Adsorption of carbon dioxide on microporous carbon adsorbent PAU-10

Carbon dioxide adsorption on the microporous carbon adsorbent PAU-10 within the 177.8—423 K temperature and 0.1—5.13·10⁶ Pa pressure intervals was studied. The isosteres of absolute adsorption are well approximated by straight lines, which do not change their slope on going to temperatures higher than the critical temperature of CO₂. An increase in the differential molar isosteric heat of adsorption (q _st) at 0 < a < 1 mmol g^–1 is explained by the influence of the endothermic effect of adsorption expansion of the adsorbent. In the region of high pressures and nonideal gas phase, q _st is temperature-dependent.     

Adsorption deformation in the microporous carbon adsorbent-benzene system and porous structure of adsorbents

The relative adsorption deformation of several microporous carbon adsorbents was studied as a function of the benzene adsorption at relative pressure ranging from 1·10⁻¹ to 1.0 and at 293 K. A correlation between the maximum compression of the sample and the characteristic energy of benzene adsorption of the Dubinin-Radushkevich equation was obtained. Using data on the adsorption deformation, it is possible to identify the region with a specific pore size that cannot be evaluated with the help of the Dubinin-Radushkevich equation. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No.6, pp. 1018–1022, June, 2000.     

Adsorption of proteins on mesoporous carbon adsorbents

A study of the sorption of bull serum albumin (BSA) on carbon adsorbents with different porous structures has shown that, for adsorbents with globular structures, sorption depends on the size of the adsorbent particles. An assumption has been made concerning the nonequilibrium nature of BSA sorption on mesoporous adsorbents associated with irreversible adsorption of the protein and the nonuniform distribution of the adsorbed protein within the adsorbent particles.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1737–1740, August, 1991.     

Adsorption of hydrogen on nanoporous carbon adsorbents

Four samples of active carbons with specific micropore volumes of 0.4—1.33 cm³g^-1 at 77 K and pressures up to 5 MPa were used to study hydrogen adsorption. The highest amount of of hydrogen adsorbed on these active carbons at the boiling point 20.38 K and pressure 0.101 MPa was calculated by methods derived from the theory of volumetric filling of micropores (TVFM). The adsorbent FAS-1-05 prepared by the liquid-phase polymerization of furfurol was shown to have the highest adsorption capacity. The amounts of hydrogen adsorbed on FAS-1-05 at temperatures 77, 196, and 300 K and pressures 7 and 20 MPa were calculated using the TVFM methods with allowance for linearity of the isosters. The results were compared with the experimental values obtained at 77 K and pressure below 5.1 MPa and at 293 K and pressures up to 16.1 MPa. The highest amounts of hydrogen adsorbed (6.2 wt.% for the adsorbent FAS-1-05) were obtained under pressures below 5.1 MPa and at 77 K.     

Heterogeneous microporous structures and adsorption properties of carbon adsorbents

A theoretical basis for calculating parameters of the pore structure of active carbons is considered. Active carbons are classified into four types according to their dispersion and mesopore surface areas. The parameters of micro- and mesopores of active carbons produced in different countries have been determined from benzene vapor adsorption isotherms at 293 K. The differences in parameters of the Dubinin—Stoeckly equation found from adsorption isotherms of different compounds are noted.For part 11, seeIzv. Akad. Nauk SSSR, Ser. Khim., 1990, 2691 [Bull. Acad. Sci. USSR, Div. Chem. Sci., 1990,39, 2438 (Engl. Transl.)].Deceased July 13, 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1373–1376, August, 1993.     

Adsorption of sodium dodecylsulfate on modified carbon adsorbents

The adsorption of anionic surfactants on carbon adsorbents modified with water-soluble derivatives of natural polymers, cellulose and chitin, is considered with sodium dodecylsulfate taken as an example. It is shown that such modification leads to changes in the adsorption structural characteristics and the particle size distribution of carbon-water suspensions of the original adsorbent, and to the emergence of new functional groups on its surface that are able to interact selectively with adsorbate molecules. It is assumed that adsorption of anionic surfactant on carbon adsorbents under equilibrium conditions proceeds via stepwise filling of the carbon??s porous structure: we first observe volume filling of micropores according to their sizes, and then the formation of a surfactant??s monolayer in mesopores and on the outer surface of the adsorbate. It is established by thermal analysis that the thermal stability of carbon adsorbents is enhanced through the preferential localization of anionic surfactants in micropores. The filling of mesopores and the outer carbon surface by surfactant molecules leads to a regular decrease in thermal stability and an increase in the adsorbent surface??s hydrophilicity.     

Correlation between crystal texture and microporous structure of carbon adsorbents

A correlation of adsorption and X-ray data for a series of both initial and modified active carbons (AC) was performed. The AC were modified by thermal treatment and progressive activation. A linear correlation between the sizes of crystallites and micropore widths of AC was established. It was shown that the adsorption of water vapor results in an increase in the parameterL _aof crystallites of active carbons.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2159–2162, November, 1995.The work was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-09550).     

Adsorption of perfluoropropane on the PAC microporous carbon adsorbent

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.     

Carbon dioxide adsorption on the microporous ACC carbon adsorbent

Adsorption isotherms of carbon dioxide on the microporous ACC carbon adsorbent and the adsorption deformation of the adsorbent were measured. The heats of adsorption at temperatures raising from 243 to 393 K and pressures from 1 to 5⋅10⁶ Pa were measured. In the low-temperature region (243 K), an increase in the amount adsorbed is accompanied by adsorbent contraction, and at high micropore fillings (a > 10 mmol g⁻¹) the ACC carbon adsorbent expands. At high temperatures, adsorbent expansion is observed in the whole region of micropore filling. At 243 K in the low filling region (a < 1 mmol g⁻¹), the heat of adsorption decreases smoothly from 27 to 24 kJ mol⁻¹. The heat of adsorption remains virtually unchanged in the interval 2 mmol g⁻¹ < a < 11 mmol g⁻¹ and then decreases to 8 kJ mol⁻¹ at a = 12 mmol g⁻¹. Taking into account the nonideal character of the gas phase and adsorbent deformation the heats of adsorption are strongly temperature-dependent in a region of high pressures. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1331–1335, June, 2005.     

Numerical modeling of adsorption on microporous adsorbents

Numerical modeling (Monte Carlo method) of the state of water adsorbed in the -cages of the Na and K forms of type A zeolite has shown that the energy parameters of adsorption are determined mainly by interaction of the adsorbed water with the exchange cations. It has been established that the difference between Na⁺ and K⁺ in effective radius has a very pronounced influence on the character of the interaction between adsorbed water and the zeolite framework. The distribution of energy of water interaction with the framework of the Na form is bimodal, but unimodal for the K form. The mean energy of water-molecule interaction with the framework in the case of the K form is practically independent of the degree of pore filling (coverage). At all degrees of filling, there is practically no hydrogen bonding between molecules of adsorbed water.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1724–1728, August, 1989.