Ferrierite crystals

Fig. 46 Evolution of concentration profiles of methanol in a ferrierite crystal for a pressure step of 0 80 mbar. a Shape and 2-D pore structure of the ferrierite crystal b concentration profiles in the z direction aty = 25 xm c 2-D concentration profiles in the entire crystal and d concentration profiles in the y direction at the center z = 120 xm) and two locations close to the edges of the crystal. Relative concentration 1.0 corresponds to the ferrierite equilibrium loading by methanol at 80 mbar...

Fig. 54 Evolution of the concentration profiles in the y direction in the left (a) and right (b) sides of the ferrierite crystal as a function of the parameter =y/. g...

Fig. 29. (a) Ferrierite crystal with a two-dimensional pore structure utilized to determine spatially resolved concentration of methanol, (b) Intercrystalline concentration profiles measured during adsorption hy interference microscopy. Reprinted from 202, cop5rright 2006, with kind permission from American Chemical Society. 

Fig. 8. Ferrierite. Crystal structure showing T-site numbering. The 8-membered ring on the intersection of the main and perpendicular chatmel (8R) as well as the 5-membered ring on the wall of the main chatmel (M5), and 6-membered ring in the cage (P6) are depicted in a tube mode. Framework Si and O atoms are in grey and red, respectively [09N1].

Fig. 9. Ferrierite crystal stmcture having 7222-space group, (a) aby plane projection, (b) (ac)-plane projection [01Y2]. (cont.)...

Fig. 60. Ferrierite crystal. Phase retardation angle (proportional to birefringence) as function of temperature for domains (1) and (2) [lOLl].

Figure 14. Shape, dimensions and transient concentration profiles during uptake of methanol in a ferrierite crystal measured by interference microscopy, (c) shows the actual profiles along the length of the crystal at the mid point, and (e) shows the same profiles normahzed by subtracting the effect of the roof-hke structures. AQ profiles are at the same times (0, 30, 130 and 370 secs). From Kortunov etal [81].

Heats of immersion in water have been determined for a number of outgassed porous crystals enriched by ion exchange in various cations (zeolites X, Y, A, chabazite, and synthetic ferrierite), and for clinoptilolite and mordenite in their Na-forms, decationated, and in various stages of de-alumination. Finally, heats of immersion were determined in NaX, NaY, NaA, and (Ca,Na) chabazite in which the crystals initially contained various known loadings of zeolitic water. From the results, the influence of the exchange cations upon integal heats of sorption of water, AH, and other derived heats have been evaluated and discussed. 

Most of the zeolite syntheses carried out under hydrothermal conditions directly results in the formation of three-dimensional crystalline frameworks. However, several zeolites, like MCM-22 or ferrierite, can be synthesized in the form of layered precursors, which can be transformed by further thermal treatment into the three-dimensional crystal structure. These layered solids arouse an interest due to their ability to intercalate guest molecules between two neighboring zeolite layers. Using a proper treatment, layered zeolite materials can be delaminated while the structure of layers is preserved, which makes accessible all active sites located on the external surface of such catalyst. By adding proper inorganic guest molecules functioning as pillars, the control of the interlayer distance can be achieved. Such materials... 

At present, MCM-22 and ferrierite represent the only two described examples of zeolites, which can be synthesized in the layered form and further transformed to 3-D crystal structures. Delamination of ferrierite led to the formation of ITQ-6 and ITQ-20 [52], while ITQ-2 can be prepared from the lamellar precursor of MCM-22 [15]. Not only aluminum but also titanium was incorporated into the siliceous ITQ-6 and evaluated in acid and oxidation reactions [52,53]. 

A Parallel EELS (PEELS) analysis of coke on ferrierite platelets was used by de Jong et aP to verify that the amorphous layer observed on the borders of the crystals was effectively amorphous carbon. 

Fig. 17 Transient concentration profiles in y-direction (i.e., along 8-ring channels) measured by interference microscopy for a adsorption and b desorption of methanol in a large crystal of ferrierite for pressure steps 5 -> 10 and 10 5 mbar. The form of the profiles shows that both surface resistance and internal diffusion (along the 8-ring chan-...

As schematically shown by Fig. 46a, ferrierite contains two mutually intersecting arrays of channels. In comparison with the strictly one-dimensional MOF crystals considered in the previous section, their analysis is additionally complicated by the existence of two rooflike parts on either side of the platelike main crystal body. It turned out, however, that these features did in no way complicate the method of analysis. Contrary to the MOFs, which required an additional activation step after each uptake experiment, methanol in ferrierite proved to be an ideal host-guest system, where one and the same crystal could alternately be subjected to adsorption and desorption without any perceptible change in the sorbate profiles. It were these special conditions under which interference microscopy could be developed to a technique of diffusion measurement in nanoporous materials of unprecedented power [63,65,70,71,88,89]. 

Thus, with the ratio jin/jos directly following from Eqs. 17 and 20, the sticking probability , i.e., the probability that a molecule, after having encoim-tered the outer crystal surface, is going to continue its trajectory in the intracrystalhne pore space, has become accessible by direct experimental determination. Eor the systems considered in Sects. 3.3.2 and 3.3.4 under the conditions of the reported experiments, i.e., for molecular uptake of isobutane by silicalite-1 at a pressure of 1 mbar and of methanol by ferrierite at a pressure of 10 mbar, it results to be 0.01 and 6 x 10 , respectively. Thus, it... 

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