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Adsorption
[SJR: 0.774] [H-I: 52] [4 followers] Follow

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1572-8757 - ISSN (Online) 0929-5607
Published by Springer-Verlag

[2353 journals]

Functionalization of carbon silica composites via in-pore synthesis of
active sites for NH $$_3$$ 3 and SO $$_2$$ 2 adsorption
- Authors: Dushyant Barpaga; M. Douglas LeVan
  Pages: 779 - 787
  Abstract: Abstract To enhance the gas adsorption of toxic industrial chemicals such as NH $_3$ and SO $_2$ , a biphasic carbon silica composite (CSC) is functionalized with combinations of potassium carbonate or potassium phosphate and various metal chlorides with divalent cations. A precipitation reaction occurs within the pores of the CSC between non-monovalent cations and anions to create essentially insoluble active sites. The adsorption capacities of these functionalized materials are measured at atmospheric pressure and low concentrations of NH $_3$ and SO $_2$ . Along with capacity performance, the synthesized materials are characterized using X-ray diffraction, porosimetry and pH measurements to analyze the structure, the incorporation, and the effects of impregnation upon functionalization. Results show that successful incorporation of all insoluble precipitates enhances adsorption capacities compared to impregnant-free substrates. Furthermore, characterization results show reduced pore volumes and surface areas of functionalized materials with structural integrity maintained. Both NH $_3$ and SO $_2$ adsorption can be improved via dual salt functionalization of metal chlorides with potassium salts which form insoluble precipitates on CSC and MCM-41 adsorbent materials. In order to target both adsorbates effectively, the incorporation of K $_2$ CO $_3$ and ZnCl $_2$ to form ZnCO $_3$ provides the highest adsorption capacities for both NH $_3$ and SO $_2$ .
  PubDate: 2017-08-01
  DOI: 10.1007/s10450-017-9898-x
  Issue No: Vol. 23, No. 6 (2017)
Nitrogen substitution and vacancy mediated scandium metal adsorption on
carbon nanotubes
- Authors: Michael Rivera Mananghaya; Gil Nonato Santos; Dennis Yu
  Pages: 789 - 797
  Abstract: Abstract First-principle calculation reveals that N containing carbon nanotubes (CNTs) can support the functionalization of transition metals such as Sc on the CNT surface. For N-substituted CNTs without a vacancy, the enhanced adsorption results from large electron affinity difference of the N adjacent to C atom. In this case, the N atom activates nearby C atom and enhances its interaction with the Sc metal on the CNT surface. Meanwhile, the formation of a vacancy in CNTs causes local reconstruction of the surface near the vacancy site. Simulation and analysis show that vacancy mediated N substitution is a more favored scheme for Sc functionalization on the surface of CNTs that suppresses the clustering of Sc. The enhanced Sc adsorption in N-doped CNTs with mono- and di-vacancy defects was attributed to strong hybridization between the Scandium d orbital and nitrogen p orbital. The results explain theoretically the mechanism of enhanced functionalization of metals on N doped CNTs and suggests that Sc functionalized nitrogen doped CNTs with vacancies is an excellent candidate for the adsorption of small molecules.
  PubDate: 2017-08-01
  DOI: 10.1007/s10450-017-9901-6
  Issue No: Vol. 23, No. 6 (2017)
Adsorption of cesium on bound porous materials containing embedded
phosphotungstic acid
- Authors: Iuliia Little; Kenneth Seaton; Esther Alorkpa; Aleksey Vasiliev
  Pages: 809 - 819
  Abstract: Abstract The adsorption of cesium on mesoporous silica materials containing embedded phosphotungstic acid (PTA) was studied. The materials contained active adsorbent and binders: γ-Al2O3, kaolin, or charcoal. The presence of Keggin units of PTA in the bound materials was confirmed by FT-IR spectroscopy. Among all materials, the formulation with γ-Al2O3 demonstrated the highest porosity and effectiveness in adsorption. Pure PTA/SiO2 contained a significant fraction of small particles between 100 and 300 nm. However, in the alumina-bound material, they were not detected. SEM imaging showed that these particles occupied interparticle space between larger γ-Al2O3 particles. The material was stable up to 540 °C. In most materials, the adsorption of cesium decreased with increase of the binder contents but not proportionally. The adsorption capacity of all materials depended on the concentration of cesium in the solutions. Maximum adsorption was achieved after 1 h. The adsorption of cesium is controlled by intraparticle diffusion while its rate can be described by the pseudo-second-order model.
  PubDate: 2017-08-01
  DOI: 10.1007/s10450-017-9905-2
  Issue No: Vol. 23, No. 6 (2017)
Enthalpy–entropy compensation for isosteric state adsorption at near
ambient temperatures
- Authors: Andrzej Mianowski; Wojciech Urbańczyk
  Pages: 831 - 846
  Abstract: Abstract The adsorption process at near ambient temperatures indicated that the EEC (enthalpy–entropy compensation) is affected by three basic thermodynamic values: ∆H, ∆S and T. The consequence is that it is possible to determine an isosteric straight (symbol H − S) without experimental studies based on the slope coefficient T iso , which is the constant arising from the expected temperature range (about 0–60 °C). Therefore, EEC curves can be obtained by appropriate modification of the temperature range. In the case of entropy of adsorption, the decisive influence is the entropy of gas. For visualization and characterization of this impact, we proposed resolute pointer µ (Eq. 25), through which it is observed that for small values of the equilibrium vapor pressure, as P → 0, there are significant deviations from the isosteric straight H − S. The case where P → P 0 followed a gradual grouping of experimental data in accordance with the relationship with H − S. We used the three-parameter equation for exothermic processes. For the extrapolated conditions, the so-called point of zero adsorption represented the enthalpy and entropy of adsorption, whose values are analogous to previous results in the literature, which can be considered an appropriate analytical method to determine these two thermodynamic values.
  PubDate: 2017-08-01
  DOI: 10.1007/s10450-017-9900-7
  Issue No: Vol. 23, No. 6 (2017)
A solid-state 1 H-NMR study of the dynamic structure of ZIF-8 and its role
in the adsorption of bulky molecules
- Authors: Takahiro Ueda; Masako Nakai; Tatsuya Yamatani
  Pages: 887 - 901
  Abstract: Abstract In order to clarify the adsorption mechanism of the zeolitic imidazolate framework, ZIF-8, for bulky molecules larger than its aperture diameter, the local structure of ZIF-8 and its host–guest interactions were studied by adsorption kinetics, potential energy analysis, and solid-state 1H nuclear magnetic resonance (1H-NMR) spectroscopy. Adsorption kinetics measurements lead to apparent diffusion coefficients for CS2, CDCl3, and CCl4 in ZIF-8 that provide residence times for each molecule in the ZIF-8 micropores. Potential energy analyses using van der Waals pairwise interactions reveal two kinds of feasible sites for bulky molecules in the ZIF-8 micropores, where there are minimal intermolecular interactions between an adsorbate and the pore wall. Each site lies on one of the four diagonal axes of the cubic lattice of the ZIF-8 unit cell. One set of sites corresponds to the side of the micropore where methyl groups form a bottleneck, and the other to the side where CH moieties form the bottleneck. Second-moment analysis of the 1H-NMR resonance line reveals that the 2-methylimidazolate rings undergo flip motions, with flip angles of ~55°, in addition to the rapid axial rotations of their methyl groups. Temperature-dependent spin–lattice relaxation time analyses indicate that adsorptions of these molecules reduce the motions of the 2-methylimidazolate rings. In particular, steric hindrance from bulky molecules such as CDCl3 and CCl4 significantly lowers the flipping frequency of the 2-methylimidazolate ring. The flipping of the 2-methylimidazolate ring results in instantaneous aperture expansion that enables bulky molecules to pass through the ZIF-8 aperture.
  PubDate: 2017-08-01
  DOI: 10.1007/s10450-017-9902-5
  Issue No: Vol. 23, No. 6 (2017)
Calculation of adsorption properties of aluminophosphate and
aluminosilicate zeolites
- Authors: Ivan V. Grenev; Vladimir Yu. Gavrilov
  Pages: 903 - 915
  Abstract: Adsorption interaction of molecular hydrogen with atomic lattice of aluminophosphate AlPO-n and aluminosilicate zeolites H-ZSM-5 has been studied using representative structural fragments including several unit cells with the volumes ranging from 32 to 144 nm3 for different zeolites. Two original methods have been suggested for description of the sorbate–sorbent system: integral and discrete ones. The integral method uses a simplified model of the pore space, which made it possible to obtain the Henry constant dependence on the channel size in an analytic form. The discrete method takes into account the adsorption interaction of the sorbate molecule with all atoms of the structural fragment. Potentials of the adsorption interaction between the sorbate molecule and the lattice atoms (O, Si, Al, P) have been calculated. Equipotential surfaces of interaction between molecules have been also calculated. The equipotential surface with zero adsorption potential Ф 0 (r) determines the shape and parameters of the zeolite microchannels.
  PubDate: 2017-08-01
  DOI: 10.1007/s10450-017-9903-4
  Issue No: Vol. 23, No. 6 (2017)
A robust dynamic column breakthrough technique for high-pressure
measurements of adsorption equilibria and kinetics
- Authors: Thomas Saleman; Gongkui Xiao; Gang Li; Eric F. May
  Pages: 671 - 684
  Abstract: Abstract Adsorption equilibria and kinetics of N2 and CH4 on four adsorbents, namely commercial activated carbon Norit RB3, zeolite 13X, zeolite 4A and molecular sieving carbon MSC-3K 172, were measured at temperatures of (273 and 303) K in the pressure range of (25–900) kPa using an improved dynamic breakthrough apparatus. Equilibrium adsorption measurements were performed with breakthrough experiments, and sorption kinetics were measured with a chromatographic pulse technique to eliminate undesirable systematics such as buoyancy and limitations imposed by heat transfer in conventional breakthrough techniques. The differential equations governing the spreading of a pulse passing through the column were solved in the Laplace domain to reduce numerical dispersion and artefacts associated with solving these equations for adsorption in the time domain on a finite grid. A method for identifying the reliable measurement range of sorption rates (mass transfer coefficients) from 10−4 to 1 s−1 was proposed and demonstrated with the four adsorbents. The sorption rates for Norit RB3 and zeolite 13X had values above the upper resolvable limit of 1 s−1. The measured sorption rates for MSC-3K 172 and zeolite 4A were compared with values obtained independently using a static volumetric method on the same adsorbents at the same temperatures but over a lower pressure range (0–110 kPa) (Xiao et al., Adsorption 23 (2017) 131–147). The sorption rates obtained for the two adsorbents via these two independent techniques were consistent within the measurement uncertainty of each method, which significantly increases the confidence with which these values can be used in simulations of industrial PSA processes.
  PubDate: 2017-07-01
  DOI: 10.1007/s10450-017-9884-3
  Issue No: Vol. 23, No. 5 (2017)
Roll-up effect of sulfur dioxide adsorption on zeolites FAU 13X and LTA 5A
- Authors: Guanghui Li; Qishuai Wang; Tao Jiang; Jun Luo; Mingjun Rao; Zhiwei Peng
  Pages: 699 - 710
  Abstract: Abstract The roll-up effect occurs as a result of the displacement of SO2 with H2O(g) when sulfur dioxide from humid flue gas is adsorbed by zeolites. It is mainly affected by SiO2/Al2O3 ratio (S/A) of zeolites, despite lack of detailed studies on use of hydrophilic zeolite. In this study, two zeolites of FAU 13X (S/A of 1.77) and LTA 5A (S/A of 1.51) were used to explore their roll-up effects using the breakthrough curve method. It is shown that the zeolite structure significantly influences the roll-up effect. The roll-up effect of FAU 13X is more significant than that of LTA 5A at the same water vapor content. The maximum roll-up ratio (η) for LTA 5A and FAU 13X are, respectively, 1.23 and 2.55 within the water vapor content range of 0.9–2.4%. Moreover, η of FAU 13X tends to decrease more rapidly than that of LTA 5A with increasing temperature or decreasing adsorption gas pressure. The presence of oxygen inhibits the roll-up effect and increases the breakthrough time of SO2. For the acid-modified zeolite, there is a positive correlation between η and concentration of Ca2+ or Na+ on zeolite surface, indicating obvious impact of cations on the roll-up effect.
  PubDate: 2017-07-01
  DOI: 10.1007/s10450-017-9887-0
  Issue No: Vol. 23, No. 5 (2017)
Selective adsorption of carbon dioxide, methane and nitrogen using
resorcinol-formaldehyde-xerogel activated carbon
- Abstract: Abstract Resorcinol–formaldehyde xerogel was prepared, carbonized and activated in specific conditions to form resorcinol–formaldehyde activated carbon xerogel (RF-ACX) that was to produce microporous nanoparticles. RF-ACX was used in the adsorption of CO2, CH4, and N2 gases. Adsorption/desorption isotherms of CO2, CH4, and N2 gases onto RF-ACX adsorbent were measured gravimetrically by a magnetic suspension microbalance at five different temperatures (20, 30, 40, 50 and 60 °C) in the pressure range of 0–1 MPa. All adsorption/desorption isotherms were found to be favorable and well correlated with dual site Langmuir’s model. The adsorption capacities of the three adsorbates increased with increasing pressure or with decreasing temperature. Nonetheless, the corresponding increase of CO2 adsorption capacity was much higher than those of CH4 and N2. The fitting parameters deduced from dual site Langmuir’s model were used to provide approximate predictions of the adsorption equilibria and selectivities of the corresponding binary mixtures (CO2/CH4, CH4/N2 and CO2/N2), which relate to separation processes of high influence to various energy and environmental applications.
  PubDate: 2017-09-15
Desorption characteristics of H 2 O and CO 2 from alumina F200 under
different feed/purge pressure ratios and regeneration temperatures
- Authors: Yun Fei Shi; Xiang Jun Liu; Yu Guo; Mohammad Ali Kalbassi; Ying Shu Liu
  Abstract: Abstract Air pre-purification is an important process for industrial air separation with cryogenic distillation method. This process is typically realized by pressure swing adsorption or temperature swing adsorption. H2O and CO2 are the two major components to be removed among the contaminants. In this paper, we establish a mathematical model describing the mass and heat balances in the adsorption bed, and the double-component adsorption/desorption equilibriums of H2O/CO2 on alumina F200. To conduct desorption performance analysis, a one-cycle process consisting of feed, blowdown, and purge step under different operating conditions, such as feed/purge pressure ratio and regeneration temperature, is numerically studied. The effect of heat on the desorption performance of H2O and CO2 is investigated by changing the purge gas temperature within 30–200 °C under feed/purge pressure ratios of 6:1.1 and 10:1.1, respectively. Detailed results of the H2O and CO2 adsorption/desorption behaviors in the bed are demonstrated. The mass and heat transfer characteristics during desorption are also analyzed. Suggestions on the optimization of the heating temperature and duration of purge gas are also proposed.
  PubDate: 2017-09-12
  DOI: 10.1007/s10450-017-9907-0
Saturation loadings on 13X (faujasite) zeolite above and below the
critical conditions. Part III: Inorganic monatomic and diatomic species
data evaluation and modeling
- Authors: Dana Abouelnasr; Kevin F. Loughlin; Alaa Al Mousa
  Abstract: Abstract The saturation loadings for subcritical adsorption of inorganic monatomic and diatomic species on 13X zeolite are modeled using the modified Rackett model of Spencer and Danner (J Chem Eng Data 17:236–240, 1972) for the saturated liquid densities combined with crystallographic data for the 13X zeolite. A similar equation is derived for supercritical adsorption involving supercritical adsorbate densities and crystallographic data for the 13X zeolite. Adsorption data from the literature are first critically evaluated and then compared to the model. Log–log plots are used to determine whether each isotherm is near saturation; isotherms that exhibit a ${{\left( {\partial \ln q} \right)} \mathord{\left/ {\vphantom {{\left( {\partial \ln q} \right)} {\left( {\partial \ln p} \right)}}} \right. \kern-0em} {\left( {\partial \ln p} \right)}}$ slope of zero at the maximum pressure point are assumed to be saturated. The highest loading is used from each isotherm that approaches saturation. Unsaturated isotherms are not considered further. The theoretical equation satisfactorily models the available experimental data for the data that are subcritical. However, a steric factor is required in the model for iodine. 80% of the data for helium, nitrogen and oxygen are in the supercritical region; this data reveals a linear decreasing trend with increasing reduced temperature Tr. For this data a new supercritical model is developed using the reduced critical adsorbate temperature, TCAR, and the slope of the decreasing linear plot against Tr. The physical phenomena causing this effect is considered to be increasing molecular vibration in the cavity reducing the total molecular loading with temperature rise.
  PubDate: 2017-08-22
  DOI: 10.1007/s10450-017-9906-1
Theoretical study of parallel radial adsorber: a novel configuration of
temperature swing gas adsorption bed
- Authors: Sina Salimi; Mohsen Gholami
  Abstract: Abstract In this study, an innovative parallel radial adsorber (here after PRA) has been presented. The motivation behind developing such a configuration was to enhance the performance of adsorption bed by broadening the possible choices of adsorbent diameter. The proposed arrangement effectively reduces the pressure drop by increasing the gas flow contact area; thus, a smaller adsorbent can be applied in the PRA bed. To quantify the performance of the proposed configuration, the governing equations of the system including conservation of energy, mass (diffusion inside the particles and convection outside the particles) and momentum (Ergun equation) were developed and solved numerically. The pressure drop, break-through time, saturation percentage, and duration of regeneration step were chosen as the key factors for evaluating such a configuration. By applying the new configuration, a magnificent diminution of pressure drop resulted. Therefore, small particles which are opted as the adsorbing media will increase the mass transfer area and subsequently mass transfer rate. The capability of handling high flow rate by the proposed configuration offered good potential for reducing the cycle time. Besides showing this potential, owing to the size of the particles in PRA beds, this configuration enhanced the saturation percentage of the column from 88% (axial bed) to 98% for the case study of natural gas dehydration.
  PubDate: 2017-07-31
  DOI: 10.1007/s10450-017-9899-9
Experimental and modelling studies of CO 2 /N 2 mixture separations using
amine functionalised silicas
- Authors: E. Tsalaporta; N. Brady; J. M. D. MacElroy
  Abstract: Abstract A combined experimental and mathematical investigation of amine modified mesoporous silicas as adsorbent materials for carbon dioxide removal from CO2/N2 gaseous mixtures is undertaken. The experiments are designed to permit the determination of CO2 adsorption equilibria and, as appropriate, the assessment of transport and adsorption/desorption reaction kinetic parameters for CO2 interacting with immobilised mono-, di- and triamine moieties. Both forward and reverse breakthrough analysis techniques and cyclic Pressure Swing Adsorption are employed to highlight the significant importance of the role of adsorbent heterogeneity in the separation process.
  PubDate: 2017-06-26
  DOI: 10.1007/s10450-017-9896-z
Adsorption of nutrients on natural Spanish clays for enriching seed
coatings
- Authors: Aránzazu Peña; Antonia Gálvez; José Antonio Rodríguez-Liébana; Concepción Jiménez de Cisneros; Alberto López Galindo; César Viseras; Emilia Caballero
  Abstract: Abstract Coating seeds with nutrients remains an effective way of supplying fertilizers for the establishment and development of seedlings. Clays have been proposed, among other coating materials, because of their low price and favorable properties. Nine natural clays (R1-R9), collected in the eastern Andalusian region (south of Spain), were evaluated for the retention of P, Mn and Zn, with the ultimate goal of designing enriched seed coatings. The clays were similar in composition, with high Ca content. Various equations were used for the fitting of kinetic and adsorption data. Adsorption rates of Mn were higher with R2, R6 was the clay in which Zn exhibited the most rapid kinetics, while P was adsorbed on R7 at the highest rate. Slower adsorption rates corresponded in all cases to Zn. The pseudo-second order model adequately explained the experimental kinetic data of Mn, Zn and P on the different sorbents. Adsorption isotherms indicated that the maximum adsorption capacity on the analyzed clays was ranged as Zn > Mn > > P. Clays were able to retain nutrients for long periods of time (up to 96 days) and desorption was inversely related with adsorption. Simultaneous addition on selected clays of Zn and Mn led to significantly higher nutrient desorption. The co-presence in clays of various compounds (nutrients and/or pesticides) affected their release, so this aspect deserves special attention in coating design. Results obtained suggest the feasibility of using these clay materials enriched with nutrients for seed coating.
  PubDate: 2017-06-20
  DOI: 10.1007/s10450-017-9897-y
Gas adsorption effect on the graphene nanoribbon band structure and
quantum capacitance
- Authors: Ali H. Pourasl; Mohammad Taghi Ahmadi; Razali Ismail; Niayesh Gharaei
  Abstract: Abstract Graphene nanoribbons (GNRs) as a quasi-one dimensional (1D) narrow strip of graphene hold great potential for applications in variety of sensors because of π-bonds that can react with chemical elements. Despite outstanding properties, graphene nanoribbons have not fully exploited for variety of application in nanoelectronic and nanosensors due to poor understanding of their physical, electrical properties and basic limitations on the synthesis. Therefore, in order to achieve analytical understanding on the interaction of the gas molecules with GNR surface and gas sensing mechanism, a theoretical method using tight binding model based on nearest neighbour approximation is developed in this study. Additionally, the adsorption effects of NO2 and CO2 gas molecules on the band structure and electrical properties of the GNRFET based gas sensor are investigated. Based on the proposed model numerical simulation is carried out which emphasizes the significant effect of the gas adsorption on the band structure and electrical properties of GNRs. On the other hand, quantum capacitance created between metal gate and channel as a sensing parameter is considered and its variations when GNR exposed to the NO2 and CO2 molecules are analytically modelled. Moreover, the adsorption energy and charge transfer occurred during gas molecules interaction with GNR surface are calculated. Also band structure and I–V characteristics are analysed using first principle calculation based on density functional theory. The current–voltage analysis clearly indicates the changes of the quantum capacitance when exposed to the gas molecules. The results of the proposed model are compared with the available experimental data or data obtained by density functional theory (DFT) calculations and good agreements are observed.
  PubDate: 2017-06-16
  DOI: 10.1007/s10450-017-9895-0
Adsorption isotherms of carbon dioxide and methane on CHA-type zeolite
synthesized in fluoride medium
- Authors: Zahra Pourmahdi; Hafez Maghsoudi
  Abstract: Abstract High-silica CHA-type zeolite was synthesized in fluoride medium using fumed silica as silica source. Adsorption isotherms of CO2 and CH4 were measured over pressure range of 0–1100 kPa and at temperatures of 298, 323, 353, and 393 K. The isotherms follow a typical Type-I shape according to the BDDT classification. All adsorption isotherms are well described by Langmuir, Toth and Sips isotherms. Adsorptive performance of the zeolite was compared with other CHA-type zeolites, i.e. SAPO-34, Si-CHA and SSZ-13 using ideal adsorption solution theory. The modeling results revealed that the zeolite has a high CO2/CH4 selectivity, e.g. 6.70 for an equimolar mixture at 298 K and 100 kPa. Isosteric heats of adsorption for both CO2 and CH4 were reasonably constant (20.6 and 24.1 kJ mol−1 at loading of 0.02 mol kg−1 for CH4 and CO2, respectively) showing that the adsorbent is energetically homogenous.
  PubDate: 2017-06-13
  DOI: 10.1007/s10450-017-9894-1
Oscillometric–gravimetric measurements of pure gas adsorption equilibria
without the non-adsorption of helium hypothesis
- Authors: J. U. Keller; M. U. Goebel; Th. Seeger
  Abstract: Abstract The adsorption of gaseous carbon dioxide (CO2) at near ambient conditions (297 K, 995 mbar) on activated carbon BAX 1100 (Ingevity), has been measured by a new oscillometric-gravimetric method. The method consists of combined gravimetric and dynamic measurements, namely observations of the frequency of small and nearly adiabatic oscillations of the sorptive gas being in equilibrium with the adsorbed phase of adsorbate. The oscillations observed are actually eigenoscillations of a sorptive gas–sorbate–sorbent system. They are initiated by small oscillations of a sphere or a cylinder positioned in a vertical tube above the vessel containing the gas and the sorbent material reversion of experiment by Rüchardt (Phys. Zeitschr XXX:58, 1929)–Flammersfeld (Z. Naturforsch. 23a:3, 1972). Experiments show that the adsorbate includes two different phases consisting respectively of molecules which are only weakly bound to sorbent’s atoms so that they can participate in the low frequency gas oscillations (<10 Hz), and other molecules being strongly bound to sorbent’s atoms so they are “stiff”, i.e. cannot participate in the gas oscillations, eigenfrequencies being in the range of (1010–1012) Hz. The theory of these measurements is outlined and data of adsorption equilibria of carbon dioxide gas on activated carbon BAX 1100 at near ambient conditions which have been measured by three different methods are presented and compared to each other.
  PubDate: 2017-06-10
  DOI: 10.1007/s10450-017-9893-2
In silico investigation of the ozone (O 3 ) binding behavior to the B 36
bowl-shaped structure
- Authors: Elham Tahmasebi; Zeinab Biglari; Ehsan Shakerzadeh
  Abstract: Abstract The binding of ozone molecule to the B36 bowl-shaped structure is scrutinized using the density functional theory (DFT) calculations. The interactions are investigated using B3LYP, B3LYP-D3, WB97XD, M06-2X and TPPSH methods. The ozone binding to the B36 structure is studied in terms of energetical, structural and electronic features. The results indicate that although ozone molecule weakly interacts with concave side of structure, it adds to the convex side and the edge of B36 structure. The ozone binding to the edge of B36 is more efficient than its convex side. The HOMO–LUMO gaps of the stable systems are reduced with respect to pure B36 sheet. This could be applied as a chemical signal. The obtained results introduce the B36 structure as an efficient ozone adsorbent.
  PubDate: 2017-05-31
  DOI: 10.1007/s10450-017-9891-4
Experimental study on the effect of inherent moisture on hard coal
adsorption–desorption characteristics
- Authors: Liang Wang; Er-tao Chen; Shimin Liu; Yuan-ping Cheng; Long-biao Cheng; Ming-yi Chen; Hai-jun Guo
  Abstract: Abstract Coal is a complex geological body that is composed of organic material, gas, and water. Generally, coal with high hardness is commonly considered to be a non-outburst risk; however, several coal mines with hard coal seams in China have experienced coal and gas outbursts. Coals with different degrees of metamorphism have different inherent moisture ranges, which has a strong influence on gas adsorption and desorption. Currently, inhomogeneous moisture wetting remains an issue in traditional preparation methods for preparing coal samples with different moisture levels. In this paper, we chose three typical hard coals with different degrees of metamorphism and systematically studied their pore structure characteristics, effect of approximate inherent moisture on the gas adsorption–desorption characteristics, and gas diffusion of hard coals. The results show that all of the coal samples have an open pore structure, but each coal sample has different development characteristics of their pore structure. The higher the moisture, the shorter the adsorption equilibrium time required and the lower pressure drop. All of the adsorption isotherm curves fit the Langmuir equation well. The gas adsorption capacity of the same coal sample decreases gradually and the amplitude of the gas adsorption capacity decreases with increasing moisture. This relationship indicates that the existence of moisture occupies a certain space of the pore structure and reduces the gas adsorption sites of coal, reducing the adsorption and desorption amount of the coal samples. Moreover, low and middle rank coal can use the bidisperse model to calculate the diffusion coefficient, while high rank coal can use the unipore model. Increasing moisture causes the macropore diffusion coefficient D a,e and micropore diffusion coefficient D i,e of the YZG and YJ samples to decrease. The effective diffusion coefficient D e of the WLH samples also reduced gradually, which suggests that moisture has an influence on the gas migration and diffusion channels of coal, reducing the gas adsorption equilibrium time, desorption rate, and diffusion rate of coal seam.
  PubDate: 2017-05-22
  DOI: 10.1007/s10450-017-9889-y
Role of chemical structures in coalbed methane adsorption for anthracites
and bituminous coals
- Authors: Yongshuai Fu; Xianfeng Liu; Boqing Ge; Zhenghong Liu
  Abstract: Abstract An in-depth investigation was conducted on four bituminous coals and three anthracites regarding the chemical structural characteristics using Fourier transform infrared spectroscopy (FTIR). The FTIR spectra of coals can be well approximated by the combination of Gaussian/Lorentzian peaks. FTIR parameters, including aromatic structures, aliphatic structures and oxygen-containing groups (C=O), were determined from curve-fitting analysis. Methane adsorption measurements were carried out through an equilibrium volumetric method, and the Langmuir equation was applied to fit the experimental data. Correlations were established for these FTIR structural parameters and methane adsorption parameters (V L and P L). From the results obtained, it can be seen that rapid changes occur for bituminous coals with the vitrinite reflectance, R o = 1.1–2.1%. The sharp variations of the apparent aromaticity, f a, and A(CH2)/A(CH3) indicate the significant intensive aromatization and the decrease of aliphatic methylene groups, respectively. As a consequence, the size of aromatic clusters is greatly enhanced with increasing coalification. However, the oxygen-containing functional groups, ´C´, varying from 0.43 for sample WJD to 0.10 for sample ZZ, presents a negative linear relationship with R o. Once R o > 2.1% (anthracite), both f a and A(CH2)/A(CH3) tend to be steady. The defects and degree of disorder in coal structure have been reduced to a large extent, and the graphite microcrystalline structure in coal is gradually perfected for anthracites. Coals with higher f a provide more adsorption sites for methane occupation on coal surface, thus demonstrating stronger adsorption capacities. However, the aliphatic methylene groups and oxygen-containing functional groups can decrease the CH4 adsorption amount at low pressure stage (<5 MPa), further reducing the adsorption properties. These findings may have great significance for accurate estimation reserves of coalbed methane and the prevention of gas disasters underground coal mine.
  PubDate: 2017-05-03
  DOI: 10.1007/s10450-017-9888-z