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1.
Methane adsorption on the microporous carbon adsorbent AUK was calculated on the basis of Dubinin’s theory of volume filling
of micropores in the temperature range 177.7—393 K and at pressures from 1 Pa to 6 MPa. The calculated isotherms of absolute
adsorption were compared with the isotherms of methane obtained experimentally. Good agreement between the calculated and
experimentally measured amounts adsorbed is observed in the area of applicability of the theory at micropore ranging in coverage
θ from 0.25 to 0.95. The adsorption isosters were calculated for the same pressure and temperature ranges. The adsorption
isosters satisfactorily represent the temperature dependence of the amount of methane adsorbed obtained experimentally. The
calculations gave for the thermal coefficient of limiting adsorption a value of 6hcalc = 1.64• 10-3 K-1., which exceeds the experimental value by ∼15%. 相似文献
2.
Hydrogen adsorption on model microporous adsorbents with slit-shaped pores was calculated on the basis of Dubinin’s theory
of volumetric filling of micropores using the property of linearity of adsorption isosters. Model adsorbents with micropore
widths of 0.5, 0.9, and 1.2 nm obtained by the successive exclusion of one, two, and three layers of hexagonal carbon in the
crystalline lattice of graphite were used. Hydrogen adsorption was calculated in the structures with single-layer and two-layer
carbon walls at temperatures 20, 33, 77, 200, 300, and 400 K and pressures up to 20 MPa. The maximal hydrogen desorption for
the AU structure (1:3) with the pressure drop from 20 to 0.1 MPa was 8 wt.% at 200K. The parameters of the porous adsorbent
structure were calculated. 相似文献
3.
Fomkin A. A. Nikiforov Yu. V. Sinitsyn V. A. Savel"ev E. G. 《Russian Chemical Bulletin》2002,51(12):2161-2164
The adsorption of perfluoropropane (N3F8) on the PAC microporous carbon adsorbent, which is close in properties to monoporous adsorbents, was studied at temperatures of 216, 243, 295, 318, and 343 K in the pressure interval from 1 to 1·105 Pa. The adsorption isosters are well approximated by straight lines in the studied interval of temperatures and pressures. The dependence of the isosteric heats of adsorption on filling is described by a curve with a maximum in the region of high fillings. Such a curve is characteristic of adsorbents with a narrow pore size distribution. 相似文献
4.
A. A. Pribylov N. A. Skibitskaya L. A. Zekel’ 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2014,88(6):1028-1036
Sorption isotherms of nitrogen, methane (in the pressure range of 0.1–40 MPa), ethane (0.1–3.7MPa), propane (0.01–1 MPa), butane (0.01–0.2 MPa), and carbon dioxide (0.1–6 MPa) are measured on two adsorbents with kerogen contents of 16 and 75% at temperatures of 303, 323, 343 K. Adsorption volumes are calculated for all adsorption systems using two independent methods. The BET technique is used to determine the surface area values of the two adsorbents on the basis of sorption data for ethane, propane, butane, and carbon dioxide. The initial and isosteric adheat of sorption values are calculated on the basis of sorption isotherms of ethane, propane, butane, carbon dioxide measured at three temperatures. It is found from comparing the dependences of isosteric heat of sorption on the two adsorbents that molecules of the above gases diffuse into its bulk (adsorbent 2) in addition to sorbing on the outside surface formed by kerogen molecules, while sorption of the same gases on the rock (adsorbent 1) is similar to sorption on a smooth hard adsorbent surface. 相似文献
5.
The isotherms describing excess adsorption of SF6 and N6I6 on carbon adsorbents with different pore structures were measured at pressures of 0.001—2.4 and 0.0001—0.1 MPa, respectively, and temperatures of 298—408 E. A linear dependence of Henry"s constant on temperature in the lnK—103/O coordinates was found for all the samples. The specific surface areas of the samples determined by the BET method from the SF6 adsorption are lower than those derived from benzene adsorption. The most pronounced difference was found for the grafitized carbon black. When SF6 was adsorbed on supermicroporous carbon AC-71 and on microporous carbons PAC and CMS, a hysteresis was found, which, unlike that on mesoporous carbon adsorbents, is observed in the initial region of the equilibrium pressures. 相似文献
6.
A. A. Pribylov I. A. Kalinnikova S. M. Kalashnikov G. F. Stoeckli 《Russian Chemical Bulletin》2000,49(4):692-700
The isotherms of excess adsorption of CH4 (atP=0.001–160 MPa), SF6 (atP=0.001–2.4 MPa), and C6H6 (atP=0.0001–0.1 MPa) on carbon adsorbents—microporous carbons CMS and FAS with developed mesoporosity and graphitized soot—were
measured in the 298–408 K temperature region. Calculation of the isotherms of absolute adsorption of the total content of
these substances requires knowledge of the adsorption volume, which was determined by different methods: by the Dubinin—Radushkevich
equation; by the experimental isotherm of excess adsorption and the equation of absolute adsorption; by the method using the
intersection of nonlinear isosteres of excess adsorption and isosteres of absolute adsorption; by the comparative plot of
values of the excess C6H6 adsorption ΓFAS—Γsoor; by the method using the difference of molecular radii of adsorptives and the surface of the specific adsorbent; and by the
calculation of the adsorption layer thickness using the FHH equation for mesoporous systems. The results of determination
of the adsorption volume for microporous systems of these carbons agree well with each other and with the passport data for
the adsorbents. Analysis of the results revealed the peculiarity of the sulfur hexafluoride adsorption related to the formation
of associates on the surface of the carbon adsorbents.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 688–696, April, 2000. 相似文献
7.
The knowledge about the adsorption and diffusion properties (specially about diffusion) of aluminophosphate molecular sieves is very scarce in the literature. These materials offer interesting properties as adsorbents as they have a polar framework and do not contain charge-balancing cations. In this work, the adsorption isotherms of nitrogen, methane and carbon dioxide over an AlPO4-11 sample synthesized in our laboratories have been measured with a volumetric method at 25, 35, 50 and 65 °C over a pressure range up to 110 kPa. The adsorption capacities of each gas are determined by the strength of interaction with the pore surface (carbon dioxide > methane > nitrogen). The equilibrium selectivity to carbon dioxide is quite high with respect to other adsorbents without cations due to the polarity of the aluminophosphate framework. The adsorption Henry’s law constants and diffusion time constants of nitrogen, methane and carbon dioxide in the synthesized AlPO4-11 material have been measured from pulse experiments. A pressure swing adsorption (PSA) process for recovering methane from a carbon dioxide/methane mixture (resembling biogas) has been designed using a dynamic model where the measured adsorption equilibrium and kinetic information has been incorporated. The simulation results show that the proposed process could be simpler than other PSA processes for biogas upgrading based on cation-containing molecular sieves such as 13X zeolite, as it can treat the biogas at atmospheric pressure, and it requires a lower pressure ratio, to produce high purity methane with high recovery. 相似文献
8.
Nitrogen adsorption isotherms on nonporous and microporous carbons were thoroughly studied at low relative pressures. For nonporous carbons low pressure measurements seem to be unaffected by analysis conditions. However, these measurements on microporous solids may be affected by analysis conditions at relative pressures below 10–4. It was shown that selection of proper equilibration time is crucial for correct measurements of equilibrium pressures during adsorption on microporous carbons. The isotherm shift induced by insufficient equilibration of the system may affect the surface heterogeneity and microporosity analysis. A comparison of the adsorption energy and pore volume distribution functions calculated from low pressure nitrogen adsorption isotherms measured at different equilibration times on a microporous carbon shows that this effect is smaller than it was expected. 相似文献
9.
Comparative analysis of methods for determination of structural characteristics of carbon adsorbents
A. A. Pribylov L. G. Shekhovtsova I. A. Kalinnikova 《Russian Chemical Bulletin》2005,54(10):2290-2298
Experimental data on the equilibrium adsorption of sulfur hexafluoride, methane, carbon dioxide, and benzene on carbon adsorbents
of different porosity obtained in a wide pressure range at 298–408 K were analyzed. The adsorption volumes, surface areas,
and sizes of slit-shaped pores of the carbons were determined using several independent methods. A method for determination
of the adsorption volume from the experimental isotherm of excessive adsorption of gases and the total content equation was
proposed. The resulting values are similar to the adsorption volumes calculated from the data for vapors. A new method for
the calculation of the adsorbent surface area is described. The method is based on the dependence of the adsorption volume
of adsorbent pores on the effective size of adsorbate molecules. A possibility to determine the average size of narrow slit-shaped
carbon pores from the difference of the initial heats of adsorption of the gas under study on the carbon black and porous
carbon adsorbent is considered.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2219–2227, October, 2005. 相似文献
10.
M. M. Dubinin K. M. Nikolaev G. A. Petukhova N. S. Polyakov 《Russian Chemical Bulletin》1991,40(1):20-23
Water vapor adsorption for various activated carbons with narrow and wide micropore volume distributions and mesopore surface areas between 40 and 300 m2/g have been investigated. For all the isotherms the point of inflection was determined, which can be taken as the point characterizing the formation of a water adsorption layer on the pore wall surface of carbon adsorbents. To do this the adsorption and desorption branches of the isotherms were approximated according to Weibull's distribution. A good correlation was obtained between values for the water monolayer capacity, calculated from the porous structure parameters of the carbons, and the adsorption values corresponding to the isotherm inflection pointsa
inf. For the group of carbons studied the values of relative pressure at the inflection point of the isotherms fell within the range 0.5–0.72.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 31–34, January, 1991. 相似文献
11.
D. Burevski 《Colloid and polymer science》1982,260(6):623-627
A study is made of the adsorption of carbon dioxide at 195 K on a series of microporous carbons. The adsorption data are analysed using the Dubinin-Astakhov equation. It is found that the adsorption isotherms obey the Dubinin-Astakhov equation over the pressure range studied.The characteristic energy of adsorption calculated from the slope of the Dubinin-Astakhov plot is shown to be in correlation with the mean value of the adsorption potential. The microporosity of carbons is interpreted in terms of the characteristic parameters of the adsorption pontential distribution, determined by means of the Dubinin-Astakhov equation. It is found good agreement between these parameters and the micropore size distribution. 相似文献
12.
G. I. Berezin R. Sh. Vartapetyan A. M. Voloshchuk G. A. Petukhova N. S. Polyakov 《Russian Chemical Bulletin》1998,47(10):1879-1885
The mechanism of adsorption of water molecules on nonporous carbon adsorbents has been suggested in terms of two different
states of adsorbed water; stretched liquid water and water that occupies an intermediate state between the liquid and vapor.
Two stages of adsorption were distinguished: condensation and pre-condensation that assumes the formation of molecular associates.
The BET model was used to describe the pre-condensation stage. The equations of the adsorption isotherm for water vapor in
the region of condensation process and the expression for the determination of the specific hydrophilic surface of adsorbents
were found. Examination of the experimental data on adsorption of water vapor on nongraphitized samples of carbon adsorbents
shows that in the region of polymolecular adsorption, all isotherms fall into a common curve determined by the equation of
the stretched liquid film and can be calculated regardless of the properties of individual liquid water. The equation for
adsorption of water vapor on the hydrophobic surface was obtained.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1933–1939, October, 1998. 相似文献
13.
A. A. Fomkin I. E. Men’shchikov A. A. Pribylov V. V. Gur’yanov A. V. Shkolin D. S. Zaitsev A. V. Tvardovskii 《Colloid Journal》2017,79(1):144-151
Methane adsorption on a microporous carbon adsorbent with a bimodal pore size distribution is studied at temperatures of 303–333 K at pressures up to 30 MPa. The total micropore volume of the adsorbent, as determined by the Dubinin method, is as large as 1.02 cm3/g. Maximum values of methane adsorption of ≈18 mmol/g are attained at a temperature of 303 K and a pressure of 30 MPa. Methane adsorption isosteres are plotted based on experimental data, and adsorption equilibria at low temperatures are calculated using the linearity of the plots. Experimental isotherms of methane adsorption are compared with the isotherms calculated by the Dubinin–Nikolaev equation with variations in parameters E and n. Temperature dependences of these parameters are determined. Specific characteristics of methane adsorption accumulation are calculated. 相似文献
14.
Mirosław Kwiatkowski 《Journal of mathematical chemistry》2017,55(10):1893-1902
The paper presents the results of research devoted to obtaining the low-cost activated carbon fibres from waste flax and jute cloth by carbonisation in inert atmosphere and activation with air as well as to the analysis of the microporous structure of materials obtained on the basis of the nitrogen, argon and benzene adsorption isotherms, using among others, the unique LBET method with implemented of the new models of the multilayer adsorption on the heterogeneous surfaces of the carbonaceous adsorbents. As part of the research conducted, imaging of the surface of the low-cost activated carbon fibres obtained has also been done using scanning electron microscopy. 相似文献
15.
G. I. Berezin M. L. Gubkina G. A. Petukhova N. S. Polyakov 《Russian Chemical Bulletin》1999,48(4):663-666
A two-stage mechanism of adsorption, including nucleation and condensation, was proposed to describe the formation of the
water liquid phase in carbon adsorbents. Adsorption is assumed to occur in cylindrical pores. Nucleation is described by a
modified BET model, and condensation is treated by the model of a stretched liquid film on a bent surface. The onset of formation
of the liquid phase (OFLP) is determined from the intersection of the adsorption isotherms for these stages. The theoretical
value of the relative pressure of OFLP varies over a wide range, decreasing with a decrease in the pore radius and reactiing
the relative vapor pressure of 0.178 for the spinodal state of water. The comparison method using isotherms of graphitized
carbon black as the reference isotherms was applied for the determination of OFLP of water in real active carbons. This resulted
in good agreement between theory and experiment.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 668–671, April, 1999. 相似文献
16.
The isotherms of the total content, isosteric and average heats of adsorption, as well as characteristic energies of adsorption were determined from the isotherms of excess adsorption of carbon dioxide on six different carbon adsorbents at temperature ranging from 293 to 423 К at pressures up to 6 MPa. The average isosteric heats are in agreement with the average heats of adsorption, which were determined from the equation relating the heat of adsorption with the characteristic energy of adsorption. 相似文献
17.
A. M. Voloshchuk M. M. Dubinin T. A. Moskovskaya G. K. Ivakhnyuk N. F. Fedorov 《Russian Chemical Bulletin》1988,37(2):204-209
1. | A standard adsorption isotherm (CAI) was plotted from the isotherms of adsorption of N2 on nonporous and mesoporous carbon adsorbents for analyzing the pore structure of carbon adsorbents. |
2. | The analysis of the pore structure of active carbon with a relatively large area of mesopores and predominantly microporous active carbon shows that the CAI obtained adequately describes the adsorption of N2 on the surface of the mesopores of these samples. |
18.
V. V. Nabiulin A. A. Fomkin A. V. Tvardovskiy 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(11):1960-1964
Adsorption isotherms of n-hexane and adsorption deformation isotherms of an AR-V carbon adsorbent are measured in a pressure range of 1 Pa to 20 kPa
at temperatures of 254.8–353 K. It is found that, except for the initial pressure range (p < 800 Pa), the relative linear deformation increases with increasing pressure and decreases with increasing temperature.
At temperatures of 254.8, 273.2, and 293 K, the curves of adsorption and adsorption deformation exhibit hysteresis in the
region close to the saturated vapor pressure. It is noted that, at pressures below 800 Pa, microporous AR-V carbon adsorbent
undergoes contraction in the range of high temperatures. It is revealed that the contraction range of the adsorbent with respect
to pressure gradually narrows with decreasing temperature and degenerates at 254.8 K. 相似文献
19.
The isotherms of absolute methane adsorption on AUK microporous carbon adsorbent are measured at pressures of 1 Pa–6 MPa and temperatures of 177.65–393 K. The pattern of the isotherms remains unchanged when passing through the critical temperature of methane (T cr = 190.77 K) and, as the temperature is elevated, the isotherms are shifted toward higher pressures in an almost symbate manner. Isosteres plotted for methane adsorption on AUK microporous carbon adsorbent within the same pressure and temperature ranges are adequately approximated by straight lines, with their slopes remaining unchanged when passing into the region of supercritical temperatures under the conditions of a pronounced imperfection of the gas phase. The Henry constant is determined for the system under consideration. It is shown that the Henry constants have close magnitudes for different methane-carbon adsorbent systems. 相似文献
20.
A. A. Pribylov S. Z. Muminov I. A. Kalinnikova L. G. Shekhovtsova 《Colloid Journal》2010,72(3):417-422
The adsorption isotherms of carbon dioxide are measured at 303, 343, 373, and 400 K and pressure P ranged from 0.1 to 6 MPa for three montmorillonites, i.e., the initial sample in the sodium form and two ion exchanged samples
in pyridinium and polyhydroxyaluminum forms. It is shown that the linear character of the isosteres of CO2 adsorption is retained for polyhydroxyaluminum and sodium montmorillonites, a deviation of the adsorption isosteres from
linearity is observed for pyridinium montmorillonite at high temperatures (373–400 K) and high surface fillings. The differential
excess entropies of CO2 adsorbate are calculated for different fillings of montmorillonites. Using various approaches, the adsorption volumes for
the systems studied are calculated. 相似文献