N. S. Polyakov

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.

Nonuniform microporous structures and adsorption properties of carbon adsorbents 11. Physical adsorption equations based on a normal distribution of micropore volume

The fundamental properties of three parameter equations for physical adsorption of vapors on nonuniform microporous structures based on the slit type model and having a normal micropore volume distribution have been considered. The widely applied two parameter Dubinin-Radushkevich equation provides for the special case of standard uniform microporous structures. Various threeparameter equations can be differentiated according to their energy coefficient k, which can be expressed as the product of the characteristic adsorption energy Eo and the maximum micropore dimension xo, taken from the distribution curve. The coefficient k requires an independent determination.

Pore structures of charcoal adsorbents and the absorbability of gases and vapors. 4. The dynamics of the adsorption of the vapors of highly volatile substances

ConclusionsIt has been shown that the mathematical apparatus developed earlier for studying the adsorption of readily adsorbable vapors can be used to estimate the dynamic characteristics of the sorption of ethyl chloride vapors through an equation involving a correction coefficient.

Pore structure of carbon adsorbents and the adsorbability of gases and vapors. 2. Analysis of the results of a study of krypton and xenon adsorption in light of the bulk micropore filling theory

Conclusions1.Analysis of the experimental data has permitted a refinement in the limits of applicability of the thermal adsorption equation of the bulk micropore filling theory.2.Adsorption on activated carbons with a broad size distribution of micropores in a relatively large range of fillings of the adsorption space may be described by a single-term adsorption equation of the bulk micropore filling theory.

Adsorption properties and porous structure of new carbon materials

The adsorption properties of the new carbon materials, sibunites, which are mesoporous samples with a developed surface of pores, were studied. The isotherms of the adsorption of benzene vapor were determined to estimate the porous structure of these materials. The principal methods for calculating the parameters of the porous structure of sibunites were analyzed. The application of the BET equation even in the presence of a small number of micropores can distort the results, therefore the most suitable method for estimating the surface of mesopores is one that is based on the Dubinin—Zaverina equation. The estimation of the surface of sibunites using water vapor adsorption is demonstrated.

The adsorptivity of organic substances with various physico-chemical properties

The adsorption isotherms of benzene,n-hexane, cyclohexane, and 1,2-dibromo-1,1,2,2-tetrafluoroethane on a nonporous carbon adsorbent, carbon black, were calculated from the results of a gas-chromatographic experiment at 373 K. A general equation of adsorption isotherm for vapors of organic substances on nonporous sorbents that was proposed earlier is shown to be valid in the range of relative pressures,p/ps, of 10−7–1 and temperatures of 293–373 K.

Adsorption behavior of Vulkan-7H graphitized carbon black

The adsorption behavior of Vulkan-7H carbon black graphitized at 3073 K was studied. Benzene adsorption isotherms at 293 K were measured by the static method and by gas chromatography. It was shown that Vulkan-7H carbon black may be considered as a supermicroporous adsorbent with a pore size of 1.05 nm.

INHOMOGENEOUS MICROPOROUS STRUCTURES AND ADSORPTION PROPERTIES OF CARBON ADSORBENTS. COMMUNICATION 5. TEMPERATURE DEPENDENCE OF ADSORPTION

Conclusions1.Based on the theory of volume filling of micropores, a generalized Dubinin equation for the adsorption of vapors by an adsorbent with an inhomogeneous microporous structure and an arbitrary shape of the micropores was obtained. The Dubinin-Stoeckli equation for a slit model of micropores is a particular case.2.The isotherms of adsorption of benzene vapors on active carbon with a broad distribution of micropores and significant development of the volume and area of mesopores were studied in detail. The equations of the theory of volume filling of micropores permit describing the adsorption isotherms with totally satisfactory precision.

Heterogeneous microporous structures and the adsorption properties of carbonaceous adsorbents. Communication 8. The γ method of determining the specific surface areas of mesopores

Conclusions1.Analysis of benzene adsorption isotherms at 293 K using a standard carbonaceous adsorbent has allowed us to determine that for activated charcoals in the range of equilibrium relative pressures 0.45–0.70, virtually only multimolecular benzene adsorption occurs.2.On the basis of this finding, the more general comparative γ′-method for determining the specific surface area of the mesopores of activated charcoals has been proposed. The method is applicable only to carbonaceous adsorbents.

Nonuniform micropore structure and adsorption properties of carbon adsorbents Communication 7. Computer-aided method for determining basic parameters of micropore and mesopore structure of carbon adsorbents

Conclusions1.A computer-aided method is proposed for determining from experimental benzene vapor adsorption isotherms the parameters of micropore and mesopore structure of carbon adsorbents with practically uniform micropores.2.The method is based on a calculated decrease in adsorption on the surface of mesopores for assigned values of the mesopore surface area, with a parallel determination of the effective parameters of the equation of Dubinin and Stoekli. The sharp drop in variance corresponds to the real parameters of the micropores and mesopores.3.The method had been justified by its application to experimental and model isotherms for the adsorption of C6H6 by carbon adsorbents.