A. L. Pulin

Adsorption and adsorption-induced deformation of NaX zeolite under high pressures of carbon dioxide

Isotherms of carbon dioxide adsorption and adsorption-induced deformation of pelletized crystalline NaX zeolite at pressures of 0.2--5.4 MPa and temperatures of 195--423 K are measured. The adsorption deformation is positive at low zeolite micropore filling (a < 1 mmol g-1) at all temperatures, i.e., the zeolite suffers expansion. Further, as the amount of the adsorbed substance increases, the adsorption deformation curves pass first through a maximum and then through a minimum. In the range of high fillings (a > 7 mmol g-1) the NaX zeolite shows dramatic expansion.

Low-temperature adsorption of methane on microporous AU-1 carbon adsorbent

In this work, isotherms of absolute adsorption of methane on microporous AU-1 carbon adsorbent have been measured in the pressure range from 30 Pa to 6 MPa and temperature range from 178 to 273 K. Adsorption isosteres of methane have been plotted according to experimental data. Isosteres are approximated well by lines in lnp = f(1/T)a coordinates. Differential molar heats of adsorption of methane on this adsorbent have been calculated on the basis of experimental isotherms. Theses regarding the structure of adsorbed substance based on thermodynamic analysis have been proved by molecular-dynamic calculations.

Adsorption-stimulated deformation of microporous carbon adsorbent

Deformation of the ACC microporous carbon adsorbent during adsorption of carbon dioxide, nitrogen, and argon in the temperature interval from 243 to 393 K and at pressures of 1—5·106 Pa was studied. The effect of adsorbent contraction was found in the initial temperature interval at relatively low pressures. However, the negative value of relative linear deformation ΔL/L smoothly transforms into positive values with the pressure increase. Only the effect of adsorbent expansion is observed at high temperatures in the whole pressure interval. The dependence of the deformation effects for different systems on the adsorbent nature was revealed.

Adsorption deformation of zeolite NaX at high pressures of xenon

The deformation of pellets of crystalline zeofite NaX upon adsorption of Xe at pressures from 0.001 to 7 MPa and temperatures from 252.5 to 333 K was studied. In the temperature range studied, the relative linear deformation of zeolite crystals is negative in the initial adsorption region. When the adsorption of Xe increases, its value passes through a minimum and then increases sharply taking positive values at high adsorption volume filling of micropores.

Methane adsorption on microporous carbon adsorbents in the region of supercritical temperatures

Methods for the description of adsorption equilibria for methane on microporous carbon adsorbents within the Dubinin theory of the volume filling of micropores are considered. Isotherms of methane adsorption on eight carbon adsorbents are calculated and compared with the experimental data in the temperature range of 170–350 K at pressures up to 20 MPa. An analysis of the errors of the description of experimental data by the methods used is performed. A method of description based on the use of two isotherms of methane adsorption (at the boiling point and critical temperature) calculated using the Dubinin-Radushkevich equation and the property of the linearity of adsorption isosteres is recommended.

Adsorption of methane on model adsorbents formed from single-wall carbon nanotubes

The theory of bulk filling of micropores is used for simulation of supramolecular structures based on single-layer carbon nanotubes arranged into triangular packing and to determine the methane-adsorption capacity at the pressures of up to 20 MPa. Structure-energy parameters of porous structures of modeled adsorbents are calculated, and structures are selected that may be in demand in engineering. The structure of adsorbed methane in the model adsorbent is determined using the numerical molecular-dynamics technique. It is shown that adsorption in the range of low coverages occurs via the mechanism of partial localization of molecules near nanotube walls. At an increase in adsorption, the mechanism changes to bulk filling and molecules are associated in the central region of pores formed by triangular-packed nanotubes.

Description of NaX zeolite deformation during adsorption of xenon

The equation describing the experimental data of NaX zeolite deformation during adsorption of xenon at pressures of 0.001–7 MPa and temperatures of 252–333 K was obtained on the basis of the generalized Lennard-Jones pair interaction potential. The temperature dependences of the constants in the equation were determined.

A study of methane adsorption and accumulation on microporous carbon adsorbent in a wide temperature range

This work studies the adsorption properties of microporous activated carbon AU-2 to determine the efficiency of methane accumulation in a wide temperature range, particularly in the low temperature range. Absolute adsorption isotherms of methane are measured in the pressure range of 20 Pa to 25 MPa and temperature range of 178–260 K. It is shown that the adsorbent accumulates up to 130 m3(ntp, CH4)/m3 at 7 MPa and 298 K. A decrease in the temperature by 55° allows reaching the value of 180 m3(ntp, CH4)/m3. The experimental data are used to plot methane adsorption isosteres that are well approximated by straight lines in the coordinates of lnp = f(1/T)a. The values of differential and integral adsorption heats of methane on the adsorbents are calculated on the basis of the experimental isotherms and are used to calculate an increase in the adsorber temperature as a result of adsorption.

Nitrogen adsorption by microporous adsorbents in the range of high pressures and supercritical temperatures

The nitrogen adsorption isotherms for the AUK microporous carbon adsorbent are measured at pressures of 1 Pa to 6 MPa and temperature of 177.7–393 K. In terms of the adsorption isotherms, in the same range of pressures and temperatures, the nitrogen adsorption isosteres are calculated. The resultant dependences are adequately approximated by linear functions. By the adsorption isosteres, the dependences of differential molar isosteric heat of adsorption on the value of adsorption and temperature are plotted. The results are compared with the literature data on nitrogen adsorption by zeolite NaX and activated carbon SKT.

Experimental study and numerical modeling: Methane adsorption in microporous carbon adsorbent over the subcritical and supercritical temperature regions

Adsorption properties of AU-4 microporous carbon adsorbent have been investigated for evaluating the effectiveness of methane accumulation over the temperature range from 178 to 360 K and at absolute pressures up to 25 MPa. It has been established that, within the pressure and temperature intervals under study, the maximum amount of methane achieved 160 nm3(СН4)/m3. Efficient accumulation of methane in the AC-4 adsorbent over the entire temperature range was possible only within the interval of pressures from 1 to 7 MPa. When the “methane−AU-4” accumulation system was used at room temperature, the highest effect of adsorption accumulation may be achieved at pressures of 3–7 MPa. The differential and integral adsorption heats have been calculated and the degrees of overheating have been evaluated for methane storage systems with adsorbent.