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1.
Capture of CO2 from flue gases produced by the combustion of fossil fuels and biomass in air is referred to as post-combustion capture. Chemisorbent processes are considered to be the most feasible method and are already at an advanced stage of development, but gas separation membranes are attracting more and more attention as a possible alternative. This paper describes a detailed parametric study of mass and energy balances for a simulated single membrane process. Typical operating conditions (CO2 concentration in the flue gas, pressure and temperature, etc.) together with the influence of the membrane quality (permeability, selectivity) and membrane area on membrane performance (CO2 separation degree and CO2 purity) are simulated over a wide range of parameters.  相似文献   

2.
An ab initio molecular potential model is employed in this paper to show its excellent predictability for the transport properties of a polyatomic gas from molecular dynamics simulations. A quantum mechanical treatment of molecular vibrational energies is included in the Green and Kubo integral formulas for the calculation of the thermal conductivity by the Metropolis Monte Carlo method. Using CO2 gas as an example, the fluid transport properties in the temperature range of 300–1000 K are calculated without using any experimental data. The accuracy of the calculated transport properties is significantly improved by the present model, especially for the thermal conductivity. The average deviations of the calculated results from the experimental data for self-diffusion coefficient, shear viscosity, thermal conductivity are, respectively, 2.32%, 0.71% and 2.30%.  相似文献   

3.
The aim of present project was to develop a microcosm experimental method for estimation of NOx and CO2 emission of microbial origin from cultivated soil. The effect of different factors (such as temperature, water supply, mineral-N source and organic matter addition, role of soil organisms and heavy metal contamination) that controlling the accumulation of N2O and CO2 in soil atmosphere and release to air was studied in closed microcosm laboratory model experiments. The headspace gas composition of closed glass vessels of 800-1200 cm3 containing 100-200 g brown forest soil sample was analysed. The N2O and CO2 concentration of gas samples was analysed by gas chromatographic methods and NO-content by means of chemiluminescent detection. Concerning the results, it can be stated that the applied microcosm experimental model proved to be a suitable tool for detecting the effect of factors influencing the NOx and CO2 release from agricultural soil. The temporal changes of N2O and CO2 concentration demonstrated the impact of the coupled microbial processes resulting in these greenhouse gases. The gas production depended on the soil moisture level, temperature and C/N ratio significantly. The inhibitory effect of toxic heavy metals (e.g. Cd) could also be affected by the C/N ratio. The appearance of NO as an intermediate of microbial processes was observed as well.  相似文献   

4.
We reported that the phase conversion of the micelles in aqueous solution prepared by sodium oleate (NaOA) and 3-(diethylamino)-propylamine (DEAPA) in the presence of carbon dioxide. This micellar structure is very sensitive to CO2 and the pH value of the solution is continuously reduced with the continuous introduction of carbon dioxide. When pH?>?10.2, the mixed solution of NaOA and DEAPA is mainly in the form of spherical micelles; when the 10.2?>?pH?>?9.6, the mixed solution mainly in the worm-like micelles (WLM), where the solution has a significant viscosity change; when the 9.6?>?pH?>?9.1, the NaOA and DEAPA mixed solution becomes the aqueous two-phase system (ATPS), which is composed of two layers, the upper layer is the vesicle structure and the lower layer is the WLM structure; when the pH between 9.1?>?pH?>?9.0, NaOA and DEAPA mixed solution form vesicles, thus realizing the regulation of CO2 on the micellar structure transition of NaOA and DEAPA mixed solution. Such these microstructures transition could be confirmed by Rheology measurement, DLS and Cryo-TEM.  相似文献   

5.
A four-armed anionic star-shaped block polymer, containing an anionic polymer poly(2-Acrylamido-2-methylpropanesulfonic acid) (PAMPS) as the core group and poly(2-(Dimethylamino)ethyl methacrylate) (PDM) as the terminal group, was synthesized by using the Atom Transfer Radical Polymerization (ATRP) method. The (PAMPS50-PDM50)4 aqueous solution exhibited both polyelectrolyte and hydrophobic associative characteristics, that is, a low concentration of NaCl results in decreasing viscosity but a high concentration of NaCl results in increasing viscosity. The four-armed anionic block polymer shows a CO2-reversible property at high concentrations of brine. Viscosity, pH, and ζ potential demonstrate the switchability jointly; the values could be switched from relatively low to high cyclically. These transitions could actually be attributed to the protonation of tertiary amine groups in PDM blocks, and the mechanism was proved by 1H NMR.  相似文献   

6.
采用沉淀法将ZIF-67负载到CeO2上,制备了具有多重活性位点的非均相催化剂ZIF-67/CeO2,并研究其催化CO2和甲醇直接反应生成碳酸二甲酯(DMC)的性能。采用X射线衍射、N2吸附-脱附、傅里叶变换红外光谱和X射线光电子能谱研究了ZIF-67/CeO2的各种理化性质。结果表明,ZIF-67的引入使ZIF-67/CeO2催化剂产生更多的氧空位。在考察的ZIF-67/CeO2系列催化剂中,0.3-ZIF-67/CeO2(0.3为Co、Ce物质的量之比)在具有高的比表面积的同时还能保持介孔结构,具有丰富的酸碱位点,并且具有较高的CO2吸附容量,表现出最好的催化性能。在反应温度为140℃、压力为4.5 MPa的条件下反应4 h,DMC收率可达到3.79 mmolDMC·gcat-1。  相似文献   

7.
采用沉淀法将ZIF-67负载到CeO2上,制备了具有多重活性位点的非均相催化剂ZIF-67/CeO2,并研究其催化CO2和甲醇直接反应生成碳酸二甲酯(DMC)的性能。采用 X 射线衍射、N2吸附-脱附、傅里叶变换红外光谱和 X 射线光电子能谱研究了ZIF-67/CeO2的各种理化性质。结果表明,ZIF-67的引入使ZIF-67/CeO2催化剂产生更多的氧空位。在考察的ZIF-67/CeO2系列催化剂中,0.3-ZIF-67/CeO2(0.3为Co、Ce物质的量之比)在具有高的比表面积的同时还能保持介孔结构,具有丰富的酸碱位点,并且具有较高的CO2吸附容量,表现出最好的催化性能。在反应温度为140℃、压力为4.5 MPa的条件下反应4 h,DMC收率可达到3.79 mmolDMC·gcat-1。  相似文献   

8.
In this work a series of solid sorbents were synthesized by immobilizing liquid amines on the surface of a mesoporous alumina. The samples were chemically characterized and BET surface areas calculated from the N2 adsorption isotherms at 77 K. The CO2 capture performance of the sorbents and their thermal stability was studied by thermogravimetric methods. The effect of amine loading on the CO2 capture performance of the prepared sorbents was also evaluated. Analysis of TG-DTG curves showed that thermal stabilization of the amines is significantly improved by immobilizing them on an inorganic support. Temperature-programmed CO2 adsorption tests from 298 K up to 373 K at atmospheric pressure, proved to be a useful technique for assessing the capacity of sorbents for CO2 capture. Alumina impregnated with diethylenetriamine presented the highest CO2 adsorption capacities throughout the tested temperature range.  相似文献   

9.
Integrally skinned asymmetric polysulfone membranes were prepared from originally dense films inducing asymmetry by the formation of the porous layer adding to one side of the membranes chloroform and supercritical CO2 (SCCO2), and then allowing the SCCO2 expansion to occur. The influence of the chloroform/polysulfone mass ratio (g CH3Cl/g PSF), SCCO2 density and depressurization rate over the thickness of both the porous and the dense skin layers, the morphology of the porous support and the pure O2 and N2 permeability and selectivity performance were studied.The results show that it is possible to induce a very-controlled asymmetry in a dense film following the procedure described in this work and as expected, the thickness of the porous layer increases while the dense skin layer decreases as the chloroform/polysulfone mass ratio increases. Images of the porous layer show that the average-pore size decreases at high SCCO2 densities and slightly decreases with increasing the CO2 depressurization rates. The O2 and N2 permeability coefficients, measured at 35 °C and 2 bar, for the polysulfone asymmetric membranes are practically the same of those determined in dense films, suggesting that the dense skins are essentially defect-free of pinholes.  相似文献   

10.
We prepared a CO2/N2-switchable pseudogemini surfactant system composed of sodium oleate (NaOA) and N, N, N’, N’-tetramethyl-1, 6-hexanediamine (TMHDA) at a mole ratio of 2:1. The two tertiary amine groups of the TMHDA can be protonated into quaternary ammonium salt when the system was bubbled with CO2, which can ‘‘bridge’’ two NaOA molecules via electrostatic attraction to form a pseudogemini surfactant. The formed pseudogemini surfactant can further self-assemble to wormlike micelles, causing a sharp increase in viscosity. The viscoelastic property and structure transitions of the pseudogemini surfactant system were investigated before and after bubbling of CO2. The pseudogemini surfactant system transformed from water-like to gel-like fluid with the bubbling of CO2, followed by white precipitate. The cryo-transmission electron microscope (cryo-TEM) characterization and rheological measurements exhibited that the sol–gel transition was attributed to a spherical-wormlike micelle transition. Moreover, this transition was switchable at least in three cycles. Finally, a reasonable mechanism of aggregate behavior transition was proposed from the viewpoint of the molecular states, micelle structures, and intermolecular interactions.  相似文献   

11.
To reveal the nature of CO2 reduction to formate with high efficiency by in situ hydrogen produced from hydrothermal reactions with iron, DFT calculations were used. A reaction pathway was proposed in which the formate was produced through the key intermediate species, namely iron hydride, produced in situ in the process of hydrogen gas production. In the in situ hydrogenation of CO2, the charge of H in the iron hydride was −0.135, and the Fe–H bond distance was approximately 1.537 Å. A C-H bond was formed as a transition state during the attack of Hδ− on Cδ+. Finally, a HCOO species was formed. The distance of the C-H bond was 1.107 Å. The calculated free energy barrier was 16.43 kcal/mol. This study may provide new insight into CO2 reduction to formate in hydrothermal reactions with metal.  相似文献   

12.
The permeability values of “TN” organomineral nanofiltration membranes to water, L, and to supercritical CO2, G, were compared. The resulting values for G were an order of magnitude higher than for L. The difference may be directly related to the viscosity difference between the two fluids. Temperature- and pressure-related variations in G were also analyzed; for this purpose, Poiseuille's model satisfactorily accounts for experimental behavior, while Knudsen's model is unsuitable. A hysteresis effect was observed on the isotherms corresponding to variations in G versus pressure, suggesting partially irreversible CO2 adsorption on the micropore walls, that would diminish the radius. This phenomenon could be enhanced by an increased fluid density and viscosity.  相似文献   

13.
以碳酸丙烯酯(PrC)为溶剂,高氯酸四丁基胺(TBAP)为电解质,利用电化学及红外光谱电化学开展了金电极上二氧化碳的还原研究。运用现场红外光谱跟踪电化学还原过程反应物及产物的生成和消失。红外光谱电化学循环伏吸法表明,在消耗CO2的同时,金电极上有CO的产生,且伴随有碳酸根的形成。结合电化学和光谱电化学结果,提出了一种电还原机理:在非水介质中,CO2电还原过程中生成了中间体CO2.-,随后CO2.-分别以两个途径进行还原,其一是直接被还原成CO,其二是与CO2结合生成C2O4.-而后歧化成CO以及CO32-。两个反应同时进行,且第一个反应是可逆过程。  相似文献   

14.
In this work we investigate the performance of high flux chemical vapour deposition (CVD) silica membranes for the separation of gas mixtures containing H2 and CO2 at various temperatures. The membranes were prepared by a counter diffusion CVD method where tetraethyl orthosilicate (TEOS) and O2 were used as reactants. Single gas permeation resulted in activated transport for the smaller kinetic diameter gases (H2 and He) whilst the larger kinetic diameter gases (CO2 and N2) showed negative activation energy. The single gas permeation of H2 increased from 5.1 × 10−7 to 7.0 × 10−7 mol m−2 s−1 Pa−1 in the temperature range 100–400 °C, and H2/CO2 and H2/N2 selectivities reached 36 and 57 at 400 °C, respectively. The H2 purity in the permeate stream also increased with temperature for H2:CO2 binary gas mixture, thus being beneficial for H2 diffusion. H2 competitively permeated through the membrane at a several range of gas mixtures, and a saturation level was achieved at H2:CO2 60:40 feed concentration, where the diffusion of CO2 molecules became negligible delivering ∼99% H2 purity in the permeate stream. These results substantiate that the counter diffusion CVD method produced thin silica film membranes with a very precise pore size control, in particular suggesting a narrow pore distribution with average pore radius of about 3.1 Å.  相似文献   

15.
The synthesis of cyclic carbonates by the reaction of oxiranes and carbon dioxide in the presence of catalytic amount of tetrabutylammonium bromide in dimethylcarbonate without any metal catalyst is reported. Significant rate acceleration in the reaction is observed in dimethylcarbonate as compared to the other solvents. Under the reaction conditions of 100 °C and 2.1 MPa in dimethyl carbonate, maximum conversion and selectivity is achieved. The dimethylcarbonate containing tetrabutylammonium bromide catalyst can be easily recovered and reused for at least six recycles with the same selectivity.  相似文献   

16.
Solid, polymer membranes fabricated from room-temperature ionic liquid monomers containing oligo(ethylene glycol) or nitrile-terminated alkyl substituents tethered to imidazolium cations were found to exhibit ideal CO2/N2 and CO2/CH4 separation factors significantly greater than those with comparable length n-alkyl substituents, with similar CO2 permeability. Polymers containing these functional groups exhibited CO2/N2 gas separation performance exceeding the “upper bound” of a “Robeson Plot”.  相似文献   

17.
The use of membranes for on-line separations in flow-through dialyser as a part of a flow system is extremely useful for automated samples preparation. In this paper a method to couple the dialysis and the UV detection on-line of Vitamin B12 from milk is proposed. Firstly, the milk samples were pre-treated with trichloroacetic and centrifuged (to eliminate proteins and fats) and later, using a dialyser coupled a flow-continuous manifold was possible dialyse the Vitamin B12, which was monitored spectrophotometrically at 361 nm. On the other hand, the milk samples were also dialysed on-line but without the acid treatment and the results were compared. The influence of various parameters, including the pump speed for both the donor and acceptor stream, dialysis time, donor and acceptor loop volume on dialysis efficiency was studied. The method was applied to different kinds of milk (skimmed and semi-skimmed milk, evaporated milk, lactose free milk and liquid and powder whole milk). The relative standard deviation (R.S.D.) of the proposed method was of 0.45% and the obtained dialysis percentage was of 5.8%. The proposed method very easy permit a pre-treatment of the sample, quick and on-line with the detection. The dialysis process permitted the pass of vitamin and avoided the pass of other analytes as proteins in the case of the milk samples without acid treatment.  相似文献   

18.
The alarming levels of carbon dioxide (CO2) are an environmental problem that affects the economic growth of the world. CO2 emissions represent penalties and restrictions due to the high carbon footprint. Therefore, sustainable strategies are required to reduce the negative impact that occurs. Among the potential systems for CO2 capture are microalgae. These are defined as photosynthetic microorganisms that use CO2 and sunlight to obtain oxygen (O2) and generate value-added products such as biofuels, among others. Despite the advantages that microalgae may present, there are still technical–economic challenges that limit industrial-scale commercialization and the use of biomass in the production of added-value compounds. Therefore, this study reviews the current state of research on CO2 capture with microalgae, for which bibliometric analysis was used to establish the trends of the subject in terms of scientometric parameters. Technological advances in the use of microalgal biomass were also identified. Additionally, it was possible to establish the different cooperation networks between countries, which showed interactions in the search to reduce CO2 concentrations through microalgae.  相似文献   

19.
A new cadmium complex, [Cd2(dcpa)·2H2O]n·H2O (1), has been synthesized by hydrothermal reaction based on the multiple acid ligand 4-(2,5-dicarboxyphenoxy)phthalic acid (H4dcpa). Single crystal X-ray diffraction analysis reveals that 1 is a three-dimensional structure with pores. The fluorescence test results show that the complex has excellent blue fluorescence. The adsorption of nitrogen and carbon dioxide gas test results show that the complex has adsorption effects on carbon dioxide.  相似文献   

20.
Although zeolites such as NaY and 13X adsorb CO2 much more than CO, the adsorption amount of CO2 and CO can be reversed if the zeolites are modified with CuCl. When zeolite NaY or 13X is mixed with CuCl and heated, high CO adsorption selectivity and capacity can be obtained. Isotherms show the adsorbents have CO capacity much higher than CO2. This is because CuCl has dispersed onto the surface of the zeolites to form a monolayer after the heat treatment and the monolayer dispersed CuCl can provide tremendous Cu(I) to selective adsorb CO and inhibit the CO2 adsorption. The monolayer dispersion of CuCl is confirmed by XRD and EXAFS studies. The loading of CuCl on the zeolites has a threshold below which the CuCl forms monolayer after heating and crystalline phase of CuCl can not be detected by XRD. An adsorbent of CuCl/NaY with CuCl content closed to the monolayer capacity shows very high CO selective adsorbability for CO2, N2, H2 and CH4. At temperature higher than room temperature, the adsorbent has even better CO selectivity for CO2. Using the adsorbent, a single-stage 4 beds PSA process, working at 70°C and 0.4 MPa to 0.013 MPa, can obtain CO product with purity >99.5% and yield >85%.  相似文献   

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