm)... 

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