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Abstract—The study investigated the physicochemical and adsorption characteristics of a micro-mesoporous carbon adsorbent obtained from wood waste by a thermochemical method with respect to the processes of the accumulation of liquefied natural gas vapors in long-term storage systems. X-ray diffraction analysis of the adsorbent showed that, as a result of synthesis of the adsorbent, its structure was an amorphous carbon phase, without signs of graphite-like phases characteristic of coal obtained from other types of raw materials. In turn, the developed porous structure of the adsorbent is represented by both micro- and mesopores, with a wide size distribution: the total pore volume was about 1.7 cm3/g. The sorption characteristics of the adsorbent at temperatures of 111.7–160 K and pressures up to 0.6 MPa were calculated based on the linearity of experimental isotherms at T from 303 to 333 K and the contribution from adsorption on the surface of mesopores in the monolayer and the capillary condensation effect (CCE). Based on sorption data, it is shown that the presence of mesopores has a predominant effect on the adsorption accumulation efficiency due to the contribution of CCE, providing an active capacity of cryogenic sorption accumulators at a level of 450 m3(NTP)/m3. [ABSTRACT FROM AUTHOR]

Structural and energy characteristics of a number of industrial and prototype samples of microporous carbon adsorbents for the technology of cyanide extraction of gold have been studied. From the results of an analysis of the structural and energy characteristics of microporous carbon adsorbents, it was concluded that adsorbents with a micropore width of about ~X0 = 1.1–1.2 nm are the most effective. The adsorption selectivity of such adsorbents is explained by molecular sieve effects with respect to the gold cyanide complex [Au(CN2)]–. [ABSTRACT FROM AUTHOR]

ES-103(1) microporous carbon adsorbent with specific micropore volume W0 = 0.80 cm3/g and pore width Х0 = 1.32 nm was prepared by thermochemical activation of wood waste in Н3РО4 at 1173 K. The specific BET surface of the adsorbent was SBET = 2115 m2/g. At 303 K and 20 MPa, the methane-adsorption capacity of the adsorbent reached ~22 wt %. In the main region of micropore fillings, the differential molar isosteric heats of methane adsorption gradually dropped from ~16 to 12 kJ/mol. To increase the energy of methane adsorption, it is necessary to use systems that provide a possibility additionally to increase the energy of adsorption due to the energy of adsorbate associating in micropores. At a pressure of 10 MPa, the methane volumetric density in ES-103(1) adsorbent compacted with a binder achieved 200 m3(NTP)/m3. [ABSTRACT FROM AUTHOR]

The possibility of effective adsorption accumulation of vapors of liquefied methane natural gas (LNG) using carbon porous structures was studied. To assess the efficiency of accumulation of the main component of methane natural gas, the structure and energy parameters and methane-adsorption capacity of model carbon adsorbents with slitlike pores of different widths were calculated in terms of Dubinin's theory of volume filling of micropores for subcritical temperatures of 120, 150, 178, and 293 K and pressures up to 6.0 bars. The results were compared with the adsorption capacity of real microporous carbon adsorbents. Based on the results of simulations, the optimal structure of the model adsorbent was chosen for LNG vapors accumulation, and the specific volumetric adsorption characteristics and differential molar heat of adsorption were calculated for this structure. [ABSTRACT FROM AUTHOR]

Based on the theory of volume filling of micropores, an analysis of the structural and energy characteristics of model carbon adsorbents for the sorption of xenon and krypton from the depleted gas–air streams was carried out. It was found that the maximum adsorption capacity for Xe and Kr was achieved at a pore size ranging from ~0.8 to 0.9 nm. The adsorption of Хе, Kr, N2, and О2 onto T-3 activated carbon with the effective width of micropores of 0.94 nm was investigated at pressures up to 100 kPa and at a temperature of 293 K. It was shown that such an adsorbent can be effectively used to capture Xe and Kr from depleted gas–air streams. [ABSTRACT FROM AUTHOR]

Adsorption of n-butane onto ACS microporous carbon adsorbent with a wide pore-size distribution was studied at a pressure as high as 0.25 MPa and the temperatures of 303, 313, 323, and 333 K. The specific volume of micropores of the adsorbent was 2.00 cm3/g. ACS adsorbent had a bimodal pore-size distribution, with the effective pore sizes of 1.42 and 3.8 nm. At a temperature of 303 K and pressure of 0.231 MPa, the maximum value of n-butane adsorption reached 18.62 mmol/g. The BET specific surface was SBET = 2560 m2/g. The initial differential molar heat of adsorption of n-butane onto ACS adsorbent was found to be 29.1 kJ/mol. The differential molar heats of adsorption of n-butane onto ACS adsorbent weakly depended on temperature and passed through a maximum of ~30 kJ/mol at the adsorption value of ~12 mmol/g. A further increase in the value of n-butane adsorption up to 16 mmol/g led to a drop in the heat of adsorption to ~25 kJ/mol. The isotherms of n-butane adsorption were described using the two-term equation of the theory of volume filling of micropores (TVFM). It was found that the bimodal equation of the TVFM well described the n-butane adsorption using the structure and energy parameters of the adsorbent determined from the data on adsorption of benzene and nitrogen vapors throughout the entire ranges of temperatures and pressures. [ABSTRACT FROM AUTHOR]

A Zn–BTB metal–organic framework structure was synthesized by the solvothermal method; it is characterized by micropore volume W0 = 0.67 cm3/g, effective radius of micropores х0 = 0.67 nm, and standard characteristic energy of benzene-vapor adsorption Е0 = 18.0 kJ/mol. The theory of volume filling of micropores was used to calculate the methane-adsorption equilibria on the synthesized Zn–BTB sample at temperatures over the range from 243 to 313 K and pressures up to 35 MPa; the differential molar isosteric heats of adsorption were evaluated. The maximum value of methane adsorption amounts to ~14.5 mmol/g at a pressure of 8 MPa and a temperature of 243 K. [ABSTRACT FROM AUTHOR]

Carbon dioxide adsorption onto model supramolecular structures with slitlike micropores was calculated based on the Dubinin theory of volume filling of micropores using the linearity property of isosteres. Models of carbon adsorbents with slitlike micropores with a width ranging from 0.5 to 2.5 nm obtained by successively eliminating one, two, etc., up to seven layers of hexagonal carbon in the crystal lattice of graphite were used in calculations. The integral energy of adsorption was calculated for the model structures and commercial carbon adsorbents. The dependence of the gravimetric density of carbon dioxide on temperature and pressure was found. [ABSTRACT FROM AUTHOR]

Carbon microporous adsorbents obtained on the basis of polymers are promising adsorbents for the tasks of adsorption storage of natural gas due to the possibility of creating a precise porous structure, as well as optimal mechanical characteristics. A study of the adsorption of methane in a carbon adsorbent based on a composite polymer of furfural and epoxy resin in the temperature range from 178 to 360 K and pressures up to 25 MPa has been carried out. The thermodynamic functions of the adsorption system—the differential molar isosteric and integral heats of adsorption, as well as the isosteric entropy, enthalpy, and heat capacity of the system are calculated. The obtained thermodynamic functions are of fundamental importance in the analysis of the properties of nanodispersed adsorbate in the micropores of the adsorbent, and can also be used as input data in modeling the thermodynamic states of experimental systems for methane storage and transportation. [ABSTRACT FROM AUTHOR]

A MIL-125 metal–organic framework structure was synthesized from titanium and 1, 4-benzenedicarboxylic acid. The specific micropore volume of the synthesized sample was found to be W0 = 0.59 cm3/g, and the specific BET surface area was SBET = 1320 m2/g. Analysis of the synthesized material revealed the possibility of its application for accumulating energetically important gases: methane and hydrogen. The adsorption of hydrogen and methane on MIL-125 was experimentally studied within the temperature range of 77−293 K for hydrogen and 213−293 K for methane at absolute pressures up to 1.5 bar. The high heats of methane and hydrogen adsorption on the synthesized sample of about 26 and 14 kJ/mol were evaluated. It was found that, due to narrow pores, the adsorbent may be effective in accumulating methane at high temperatures. MIL-125 exhibited the best adsorption performance for hydrogen. At the temperature of 77 K and atmospheric pressure, the sample can accumulate up to 2.3 wt % hydrogen. [ABSTRACT FROM AUTHOR]

An EC-103 microporous carbon adsorbent was synthesized from wood using thermochemically activation with Н3РО4 as an activating agent. Methane adsorption on the EC-103 adsorbent was studied within the temperature range from 303 to 333 K and at pressures up to 40 MPa. The total volume of sorbing pores was 1.71 cm3/g. The maximum values of methane adsorption were obtained at the temperature of 303 K and pressure of 40 MPa. The differential molar isosteric heat of methane adsorption 14.5 mmol/g (23.2 wt %) was on the average of 12−14 kJ/mol. Methane adsorption on the EC-103 adsorbent was calculated based on the Dubinin theory of volume filling of micropores (TVFM). It was shown that the Dubinin-Radushkevich equation and basic TVFM pattern provided the best description of experimental data on methane adsorption with the use of only the standard structural and energy characteristics of the adsorbent. [ABSTRACT FROM AUTHOR]

A one-step notion of synthesis was developed to prepare microporous activated carbons from walnut shell by physical gas activation in a CO2 atmosphere for a low-temperature methane accumulation system operating at 120, 160, and 178 K. The raw material was carbonized within a temperature range from 240 to 950°C. Temperatures close to 900°С were found to be optimal for the development of microporosity in the adsorbent in a CO2 atmosphere. Activation under these conditions made it possible to achieve a burnoff degree up to 70% and form an optimal porous structure for adsorption accumulation of liquefied natural gas (LNG) vapors. The adsorbent thus obtained exhibits a high micropore volume W0 = 0.59 cm3/g, mesopore volume WМЕ = 0.33 cm3/g, specific surface SBET = 1490 m2/g, and half-width of micropores of 0.59 nm, which provided a high methane adsorption capacity. The presence of mesopores can make additional contribution to the adsorption process due to capillary condensation. The theoretical assessment of the methane adsorption capacity of the adsorbent showed that at temperatures of 120, 160, and 178 K and pressures up to 6 bars, the values of equilibrium adsorption were 15, 13.5, and 12 mmol/g, respectively. [ABSTRACT FROM AUTHOR]

A Zr–BDC metal–organic framework was synthesized by the solvothermal method using N,N‑dimethylformamide as an organic solvent at the temperature 110°С. The adsorbent thus obtained is characterized by a developed porous structure with specific BET surface SBET = 1060 m2/g, micropore volume W0 = 0.44 cm3/g, and average micropore radius х0 = 0.54 nm, which is indicative of a potentially effective adsorbent for adsorbed natural gas storage systems. The shaping parameters were determined for the Zr–BDC-based composites with polyvinyl alcohol as a binder and without the use of any binder at various compacting pressures. The influence of the shaping pressure on the packing density and structural and energy characteristics of the obtained samples was investigated. Based on the Dubinin theory of volume filling of micropores, the pressure dependences of the methane deliverable capacity both in the initial powdered and shaped Zr–BDC adsorbents at the temperatures of 243, 273, and 303 K were calculated for the pressures up to 100 bar. The deliverable volumetric methane capacity of the adsorption system based on the shaped Zr–BDC samples was measured in the specified thermodynamic conditions. [ABSTRACT FROM AUTHOR]

Adsorption isotherms of methane on AUK, АU-1, and Р-300 active carbons, which possess completely different structural-energy characteristics at the temperatures of 120, 160, and 180 K and pressures of up to 6 bar, as well as the dependences of the specific amount of accumulated methane on these adsorbents on pressure, have been calculated based on the Dubinin's theory of volumetric filling of micropores. Optimal carbon adsorbent has been chosen for storage of the liquefied natural gas vapors derived from the results. The dependences of differential molar isosteric heat of methane adsorption on the adsorption value at various temperatures have been calculated and plotted for these adsorption materials. An approach to the retention of excess vapor volume that is formed upon storage of liquefied natural gas using adsorption accumulation has been suggested. [ABSTRACT FROM AUTHOR]

The isotherms of absolute methane adsorption in an Fe–BDC metal–organic porous structure after long-term storage were measured at a pressure as high as 40 MPa and the temperatures of 303, 313, 323, and 333 K. The dependences of differential molar isosteric heats of adsorption and entropies of adsorption on methane uptake were calculated. It was shown that taking into account the nonideality of a gaseous phase and steepness of the isotherm of adsorption leads to a temperature dependence of thermodynamic functions of adsorption. Both a sharp drop in the heat of adsorption and a local maximum of the entropy at the maximum values of methane uptake are indicative of rearranging the adsorbate structure and the probable formation of molecular methane associates in micropores. [ABSTRACT FROM AUTHOR]

Methane adsorption in MPU-007 microporous carbon adsorbent with a wide pore size distribution was studied at a pressure as high as 40 MPa and the temperatures of 303, 313, 323, and 333 K. The maximum value of methane adsorption of 43.36 wt % was achieved at 303 K and 40 MPa. The isosteres of adsorption derived from the obtained data were satisfactorily approximated by a linear function in coordinates ln P–1/Т at a constant value of adsorption. The dependences of differential molar isosteric heats of methane adsorption in MPU-007 microporous adsorbent on the value of methane adsorption were calculated at the temperatures of 303, 313, 323, and 333 K. The heat of methane adsorption of 14 kJ/mol was constant at a filling of micropores as low as ≈5 mmol/g. Then it declined evenly to 8 kJ/mol at 25 mmol/g and 303 K and to 2 kJ/mol at 24 mmol/g and 323 K. Such a run of the curves describing the heats of adsorption versus adsorption value might be caused by a wide pore size distribution and the association processes in the adsorbate. [ABSTRACT FROM AUTHOR]

In the present work, a method for producing new shaped composite materials by introducing a metal-organic framework structure Cu-BTC110 into a matrix of carbon material has been suggested. Powdered microporous activated carbons prepared from vegetable, polymer, and peat raw materials were used as carbon matrices. Physicochemical properties and structure-energy characteristics of the initial materials and shaped composites based on them were determined. It was demonstrated that the Cu-BTC110 composite with active carbon prepared from peat enabled one to achieve a balance between structure-energy characteristics, mechanical characteristics, and methane adsorption capacity. Depending on the temperature, the amount of accumulated methane can achieve 160–200 m3 (NTP)/m3 within a pressure range from 3.5 to 10.5 MPa. [ABSTRACT FROM AUTHOR]

The effects of different types of bindings, the pressure of shaping and carbon-containing additives on the structural and energy characteristics, density, and mechanical properties of the shaped composite adsorbents prepared based on metal-organic framework structures are studied. Their adsorption behaviors are also examined for application to methane accumulation systems. [ABSTRACT FROM AUTHOR]

Adsorption of hydrogen in four types of activated carbons of different origin with specific micropore volumes ranging from 0.46 to 0.96 cm3/g is studied at temperatures of 303, 313, 323, and 333 K and pressures up to 20 MPa. The saturation adsorption of hydrogen vapors in the considered types of activated carbons is calculated at the hydrogen boiling point (20.38 K) and a pressure of 0.101 MPa using the Dubinin theory of volume filling of micropores (TVFM). The theoretical calculations show that the type FAS-2008 adsorbent, which is produced using liquid-phase furfural polymerization, has the highest adsorption capacity. Using the TVFM and taking into account linearity of the adsorption isosteres, we also estimate adsorption of hydrogen in the type AU3:5 slit-shaped microporous carbon adsorbent at a temperature of 303 K and pressures 10 and 20 MPa. The collected experimental data and theoretical calculations are compared to the data for 101 kPa and 20.38 K. The highest hydrogen adsorption, 7.9 wt %, at 20 MPa and 303 K is predicted for a model slit-shaped microporous graphene-based adsorbent, type AU3:5. [ABSTRACT FROM AUTHOR]

A microporous carbon adsorbent labeled as LCN was prepared by thermochemical synthesis from lignocellulose, and methane adsorption on it was studied within the temperature range from 303 to 333 K and at pressures up to 40 MPa. The total pore volume was determined to be 0.68 cm3/g. The maximum values of methane adsorption of ~14.5 mmol/g (23.2 wt %) were obtained at the temperature of 303 K and the pressure of 40 MPa. The calculated differential molar isosteric heat of methane adsorption is, on average, ~12–13 kJ/mol. Methane adsorption on LCN was calculated with the use of the Dubinin–Radushkevich and Dubinin–Astakhov equations, as well as the linearity of adsorption isosteres. It was shown that the Dubinin–Radushkevich and fundamental regularities of the theory of volume filling of micropores provide the best description of experimental data using only the standard structural and energy characteristics of the adsorbent. [ABSTRACT FROM AUTHOR]

Adsorption of natural gas (methane) on the synthesized metal–organic framework (MOF) Al-BTC with specific surface area SBET = 1422 m2/g was studied at pressures up to 40 MPa and temperatures of 303, 313, 323, and 333 K. The maximum adsorption of methane on Al-BTC reaches 10.36 mmol/g at 303 K and 40 MPa, and the initial heat of adsorption is ~14 kJ/mol. The amount of methane accumulated in a system with Al-BTC attains a value of 120–130 m3(NTP)/m3 in a range of pressures from 3.5 to 10.0 MPa, which is the most relevant for methane accumulation. The volumes of methane stored in the systems with Al-BTC and without an adsorbent differ by a factor of about 2 at 3.5 MPa, there is almost no distinction between these options of methane storage at 7.0 and 20.0 MPa, and the amount of gas in the system without an adsorbent exceeds by 25% that in Al-BTC. The pressure range from 3.5 to 6.0 MPa is most efficient for the methane adsorption accumulation in the MOF structure Al-BTC. The absolute efficiency of methane adsorption accumulation increases with lowering of temperature. [ABSTRACT FROM AUTHOR]

Abstract: A metal-organic framework, Fe-BDC, was synthesized by solvothermal method from iron salt and terephthalic acid using N,N-dimethylformamide as the solvent. The data from the study of structural-energy characteristics calculated by the Dubinin-Radushkevich, Kelvin, and BET equations are given. The resulting Fe-BDC sample has a specific surface area of SBET = 2240 m2/g and a specific micropore volume of W0 = 0.83 cm3/g. The morphological and X-ray characteristics of this sample were studied. [ABSTRACT FROM AUTHOR]

The Dubinin theory of volume filling of micropores and the linearity of adsorption isosteres were used to calculate the adsorption of hydrogen on model microporous adsorbents with slitlike pores. In calculating, the model adsorbents were considered the micropores of which were formed through a progressive removal of one, two, and so on to seven layers of hexagonal carbon in a graphite crystalline structure, while the micropore sizes varied within a range from 0.5 to 2.5 nm. The integral energy of adsorption was evaluated for the model structures and most of industrial carbon adsorbents. The obtained results were compared with experimental data. Dependences of the gravimetric density of hydrogen on temperature and pressure were analyzed. [ABSTRACT FROM AUTHOR]

The Dubinin theory of volume filling of micropores (TVFM) was used to study the structure-energy characteristics of metal-organic frameworks based on salts of copper (C300), aluminum (A520), and zinc (Z205) produced by BASF. Isotherms of absolute adsorption of methane were measured on these adsorbents at the temperatures of 303, 313, 323, and 333 K and pressures up to 40 MPa. Dependences of differential molar isosteric heats of methane adsorption on the adsorption value and the dependence of the specific volume capacity of methane accumulation on pressure are calculated. In the technically significant range of pressures up to 10 MPa, adsorbents with high values of specific surface area cannot guarantee high specific capacities of methane accumulation. The thermodynamic Р,Т-parameters of adsorption systems of methane accumulation determine the optimum structural and energy characteristics of adsorbents suitable for high-performance methane accumulation. [ABSTRACT FROM AUTHOR]

Differential molar isosteric and integral heats of methane adsorption on a range of microporous carbon adsorbents of different origin have been calculated. The values of densities of integral heats Ω of methane adsorption on the sorbents under study Ω have been determined as the ratio between integral heat of adsorption and micropore volume. The dependence of density of integral heat of adsorption on standard characteristic energy of adsorption E has been estimated. It has been shown that the value of density Ω increases as E increases. The results of calculation of specific amount of accumulated methane V depending on energy and structural parameters of adsorbents have been presented. [ABSTRACT FROM AUTHOR]

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 nm(СН)/m. 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. [ABSTRACT FROM AUTHOR]

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 m(ntp, CH)/m at 7 MPa and 298 K. A decrease in the temperature by 55° allows reaching the value of 180 m(ntp, CH)/m. The experimental data are used to plot methane adsorption isosteres that are well approximated by straight lines in the coordinates of ln p = f(1/ T). 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. [ABSTRACT FROM AUTHOR]

Temperature dependences of parameters n and E are calculated according to the adsorption equation of Dubinin-Astakhov for methane adsorption on eight active carbons in the range of supercritical temperatures of 170-340 K and pressures of 0-20 MPa. At temperatures above ~240 K, characteristic adsorption energy E of methane grows linearly at an increase in temperature. The temperature coefficients of characteristic energy of methane adsorption on active carbon tend to decrease at an increase in standard characteristic adsorption energy E . The average value of parameter < n> for the studied adsorbents tends to grow at an increase in standard characteristic adsorption energy E . [ABSTRACT FROM AUTHOR]

Synthesis of an adsorbent based on an organometallic framework of the MOF-199 type is performed. The Dubinin-Radushkevich equation is used to calculate the structure-energy characteristics of adsorbents on the basis of data on nitrogen adsorption at 77 K as per benzene. Methane adsorption is studied on the obtained MOF-199 adsorbent, and adsorption isosteres are plotted. The capacitive characteristics of the adsorption system for methane storage with the synthesized adsorbent are determined. Differential molar isosteric and integral adsorption heats are calculated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]