“…The case of the E parameter is very peculiar since the values calculated for ethyl benzene at 40 °C are closer to the respective values for toluene, than the values at 25 °C which are quite low. This difference is a consequence of the unusual result found in the ethyl benzene isotherms at the two temperatures and can be analyzed in more detail if the E values, which depend on vapor-adsorbent system, are converted to the characteristic energy of the adsorbent 26 ( E 0 ) using the vapor parameters estimated from the molecular parachors of the corresponding vapor. , As can be seen in Figure , even in the more favorable case of the E 0 values calculated for ethyl benzene at 40 °C, the values for the two activated carbons are lower than those calculated from the toluene adsorption. This is an indication that the ethyl benzene adsorption process on these two materials is somehow different from what occurs with toluene, although at 40 °C the situation is similar.…”
Section: Resultsmentioning
confidence: 99%
“…This energy difference corresponds to the difference between the experimental values and what would be expected from the Dubinin theory if the adsorption process of the toluene and ethyl benzene molecules were similar, that is, if the conformational effects would not occur. 4 Value of the E 0 of the different adsorbent materials calculated from the average of the E values for toluene (Table ) and from the ethyl benzene E values at 40 °C (Table ), using β estimated from the parachors . The symbols are: × toluene and ○ ethyl benzene; with the respective error bars representing the confidence intervals at 95%.…”
Section: Resultsmentioning
confidence: 99%
“…This equation has been applied to the adsorption of a large variety of organic molecules in different adsorbents. , In this work, the parameters w 0 , E , and n for each adsorbent were obtained by fitting this equation to the toluene and ethyl benzene adsorption data in a given adsorbent. Particular attention was given to testing the validity of the temperature independence of these parameters, and also to predictions of the adsorption of ethyl benzene from the data of the toluene adsorption. , …”
Section: Introductionmentioning
confidence: 99%
“…Particular attention was given to testing the validity of the temperature independence of these parameters, and also to predictions of the adsorption of ethyl benzene from the data of the toluene adsorption. 32,33 The predictions of the ethyl benzene adsorption, made by eqs 1 and 4, were compared with the experimental results, and the deviations found were interpreted in terms of the possible conformational effects of the adsorbed phase, particularly for the ethyl benzene molecule. In the case of the HK equation, the adsorption potential of two extreme conformations of the ethyl benzene molecule in slit pores are compared with the experimentally obtained values in the two activated carbons used.…”
Adsorption isotherms of toluene and ethyl benzene, at 25 degrees C and 40 degrees C, were determined in two microporous activated carbons and one zeolite. Significant differences were found in the adsorption behavior, at low pressures, between the two vapors on the same adsorbent material. The quantities of adsorbed ethyl benzene at 25 degrees C, in the low-pressure region, were lower than what was observed at 40 degrees C in all the studied adsorbents, contrary to what was found for toluene. This fact was not related to kinetic effects at the two temperatures nor to vapor swelling of the adsorbents structure. Also, there was no molecular sieving since at high pressures the toluene and ethyl benzene occupied the same adsorption space. The differences found in the ethyl benzene adsorption at the two temperatures pose difficulties in the analysis of the adsorption data and, therefore, in the prediction of results. This is discussed in the analysis of the results with the application of the Dubinin-Astakhov equation and in the estimation of the isosteric heats of adsorption. The adsorption potentials of two possible ethyl benzene conformations were estimated for the adsorption in the pores of activated carbon from the Horvath and Kawazoe model, and the values compared with those found experimentally. The results were interpreted in terms of the ethyl benzene conformation effects when the molecule is confined in pores that are about the same size of one of the conformations.
“…The case of the E parameter is very peculiar since the values calculated for ethyl benzene at 40 °C are closer to the respective values for toluene, than the values at 25 °C which are quite low. This difference is a consequence of the unusual result found in the ethyl benzene isotherms at the two temperatures and can be analyzed in more detail if the E values, which depend on vapor-adsorbent system, are converted to the characteristic energy of the adsorbent 26 ( E 0 ) using the vapor parameters estimated from the molecular parachors of the corresponding vapor. , As can be seen in Figure , even in the more favorable case of the E 0 values calculated for ethyl benzene at 40 °C, the values for the two activated carbons are lower than those calculated from the toluene adsorption. This is an indication that the ethyl benzene adsorption process on these two materials is somehow different from what occurs with toluene, although at 40 °C the situation is similar.…”
Section: Resultsmentioning
confidence: 99%
“…This energy difference corresponds to the difference between the experimental values and what would be expected from the Dubinin theory if the adsorption process of the toluene and ethyl benzene molecules were similar, that is, if the conformational effects would not occur. 4 Value of the E 0 of the different adsorbent materials calculated from the average of the E values for toluene (Table ) and from the ethyl benzene E values at 40 °C (Table ), using β estimated from the parachors . The symbols are: × toluene and ○ ethyl benzene; with the respective error bars representing the confidence intervals at 95%.…”
Section: Resultsmentioning
confidence: 99%
“…This equation has been applied to the adsorption of a large variety of organic molecules in different adsorbents. , In this work, the parameters w 0 , E , and n for each adsorbent were obtained by fitting this equation to the toluene and ethyl benzene adsorption data in a given adsorbent. Particular attention was given to testing the validity of the temperature independence of these parameters, and also to predictions of the adsorption of ethyl benzene from the data of the toluene adsorption. , …”
Section: Introductionmentioning
confidence: 99%
“…Particular attention was given to testing the validity of the temperature independence of these parameters, and also to predictions of the adsorption of ethyl benzene from the data of the toluene adsorption. 32,33 The predictions of the ethyl benzene adsorption, made by eqs 1 and 4, were compared with the experimental results, and the deviations found were interpreted in terms of the possible conformational effects of the adsorbed phase, particularly for the ethyl benzene molecule. In the case of the HK equation, the adsorption potential of two extreme conformations of the ethyl benzene molecule in slit pores are compared with the experimentally obtained values in the two activated carbons used.…”
Adsorption isotherms of toluene and ethyl benzene, at 25 degrees C and 40 degrees C, were determined in two microporous activated carbons and one zeolite. Significant differences were found in the adsorption behavior, at low pressures, between the two vapors on the same adsorbent material. The quantities of adsorbed ethyl benzene at 25 degrees C, in the low-pressure region, were lower than what was observed at 40 degrees C in all the studied adsorbents, contrary to what was found for toluene. This fact was not related to kinetic effects at the two temperatures nor to vapor swelling of the adsorbents structure. Also, there was no molecular sieving since at high pressures the toluene and ethyl benzene occupied the same adsorption space. The differences found in the ethyl benzene adsorption at the two temperatures pose difficulties in the analysis of the adsorption data and, therefore, in the prediction of results. This is discussed in the analysis of the results with the application of the Dubinin-Astakhov equation and in the estimation of the isosteric heats of adsorption. The adsorption potentials of two possible ethyl benzene conformations were estimated for the adsorption in the pores of activated carbon from the Horvath and Kawazoe model, and the values compared with those found experimentally. The results were interpreted in terms of the ethyl benzene conformation effects when the molecule is confined in pores that are about the same size of one of the conformations.
“…Several researchers have reported modifications to Polanyi's approach, namely, Manes (Grant and Manes, 1966;Manes and Hofer, 1969) and Dubinin (1979Dubinin ( , 1975. To obtain a sorbent's characteristic curve and accommodate sorbates of widely varying molecular properties, three normalizing parameters have commonly been incorporated: molecular parachor (Duisterwinkel, 1993), molar polarization (Wood, 1992), and liquid molar volume (Grant and Manes, 1966;Noll et al, 1989). There appears to be some dispute as to which of the above parameters best normalizes results.…”
The performance of Friedel−Crafts modified polystyrene (FCMPS)
as a volatile organic compound
(VOC) sorbent is compared with commercially available polymers and
activated carbon. Detailed
analyses of the equilibrium isotherms are presented, including vapor
phase isotherm temperature
dependence and isosteric heats of sorption. Although significant
absorption contributions are
observed for the polymeric sorbents of this study, the data are
mathematically well represented
by Polanyi potential analysis. FCMPS can be synthesized with
desirable performance qualities
such as ultimate VOC sorption capacity of ∼2 mL/g, competitively high
capacity in dilute streams
versus activated carbon, insensitivity to humidity in vapor phase
applications, and comparative
ease of regeneration.
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