Adsorption of benzene

Calculate the rotational contribution to the entropy of adsorption of benzene on carbon at 35°C, assuming that the adsorbed benzene has one degree of rotational freedom. 

Fig. 4.17 Plot of log,o(n/(mmol g ) against logfo (p7p) for the adsorption of benzene at 20°C on a series of progressively activated carbons prepared from sucrose. (Courtesy Dubinin.)...

Adsorption of benzene by carbon 8P. Height (A) of hysteresis loop at p/p — 0-25, and uptake at saturation (w,). Runs were carried out in the order givent... 

The pore size of Cs2.2 and Cs2.1 cannot be determined by the N2 adsorption, so that their pore sizes were estimated from the adsorption of molecules having different molecular size. Table 3 compares the adsorption capacities of Csx for various molecules measured by a microbalance connected directly to an ultrahigh vacuum system [18]. As for the adsorption of benzene (kinetic diameter = 5.9 A [25]) and neopentane (kinetic diameter = 6.2 A [25]), the ratios of the adsorption capacity between Cs2.2 and Cs2.5 were similar to the ratio for N2 adsorption. Of interest are the results of 1,3,5-trimethylbenzene (kinetic diameter = 7.5 A [25]) and triisopropylbenzene (kinetic diameter = 8.5 A [25]). Both adsorbed significantly on Cs2.5, but httle on Cs2.2, indicating that the pore size of Cs2.2 is in the range of 6.2 -7.5 A and that of Cs2.5 is larger than 8.5 A in diameter. In the case of Cs2.1, both benzene and neopentane adsorbed only a little. Hence the pore size of Cs2.1 is less than 5.9 A. These results demonstrate that the pore structure can be controlled by the substitution for H+ by Cs+. 

Results of Figures 4 and 5 suggest that the pore size of these materials can be precisely and nearly continuously modified by the Cs content, and accordingly the catalytic function is controlled. The pore size of Cs2.1 was smaller than that of Cs2.2, as was estimated to be less than 5.9 A finm the adsorption of benzene. In accordance with this, Cs2.1 had an activity for the dehydration of 2-hexanol, but was inactive for other reactions, irrespective of its considerably high sxuface area measure by N2 (55 m g" ). 

Few studies have been made of benzene chemisorption by the volumetric method. Zettlemoyer et al. (8) have examined the adsorption of benzene vapor at 0°C on powders of nickel and of copper. First, the monolayer coverage of argon (vm) A, was measured. The argon was then removed by pumping and the amount of benzene required to form a monolayer, (vmi) Bz, was measured. Weakly adsorbed benzene was then removed by pumping, after which further benzene adsorption provided the value (vm2) Bz. Some results are reproduced in Table I. On the assumption that the same extent of surface is accessible both for argon and for benzene adsorption, it is clear that complete monolayers of benzene were not achieved, that some (Ni) or all (Cu) of the benzene was adsorbed reversibly. It was considered that only the irreversibly adsorbed benzene was chemisorbed, the remainder being physically adsorbed. Thus chemisorption of benzene on copper appeared not to occur. The heat of adsorption of benzene on nickel at zero... 

Benzene chemisorption on platinum-alumina in the range 26°-470°C has been measured in a flow system by Pitkethly and Goble (7). A small dose of benzene was injected into a stream of inert carrier gas and transported to the reactor the effluent was then sampled repeatedly and analyzed by gas-liquid chromatography. Information concerning the adsorption and desorption of benzene was obtained from the shape of the subsequent benzene concentration versus time curves. Evidence was obtained for four types of adsorption of benzene ... 

Adsorption of benzene on sulfur- and oxygen-contaminated (110) faces of nickel revealed that the ordered layers formed differed from those obtained at the clean Ni(110) surface (23, 29). 

To summarize, the use of heavy water as a deuterium source has provided a wealth of experimental information. Evidence for the associative ir-adsorption of benzene [species (I) J is secure (2). Evidence for hydrogen exchange in the benzene ring by an abstraction-addition mechanism is less well established, partly because of uncertainties that surround the mode of chemisorption and reaction of water at metal surfaces. Nevertheless, it would be wrong to deny that Scheme 6 is consistent with a large body of experimental work. 

Freundlich equation, for adsorption of benzene of cobalt, 23 126 Friedel-Crafts... 

Kolosov, E. N., N. I. Starkovskii, S. G. Gul yanova and V. M. Gryaznov. 1988. Oxygen permeability of thin silver membranes Effect of the adsorption of benzene on the oxygen transfer process. Russian J. Phys. Chem. 62(5) 661-663. 

Only a few systematic studies have been carried out on the mechanism of interaction of organic surfactants and macromolecules. Mishra et al. (12) studied the effect of sulfonates (dodecyl), carboxylic acids (oleic and tridecanoic), and amines (dodecyl and dodecyltrimethyl) on the electrophoretic mobility of hydroxyapatite. Vogel et al. (13) studied the release of phosphate and calcium ions during the adsorption of benzene polycarboxylic acids onto apatite. Jurlaanse et al.(14) also observed a similar release of calcium and phosphate ions during the adsorption of polypeptides on dental enamel. Adsorption of polyphosphonate on hydroxyapatite and the associated release of phosphate ions was investigated by Rawls et al. (15). They found that phosphate ions were released into solution in amounts exceeding the quantity of phosphonate adsorbed. 

The BET C02 surface areas of the extracts are shown in Table III. These data show that surface area decreases with increasing size of the added alkyl group. We expect that adsorption of benzene onto surfaces to be most important for the untreated and O-methylated extract and the least important for the O-octylated extract. 

As discussed above, we believe adsorption becomes less important and absorption (swelling) becomes more important as the size of the added alkyl group increases. Since the x parameter describes the "goodness" of the solvent-polymer solution, and has nothing to do with surface interactions, the more reliable x parameter will be obtained for the O-octylated extract-benzene system. Even so, the ground O-octylated extract possesses considerable surface area and any adsorption of benzene onto surfaces will lead to errors in x-Sorption experiments were therefore conducted on the unground extract, which possessed only 11 w /g surface area, x was determined to be 0.65, which was independent of pressure. 

Initial state (2) adsorption of benzene and O2 (3) transition state and (4) formation of phenol and atomic oxygen. 

In the case of the adsorption of benzene vapour by mercury examined by Iredale (p. 67) at a pressure of 12-5 mm. at 300° K., 0-564 of the surface is covered with benzene and 0-436 is bare. From the Herz-Knudsen equation it can be calculated that 0 902 x 10 gm. mols of benzene hit this bare surface per second, whilst on the covered surface 0 443 x 10 gm. mols are present. Thus the life of a benzene molecule on the mercury surface is 4 9 x 10 seconds. Over a free benzene surface, if the orientation of the molecules be similar to that on mercury, 1 666 x 10 gm. molecules evaporated per second or the life of a benzene molecule on a benzene surface is 4 7 X 10 seconds. 

Adsorption of benzene on Ag(llO) has been investigated by Pascual, Kelly et al. [148-151]. 

The adsorption of cyclohexadiene on the Pt(l 11) surface produces the same two surface structures that were found during the adsorption of benzene on this crystal face Thus, this molecule readily dehydrogenates on this platinum surface to benzene at 300 K. 

The method of Example 7.5 applied to the adsorption of benzene, naphthalene, and anthracene on carbon black from heptane solutions gives values of 0.42, 0.67, and 0.83 nm2, respectively, for a°. The progression of sizes indicates that the molecules lie flat on the surface of the carbon. 

Fig. 28. Change of the photoelectric yield at X = 265.5 mp. of a platinum foil (in vacuo on the adsorption of benzene molecules at T = SS K. At the points marked by arrows, benzene vapor of low pressure was admitted [according to (76)].

While the adsorption of benzene molecules before the maximum was reached increased the sensitivity, the molecules condensed on the platinum surface after the maximum had been reached decreased the sensitivity (C, D, and F in Fig. 28). The excess of the benzene molecules, however, can be desorbed in about 30 min. if no further molecules strike the surface E and G in Fig. 28). The work function was lowered by the adsorption of the optimum benzene layer from 4.54 volts (in J.) to 4.11 volts (in JS). The ir electrons were therefore displaced to the metal surface by the adsorption. 

Fig. 29. Decrease of resistance of a transparent nickel film (90 X 10 atoms/ sq. cm.) on the adsorption of benzene molecules at T = 90.3°K. [according to (18)].

The electronic interaction between benzene and the metal surface may be made up of two effects the polarization of the molecule, which may be concluded from the above-described research, and the shifting of the v electrons to the metal surface to become part of the metal electron gas, which has been hypothesized by Polanyi (77). The first effect has been shown in Fig. 28, the second apparently can be seen from the research (18) illustrated by Fig. 29, in which the change of resistance of a transparent nickel film was studied during the adsorption of benzene molecules. As the temperature of the benzene capsule was 90°K., the evaporation velocity was so low that only a small number of benzene molecules struck the surface in unit time. The resistance therefore diminished only... 

A similar behavior of the resistance of transparent nickel films was observed with the adsorption of triphenylmethane and naphthalene. In these cases the resistance decreased by 0.033 and 0.035% (18). As does the adsorption of benzene, the adsorption of triphenylmethane and of copper phthalocyanine lowers the electronic work function of a platinum surface (76). 

The OH bands of porous glass and of alumosilicagel exhibit subsidiary weak maxima at 7220 and 7150 cm 1 respectively upon adsorption of benzene and toluene, besides the shifted main maxima 7090 and 7020 cm-1, respectively, given in Table 1 (Fig. 1). 

Knowing the problems associated with the analysis of volatile organic compounds, you inquire about the handling of the samples. Here we go The samples (100 mL) were put into 1 L flasks, which were then sealed and stored at 5°C for several days. Then, in the cooling room, an aliquot of the water was withdrawn and analyzed for benzene. What was the original concentration of benzene in the water sample Assume that equilibrium is established between the gas phase and the water and neglect adsorption of benzene to the glass walls of the bottle. The data required to answer this question can be found in Table 3.4. 

The complexity of modeling the adsorption of benzene in silicalite has already been discussed in the section concerned with diffusion. A TST study by Snurr et al. (106) led to the identification of 27 unique sorption minima in the asymmetric unit. Given this result, it is unsurprising that there have been relatively few simulation studies of this system. However,... 

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