Propanol, adsorption

To examine the surface modification upon 1 - propanol adsorption as a function of the coverage level, we analyze the dependence of the energy gap on the coverage with 1 - propanol (or its fragments). Table 14-4 shows their values for the physisorbed configurations 1-1 and 1-2, and the chemisorbed configurations F-l and F-2 with 0.125 ML, 0.25 ML, 0.5 ML and 1.0 ML. 

Table 14-4. Energy gaps AE (eV) of the Si(001)-(2 x 1) pure surface compared to those of the 1-propanol adsorption structures 1-1, 1-2, F-l, and F-2 on Si(001) at four levels of coverage...

Figure 6 n-propanol adsorption (froe dilute aqueoua n propanol solutions) of MFI-type seolitee prepared (a) in alkaline medium and (b) in fluoride Medium. ... 

The dependence of propanol adsorption capacity of the germanium surfaces on the outgassing conditions is essentially decided by the chemisorption, since... 

An interesting avenue for investigation is to examine the adsorption characteristics on single crystals concurrently with electrical measurements. Thus, any relationship which possibly exists between the slow states and the chemisorption might be positively revealed. Examination of the adsorption characteristics of reduced germanium crystals and the effect of the fast states would also be of interest. These studies have been initiated. It remains clear at this time, however, that the semiconductor properties of the germanium influence the surface properties of the thin oxide films supported thereon. The influence is clear in the case of propanol adsorption and the differences are even more dramatic in the case of water adsorption. 

The -propanol adsorption from the gas phase significantly decreases the adhesion force between the silicon oxide surfaces measured with AFM. Fig. 7 illustrates the adhesion force measured with a single tip (2.2 N/m) at various partial pressures of n-propanol. The adhesion force decreases 40% compared with the dry Ar case upon initial introduction of n-propanol partial pressure. This reduction is not as drastic upon further increase of the n-propanol partial pressure. A sudden change in adhesion with only 10% partial pressure indicates that a few monolayer thick n-propanol film, as shown in Fig. 4, is sufficient to reduce the adhesion between the silicon oxide surfaces. This behavior is in sharp contrast to the relationship between the adhesion force and the water adsorption isotherm. In the case of water, the adhesion force increases several fold when the relative humidity increases from zero to... 

Samra, S.E. Youssef A M, and Girgis. B.S.. Catalytic properties of silica-supported 12-molybdophosphoric acid in the conversion of 2-propanol, Adsorpt. Sci. Technol.. 12(3). 191-202 (1995). 

Fig. X-1. Adsorption isotherms for n-octane, n-propanol, and n-butanol on a powdered quartz of specific surface area 0.033 m /g at 30°C. (From Ref. 23.)...

The adsorption isotherms calculated from their data are shown in Figure 3. It is seen that the propanol and butanol rapidly cover the surface at low moderator... 

FIGURE 4.24 Adsorption chromatography of small molecules with a TSK-GEL G2500PWxl column. Column TSK-GEL G2500PWxl, 6 /tm, 7.8 mm X 30 cm. Sample (I) phenylacetic acid. (2) 3-phenylpropionic acid, (3) 4-phenylbutyric acid, (4) benzylamine, (5) 2-phenylethylamine, (6) 3-phenylpropylamine, (7) benzyl alcohol, (8) 2-phenylethanol, and (9) 3-phenyl-1 -propanol. Elution 0.1 M NaCIO, in water. Flow rate 2.0 ml/min. Temperature 65 C. Detection UV at 215 nm. 

If the mixture to be separated contains fairly polar materials, the silica may need to be deactivated by a more polar solvent such as ethyl acetate, propanol or even methanol. As already discussed, polar solutes are avidly adsorbed by silica gel and thus the optimum concentration is likely to be low, e.g. l-4%v/v and consequently, a little difficult to control in a reproducible manner. Ethyl acetate is the most useful moderator as it is significantly less polar than propanol or methanol and thus, more controllable, but unfortunately adsorbs in the UV range and can only be used in the mobile phase at concentrations up to about 5%v/v. Above this concentration the mobile phase may be opaque to the detector and thus, the solutes will not be discernible against the background adsorption of the mobile phase. If a detector such as the refractive index detector is employed then there is no restriction on the concentration of the moderator. Propanol and methanol are transparent in the UV so their presence does not effect the performance of a UV detector. However, their polarity is much greater than that of ethyl acetate and thus, the adjustment of the optimum moderator concentration is more difficult and not easy to reproduce accurately. For more polar mixtures it is better to explore the possibility of a reverse phase (which will be discussed shortly) than attempt to utilize silica gel out of the range of solutes for which it is appropriate. 

HPTLC plates Silica gel 60 F254 (Merck) before application of the samples the layers were washed by immersing them for 4 h in 2-propanol, then dried at 110°C for 30 min, before being stored over silica gel in a desiccator. When the samples were being applied the layer above the application zone was covered with a glass plate to avoid adsorption of moisture from the atmosphere. 

Adsorption phenomena from solutions onto sohd surfaces have been one of the important subjects in colloid and surface chemistry. Sophisticated application of adsorption has been demonstrated recently in the formation of self-assembhng monolayers and multilayers on various substrates [4,7], However, only a limited number of researchers have been devoted to the study of adsorption in binary hquid systems. The adsorption isotherm and colloidal stabihty measmement have been the main tools for these studies. The molecular level of characterization is needed to elucidate the phenomenon. We have employed the combination of smface forces measmement and Fomier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR) to study the preferential (selective) adsorption of alcohol (methanol, ethanol, and propanol) onto glass surfaces from their binary mixtures with cyclohexane. Om studies have demonstrated the cluster formation of alcohol adsorbed on the surfaces and the long-range attraction associated with such adsorption. We may call these clusters macroclusters, because the thickness of the adsorbed alcohol layer is about 15 mn, which is quite large compared to the size of the alcohol. The following describes the results for the ethanol-cycohexane mixtures [10],... 

The prepared MAC adsorbents were tested for benzene, toluene, 0-, m-, p-xylene, methanol, ethanol, iso-propanol, and MEK. The modified content of all MACs was 5wt% with respect to AC. The specific surface areas and amounts of VOC adsorbed of MACs prepared in this study are shown in Table 1. The amounts of VOC adsorbed on 5wt%-MAC with acids and alkali show a similar tendency. However, the amount of VOC adsorbed on 5wt%-PA/AC was relatively large in spite of the decrease of specific surface area excepting in case of o-xylene, m-xylene, and MEK. This suggests that the adsorption of relatively large molecules such as 0-xylene, m-xylene, and MEK was suppressed, while that of small molecules was enhanced. It can be therefore speculated that the phosphoric acid narrowed the micropores but changed the chemical nature of surface to adsorb the organic materials strongly. 

The reason for enhancement of adsorption performance of PA/AC was considered to be due to combination effect of increase of BET surface area and chemical modification by the treatment with PA. Consequently, lwt%-PA/AC was determined to be a best candidate as an adsorbent for removing benzene, toluene, p-xylene, methanol, ethanol, and iso-propanol. Therefore, lwt%-PA/AC was used as the adsorbent to investigate the adsorption isotherm, adsorption and desorption performance. 

Prus and Kowalska [75] dealt with the optimization of separation quality in adsorption TLC with binary mobile phases of alcohol and hydrocarbons. They used the window diagrams to show the relationships between separation selectivity a and the mobile phase eomposition (volume fraction Xj of 2-propanol) that were caleulated on the basis of equations derived using Soezewiriski and Kowalska approaehes for three solute pairs. At the same time, they eompared the efficiency of the three different approaehes for the optimization of separation selectivity in reversed-phase TLC systems, using RP-2 stationary phase and methanol and water as the binary mobile phase. The window diagrams were performed presenting plots of a vs. volume fraetion Xj derived from the retention models of Snyder, Schoen-makers, and Kowalska [76]. 

A review on TLC and PLC of amino adds, peptides, and proteins is presented in the works by Bhushan [24,25]. Chromatographic behavior of 24 amino acids on silica gel layers impregnated tiraryl phosphate and tri-n-butylamine in a two-component mobile phase (propanol water) of varying ratios has been studied by Sharma and coworkers [26], The effect of impregnation, mobile phase composition, and the effect of solubility on hRf of amino acids were discussed. The mechanism of migration was explained in terms of adsorption on impregnated silica gel G and the polarity of the mobile phase used. 

The Au/Ti02 catalyst shows activity for photocatalytic dehydrogenation of 2-propanol at 298 K. The activity of Au/Ti02 is attributed to its unique capability for producing photogenerated electrons evidenced by the featureless IR adsorption during UV-irradiation. 

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