Glass zeolitization

Identification of the acid sites (especially the Brpnsted acid sites) on supports such as Vycor glass, zeolites, silica, and alumina is important in... 

Gelatin Collagen Silk Albumin Bone Glass, controlled pore glass Zeolites Silica Sol-gel Alumina Metal Oxides Metals... 

Nowadays, a wider variety of inorganic membranes are commercialized. A rough classification can be based on the type of the inorganic materials (e.g., carbon, metal, ceranfic, glass, zeolite) and on the structure (e.g., porous or dense). The final catalytic membrane can be a composite of different inorganic or organic-inorganic materials. 

In this chapter are described the phenomena of gas flow in glasses and in crystals. While the structure of alkali halides and similar more simple crystals is well known, it is not so with the large families of derivatives of silica. Nevertheless, considerable advance has been made towards an understanding of structural relationships in some at least of these families of compounds. Since many silicates are of importance to the present chapter, a few of the known structural relationships will be given for substances such as silica, silicate glasses, zeolites, mica, clays, feldspars and ultramarines, the first four of which are of great importance in discussing the permeability data. 

J. A. Tossell, Theoretical and Experimental Studies on NMR Shieldings in Mineral Glasses, Zeolites and Related Silsesquioxanes , Annu. Rep. NMR Spectrosc., 2008, 64, 1. 

Silver technologies (glass, zeolite, ceramic, inorganic carriers)... 

Silicates Si02 Na2[Si03], Na2Si20s, Na2Si40g Glass, zeolites Vogel (2006)... 

Polymeric hollow fiber membranes cost approximately 20-50/m. It is diflicult to evaluate the CMSM module cost because no commercial CMSM module is available. Kotos and Mahajan [4] stated that caibon, glass, zeolite and other inorganic membranes could cost fiom one to three orders of magnitude higher than polymeric membranes. Hence, the cost of the CMSM module was chosen to be SO-SOO/m for the simulation work. 

The kinetics of polymer adsorption on porous substrates is much more difficult to tackle. Besides adsorption, desorption, and exchange, size exelusion has to be taken into account. Also, most in situ methods are not applicable to porous substrates. A major difficulty is that with all available methods smeared-out properties are measured while it is likely that strong gradients in the axial direetion of the cylindrical pore are present. The process of axial equilibration is poorly understood and in many cases extremely slow. Most studies were performed with porous substrates with broad pore size and shape distributions. Controlled-pore glasses, zeolites, or porous membranes could be used as model systems with pores of molecular size. Application of glass capillaries is interesting for controlling the hydrodynamics in a curved system. 

An interesting point is that infrared absorptions that are symmetry-forbidden and hence that do not appear in the spectrum of the gaseous molecule may appear when that molecule is adsorbed. Thus Sheppard and Yates [74] found that normally forbidden bands could be detected in the case of methane and hydrogen adsorbed on glass this meant that there was a decrease in molecular symmetry. In the case of the methane, it appeared from the band shapes that some reduction in rotational degrees of freedom had occurred. Figure XVII-16 shows the IR spectrum for a physisorbed H2 system, and Refs. 69 and 75 give the IR spectra for adsorbed N2 (on Ni) and O2 (in a zeolite), respectively. 

Similar, very detailed studies were made by Ebert [112] on water adsorbed on alumina with similar conclusions. Water adsorbed on zeolites showed a dielectric constant of only 14-21, indicating greatly reduced mobility of the water dipoles [113]. Similar results were found for ammonia adsorbed in Vycor glass [114]. Klier and Zettlemoyer [114a] have reviewed a number of aspects of the molecular structure and dynamics of water at the surface of an inorganic material. 

Changes in relative peak intensity and marginal line shifts have been observed for benzene adsorbed on porous glass (26). More significantly, infrared spectroscopic evidence had been found in the appearance of inactive fundamentals for the lowering of molecular symmetry of benzene on adsorption on zeolites (47). 

For other centrosymmetric adsorbates such as C02 on zeolites X and Y (1) and ethene on porous Vycor glass (3), only marginal changes in line position were observed. 

The zeolite fixed into the reactor ijras dried by carbon dioxide at 623K fw lb. The CHO dissolved into methanol (SO ma %) was si lied by a micio f der at constant flow tate to e poiator. The vapor diluted by carbon dioxide P0mol%) was fed to flie tssiAor. The n ctor effluent was collected at prescribed time intervals to and analyzed by a gas chromah aph equipped glass with column (40m). 

Chemical and electrochemical techniques have been applied for the dimensionally controlled fabrication of a wide variety of materials, such as metals, semiconductors, and conductive polymers, within glass, oxide, and polymer matrices (e.g., [135-137]). Topologically complex structures like zeolites have been used also as 3D matrices [138, 139]. Quantum dots/wires of metals and semiconductors can be grown electrochemically in matrices bound on an electrode surface or being modified electrodes themselves. In these processes, the chemical stability of the template in the working environment, its electronic properties, the uniformity and minimal diameter of the pores, and the pore density are critical factors. Typical templates used in electrochemical synthesis are as follows ... 

Reaction conditions 0.1 g of the zeolite Y modified catalyst, tested in a conventional glass microreactor with racemic butan-2-ol (7.35 x 10" mol h-1), prevaporized in a nitrogen diluent (6.2 -6.7 x 10" mol h-1). Products were analyzed using on-line GC with a 40m capillary y- cyclodextrin colimm with trifluoroacetyl stationary phase, temperature programmed from 25-70 "C with a split ratio of 120 1. 

Catalytic Reactions. The copper catalysts were pre-reduced at 270°C with H2 before the catalytic test. Citral (0.1 g) was dissolved in toluene or heptane dehydrated over zeolites (8 ml) or not and the solution transferred under N2 into a glass reaction... 

A number of matrices have also been used for the preparation of semiconductor nanoparticles, whereby the particulate material is grown within and subsequently fills the cavities of the host material. These includes zeolites,361 glasses,362 and molecular sieves,363-365 and can be viewed as nanochambers which limit the size to which crystallites can grow. Other synthetic methods include micelles/microemulsions,366-369 sol-gels,370,371 polymers,372-377 and layered solids.378... 

A glass tube fixed-bed reactor was used as a closed static reactor. The cyclotron produced nC-radioisotope (Ti/2=20.4 min) was used for nC-labeled methanol production by radiochemical process. The nC-labeled methanol (shortly nC-methanol, - 3pmol, -600 MBq) was then introduced into 250 mg of zeolite at ambient temperature by He gas flow. Afterwards, equivalent volume of liquid methyl iodide was injected into nC-methanol to have mixture of methanol and methyl iodide and introduced into catalyst for investigation of methyl iodide influence. After adsorption (2 min), the catalyst was heated up to the required temperature. 

All zeolite samples ( 1,4g) were used after dehydration procedure at 773 K under Ar. Then, weighted amount of DPP corresponding to 1 molecule per zeolite unit cell (UC) was added under dry argon at 293 K and the powders were shaken in the dark. Powders were transferred under dry argon in quartz glass Suprasil cell or in cylindrical EPR quartz tube and sealed. 

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