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Microporous silica gels

Fig. 5.18 Adsorption isotherm of water vapour at 25°C on microporous silica gel E outgassed at 25°C. O. Adsorption,. desorption. Fig. 5.18 Adsorption isotherm of water vapour at 25°C on microporous silica gel E outgassed at 25°C. O. Adsorption,. desorption.
Si02 gel DDAB/toluene/water (48.7% DDAB, 19.5% decane, 31.8% aqueous silica sol) TMOS (partially hydroiyzed)/H20 (+ 0.4-10 wt%HF) Bicontinuous p,Es used as templates for microporous silica gels monodisperse pores (2 nm pore radius) large specific surface area (—103 m2/g) (51)... [Pg.154]

The isotherms and corresponding as-plots in Figures 10.8 and 10.9 are for the adsorption of nitrogen on representative mesoporous and microporous silica gels (Bhambhani et al., 1972). The derived values of the specific surface area are given in Table 10.8. The values of the BET nitrogen area, a(BET), in Table 10.8 are based on the usual assumption that the adsorbed molecules were close-packed in the completed monolayer (i.e. a(N2) 0.162 nm2). The corresponding values of a(S, N2) were calculated from the initial slope of the as-plots by die relation... [Pg.303]

Figure 10.9. Nitrogen isotherms (top) and as-plots (bottom) for microporous silica gels D and E (from Bhambhani et al., 1972). Figure 10.9. Nitrogen isotherms (top) and as-plots (bottom) for microporous silica gels D and E (from Bhambhani et al., 1972).
Figure 10.10. Argon and nitrogen isotherms at 77 K on mesoporous silica gel B (top) and microporous silica gel C (bottom) (Payne et al 1973). Figure 10.10. Argon and nitrogen isotherms at 77 K on mesoporous silica gel B (top) and microporous silica gel C (bottom) (Payne et al 1973).
A. Kiselev developed the adsorption-structural method of investigation (129), which made possible a rational classification of adsorbents (130-132). Dubinin, Radushkevitch, Bering, Serpinsky, and others have developed on the basis of their experimental results a theory on the physical adsorption of gases and vapors in microporous adsorbents that they call the theory of volume filling of micropores. The theory is applicable to almost all the adsorption systems, including microporous silica gels and porous glasses (133, 134). [Pg.613]

Adsorption of anionic and nonionic surfactants on sorbents of various nature, such as coal, microporous silica gel, aluminium oxide, has been studied in detail by Klimenko et al. [320]. It has been shown that, at c>CMC, the adsorption is polymolecular in nature which can be an explanation for the data obtained in [319]. [Pg.598]

Carbon/silica adsorbents or carbosils have been prepared by both conventional and microwave heating. These materials were produced by pyrolysis of CH2CI2 on microporous silica gel surfaces for 30 min to 6 h at 550 °C. The resultant materials were hydrothermally treated with steam or liquid water using either a conventional autoclave or a microwave unit. As with the clay materials, hydrothermal treatment using microwave irradiation leads to a significant increase of surface area and total pore volume of the carbosils, as compared to conventional methods. [Pg.208]

Burban et al. [53] reported the preparation of microporous silica gels by polymerization of partially hydrolyzed tetramethoxysilane gels present in the aqueous phase of bicontinuous microemulsions stabilized with didodecylammonium bromide. When vacuum dried, the gels made in microemulsions had about twice as much specific surface area as conventional vacuum-dried silica gels. [Pg.700]

Microporous silica gels monodisperse pores (2 nm pore radius), large specific surface area ( 103 m /g) [61]. [Pg.843]

Yamashita and others [188] synthesized microporous silica gel particles by... [Pg.83]

H. Yamashita, M. Demiya, H. Mori and T. Maekawa, Synthesis of microporous silica-gel par-... [Pg.191]

The deposits from hot deep-well brine near the Salton Sea in California build up very rapidly as the brine cools while going through pipes. The silica content is 400 ppm in a solution containing up to 15% Nad as well as a few percent of CaCl, and KCI. The brine is slightly acidic, so there is no interaction of silica with calcium ion, but iron, which is present at only 0.2%, is adsorbed on silica at this pH and is a major component of the scale. More striking is that up to 20% copper and 6% silver are found in the scale as sulfides. The deposit is amorphous to X-rays and consists of a hydrated silica, classed as opal, but is actually a microporous silica gel, under the coagulating influence of the metal ions. Since the brine contains 1-2 ppm H,S, the... [Pg.93]

There are many patents disclosing combinations of acids with additional sodium salts, or ammonium salts that act both as acids and salts. Often there is additional free ammonia. When the reactions occur at ordinary temperature there seems little doubt that the precipitates consist of microscopic particles of microporous silica gels. These are of little use as dispersible fillers, but find many other applications. When the reactions are carried out in hot solutions quite different products are formed and, in this case, some readily dispersible materials appear to be obtained. [Pg.560]

The silica, having been formed by polymerization at ordinary temperature, probably consists of close-packed ultimate particles of SiO with surfaces of SiOH groups and with water held tightly in the micropores between these small particles as in microporous silica gels formed in the laboratory. If suitably dried, such gel should have a specific surface area of more than 400-600 m g. ... [Pg.743]

In any equilibrium partitioning experiment using a micro-porous adsorbent and an external solution, one varies C°, and Ws for a given adsorbent. From equation (4.1.65), a plot of C° vs. Ws for a given adsorbent will be linear, the slope being equal to the quantity in brackets on the right-hand side of equation (4.1.65). Unless Vp > r it is clear that Kim = cy Cii will be less than 1, and the determination of the pore surface adsorption equilibrium relation (between and Ca) will be influenced by k, . This was demonstrated clearly in the adsorption of aromatic compounds (for example, napthalene) on microporous silica gel adsorbents by Alishusky and Fournier (1990). [Pg.228]

The potential applications of such a polymerization technique for preparing novel polymeric materials include microfiltration, separation membranes, polymer blends with a unique microstructural morphology, and porous microcarriers for cultures of living cells and enzymes [7]. Some other interesting ideas about the preparation of novel materials include the conductive composite film [95] and microporous silica gel [96]. [Pg.170]

Fig. 1. N2 and Ar adsorption isotherms at 77 K on a microporous silica gel outgassed at various temperatures. Fig. 1. N2 and Ar adsorption isotherms at 77 K on a microporous silica gel outgassed at various temperatures.

See other pages where Microporous silica gels is mentioned: [Pg.303]    [Pg.28]    [Pg.320]    [Pg.190]    [Pg.551]    [Pg.560]    [Pg.736]    [Pg.4677]    [Pg.1013]   
See also in sourсe #XX -- [ Pg.305 , Pg.307 , Pg.310 ]




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