CO2 Gas Adsorption Research Articles

Simulated Adsorption and Diffusion of CO2 Gas Across a Meso-Porous Material by Using Convective Flow Models

Simulated Adsorption and Diffusion of CO2 Gas Across a Meso-Porous Material by Using Convective Flow Models

Monte Carlo simulations of the adsorption of CO2 on the MgO(100) surface

The adsorption of CO2 gas on the MgO (100) crystal surface is investigated using grand canonical Monte Carlo simulations. This allows us to obtain adsorption isotherms that can be compared with experiment, as well as to explore the possible formation of monolayers of different densities. Our model calculations agree reasonably well with the available experimental results. We find a "low-density" adsorbed monolayer where each CO2 molecule is bound to two Mg2+ ions on the MgO substrate. We also observe the formation of monolayers of higher density, where some of the CO2 molecules have rotated and tilted to expose additional binding sites. Low-temperature simulations of both the low- and high-density monolayers reveal that these states are very close in energy, with binding energies of approximately 7 kcal/mol at T=5 K. The high-density monolayer given by our model has a density that is significantly less than the reported experimental value. We discuss this discrepancy and offer suggestions for resolving it.

Metallocorroles as sensing components for gas sensors: remarkable affinity and selectivity of cobalt(III) corroles for CO vs. O2 and N2.

Most commercially available CO detectors are based upon metal oxides or electrochemical cell technologies. None of these approaches use the selective adsorption of CO gas on a molecular complex. Conversely, cobalt(III) corroles can bind small gaseous molecules allowing them for an application as sensing components for gas detectors. Here we describe the ability of cobalt corroles to selectively coordinate carbon monoxide vs. dinitrogen and dioxygen. The coordination properties were determined in the solid state and the adsorption characteristics were compared to those of the reference compound (To-PivPP)Fe(1,2-Me2Im), known for its remarkable CO binding properties. The adsorption data evidence that the selectivity, affinity and capacity of the cobalt(III) corroles for CO are larger than those of the porphyrin complex. However, from a chemical point of view, the selectivity of cobalt(III) corroles for CO vs. O2 is infinite since these derivatives do not bind O2 while (To-PivPP)Fe(1,2-Me2Im) does with an M value (PO2(1/2)/PCO(1/2)) equal to 51. In this manuscript we also show that the affinity of cobalt(III) corroles for CO is closely related to the Lewis acid character of the central cobalt(III) ion and therefore to the nature of the substituents at the periphery of the corrole macroring.

NO 2 and CO gas adsorption on carbon nanotubes: Experiment and theory

In this work a combined experimental and theoretical study on carbon nanotube (CNT) based system for gas sensing applications is reported. Carbon nanotubes thin films have been deposited by plasma-enhanced chemical vapor deposition on Si3N4/Si substrates provided with Pt electrodes. Microstructural features as determined by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy highlight the growth of defective tubular carbon structures. The electrical resistivity of the CNT film shows a semiconductinglike temperature dependence and a p-type response with decreasing electrical resistance upon exposure to NO2 gas (100 ppb). No response has been found by exposing the film to CO gas in the temperature range between 25 and 250 °C. In order to obtain a theoretical validation of the experimental results, the equilibrium position, charge transfer, and density of states are calculated from first principles for the CNT+CO and CNT+NO2 systems. Our spin-unrestricted density functional calculations show that NO2 retains its spin-polarized state upon adsorption. Both CO and NO2 molecules adsorb weakly on the tube wall, with essentially no charge transfer between the tube and molecules. The electronic properties of CNTs are sensitive to the adsorption of NO2, due to an acceptorlike peak close to the tube valence-band maximum, while they are insensitive to the CO adsorption. According to the experimental findings, our theoretical results suggest that gas-induced modification of the density of states close to the Fermi level might significantly affect the transport properties of nanotubes.

Adsorption of CO2, N2, and O2 on Natural Zeolites

Pressure swing adsorption (PSA) and temperature swing adsorption are potential techniques for removing CO2 from high-pressure fuel gas streams. Natural zeolites are suitable candidate sorbents for use in the PSA process. Studies of volumetric gas adsorption of CO2 ,N 2, and O2 on three natural zeolites, with different major cations, were conducted at 25 °C up to a pressure of 300 psi (2 10 6 Pa). Preferential adsorption of CO2 was observed with all three zeolites. The natural zeolite with the highest sodium content and highest surface area showed the highest CO2 adsorption capacity. Competitive gas adsorption studies also showed that the zeolite with the highest sodium content gave the best separation of CO2 from the gas mixtures. Contact time did not affect the extent of adsorption of the zeolites. Temperature-programmed desorption studies indicated that the majority of the physically adsorbed CO2 was desorbed at room temperature, while some strongly bound CO2 was desorbed at 115 °C.

The effect of impregnation of activated carbon with SnCl 2.2H 2O on its porosity, surface composition and CO gas adsorption

Activated carbon was impregnated with different concentrations of SnCl 2.2H 2O. Unimpregnated and impregnated activated carbons were analysed by means of physical adsorption and XPS and were tested for CO gas adsorption in a PSA system. The adsorption isotherms of N 2 at 77 K were measured and showed a Type I isotherm indicating microporous carbon for all the samples. The surface area, pore volume and pore size distribution were reduced with impregnation. XPS analysis showed an increase in the intensity of Sn3d peak with impregnation. The impregnated activated carbon showed a very good adsorption ability of CO gas compared to the unimpregnated sample. The adsorptive species responsible for CO gas adsorption was confirmed to be SnO 2 instead of SnO due to the former’s comparative thermodynamic stability.

O2, CH4 and CO2 gas retentions by acid smectites before and after thermal treatment

Acid smectites in natural condition and after thermal treatment up to 900 °C were studied for their O2, CH4 and CO2 gas retentions at 25 °C and 1 kg/cm2. Two smectites, one dioctahedral and one trioctahedral, were treated with 5.0 N sulphuric acid solution for 15 and 60 min. The gas adsorptions by the smectites increased after acid treatments. The O2 (0.014–0.030 mmol/g) and CH4 (0.045–0.063 mmol/g) gas retention values were small whereas the values corresponding to CO2 (0.206–0.357 mmol/g) retentions were high for acid smectites. The acid trioctahedral smectite showed higher gas adsorption values than acid dioctahedral smectite. The CO2 gas adsorption values by acid smectites heated up to around 600 °C, decreased around 10% and 20% for acid trioctahedral and dioctahedral smectites, respectively. After that drastically decreased and at 900 °C both acid smectites showed very small adsorption values. The chemical composition, the structure and the texture of the smectites influenced the gas retention.

Effect of oxygen plasma treatment on gas adsorption behavior and surface structure of carbon spheres derived from phenol resin

Plasma treatment was applied on glasslike carbon spheres to modify their gas adsorption behavior. After the oxygen plasma treatment, a selective adsorption of CO2 gas was obtained, almost no nitrogen adsorption being detected, at low temperatures. Surface morphology observed by using field-emission scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy was found to be changed after the oxygen plasma treatment.

Molecular simulation for gas adsorption at tio 2 (rutile and anatase) surface

In this study, the simulation for gas adsorption on TiO 2 was performed using the “SORPTION” module in the software of molecular simulation. The properties of gas adsorption at the surface of TiO 2 are predicted by Monte-Carlo method. The open force field theory is used to calculate the interaction energies between CO gas and rutile or anatase TiO 2 surface. Existence of different energy peaks in energy analysis suggests that adsorption of CO gas occurs at various atomic sites of rutile or anatase TiO 2 surface.

Magnetic easy axis engineering in ultrathin Cu/Co/Cu[110] structures

The magneto-optic Kerr effect in-situ has been used to investigate the effects of exposing ultrathin Co/Cu(llO) films (6ML<d_<Co<30ML) to CO gas and the subsequent effects of depositing submonolayer quantities of Cu. After a given deposition of CO, the adsorption of CO gas (but, not O₂, H₂) is found to cause the magnetic easy axis to switch 90&#x000B0; from the [00l] to the [1-10] direction. The deposition of submonolayer Cu overlayers are observed to reverse the effect of the adsorbed CO thereby switching the easy axis back to [00l]. For thin CO films (d_Co<15ML), Cu overlayers switch the magnetic easy axis back to the [00l] direction abruptly. In thicker CO films (>15ML) the easy axis is found to shift gradually from the [l-10] to the [00l] direction, and it allows us to controllably engineer the direction of the magnetic easy axis at a constant CO thickness.

Characteristics of CO gas adsorption on modified natural zeolite

The characteristics of CO gas adsorption on chemically treated natural zeolite from the Kampo area of Korea were investigated. Acid treatment was more effective in liquid adsorption than alkali treatment because the exchanged H + ion attributed to the enlargement of pore size. However, in gas adsorption, a different tendency was observed. In HCl treated zeolite, 80% of the pore area, which was derived from a higher portion of micropores around 10 Å, led to hindrance of the gas diffusion rate. Though the pore and surface area decreased in NaOH treatment, an increase in the gas adsorption amount was found, and it could be supposed that the exchanged Na + ion located on the surface served as an adsorption site. The NaOH treated natural zeolite showed a higher value and 0.017 g of the adsorption amount at 5 N NaOH compared with 0.011 g at 5 N HCl.

Adsorption of CO2 and N2 on Soil Organic Matter: Nature of Porosity, Surface Area, and Diffusion Mechanisms

The surface area of soil organic matter (SOM) is a crucial parameter for the interpretation of sorption mechanisms of organic contaminants. The surface area of three SOM samples was studied by using CO2 and N2 gas adsorption, revealing that SOM is a microporous material with a high surface area of 94−174 m2 g-1. The ethylene glycol monoethyl ether (EGME) retention technique has major drawbacks for application to SOM samples, as liquid EGME changes the SOM solid phase density. Nitrogen (N2) is subject to molecular sieving at 77 K due to activated diffusion in micropores. CO2 is not limited by activated diffusion since higher experimental temperatures are applied (273 K). About 95−99% of the SOM surface area is formed by micropores with maximum restrictions of approximately 0.5 nm. Results suggest that the diffusion coefficient of CO2 is influenced by the cross-linking density of the matrix and that the microporous structure is not strongly affected by hydration of the sample. On the basis of pore dimension...

Resistivity Oscillation of Ti Film During Growth

Very thin Ti films have resistivities with film-thickness-dependent osciliatory characteristics. Experimental results show that with H2, CO2 and O2 gas adsorption on the film surface, the film structure and film components have little influence on the resistivity oscillation. Furthermore, the oscillation amplitudes are sensitive to the surface flatness. The resistivity oscillation is considered to occur by a modulation of the electron transmission, in the matching of two electron wave-functions at the interface of film/substrate and vacuum/film.

Change in the chemical structures of carbon black and active carbon caused by CF4 plasma irradiation

Carbon black and active carbon were fluorinated by exposure to CF4 plasma. Their surface chemical structures were studied by means of elemental analysis, X-ray photoelectron spectroscopy, and inverse gas chromatography as a function of treatment time. Fluorine is mainly introduced onto the carbon black and active carbon surfaces during the CF4 plasma treatment. The amount and type of carbon-fluorine (C-F) functionality formed on the surfaces of the carbon materials depends on the C-C framework structure as well as the plasma treatment time. C1s chemical shifts caused by C-F bonds on the fluorinated active carbon and carbon black surfaces are slightly different from those reported on the various types of fluorinated organic polymers, and have a somewhat ionic character. For the fluorinated active carbon the C-F bond is relatively stable, whereas for the fluorinated carbon black the C-F bond is unstable and has a significant ionic character. In addition, CO2 gas adsorption characteristics on the fluorinated active carbon can be controlled by the surface C-F functionality.

LEED-AES observations of the vacuum-cleaved BiSrCaCuO single crystals

We carried out the first observations of low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES) from surfaces obtained by cleaving the 7- and 80 K-phase BiSrCaCuO single crystals in vacuum. By comparing the results from these surfaces with those from the surfaces obtained by heating the single crystals in vacuum after cleaving in air, we found that the clean surface of 7- or 80 K-phase single crystals was also obtained by heating the single crystals in vacuum after cleaving in air. The adsorption of CO gas on the clean surface of the 80 K-phase single crystal was confirmed by LEED observations, while the adsorption of O 2, CO 2 and CH 4 gases were not confirmed.

Sorption of binary gas mixtures in zeolites

The adsorption of pure CO2 and N2 gases, and their mixtures have been determined on a very high silica form of the zeolite ZSM-5 using a newly developed isosteric technique. Unlike more traditional methods, this method allows one to measure mixture isotherms at fixed sorbed phase composition. The shape of the mixture isotherms and the isosteric heats of sorption for the mixture have been identified as functions of the equilibrium gas phase composition, which itself is a temperature dependent function of the sorbed phase composition. None of the isotherms approached saturation at the temperatures and pressures used. The ratio of Henry's constants for the two pure gases gives a reasonable estimate of the separation factor measured experimentally. Selective sorption of CO2 is marked even at 70°C. Binary mixture sorption isotherms predicted from pure gas data using the ideal adsorbed solution (IAS) theory, are shown to be in close agreement with the experimental data.

Adsorption and reaction of CO2 gas on the surface of ZnO fine particles in the atmosphere.

In order to clarify adsorption and reaction on the fine ZnO particle surfaces in the atmosphere, the heating desorption analysis of the particles, which had previously adsorbed CO2 gas or CO2 gas containing water, was carried out using FID and TCD gas chromatography. The prism-like and the needle-like ZnO fine particles were synthesized by gas phase oxidation of zinc vapor. The effects of water vapor and of the surface crystal structure of these particles were examined, and the reaction of CO2 gas with H2O adsorbed on the crystal surface was studied. The results revealed that adsorption of H2O on the ZnO surface gave great influence upon the reaction with CO2 in the atmosphere. It was concluded that a thin layer of hydrozincite or smithsonite, depending upon the degree of stabilization of crystal surface, was probably formed.

ISS observations of molybdenum samples as limiter and first wall materials after various preparation methods

Molybdenum is now commercially available by three kinds of metallurgical techniques, which are electron beam melting, arc melting and sintering. In order to point out what differences occur in the observed surface impurities on each Mo sample manufactured by the above different metallurgical processes, an ion scattering spectrometer (ISS) is used as a diagnostic method of surface observation because it has very high sensitivity to the topmost layers of the solid sample. The observed surface impurities are C, O, Na, K, S and Fe. C, O and S are common impurities for each Mo sample. Na and K are observed mainly on the arc melted Mo sample. Fe is detected only on the electron beam melted one. Impurities such as Na, K, S and Fe are segregated from the bulk to the surfaces depending on sample temperature. C and O are supplied to the surface by adsorption of CO gas in the ultrahigh vacuum system. The sputtering cross sections of CO and O 2 gases on the Mo surface by He ion bombardment have been measured.

The adsorption of CO gas by metals supported on silica

The adsorption of CO gas by the metals Rh, Ir, Os, Re, Ru and Au supported on silica was studied. From electron micrographs and measurements of the surface area of metal covered silica, the metal particles appear as thin clusters on the silica surface ranging from about 20 Å in diameter and probably approaching monolayer thickness. The infrared spectra shows adsorbed CO species of the type M-CO, M 2-CO and M-(CO) 2. At the higher pressures used with Rh, Ir and Os, a band at 2080 cm −1 is attributed to a weakly held CO in sites already containing one chemisorbed CO. The possible occupancy of corner and edge sites in Re and Ru by more than two CO molecules is discussed. A correlation is presented between the force constant of M-CO species and the number of d holes of the metal indicating a decrease of the bond order of adsorbed CO on account of the formation of metal-carbon bonds. The correlation is additional evidence of the role of d electrons in adsorption.

アルカリ及びアルカリ土金屬炭酸鹽が2CO〓+CO&lt;sub&gt;2&lt;/sub&gt; を促進する機構に就て (II)

For the synopsis of this work see the Report I. [This journal, 1 (1937), 26]