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1.
MER型沸石在吸附分离CO 2/CH 4方面展现出良好的工业应用前景,受到广泛关注,但还缺乏理论基础数据。本文采用巨正则蒙特卡洛(GCMC)模拟方法,以全硅MER型沸石作为对照,模拟分析了CO 2/CH 4在Na +、K +、Cs +和Ca 2+交换的MER型沸石中的吸附分离行为。结果表明:不同阳离子交换的MER型沸石对CO 2和CH 4的吸附符合Langmuir-Freundlich吸附等温线模型,平衡吸附量的大小顺序为:Ca-MER>Na-MER>K-MER>Cs-MER,与沸石的自由体积和比表面积大小顺序一致,且近似成线性关系,选用高价阳离子MER型沸石可以提高吸附量;CO 2和CH 4主要分布在沸石的pau笼中,在d8R笼和ste笼中也有少量分布;骨架外阳离子与CO 2的强吸附作用和独特的八元环窗口孔径是MER型沸石对CO 2/CH 4混合组分表现出超高吸附选择性的原因,吸附选择性高达1000以上。综合吸附量、吸附热和吸附选择性分析指出,Na-MER和K-MER型沸石是优良的CO 2吸附剂。本研究为MER型沸石吸附分离CO 2/CH 4提供了理论依据和实验指导。 相似文献
2.
利用嫁接法和浸渍法分别在以1,3,5-三苯基苯为单体的有机多孔聚合物( nTPB)上成功掺杂乙二胺,分别研究了乙二胺的不同掺杂模式对多孔聚合物的结构性质以及CO 2吸附性能的影响。结果表明,嫁接法和浸渍法皆可在 nTPB上均匀掺杂乙二胺,且 nTPB的比表面积和孔容均有所下降。在乙二胺掺杂量相同的前提下,由于浸渍法完全利用 nTPB的孔道吸收乙二胺, nTPB的孔道堵塞更明显。两种掺杂乙二胺的模式均可显著提升 nTPB对CO 2的吸附选择性,但只有嫁接法对 nTPB的CO 2吸附量有明显促进(从4.4 mmol/g升高为5.2 mmol/g;0℃,10 5 Pa);浸渍法由于过度堵塞 nTPB孔道,且乙二胺的吸附位点被包埋,导致CO 2的吸附量反而下降(仅有3.4 mmol/g;0℃,10 5 Pa)。此外,嫁接法掺杂乙二胺的 nTPB表现出与 nTPB基质相同的良好重复利用性。 相似文献
3.
Solubility data of carbon dioxide (CO 2) (1) in methanol (2), 1-octyl-3-methylimidazolium bis(trifluoro- methylsulfonyl)imide ([omim] +[Tf 2N] -) (3), and their mixtures (w 3 0.2, 0.5, and 0.8) at temperatures 313.2 and 333.2 K and pressures up to 7.0 MPa were measured by a high-pressure view-cell technique. The solubility of CO 2 in methanol (w 3=0), [omim] +[Tf 2N] - (w 3=1.0) and their mixtures follows the order of (w 3=0)<(w 3=0.2)< (w 3=0.5)<(w 3=0.8)<(w 3=1.0) at the same temperature and pressure, while the magnitude of Henry's constants follows the reverse order at a given temperature, which is consistent with the COSMO-RS (conductor-like screening for real solvents) calculation. The solubility data of CO 2 in methanol and [omim] +[Tf 2N] - are correlated with the Peng-Robinson equation of state, and the solubility of CO 2 in the mixtures of methanol and [omim] +[Tf 2N] - can be well predicted based on the mole fraction average of methanol and [omim] +[Tf 2N] - over the solubility of CO 2 in pure methanol and [omim] +[Tf 2N] -. The mixtures of methanol and [omim] +[Tf2N] - may be used as physical solvents for capturing CO 2 with high partial pressures since they combine the advantages of organic solvents and ionic liquids. 相似文献
4.
In this study solid-state NMR spectroscopy was used to identify structure and guest distribution of the mixed N 2 + CO 2 hydrates. These results show that it is possible to recover CO 2 from flue gas by forming a mixed hydrate that removes CO 2 preferentially from CO 2/N 2 gas mixture. Hydrate phase equilibria for the ternary CO 2–N 2–water system in silica gel pores were measured, which show that the three-phase H–L w–V equilibrium curves were shifted to higher pressures at a specific temperature when the concentration of CO 2 in the vapor phase decreased. 13C cross-polarization (CP) NMR spectra of the mixed hydrates at gas compositions of more than 10 mol% CO 2 with the balance N 2 identified that the crystal structure of mixed hydrates as structure I, and that the CO 2 molecules occupy mainly the abundant 5 126 2 cages. This makes it possible to achieve concentrations of more than 96 mol% CO 2 gas in the product after three cycles of hydrate formation and dissociation. 相似文献
5.
在模拟燃煤热烟气为热源和介质条件下,以准东褐煤为原料,通过一维沉降炉进行炭化活化(一步法)制备粉状活性焦,考察了活性焦对Hg 0的吸附能力,探索了SO 2、H 2O、O 2、CO 2、H 2O+O 2、SO 2+O 2及H 2O+SO 2+O 2气氛对活性焦吸附Hg 0的影响机理。结果表明:一步法获得的活性焦对Hg 0具有较高的吸附性能。N 2气氛作对比,H 2O、H 2O+O 2、CO 2和SO 2气氛下抑制活性焦对Hg 0的吸附;O 2、SO 2+O 2和H 2O+SO 2+O 2促进活性焦对Hg 0的吸附。通过Hg 4f的XPS分析证明了不同气氛组成对活性焦吸附Hg 0的抑制和促进机理。H 2O覆盖在活性焦活性位上和堵塞孔隙而抑制活性焦对Hg 0的吸附;SO 2与Hg 0在活性焦上发生竞争吸附而抑制对Hg 0的吸附;CO 2 吸附在活性焦微孔上而抑制对Hg 0的吸附;O 2气氛下主要形成了HgO, SO 2+O 2气氛下Hg 0被氧化成HgSO 3,进一步氧化成HgSO 4; H 2O+SO 2+O 2气氛下,Hg 0被氧化成HgO和HgSO 4。 相似文献
6.
一氧化碳/二氧化碳(CO/CO 2)转化利用是碳一化学与CO 2捕集利用中的重要环节,也是当今碳资源的非石油路线利用最具挑战性的方向之一。CO 2的高效活化与定向转化是CO 2利用过程中的关键问题,而CO加氢转化最大的瓶颈问题为如何有效控制C-O键的活化、C—C键的形成、碳链增长及终止。本文主要综述 CO/CO 2加氢高选择性合成重要化工原料低碳烯烃(C 2 =~C 4 =)以及一步高效合成汽油馏分(C 5~C 11)等方面取得的突破性进展。目前,CO/CO 2加氢主要经过费托合成与氧化物/分子筛双功能两条路线合成低碳烯烃与汽油燃料。针对费托合成C 2 =~C 4 =,分析表明棱柱状碳化钴得到的烃类产物分布可以显著突破Anderson-Schulz-Flory(ASF)分布的限制,而分子筛已被广泛用于构建双功能费托催化剂,由于酸性分子筛具有加氢裂化、低聚与异构化等功能,使得CO/CO 2还可以直接高选择性地转化为C 5~C 11烃类。另一方面,将可以活化CO或CO 2到甲醇的可还原型氧化物与具有C—C偶联功能的SAPO-34或HZSM-5分子筛进行耦合,也可以实现CO/CO 2加氢一步合成低碳烯烃或汽油且具有非常优异的选择性和高转化率。今后,借鉴纳米合成领域新方法,使产物分布打破经典ASF限制,最大限度地提高目标烃类化合物的选择性并显著减少甲烷的生成是研究关键。 相似文献
7.
采用溶胶-凝胶法以铜、锌、锆硝酸盐和柠檬酸为原料,改变柠檬酸用量,制备出一系列Cu-ZnO-ZrO 2催化剂。通过X射线衍射仪(XRD)、热重分析仪(TG-DTG-DTA)、H 2程序升温还原(H 2-TPR)、CO 2程序升温脱附(CO 2-TPD)、红外光谱仪(FTIR)及BET比表面积等表征手段对干凝胶及催化剂理化性能进行测试,并在催化反应活性评价装置上对催化剂的CO 2加氢合成甲醇反应活性进行评价,研究凝胶过程中Cu 2+、Zn 2+、Zr 4+与柠檬酸结合方式对催化剂性能的影响。结果表明:改变柠檬酸用量可调控Cu 2+、Zn 2+、Zr 4+与羧酸的配位方式,配位能力较强的Cu 2+、Zn 2+在凝胶制备过程中参与三维网络的构筑,而配位能力相对较弱的Zr 4+游离于三维网络之外,从而差异化地调控催化剂中活性组分CuO、ZnO、ZrO 2晶粒尺寸大小。当柠檬酸的摩尔量为金属离子摩尔量的1.5倍时,催化剂中的活性成分CuO、ZnO、ZrO 2晶粒尺寸相互匹配,表现出较好的CO 2加氢合成甲醇催化性能。 相似文献
8.
以淀粉糖(主要成分为葡萄糖)为碳前体,制备了一系列多孔碳材料(C-GLCs-800),对其进行孔隙结构分析,并应用FT-IR、SEM、TGA对其进行了表征,测定了材料在288、298和308 K下的CO 2和CH 4吸附等温线,根据IAST理论预测了材料对CO 2/CH 4二元体系的吸附选择性。实验结果显示,活化条件对材料的孔隙结构有明显影响,随着KOH/C质量比的增加,所制备的C-GLCs-800比表面积和总孔容先增加后降低。其中C-GLC-800-4的BET比表面积高达3153 m 2·g -1,总孔容为2.056 cm 3·g -1。C-GLC-800-2的窄微孔(V d<1 nm,孔容0.3538 cm 3·g -1)含量最高,为30.63%。C-GLC-800-2在298 K和10 5 Pa下对CO 2吸附量高达3.96 mmol·g -1,明显高于许多传统吸附材料和MOFs材料在相同条件下对CO 2的吸附容量。应用Clausiuse-Clapeyron方程计算了CO 2和CH 4在材料上的吸附热,应用IAST理论计算了CO 2/CH 4的吸附选择性,结果显示C-GLC-800-2对CO 2/CH 4的吸附选择性为8.35。 相似文献
9.
The exhaust gases, including SO_2,NH_3, H_2S, NO_2, NO, and CO, are principal air pollutants due to their severe harms to the ecological environment.Zeolites have been considered as good absorbent candidates to capture the six exhaust gases.In this work, we performed grand canonical ensemble Monte Carlo(GCMC) simulations to examine the capability of 95 kinds of all-silica zeolites in the removal of the six toxic gases, and to predict the adsorption isotherms of the six gases on all the zeolites.The simulation results showed that, H_2S, NO, NO_2, CO and NH_3 are well-captured by zeolite structures with accessible surface area of 1600–1800 m~2·g~(-1) and pore diameter of 0.6–0.7 nm, such as AFY and PAU, while SO_2 is well-adsorbed by zeolites containing larger accessible surface area(1700–2700 m~2·g~(-1)) and pore diameter(0.7–1.4 nm) at room temperature and an atmospheric pressure.However, at saturated adsorption, zeolites RWY, IRR, JSR, TSC, and ITT are found to exhibit better abilities to capture these gases.Our study provides useful computational insights in choosing and designing zeolite structures with high performance to remove toxic gases for air purification, thereby facilitating the development and application of exhaust gas-processing technology in green industry. 相似文献
10.
Carbon dioxide is a greenhouse gas that is believed to be a major contributor to global warming. Studies have shown that significant amounts of CO 2 are released into the atmosphere as a result of fossil fuels combustion. Therefore, considerable interest exists in effective and economical technologies for the removal of CO 2 from fossil fuel combustion gas streams. This work evaluated the use of autotrophic microbes for the removal of CO 2 from coal fired power plant combustion gas streams. The CO 2 removal rates of the following autotrophic microbes were determined: Chlorella pyrenoidosa, Euglena gracilis, Thiobacillus ferrooxidans, Aphanocapsa delicatissima, Isochrysis galbana, Phaodactylum tricornutum, Navicula tripunctata schizonemoids, Gomphonema parvulum, Surirella ovata ovata, and four algal consortia. Of those tested, Chlorella pyrenoidosa exhibited the highest removal rate with 2.6 g CO 2 per day per g dry weight of biomass being removed under optimized conditions. Extrapolation of these data indicated that to remove CO 2 from the combustion gases of a coal fired power plant burning 2.4 × 10 4 metric tons of coal per day would require a bioreactor 386 km 2 × 1 m deep and would result in the production of 2.13 × 10 5 metric tons (wet weight) of biomass per day. Based on these calculations, it was concluded that autotrophic CO 2 removal would not be feasible at most locations, and as a result, alternate technologies for CO 2 removal should be explored. 相似文献
11.
采用密度泛函理论研究金属离子(La~(3+),Ce~(3+),Y~(3+),Ga~(3+),Cr~(3+),Zn~(2+),Cu~(2+))改性Y型分子筛的水热化学。结果表明,金属离子取代Y型分子筛骨架Al的能力较弱,以M(OH)(Z-1)+形式存在的金属离子能够进入分子筛β笼,且更倾向定位于β笼Ⅰ'位,增强分子筛Al和相邻骨架O原子之间的作用力,提高分子筛的结构稳定性。探讨制备金属离子改性Y型分子筛应考虑金属离子性能和金属离子与分子筛骨架元素的作用。 相似文献
12.
以超临界CO 2为发泡剂,采用间歇发泡法制备了聚醚砜(PES)泡沫。采用旋转流变仪和扫描电子显微镜分析表征了PES发泡的均相成核行为,继而分别以滑石粉和二氧化硅(SiO 2)作为异相成核剂,探究了PES发泡过程中的异相成核行为。结果表明,间歇发泡法制备PES泡沫的发泡区间为200~230 ℃;最佳浸泡压力为20 MPa;最佳浸泡时间为3 h;未改性PES的泡孔直径均可在10 μm以下,泡孔密度在10 9~10 10 个/cm 3之间,但泡孔壁较厚;SiO 2相对于Talc,表现出更显著的异相成核作用;在210 ℃、3 h、20 MPa的发泡条件下,添加0.9 %(质量分数,下同)的SiO 2,可得到泡孔直径为0.77 μm,泡孔密度为7.14×10 11 个/cm 3的PES微孔泡沫。 相似文献
13.
The zeolites with MEL structure were synthesized via the hydrothermal method and the zeolites-supported catalysts, such as Cu 2+, Ga 3+, Co 3+, Ce 2+ and VO 2+/zeolites, were prepared by the incipient wetness impregnation. The structures of the synthesized zeolites were characterized by techniques of XRD, FT-IR, SIMS, 29Si and 27Al MAS NMR. The selective catalytic reduction (SCR) of NO by ammonia was carried out with a glass reactor under a downstream flow. The synthesized TS-2 showed no significant DeNO x activity, instead of catalyzing the ammonia oxidation at a high temperature. Furthermore, the catalytic activity of TS2 zeolite can be effectively modified and tuned up through incorporating second metal ion such as Fe 3+, Co 3+, and Al 3+ into the framework (i.e., [Fe,Ti]Z11, [Co,Ti]Z11, and [Al,Ti]Z11). Among the synthesized bimetallosilicates, the [Fe,Ti]Z11 zeolite is the most active catalyst for the SCR DeNO x with ammonia; the NO conversion and the N 2 yield reach around 80%. In addition, impregnating the metal ions on TS2 or bimetallosilicates is also a very effective way to improve the SCR DeNO x activity. Ga 3+/[Fe40,Ti40]Z11 and Co 3+/[Fe40,Ti40]Z11 are the most active catalysts and show a potential for the practical applications. 相似文献
14.
CO 2的捕获和分离具有重要的工业和环境意义。采用溶剂热法,以羧基和路易斯碱位点功能修饰的配体和锌离子构筑了阴离子型金属有机框架材料{[Zn 2(N)·(DMF) 3·(CH 3) 2NH 2]·(DMF) 2} n (NEM-7-Zn)。为了提高骨架的稳定性,通过金属离子置换工艺,将NEM-7-Zn转化为高稳定性的铜基框架材料NEM-7-Cu。采用EA、PXRD、TGA及比表面积分析等技术对多孔材料进行综合表征,并测定了NEM-7-Cu对二氧化碳、乙炔和甲烷单组分气体的吸附等温线。实验结果表明,NEM-7-Cu不仅具有较高的CO 2 吸附性能(74 cm 3·g -1),更表现出优异的CO 2/CH 4(11.5)和C 2H 2/CH 4(7.1)吸附选择性。通过巨正则Monte Carlo方法(GCMC)计算得到CO 2在NEM-7-Cu中的主要吸附位点为功能基团羧基与路易斯碱位点附近以及Cu的金属团簇附近。 相似文献
15.
基于化学活性颗粒强化气液吸收机理,建立了磷石膏悬浮液强化氨法烟气CO 2捕集模型。以液膜内量纲一传质距离λ *为特征参数,增强因子E=1/λ *+qβλ */2。用恒温反应器在不同搅拌转速及磷石膏颗粒固含量下实验测定CO 2吸收增强因子对模型进行检验,结果表明:随颗粒固含量由5%增加到30%(质量分数),增强因子由1.69增加到2.10;而随搅拌转速从150 r·min -1增加到300 r·min -1,增强因子仅由1.75略增到1.80,表明磷石膏颗粒固含量及溶解速率是影响增强因子的控制性因素。实验结果与模型预测值吻合良好, 偏差小于10%。 相似文献
16.
Cu 2+ ion-exchanged pillared clays are substantially more active than Cu 2+-ZSM-5 for selective catalytic reduction (SCR) of NO by hydrocarbons. More importantly, H 2O (or SO 2) has only mild effects on their activities. First results on Cu 2+-exchanged TiO 2-pillared montmorillonite were reported by this laboratory (Yang and Li, Ref. [1]), that showed overall activities two to four times higher than Cu 2+-ZSM-5. A delaminated pillared clay was subjected to Cu2+ ion-exchange and studied for SCR by C2H4 in this work. The Cu2+ ion-exchanged delaminated Al2O3-pillared clay yielded substantially higher SCR rates than both Cu2+-exchanged TiO2-pillared clay and Cu2+-ZSM-5 at temperatures above 400°C. The peak NO conversion was 90% at 550°C and at a space velocity of 15,000 h−1 (with O2 = 2%). The peak temperature decreased as the concentration of O2 was increased. The macroporosity in the delaminated pillared clay was partially responsible for its higher peak temperatures (than that for laminated pillared clays). At 1000 ppm each for NO and C2H4, the NO conversion peaked at 2% O2 for all temperatures. H2O and SO2 caused only mild deactivation, likely due to competitive adsorption (of SO2 on Cu2+ sites and H2O on acid sites). The high activity of Cu2+-exchanged Al2O3-pillared clay was due to a unique combination of the redox property of the Cu2+ sites and the strong Lewis acidity of the pillared clay. The suggested mechanism involved NO chemisorption (in the presence of O2) on Cu2+OAl3+-on the pillars, and C2H4 activation on the Lewis acid sites to form an oxygenated species. 相似文献
17.
The Potts Monte Carlo simulation was used to simulate microstructural evolution in uranium dioxide fuel rods. During service, grain growth, pore migration, and thermal segregation of the pores and UO 2 occur in the rods in a thermal gradient. In this investigation, we developed a model which simulates simultaneous grain growth, pore migration, and thermal segregation of the pores and UO 2 in a temperature gradient. Grain growth in a thermal gradient was simulated using the Monte Carlo Potts model technique developed by Anderson, Srolovitz, and co-workers. Pore migration was simulated using conserved dynamics with minimum-energy exchanges at a finite temperature. A temperature gradient was introduced into the model via interfacial mobility gradient. Finally, thermal segregation of the pores and UO 2 was achieved by introducing a heat of migration term, Δ E t, which biased the motion of porosity to the high-temperature region. The development of this model is described and the incorporation of the proper physics of pore migration and thermal segregation is discussed. 相似文献
18.
Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors: calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299mg·g-1. The morphology of those sorbents was examined by scanning electron microscope (SEM), and the changes of composition before and after carbonation were also determined by X-ray diffraction (XRD). Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca(OH)2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area, larger pore volume and appropriate pore size distribution than that of CaO-CaO and Ca(OH)2-CaO. 相似文献
19.
The photocatalytic oxidation of CO into CO 2 with oxidants such as NO, N 2O and O 2 proceeded efficiently on a Mo/SiO 2 with high Mo dispersion under UV light irradiation. It was found that the reaction rate greatly depended on the kind and concentration of the oxidant. Photoluminescence investigations reveal the close relationship between the reaction rate and the relative concentration of the photo-excited Mo 6+-oxide species, i.e. charge transfer–excited–triplet state (Mo 5+–O −) *, under steady-state reaction conditions. Moreover, the photocatalytic oxidation of CO with O 2 in excess H 2 was carried out to test suitability for applications to supplying pure H 2. This reaction was seen to proceed efficiently on Mo/SiO 2 with a high CO conversion of 100% and CO selectivity of 99% after 180 min under UV light irradiation, showing higher photocatalytic performance than TiO 2 (P-25) photocatalyst. UV–vis, XAFS, photoluminescence and FT-IR investigations revealed that the high reactivity of the charge transfer–excited–triplet state (Mo 5+–O −) *, with CO as well as the high reactivity of the photoreduced Mo-oxide species (Mo 4+-species) with O 2 to produce the original Mo-oxide species (Mo 6+O 2−), played a crucial role in the reactions. 相似文献
20.
以Na 2CO 3为沉淀剂,初步研究了多组分氯盐混合体系(0.6 mol MgCl 2+1.1 mol LiCl+3.2 mol NaCl)中选择性沉镁的工艺规律。结果表明:在25~80 ℃,总C与总Mg物质的量比[ n(C T)/ n(Mg T)]为 0.8~1.1时,25 ℃形成针状MgCO 3·3H 2O,40 ℃以上形成Mg 5(CO 3) 4(OH) 2·4H 2O不规则片状团聚微球,其中40~50 ℃形成的片状物较为分散且粒径较小,导致固液分离困难。40 ℃时沉镁率最低。温度越高,Li 2CO 3越易形成,沉锂率越大。 n(C T)/ n(Mg T)越大沉镁率和沉锂率越高。室温(25 ℃)、 n(C T)/ n(Mg T)=1.0时,沉镁率达98%以上,且沉锂率<0.1%,镁锂分离效果最好。 相似文献
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