On porous glass

Fig. 3.2 Adsorption isotherms for argon and nitrogen at 78 K and for n-butane at 273 K on porous glass No. 3. Open symbols, adsorption solid symbols, desorption (courtesy Emmett and Cines). The uptake at saturation (calculate as volume of liquid) was as follows argon at 78 K, 00452 nitrogen at 78 K, 00455 butane at 273 K, 00434cm g .

Fig. 4.25 Adsorption isotherms showing low-pressure hysteresis, (a) Carbon tetrachloride at 20°C on unactivated polyacrylonitrile carbon Curves A and B are the desorption branches of the isotherms of the sample after heat treatment at 900°C and 2700°C respectively Curve C is the common adsorption branch (b) water at 22°C on stannic oxide gel heated to SOO C (c) krypton at 77-4 K on exfoliated graphite (d) ethyl chloride at 6°C on porous glass. (Redrawn from the diagrams in the original papers, with omission of experimental points.)...

Figure 2 BET plots for N2 at 90 K (filled circles) and > 77 K (filled triangles) on porous glass. ...

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). 

Methyl radicals formed on a silica gel surface are apparently less mobile and less stable than on porous glass (56, 57). The spectral intensity is noticeably reduced if the samples are heated to —130° for 5 min. The line shape is not symmetric, and the linewidth is a function of the nuclear spin quantum number. Hence, the amplitude of the derivative spectrum does not follow the binomial distribution 1 3 3 1 which would be expected for a rapidly tumbling molecule. A quantitative comparison of the spectrum with that predicted by relaxation theory has indicated a tumbling frequency of 2 X 107 and 1.3 X 107 sec-1 for CHr and CD3-, respectively (57). 

Scheme 7.122 Heck couplings utilizing palladium on porous glass.

In the same report, the Strauss group furthermore presented the effective use of palladium on porous glass to achieve quantitative conversions in couplings of phe-nylacetylene with iodobenzene and 4-bromobenzaldehyde. Additionally, satisfactory results were obtained for couplings of phenylacetylene with 4-bromoacetophenone and 2-bromopyridine [146]. 

A new oxidation-dehydrogenation-Heck coupling catalyzed by Pd on porous glass or Pd(OAc)2 also proceeded under microwave heating in the MBR (Scheme 2.18) [36]. With an excess of Phi, saturated alcohols including 1-propanol and 3-phenylpro-panol afforded 3,3-diphenylpropenal as the major product, and trans-2,3-diphenylpro-penal by a concerted process taking 10 min at 220 °C. The yields of this remarkable transformation were low, however, and further work into several aspects is required to make them more respectable. 

Cells immobilized in gels showed lower volumetric rates of hydrogen photoproduction as compared with immobilization on porous glass. In some cases, the diflusion limitation of the process rate was the main reason as shown above. In other cases thick layer of dense culture was insufficiently illuminated. The observation, that hydrogen production rate was higher when the layer of matrix was thinner, supports this suggestion (Tab. 3). 

Photobioreactor [Tsygankov et al., 1994] withitt. sphaeroides RV immobilised on porous glass (125x50x0.5 mm3) with continuous medium flow (5 ml h 1 reactor 1) was illuminated from face (thickness 0.5 mm curve 1) or side position (thickness 50 mm curve 2) by halogen lamp [Tsygankov, Miyake, unpublished]. 

A. A. Tsygankov, Y. Hirata, M. Miyake, Y. Asada, J. Myake (1994) Photobioreactor with photosynthetic bacteria immobilized on porous glass for hydrogen photoproduction. J. Ferm. Bioengineering, 77 575-578. 

Various methods ofachieving preconcentration have been applied, including Hquid -hquid extraction, precipitation, immobihzation and electrodeposition. Most of these have been adapted to a flow-injection format for which retention on an immobihzed reagent appears attractive. Sohd, sihca-based preconcentration media are easily handled [30-37], whereas resin-based materials tend to swell and may break up. Resins can be modified [38] by adsorption of a chelating agent to prevent this. Sohds are easily incorporated into flow-injection manifolds as small columns [33, 34, 36, 39, 40] 8-quinolinol immobilized on porous glass has often been used [33, 34, 36]. The flow-injection technique provides reproducible and easy sample handhng, and the manifolds are easily interfaced with flame atomic absorption spectrometers. 

A. Effects Due to the Presence of Surface OH Groups on Porous Glass.. 290... 

The above experiments agree with Sidorov s results at low pressures (.146), which showed that water is not adsorbed on the free OH groups under these conditions. No detailed comparison can be made, since Sidorov gave no surface area or coverage values for his glass. Similar observations have been reported by Nikitin et al. (151), but have been questioned by McDonald (153), whose results with Cabosil are at variance with those on porous glass. 

Risinger incorporated ion-exchange into the manifold of Fig. 4.14. A in order to improve the determination of copper by using an ISE for the metal ion and a column containing 8-quinolinol immobilized on porous glass for... 

Initially, the possibility to use the preparations of the viral Ag s commercially produced by the Leiconad company (Ukraine) and by the Kursk Pharmaceutical Plant (Russian Federation) for the RID test were tested. It was stated by the manufacturers that these preparations require additional purification to increase the concentration of the Ag markers which should be immobilized on the transducer surface. We used the antigen after the extra purification by chromatography on porous glass for our following experiments. 

It undergoes marked self-association and can be purified readily by chromatography on porous glass. The enzyme has a molecular weight of about 89 kDa, a pH optimum of 6.8-7.0, and a temperature optimum of 35°C. Its amino acid composition, its requirement for iron but not for molybdenum and FAD, and the catalytic properties of the enzyme, indicate that sulphydryl oxidase is a distinct enzyme from xanthine oxidase and thiol oxidase (EC 1.8.3.2). 

Finally, we described the permeation characteristics of a thermosensitive gel supported on porous glass. The switch functional ability of the membrane was demonstrated in permeation experiments. It was pointed out that the change in the permeation characteristics resulted from that in the pore structure in the gel. 

Supported Crystallization of MFI- and FER-type Molecular Sieves on Porous Glasses... 

Values of kd/kc of 0.055 and 0.28 (kd is the rate constant for the disproportionation process and kc is that for the coupling process) were measured for cumyl radicals (36) in benzene and on silica, respectively (Scheme 21) [161], Similarly, increases in the yields of disproportionation products have been observed for a-methylbenzyl radical pairs at low temperature on porous glass and several types of silica [101]. For example, kd/kc ratios of 0.054 and 1.33 were obtained in pentane and on porous glass at... 

A methyl-rich spectrum from propene adsorption had been earlier observed after hydrogenation during work on Pt supported on porous glass (250). The marked contrast between this spectrum and that from a n-propyl group chemisorbed on a Ni catalyst had led to the hypothesis that the former arose from chemisorbed 2-propyl species. It was subsequently shown to be caused instead by physically adsorbed propane that was present because of the greater propensity for complete hydrogenation of the initial surface species on Pt. 

Yaroslavskii and Terenin found that the 1.365- t band, due to surface OH groups on porous glass, decreased in intensity and in some cases disappeared when benzene, toluene, aniline, phenol, or pyridine were adsorbed at 20° C. 

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