Amount Of Adsorbed CO Research Articles

Water effect on amine-modification of adsorbents for separation of CO2/N2

The adsorption of CO2 can be enhanced through loading amines on adsorbents, therefore, the separation of CO2 from other gases is promoted. Water plays an important role in this process. Water increases both the adsorption amount of CO2 and the separation coefficient with N2 for all amines loaded. However, the effect of loading trialkylamines is not remarkable in the absence of water. The effect of loading dialkylamine does not depend on water, but the adsorbent cannot be regenerated at ambient temperature. In comparison, an adsorbent loading trialkylamine can be regenerated at ambient temperature even in the presence of water with fairly good stability.

Reversible Pore Size Control of Elastic Microporous Material by Mechanical Force

Nanoporous materials, such as zeolites, activated carbons, and metal-organic frameworks (MOFs), are peculiar platforms in which a variety of guest molecules are stored, reacted, and/or separated. The size of the nanopores is essential to realize advanced functions. In this work, we demonstrate a very simple but innovative method for the control of nanopore size, that is, reversible and continuous control by mechanical force loaded to soft nanoporous materials. The elastic properties of several microporous materials, including zeolites, zeolite-templated carbon (ZTC), activated carbon, and MOFs (e.g., ZIF-8), are examined and it is found that ZTC is a material that is suitable for the aforementioned idea thanks to its extraordinary soft properties compared to the others. The original pore size of ZTC (1.2 nm) can be contracted to 0.85 nm by using a relatively weak loading force of 135 MPa, whereas the other microporous materials barely contracted. To demonstrate the change in the physical properties induced by such artificial deformation, in situ gas adsorption measurements were performed on ZTC with and without loading mechanical force, by using CO2, CH4, and H2, as adsorbates. Upon the contraction by loading 69 or 135 MPa, CO2 adsorption amount is increased, due to the deepening of the physisorption potential well inside the micropores, as proved by the increase of the heat of adsorption. Moreover, the adsorption amount is completely restored to the original one after releasing the mechanical force, indicating the fully reversible contraction/recovery of the ZTC framework against mechanical force. The experimental results are theoretically supported by a simulation using Grand Canonical Monte Carlo method. The similar adsorption enhancement is observed also on CH4, whereas H2 is found as an exception due to the weak interaction potential.

Adsorptive Removal of Carbon Dioxide Using Polyethyleneimine Supported on Propanesulfonic-Acid-Functionalized Mesoporous SBA-15

One-step synthesized sulfonic-acid-functionalized SBA-15 (denoted as αSSBA-15) impregnated with polyethyleneimine (PEI) was used for CO2 capture in this study. The resulted sorbents were characterized via a range of analytical techniques, including transmission electron microscopy (TEM), 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR), infrared (IR), thermogravimetry–differential scanning calorimetry (TG–DSC), etc. Experimental results showed that the incorporation of propanesulfonic acid groups into the inner structure of the silica support had brought dramatic improvement in CO2 adsorption capacity, of which PEI/5SSBA-15 showed the highest CO2 adsorption amount. The main reason of this increased capacity could be attributed to the enhanced CO2 diffusion into bulk networks of PEI polymers because of its better dispersion in the pores of support, where the extended propanesulfonic acid groups on the inner surface could spatially disperse the subsequent loaded PEI molecules. Furthermore, the PEI/5SSBA-15 also exhibited superior stable cyclic adsorption/desorption performance compared to PEI/SBA-15, especially after 5 cycles. This was assumed because the enhanced surface acidity of PEI/5SSBA-15 anchored the NH2/NH groups through acid–base interaction, reducing the loss of active sites.

Amine-functionalized monodispersed porous silica microspheres with enhanced CO2 adsorption performance and good cyclic stability

Carbon dioxide capture using solid adsorbent has caused more and more attention in the world. Herein, amine-functionalized monodispersed porous silica microspheres (MPSM) were prepared by the hydrolysis and condensation of tetraethoxysilane (TEOS) in a water–ethanol–dodecylamine mixed solution, then calcined at 600°C, and finally functionalized with tetraethylenepentamine (TEA). The CO2 adsorption performance of the prepared samples was measured using a Chemisorb 2720 pulse chemisorption system (Micromeritics, USA). The results showed that the specific surface area and pore volume of the 600°C-calcined SiO2 microspheres reached 921m2/g and 0.48cm3/g, respectively. All the TEA-functionalized samples exhibited good CO2 adsorption performance, which were related to the amount of loaded TEA, adsorption temperatures, and the specific surface areas of the prepared samples. An optimal TEA loading amount (34wt%) and adsorption temperature (75°C) were determined. The maximum CO2 adsorption amount (4.27mmolg−1 adsorbent) was achieved on the 600°C-calcined SiO2 microsphere sample with TEA loading of 34wt%. Repeated adsorption/desorption cycle experiments revealed that the TEA-functionalized SiO2 microspheres were good CO2 adsorbents exhibiting excellent cyclic stability.

Adsorption separation of CO2/CH4 gas mixture on the commercial zeolites at atmospheric pressure

In this work, six kinds of the commercially common zeolites (NaX, CaX, NaA, CaA, ZSM-5 and Y) were selected as candidate for separating CO2 from CH4. In to study adsorption behavior of all zeolites and screen excellent adsorbents, adsorption experimental of pure gases was performed. NaX had the greatest adsorption amount of CO2 at 0.1MPa, and CaX had the highest affinity of CO2. The selectivity predicted by IAST model was 76 for NaX at 0.1MPa, yCH4=0.5, and 74 for CaA at 0.1MPa, yCH4=0.9. These two zeolites with excellent separation performance had been used for subsequent experiments about the effect of moisture and desorption. The moisture tremendously weakened separation performance of zeolites, and the pre-drying of zeolite and pre-dehydration of gas mixture is an essential step. The thermal desorption was more suitable for the regeneration of NaX and CaA than the vacuum desorption, and the CO2 adsorbed on zeolites could be wholly desorbed at 300°C. From the study of the adsorption heat and IR spectrum, we found that the adsorption of CO2 on NaX and CaA is a physical adsorption process in our experimental condition (atmospheric pressure and room temperature), because carbonate species have not been found in the zeolites after adsorbing CO2.

Near-Surface Accumulation of Hydrogen and CO Blocking Effects on a Pd–Au Alloy

Alloying Pd with Au has remarkable features of enhancement of hydrogen solubility compared to Pd and catalytic activity for reactions such as partial hydrogenation of unsaturated hydrocarbons. A key to understanding these phenomena is clarification of hydrogen behavior in the near-surface region. In the present work, by applying nuclear reaction analysis for high-resolution depth profiling of hydrogen in combination with thermal desorption spectroscopy, we show that hydrogen substantially accumulates in the near-surface region and is absorbed in the bulk of a single-crystal Pd70Au30(110) alloy. We also demonstrate a molecular cap effect of CO, where a small amount of CO adsorption greatly changes the hydrogen absorption and desorption behavior by blocking the entrance/exit channel for hydrogen. These findings lead to understanding and controlling the catalytic activity of the Pd–Au alloy and Pd-related surfaces and also open up a new method to control hydrogen transport across metal surfaces.

Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite: comparison of carbon dioxide and methane adsorption with the all-silica DD3R zeolite

Adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0–190 kPa and temperatures of 298, 323, and 348 K. Acid gases adsorption isotherms on this type of zeolite are reported for the first time. The isotherms follow a typical Type-I shape according to the Brunauer classification. Both Langmuir and Toth isotherms describe well the adsorption isotherms of methane and acid gases over the experimental conditions tested. At room temperature and pressure of 100 kPa, the amount of CO2 adsorption for Si-CHA zeolite is 29 % greater than that reported elsewhere (van den Bergh et al. J Mem Sci 316:35–45 (2008); Surf Sci Catal 170:1021–1027 (2007)) for the pure silica DD3R zeolite while the amounts of CH4 adsorption are reasonably the same. Si-CHA zeolite showed high ideal selectivities for acid gases over methane at 100 kPa (6.15 for H2S and 4.06 for CO2 at 298 K). Furthermore, H2S adsorption mechanism was found to be physical, and hence, Si-CHA can be utilized in pressure swing adsorption processes. Due to higher amount of carbon dioxide adsorbed and lower heats of adsorption as well as three dimensional channels of Si-CHA pore structure, this zeolite can remove acid gases from methane in a kinetic based process such as zeolite membrane.

Adsorption of Carbon Dioxide, Methane, and Their Mixtures in Porous Carbons: Effect of Surface Chemistry, Water Content, and Pore Disorder

The adsorption of carbon dioxide, methane, and their mixtures in nanoporous carbons in the presence of water is studied using experiments and molecular simulations. Both the experimental and numerical samples contain polar groups that account for their partially hydrophilicity. For small amounts of adsorbed water, although the shape of the adsorption isotherms remain similar, both the molecular simulations and experiments show a slight decrease in the CO2 and CH4 adsorption amounts. For large amounts of adsorbed water, the experimental data suggest the formation of methane or carbon dioxide clathrates in agreement with previous work. In contrast, the molecular simulations do not account for the formation of such clathrates. Another important difference between the simulated and experimental data concerns the number of water molecules that desorb upon increasing the pressure of carbon dioxide and methane. Although the experimental data indicate that water remains adsorbed upon carbon dioxide and methane adsorption, the molecular simulations suggest that 40 to 75% of the initial amount of adsorbed water desorbs with carbon dioxide or methane pressure. Such discrepancies show that differences between the simulated and experimental samples are crucial to account for the rich phase behavior of confined water-gas systems. Our simulations for carbon dioxide-methane coadsorption in the presence of water suggest that the pore filling is not affected by the presence of water and that adsorbed solution theory can be applied for pressures as high as 15 MPa.

Adsorption of carbon dioxide on Al/Fe oxyhydroxide

The structure and reactivity of 0–70mol% Al/Fe iron oxyhydroxides (ferrihydrite in the absence and presence of Al) toward gaseous CO2 were investigated with X-ray photoelectron spectroscopy (XPS), atomic absorption (AA), scanning transmission electron microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), X-ray diffraction (XRD), and attenuated total reflectance Fourier transform Infrared spectroscopy (ATR-FTIR) combined with density functional theory (DFT) calculations. Results showed that Al/Fe oxyhydroxide particles containing more than 20mol% Al consisted at least in part of Fe-oxyhydroxide with incorporated Al and a discrete AlOOH phase. Results from ATR-FTIR experiments and DFT calculations suggested that the bicarbonate complex formed by passing CO2 over the particles was accommodated on at least three distinct binding sites. At the lowest Al concentrations bicarbonate was bound to individual sites with primarily Fe or Al character. At the highest concentrations of Al (>20mol%) bicarbonate bound to discrete AlOOH phases became apparent. Results also suggested that the amount of CO2 adsorption for a given particle mass increased as the Al concentration was increased from 0 to 30%. This increase was likely due in large part to differences in the morphology of the particle aggregates that formed in the dry state, which would be expected to affect the amount of surface that was available to adsorb CO2.

Error analyses in volumetric method for measuring methane and CO<SUB align="right">2 adsorption on coal

CO2 sequestration in deep coal seams with enhanced coalbed methane recovery (CO2-ECBM) is emerging as a promising option to stabilise CO2 concentration in the atmosphere. Volumetric method for measuring methane and CO2 adsorption on coal can generate the critical information of the coalbed methane recovery and CO2 storage amount of the target coal seams. In this work, the potential sources of error involved in volumetric method including sample mass, volume, temperature, pressure and compressibility factor and their impact on the measured methane and CO2 adsorption amount have been studied using the law of error propagation. Feasible measures to improve the measured precision based on ‘fixed volume’ method have also been put forward.

Hierarchically structured metal–organic framework/vertically-aligned carbon nanotubes hybrids for CO2 capture

A novel carbon/metal–organic framework composite was synthesized by confined growth of HKUST-1 in the interspace of the vertically-aligned carbon nanotube (VACNT) arrays. The grown HKUST-1 crystals are much smaller than the HKUST-1 crystals produced without the confinement growth. The derived HKUST-1/VACNT hybrids possess a hierarchical microporous–mesoporous structure. In comparison to the calculated hypothetical value assuming the physical mixture of the components, the synthesized HKUST-1/VACNT composites exhibit larger surface area and porosity, higher CO2 adsorption amount, and better CO2/N2 selectivity, which indicate the positive synergistic effect between HKUST-1 and VACNT. Besides the superior adsorption properties of hybrids, they are easier to handle than powder adsorbent for gas storage/separation.

Competitive Adsorption Between Phenol, Aniline and n-Heptane in Tailrace Coking Wastewater

The competitive adsorption of organic pollutants—phenol, aniline and n-heptane—from biologically treated coking wastewater on powdered activated carbon (PAC) was studied. Firstly, batch adsorption experiments of coking wastewater were conducted to investigate the effect of pH and temperature on their adsorption. Results showed that long-chain alkanes, benzoic, halogenated and phenolic compounds were adsorbed well under acidic condition, while amines were adsorbed well under alkaline condition; maximum co-adsorption amount of all kinds of organic compounds occurred at around pH 5. Then, Lagergren kinetic model and pseudo-second-order kinetic model were used to describe the adsorption process of phenol and aniline on PAC. The data were fitted very well with pseudo-second-order kinetics, and the adsorption capacity decreased with an increase in temperature, belonging to Freundlich multi-layer physical adsorption. The adsorption speed and capacity of phenol were superior to aniline in unitary and binary solution. The adsorption amount of n-heptane decreased by 26.6 % from ternary competitive absorption system of phenol, aniline and n-heptane compared with that in unitary solutions, which showed that phenol and aniline caused spatial adsorption steric hindrance to n-heptane.

Surface characteristics and carbon dioxide capture characteristics of oxyfluorinated carbon molecular sieves

A carbon molecular sieve (CMS) was modified through oxyfluorination to investigate its carbon dioxide (CO2) adsorption characteristics. The oxyfluorination was performed at various F2/O2 ratios at room temperature. The surface chemical properties and pore size distributions on the CMSs were altered by oxyfluorination and analyzed through XPS and isothermal gas adsorption. The CO2 adsorption capacity on the oxyfluorinated CMSs was different from that of unmodified CMSs due to changes in the functional groups on the carbon surface. The CO2 uptake at 273K was unchanged compared with untreated CMS and measured approximately 2.5mmol/g. However, at 298K, the CO2 adsorption capacity increased from 1.61mmol/g for an unmodified CMS to 2.07mmol/g for the oxyfluorinated CMS. We suggest that introduced oxygen and fluorine functional groups on carbon surface by oxyfluorination increased basicity on carbon surface. Consequently, interaction energy between functional groups and CO2 molecular are increased at room temperature and it contributed to enhance CO2 adsorption amount.

Fabrication and CO2 adsorption performance of bimodal porous silica hollow spheres with amine-modified surfaces

Carbon dioxide capture and storage (CCS) solutions have received enormous attention because CO2 is a primary greenhouse gas and plays a key role in global warming and climate change. In this work, bimodal meso-/macroporous SiO2 hollow sphere (BMSHS) samples with high specific surface areas were prepared by a hydrothermal method. Cetyltrimethylammonium bromide (CTAB) and perfluorododecanoic acid (PFDOA) were used as cotemplates and the CTAB/PFDOA weight ratio (R) was varied. The prepared samples were further modified with tetraethylenepentamine (TEPA), and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), differential thermal analysis (DTA), thermal gravimetric analysis (TGA), and N2 physisorption techniques. This was followed by CO2 capture tests using a pure CO2 stream in the temperature range of 35–130 °C. The results showed that all of the prepared samples contained small mesopores with a peak pore size of ca. 3–4 nm and larger mesopores or macropores with a peak pore diameter of ca. 103 to 117 nm. The mesopores and macropores are from the shell and the cavity of hollow spheres, respectively. The R exhibited a significant influence on the specific surface area, as the specific surface areas increased with increasing R. All of the TEPA-modified samples exhibited good CO2 adsorption abilities, which were related to the amount of loaded TEPA, adsorption temperature, and the specific surface areas of the samples. A optimal amount of TEPA loading (about 50 wt%) and adsorption temperature (about 110 °C) were determined. The CO2 adsorption amount increased proportionally with the specific surface area. The maximum CO2 adsorption amount (4.41 mmol g−1 adsorbent) was achieved on the BMSHS sample prepared at R = 40 and TEPA loading of 50 wt%. The present study provides new insight into the design and synthesis of novel porous materials for CO2 capture.

Displacement Behavior of Methane Adsorbed on Coal by CO2 Injection

The displacement behavior of methane adsorbed on coals by CO2 injection has been experimentally studied. With the assumption of the additive property of the adsorbed-phase volume, a novel data processing method is established to obtain the absolute adsorption amount of methane and CO2 as well as the amount of methane recovery. The results show that the adsorption of CO2 on low-rank Bulianta coal initially saturated with methane is higher than that on high-rank Qinshui coal. For comparison, the adsorption isotherms of pure methane and CO2 on coal without initial methane saturation have been conducted. It is found that, for the coal sample without methane saturation, the CO2 adsorption capacity of high-rank Qinshui coal is superior to that of low-rank Bulianta coal. A conceptual model is proposed to give the explanation. It is indicated that for carbon dioxide sequestration on coal with enhanced coal bed methane recovery (CO2-ECBM), it would be better to inject CO2 after partial desorption of methane by depressurizing in order to improve CO2 storage. The selectivity ratio of CO2 and effects of operation parameters such as pressure and temperature have been discussed. On the basis of the results, a recommended depth of CO2 sequestration in coal seams has been put forward.

Advanced adsorbents based on MgO and K2CO3 for capture of CO2 at elevated temperatures

We report here our study on development of adsorbents suitable for capturing CO2 from synthesis gas (syngas) at high temperatures (>100°C). Our adsorbents are based on double salts of MgCO3 and K2CO3 in which samples with different ratios of Mg:K were prepared by the wet mixing method of magnesium nitrate and potassium carbonate. The adsorbents were characterized by X-ray diffraction analysis, thermogravimetric analysis (TGA), and N2 adsorption and desorption at 77K. The morphology of the samples was observed with scanning electron microscopy (SEM). CO2 adsorption experiments were performed at four temperatures, 300°C, 350°C, 375°C, and 400°C, which correspond to the operating temperature range of gases exiting a typical water gas shift reactor and entering a gas turbine in the Integrated Gasification Combined Cycle (IGCC) process. The CO2 adsorption amounts were 1.65wt%, 8.47wt%, 8.55wt%, and 0.63wt% respectively at a CO2 partial pressure of 100kPa. These adsorbents also exhibited excellent cycling stability both in temperature swing adsorption and pressure swing adsorption operation. The kinetics of CO2 adsorption at different temperatures was obtained by using the linear driving force (LDF) model and a diffusion activation barrier of 21kJ/mol was also inferred.

Adsorption of carbon dioxide on ionic liquids-modified active carbons and amino-modified polymer

Active carbons with various particle sizes (38–150, 300–500 and 800–1,200 μm) were modified by ionic liquids (ILs), and organic polymer was modified by acrylamide using a simple procedure, and these materials were applied to capture carbon dioxide (CO2). The CO2 adsorption amounts were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influences of gas pressure, particle size and temperature on adsorption were discussed. Experimental results showed that the CO2 adsorption capacity of ILs-modified active carbons was better than amino-modified polymer, and the smaller particle size (38–150 μm) ILsmodified active carbons had the largest adsorption capacity at 298.15 K. Compared with previous research about polyethyleneimine (PEI)-modified silica gel, the adsorption amount of CO2 on ILs-modified active carbons has been greatly improved with lower cost.

Reaction between Carbon Dioxide and Mechanically Activated Metal Powder

A fundamental study on the reaction between CO2 and mechanically activated metal powders has been conducted. In this research, the behavior and mechanism of CO2 reaction under various grinding conditions were investigated to fix and reduce CO2. The powder used was placed inside a grinding vessel, and was ground together with the SUJ2 balls in CO2 atmosphere. It was found that only the adsorption of CO2 gas on the ground samples was observed, whereas the decomposition of CO2 was not occurred. The CO2 adsorption increased proportionally with the increase in the grinding speed, weight of sample and number of SUJ2 balls. Furthermore, the CO2 adsorption increased with the decrease in the standard free energy of formation of each metal oxide. The morphology of the sample observed by SEM showed that the samples were not crushed into finer particles, but were only grazed on the sample’s surface. Therefore, it can be said that the CO2 can be adsorbed on the mechanically activated samples by using the centrifugal type ball mill, but in order to enhance the amount of CO2 adsorption, another type of machine with higher grinding intensity should be considered.

CO2 isothermal adsorption models of coal in the Haishiwan Coalfield

Since the capacity of CO2 adsorption of coal is a key factor in coal and CO2 outbursts, an experimental study was carried out on CO2 isothermal adsorption with high-pressure volumetry with dry coal samples from the No.2 coal seam in the Haishiwan Coalfield. Four different equations (Langmuir, BET, D-R and D-A) were used to fit the experimental data. We discuss adsorption mechanisms. The results show that the amount of CO2 adsorption increases rapidly under low relative pressure, i.e., the ratio of equilibrium pressure and saturated vapor pressure, which indicates that molecular layer adsorption or micropore filling may occur in coal. No clear equilibrium state was observed on the isothermal adsorption curves under relative pressure (P/P0) ranging from 0 to 0.8. The fitted results show that the accuracy of the D-A equation is highest with n=1. Micropores are more developed in coal by comparing the BET equation with a pressure mercury injection method on the surface area. The D-A equation (n=1) provides the best fit. By comparing the calculated specific surface area of the BET equation and the mercury intrusion method, it is found that micropore adsorption of CO2 occupies a dominant position.

DRIFTS study of Cu–Zr–Ce–O catalysts for selective CO oxidation

The effects of different components in Cu 1Zr 1Ce 9O δ catalyst and the variations of the feed stream on the catalytic performance of selective CO oxidation were investigated by diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) technique. It is found that the active sites of Cu 1Zr 1Ce 9O δ catalyst are mainly Cu + species. Formate species is formed through the reaction between CO gas and hydroxyl groups on the reduced cerium surface. CeO 2 in the Cu 1Zr 1Ce 9O δ catalyst facilitates the formation of Cu + species and improves the amount of CO adsorption whereas it is unfavorable to the deep reduction of Cu + species. ZrO 2 doped into the Cu 1Zr 1Ce 9O δ catalyst increases the Cu coverage and CO adsorption capacity, while it decreases the adsorption of CO 2 on the catalyst surface. The adsorption capacities of oxygen and CO are associated with the catalytic performance for the selective CO oxidation at lower and higher temperatures, respectively. The presence of CO in the feed stream promotes the reduction of Ce 4+ species and the production of geminal OH group on the reduced ceria surface. Hydrogen in the feed diminishes the CO adsorption ability but stimulates the CO desorption. CO 2 in the feed occupies the active sites and decreases the adsorption of the reactants, thus deteriorates the catalytic performance for the selective CO oxidation.