共查询到20条相似文献,搜索用时 15 毫秒
1.
《Journal of membrane science》1999,160(1):115-125
Single gas and mixture permeances of CO2 and CH4 were measured as functions of pressure and temperature through three MFI zeolite membranes that have different fractions of their permeances through non-zeolite pores. The effect of pressure on CO2 permeance, which was different for each membrane, was fit by a modified surface diffusion model. The differences in the pressure behavior of the membranes are attributed to pores with viscous and Knudsen flow. Membranes with the largest permeation through non-zeolite pores have the lowest CO2/CH4 mixture selectivity. The highest CO2/CH4 mixture selectivity is 5.5 at room temperature and decreases with temperature because of a decrease in competitive adsorption. Although increasing pressure at constant pressure drop increases the apparent CO2/CH4 selectivity, the ratio of the CO2 and CH4 fluxes decreases. 相似文献
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Michael Rubal Cletus W. Wilkins Jr Patrick E. Cassidy Chris Lansford Yasuharu Yamada 《先进技术聚合物》2008,19(8):1033-1039
The purpose of this project was to synthesize fluorinated polyimide (PI) nanocomposite membranes in order to study the gas permeation rates and selectivity of carbon dioxide and methane. PIs were synthesized from 2,2‐bis(3,4‐anhydrodicarboxyphenyl)hexafluoropropane (6F dianhydride, 6FDA) and 4,4′‐diaminodiphenyl ether (oxydianiline, ODA) into which were incorporated nanoparticulate additives as follows: in situ TiO2, both plain and treated with dodecyl sulfate surfactant, and organo‐clay (Cloisite®‐10 Å) at loads of 1, 3, and 5 wt% to the polyamic acid. Polyamic acid films were solvent cast, cured at 200°C then post‐cured at 300°C and measured for permeation data and for thermal properties. Glass transition temperatures ranged from 124 to 140°C for the cured PIs and from 142 to 147°C for the post‐cured materials, the nano‐inclusions having little discernable effect on this property. Thermogravimetric analysis (TGA) data show that the inclusion of Cloisite® or TiO2 caused a small decrease of thermal stability from 555°C to about 532 to 541°C. The inclusion of clay causes a decreased permeation rate while the addition of TiO2 improves the rate and selectivity. Treating the nanofillers with surfactant decreases selectivity and marginally increases rate of permeation of CO2. Post‐curing caused a darkening of the composites, but not the neat PI. This heat treatment also resulted in a significantly decreased permeation rate, but a significantly increased selectivity. The resulting material shows superior gas separation properties to the commercially available PI, Matrimid® produced by Ciba‐Geigy. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Sizova A. A. Grintsevich S. A. Kochurin M. A. Sizov V. V. Brodskaya E. N. 《Colloid Journal》2021,83(3):372-378
Colloid Journal - Grand canonical Monte Carlo simulations were performed to study the occupancy of structure I multicomponent gas hydrates by CO2/CH4, CO2/N2, and N2/CH4 binary gas mixtures with... 相似文献
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M. A. Kurbanov V. R. Rustamov Kh. F. Mamedov Z. I. Iskenderova 《Journal of Radioanalytical and Nuclear Chemistry》1987,119(2):95-100
The purification of methane from hydrogen sulphide at room temperature as affected by U.V.-light and ionizing radiation has been studied. A probable reaction mechanisms is discussed. 相似文献
6.
Two models for the permeability of pure gases have been extended to include binary gas mixtures. The first is an extension of a pure gas permeability model, proposed by Petropoulos, which is based on gradients of chemical potential. This model predicts the permeability of components in a gas mixture solely on the basis of competition for sorption sites within the polymer matrix. The second mixed gas model follows an earlier analysis by Barrer for pure gases which includes the effects of saturation of Langmuir sites on the diffusion as well as the sorption processes responsible for permeation. This generalized “competitive sorption/diffusion” model includes the effect of each gas component on the sorption and diffusion of the other component in the mixture. The flux equations from these two models have been solved numerically to predict the permeability of gas mixtures on the basis of pure gas sorption and transport parameters. Both the mixed gas Petropoulos and competitive sorption/diffusion model predictions are compared with predictions from the earlier simple competitive sorption model based on gradients of concentration. An analysis of all three models is presented for the case of CO2/CH4 permeability in poly(phenylene oxide) (PPO). As expected, the competitive sorption/diffusion model predicts lower permeability than either of the models which consider only competitive sorption effects. The permeability depression of both CO2 and CH4 predicted by the competitive sorption/diffusion model is roughly twice that predicted by the competitive sorption model, whereas the mixed gas Petropoulos model predictions for both gases lie between the other two model predictions. For the PPO/CO2/CH4 system, the methane permeability data lie above the predictions of all three models, whereas CO2 data lie below the predictions of all models. Consequently, the competitive sorption/diffusion model gives the most accurate prediction for CO2, while the simple competitive sorption model is best for methane. The effects of mixed gas sorption, fugacity, and CO2-induced dilation were considered and do not explain the inaccuracies of any of the models. The relatively small errors in mixed gas permeability predictions using either of the three models are likely to be related to “transport plasticization” of PPO owing to high levels of CO2 sorption and its effect on polymer segmental motions and gas diffusivity. 相似文献
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Nakayama T Takahashi K Matsumi Y Toft A Andersen MP Nielsen OJ Waterland RL Buck RC Hurley MD Wallington TJ 《The journal of physical chemistry. A》2007,111(5):909-915
FTIR-smog chamber techniques were used to study the products of the Cl atom and OH radical initiated oxidation of CF3CH=CH2 in 700 Torr of N2/O2, diluent at 296 K. The Cl atom initiated oxidation of CF3CH=CH2 in 700 Torr of air in the absence of NOx gives CF3C(O)CH2Cl and CF3CHO in yields of 70+/-5% and 6.2+/-0.5%, respectively. Reaction with Cl atoms proceeds via addition to the >C=C< double bond (74+/-4% to the terminal and 26+/-4% to the central carbon atom) and leads to the formation of CF3CH(O)CH2Cl and CF3CHClCH2O radicals. Reaction with O2 and decomposition via C-C bond scission are competing loss mechanisms for CF3CH(O)CH2Cl radicals, kO2/kdiss=(3.8+/-1.8)x10(-18) cm3 molecule-1. The atmospheric fate of CF3CHClCH2O radicals is reaction with O2 to give CF3CHClCHO. The OH radical initiated oxidation of CxF2x+1CH=CH2 (x=1 and 4) in 700 Torr of air in the presence of NOx gives CxF2x+1CHO in a yield of 88+/-9%. Reaction with OH radicals proceeds via addition to the >C=C< double bond leading to the formation of CxF2x+1C(O)HCH2OH and CxF2x+1CHOHCH2O radicals. Decomposition via C-C bond scission is the sole fate of CxF2x+1CH(O)CH2OH and CxF2x+1CH(OH)CH2O radicals. As part of this work a rate constant of k(Cl+CF3C(O)CH2Cl)=(5.63+/-0.66)x10(-14) cm3 molecule-1 s-1 was determined. The results are discussed with respect to previous literature data and the possibility that the atmospheric oxidation of CxF2x+1CH=CH2 contributes to the observed burden of perfluorocarboxylic acids, CxF2x+1COOH, in remote locations. 相似文献
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Dr. Sara Realista Janaína C. Almeida Sofia A. Milheiro Dr. Nuno A. G. Bandeira Dr. Luis G. Alves Dr. Filipe Madeira Prof. Dr. Maria José Calhorda Dr. Paulo N. Martinho 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(50):11670-11679
Three CoII octaazacryptates, with different substituents on the aromatic rings (Br, NO2, CCH), were synthesised and characterised. These and the already published non-substituted cryptate catalysed CO2 photoreduction to CO and CH4 under blue visible light at room temperature. Although CO was observed after short irradiation times and a large range of catalyst concentrations, CH4 was only observed after longer irradiation periods, such as 30 h, but with a small catalyst concentration (25 nm ). Experiments with 13C labelled CO2 showed that CO is formed and reacts further when the reaction time is long. The CCH catalyst is deactivated faster than the others and the more efficient catalyst for CH4 production is the one with Br. This reactivity trend was explained by an energy decomposition analysis based on DFT calculations. 相似文献
9.
Peng Liu Yu-Long Men Xin-Yu Meng Prof. Chong Peng Yiyi Zhao Prof. Yun-Xiang Pan 《Angewandte Chemie (International ed. in English)》2023,62(38):e202309443
By supporting platinum (Pt) and cadmium sulfide (CdS) nanoparticles on indium oxide (In2O3), we fabricated a CdS/Pt/In2O3 photocatalyst. Selective photoreduction of carbon dioxide (CO2) to methane (CH4) was achieved on CdS/Pt/In2O3 with electronic Pt−In2O3 interactions, with CH4 selectivity reaching to 100 %, which is higher than that on CdS/Pt/In2O3 without electronic Pt−In2O3 interactions (71.7 %). Moreover, the enhancement effect of electronic Pt-(metal-oxide) interactions on selective photoreduction of CO2 to CH4 also occurs by using other common metal oxides, such as photocatalyst supports, including titanium oxide, gallium oxide, zinc oxide, and tungsten oxide. The electronic Pt-(metal-oxide) interactions separate photogenerated electron-hole pairs and convert CO2 into CO2δ−, which can be easily hydrogenated into CH4 via a CO2δ−→HCOO*→HCO*→CH*→CH4 path, thus boosting selective photoreduction of CO2 to CH4. This offers a new way to achieve selective photoreduction of CO2. 相似文献
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Zirconium-metal organic frameworks (Zr-MOFs) were synthesized with or without ammonium hydroxide as an additive in the synthesis process. It was found that addition of ammonium hydroxide would change the textural structure of Zr-MOF. The BET surface area, pore volume, and crystal size of Zr-MOF were reduced after addition of ammonium hydroxide. However, the crystalline structure and thermal stability were maintained and no functional groups were formed. Adsorption tests showed that Zr-MOF presented much higher CO(2) adsorption than CH(4). Zr-MOF exhibited CO(2) and CH(4) adsorption of 8.1 and 3.6 mmol/g, respectively, at 273 K, 988 kPa. The addition of ammonium hydroxide resulted in the Zr-MOF with a slight lower adsorption of CO(2) and CH(4), however, the selectivity of CO(2)/CH(4) is significantly enhanced. 相似文献
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Johan van den Bergh Weidong Zhu Freek Kapteijn Jacob A. Moulijn Kenji Yajima Kunio Nakayama Toshihiro Tomita Shuichi Yoshida 《Research on Chemical Intermediates》2008,34(5-7):467-474
The permeation of CO2 and CH4 and their binary mixtures through a DDR membrane has been investigated over a wide range of temperatures and pressures. The synthesized DDR membrane exhibits a high permeance and maintains a very high selectivity for CO2. At a total pressure of 101 kPa, the highest selectivity for CO2 in a 50∶50 feed mixture was found to be over 4000 at 225 K. This is ascribed to the higher adsorption affinity, as well as to the higher mobility for the smaller CO2 molecules in the zeolite, preventing the bypassing of the CH4 through the membrane. An engineering model, based on the generalized Maxwell-Stefan equations, has been used to interpret the transport phenomena in the membrane. The feasibility of DDR membranes as applied to CO2 removal from natural gas or biogas is anticipated. 相似文献
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Ahmed N Suresh V Shirinfar B Geronimo I Bist A Hwang IC Kim KS 《Organic & biomolecular chemistry》2012,10(10):2094-2100
Cyclo-bis-(urea-3,6-dichlorocarbazole) (1) forms a 1 : 2 complex with CH(3)CO(2)(-) and H(2)PO(4)(-) through hydrogen bonding with the two urea moieties, resulting in fluorescence enhancement via a combined photoinduced electron transfer (PET) and energy transfer mechanism. The binding mechanism involves a conformational change of the two urea receptors to a trans orientation after binding of the first anion, which facilitates the second interaction. 相似文献
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《Arabian Journal of Chemistry》2023,16(2):104454
The physico-chemical effects caused by supercritical CO2 (ScCO2) exposure is one of the leading problems for CO2 storage in deep coal seams as it will significantly alter the flow behaviors of gases. The main objective of this study was to investigate the effects of ScCO2 injection on diffusion and adsorption kinetics of CH4, CO2 and water vapor in various rank coals. The powdered coal samples were immersed in ScCO2 for 30 days using a high-pressure sealed reactor. Then, the diffusion and adsorption kinetics of CH4, CO2 and water vapor in the coals both before and after exposure were examined. Results indicate that the diffusivities of CH4 and CO2 are significantly increased due to the combined matrix swelling and solvent effect caused by ScCO2 exposure, which may induce secondary faults and remove some volatile matters that block the pore throats. On the other hand, the diffusivities of water vapor are reduced due to the elimination of surface functional groups with ScCO2 exposure. It is concluded that density of the surface function groups is the controlling factor for water vapor diffusion rather than the pore properties. The unipore model and pseudo-first-order equation can simulate the diffusion and adsorption kinetics of CH4 and CO2 very well, but the unipore model is not capable of well describing water vapor diffusion. The effective diffusivity (De), diffusion coefficient (D) and adsorption rates (k1) of CH4 and CO2 are significantly increased after ScCO2 exposure, while the values of water vapor are decreased notably. Thus, the injection of ScCO2 will efficiently improve the transport properties of CH4 and CO2 but hinder the movement of water molecules in coal seams. 相似文献
17.
《Journal of the Less Common Metals》1984,96(2):223-230
The kinetics of the pressure-induced repetitive hydriding and dehydriding of the alloy Ti1.2Mn1.8 and the related compound Ti0.98Zr0.02V0.45-Fe0.1Cr0.05Mn1.4 using hydrogen mixtures containing CO or CH4 was investigated at room temperature. The absorption rates of both alloys were slightly retarded in hydrogen containing 5 vol.% CH4, whereas the reversible storage capacities remained unchanged. However, the decrease in the absorption rate of Ti0.98Zr0.02V0.45Fe0.1Cr0.05Mn1.4 could not be explained by the lower partial pressure of hydrogen alone. Contamination of hydrogen by CO leads to passivation of both alloys after several hydriding-dehydriding cycles. If the samples are only partially passivated by CO, reactivation without any heat treatment is possible. A fully passivated sample of Ti0.98Zr0.02V0.45Fe0.1Cr0.05Mn1.4 cannot be reactivated to the initial state by means of heat treatment. 相似文献
18.
《Journal of Energy Chemistry》2014,23(4):453-460
In this paper we used MOF-5 and Cu3(BTC)2 to separate CO2/CH4 and CH4/N2 mixtures under dynamic conditions. Both materials were synthesized and pelletized, thus allowing for a meaningful characterization in view of process scale-up. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). By performing breakthrough experiments, we found that Cu3(BTC)2 separated CO2/CH4 slightly better than MOF-5. Because the crystal structure of Cu3(BTC)2 includes unsaturated accessible metal sites formed via dehydration, it predominantly interacted with CO2 molecules and more easily captured them. Conversely, MOF-5 with a suitable pore size separated CH4/N2 more efficiently in our breakthrough test. 相似文献
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Solvent-free Synthesis of Tetramethylammonium Salts: Synthesis and Characterization of [N(CH3)4]2[C2O4], [N(CH3)4][CO3CH3], [N(CH3)4][NO2], [N(CH3)4][CO2H], and [N(CH3)4][O2C(CH2)2CO2CH3] A general procedure to synthesize tetramethylammonium salts is presented. Several tetramethylammonium salts were prepared in a crystalline state by solvent-free reaction of trimethylamine and different methyl compounds at mild conditions: [N(CH3)4]2[C2O4] (cubic; a = 1 114.8(3) pm), [N(CH3)4][CO3CH3] (P21/n; a = 813.64(3), b = 953.36(3), c = 1 131.3(4) pm, β = 90.03(1)°), [N(CH3)4][NO2] (Pmmn; a = 821.2(4), b = 746.5(3), c = 551.5(2) pm), [N(CH3)4][CO2H] (Pmmn; a = 792.8(7), b = 791.7(3), c = 563.3(4) pm) and [N(CH3)4][O2C(CH2)2CO2CH3] (P21; a = 731.1(2), b = 826.4(3), c = 1 025.2(3) pm, β = 110.1(1)°). The tetramethylammonium salts were characterized by IR-spectroscopy and X-ray diffraction. The crystal structures of the methylcarbonate and the nitrite are described. 相似文献
20.
An ionic porous coordination framework exhibiting high CO2 affinity and CO2/CH4 selectivity 总被引:1,自引:0,他引:1
An ionic porous coordination polymer possessing partially exposed uncoordinated nitrogens exhibits strong interaction with CO(2) and high CO(2)/CH(4) selectivity, and the adsorption mechanism is illustrated by the structure of its CO(2)-loaded single-crystal. 相似文献