氢在碳基材料穿插MIL-101(Cr)试样上的吸附平衡

为了实现由碳基材料穿插提高金属有机框架物(MOFs)储氢容量的目的，选择质量分数分别为1%的活性炭和石墨烯穿插MIL-101(Cr)。通过试样的结构表征、微观形貌观察与氢吸附等温线测试，从吸附平衡模型和吸附热两方面来比较其储氢行为。结果表明，在77.15～87.15 K、0～6 MPa，氢在AX-21活性炭穿插(AM-01)和氧化石墨烯(GO)穿插(GM-02)试样上的储氢量比穿插前提高了41.1%和17.4%；相对于Langmuir方程和Langmuir-Freundlich(L-F)方程，Toth方程的预测精度最高，77.15 K时，Toth方程预测氢在AM-01和GM-02上吸附量的平均相对误差分别为0.55%、0.41%；氢在AM-01和GM-02上的等量吸附热分别为2.96～8.64 k J·mol^-1、3.06～8.57 k J·mol^-1。由GO或高比表面积的活性炭穿插可增大储氢容量，吸附平衡分析可选用Toth方程。     

复合固化吸附储氢材料的传热性能测试及仿真

针对目前金属氢化物储氢技术中面临的粉化后传热性能不佳等问题,采用膨胀石墨为基质配制固化的金属氢化物吸附剂。使用Hotd isk热物性分析仪,测试了固化吸附剂的热物性参数,并对固化吸附床的传热及相应的储氢特性进行了仿真。研究结果表明,固化混合吸附剂相对于散装的储氢合金,轴向导热系数最高提高了52倍左右,径向导热系数最高提高了12倍左右。通过仿真发现,在相同的80℃热源温度下,固化混合吸附床所需要的加热时间相对于散装储氢合金吸附床可以缩短17%,吸氢速率可以提高24%。     

氢在YK-1活性炭上的吸附平衡

运用容积法在温度区间113—293 K、压力范围0—12.5 MPa测定氢在椰壳活性炭YK-1上的吸附等温线,由等量吸附线标绘和低覆盖率区域等温线的亨利定律标绘确定等量吸附热和极限吸附热,引入格子理论Ono-Kondo方程对吸附等温线进行模型分析。结果表明,氢在YK-1活性炭上等量吸附热随吸附量的变化平缓,等量吸附热的平均值和极限值分别为4.64 kJ/mol和5.37 kJ/mol;基于Ono-Kondo模型的方程能较好地预测吸附等温线,氢在吸附空间的最大吸附容量随温度变化,其值比液氢在相同吸附空间的吸附容量小。须改善材料结构和降低储存系统温度才能提高活性炭的储氢性能。     

基于物理吸附的微孔储氢材料研究进展

介绍了氢能源的应用背景,总结了当前氢储存技术存在的问题,分析了微孔物理吸附材料,如金属有机骨架、沸石、碳基材料等,在储氢领域的应用现状以及研究进展,最后,对未来储氢材料的研究和发展进行了展望。     

氢在多壁碳纳米管上的等量吸附热

为说明氢在多壁碳纳米管(MWCNTs)上所受吸附作用的强弱,文中基于氢和77 K氮的吸附数据,比较了由非局域密度泛函理论(NDFT)、等量吸附线和归一化等温线线性化确定的等量吸附热。结果表明,氢在MWCNTs上等量吸附热随温度变化且表现出在弱的能量不均匀表面吸附的特点,平均值约为3—4 kJ/mol;由77 K氮吸附等温线确定的孔大小分布(PSD)和比表面积影响NDFT计算初始吸附时的精度;在吸附量和吸附温度都较低时,等量吸附线标绘结果与归一化等温线线性化方程确定的等量吸附热之间的偏差较小,在200—290 K温度区间则与ND-FT计算结果更为接近。然而,当温度大于310 K时,3种方法计算结果间的偏差较大。     

储氢材料85Mg10C4Ni1Al的制备及性能研究

在Mg粉中添加微晶碳及少量Ni和Al,用机械力化学法氢气反应球磨制备储氢材料.球磨2～3 h即可使Mg完成氢化,Ni和Al的添加可提高储氢密度,降低初始放氢温度和放氢高峰温度,加快放氢速度.储氢材料85Mgl0CANilAl的粒度约为100～300 nm,其储氢密度达6.0%,初始放氢温度仅220℃,与传统Mg基储氢材料相比其储氢性能有较大改善.     

吸附法净化室内甲醛研究进展

吸附法技术成熟、操作简单、现有系统完善,且一次性固定投资小,被广泛应用于室内气相污染物的净化处理。本文简单综述了吸附法在净化室内甲醛方面的研究,从原生碳吸附剂、改性碳吸附剂、无机非碳基吸附剂和有机非碳基吸附剂几个方面介绍了不同类型吸附剂的研究现状,对比了吸附性能,简要介绍了甲醛与吸附剂表面的作用机理,并详细总结了影响吸附效果的主要因素。指出整体上改性碳吸附剂性能最优,其他类型吸附剂之间差异不大,并与商品吸附剂没有明显差别;吸附剂结构和表面物化性质是影响吸附效果的首要因素,其织构特征、表面酸碱性、表面含氧/含杂原子官能团以及表面第二相等均对吸附效果产生重要影响。评述了吸附条件如甲醛浓度、吸附温度和湿度、吸附剂粒径等同样影响最终吸附效果。     

燃煤烟气中单质汞吸附与氧化机理研究进展

燃煤电厂汞排放控制是当前的研究热点,实现燃煤烟气中汞的脱除涉及两个非常重要的过程：吸附与氧化。本文概述了汞在吸附剂表面吸附的相关理论和单质汞的催化氧化机理,结合碳基和非碳基吸附剂相关吸附特性的研究现状,对汞的吸附机理进行了讨论,回顾了SCR、碳基、以及金属和金属氧化物三种常见催化剂对单质汞的催化氧化性能并总结了其可能存在的机理。指出吸附剂表面活性位是决定其对汞吸附效果的关键因素,异相反应是单质汞氧化的重要途径,吸附和氧化是相辅相成的,不同催化剂不同气氛下氧化机理不同。并提出通过氯化物等物质改性能够提高吸附剂的吸附效果,深入研究汞的异相反应机理并开发经济有效的汞脱除方法是今后的研究方向。     

多孔吸附储氢材料研究进展

综述了氢存储研究的重要性和国内外多孔吸附储氢材料的研究工作,对碳基多孔材料、纳米管材料、多孔矿物材料和金属有机物多孔材料在锗氢中的研究热点和存在问题进行了详细介绍,并对未来多孔吸附储氢材料的研究工作进行了展望。     

碳微晶结构对球磨制备镁基储氢材料的影响

以杏壳活性炭和煤基碳作为镁粉的助磨剂,用氢气反应球磨法制备了镁基储氢材料,对比研究了这两种不同微晶结构的碳在制备镁基储氢材料时作用的差异。结果表明,杏壳活性炭和煤基碳都是镁粉的有效助磨剂,能防止镁粉发生"冷焊"及粘附现象,得到分散的纳米级镁基储氢材料。杏壳活性炭对镁粉的分散性优于煤基碳,但用煤基碳作助磨剂所制得粉体的粒度更小,储氢密度更大,放氢温度更低。     

甲烷在单壁碳纳米管中的吸附的密度泛函研究

纳米微孔材料的出现使得有可能在中低压下微孔介质中吸附存储天然气 .由于天然气的主要成分是甲烷 ,其吸附存储为研究者所关注 .碳纳米管由单层或几层纯碳同轴圆柱状结构层组成 ,每个管状层由碳六边形构成 ,与石墨内结构相似 .单壁的碳纳米管称为单壁碳纳米管 (ＳｉｎｇｌｅＷａｌｌｅｄＣａｒｂｏｎＮａｎｏｔｕｂｅ ,ＳＷＮＴ) .它作为一种吸附材料在实验和理论研究中受到高度重视 .在ＳＷＮＴ中吸附的密度泛函理论 (ＤＦＴ)研究与计算机模拟相比较少 .文献中只有Ｇｏｒｄｏｎ等[1] 在 1999年采用密度泛函的方法和过分简化的氢分子势能函…     

Isosteric heats of adsorption in the Henry’s law region for carbon single wall cylindrical nanopores and spherical nanocavities

The isosteric heat of adsorption in the Henry’s law region is calculated as a function of the pore width for carbon single wall cylindrical nanopores and spherical nanocavities. The maximum isosteric heat of adsorption is obtained for six gas molecules: argon, methane, carbon dioxide, hydrogen, helium, and nitrogen. In addition, the results for cylindrical carbon nanopores are compared with adsorption data on single-wall carbon nanotubes from the literature. We find the pore width where the isosteric heat of adsorption is a maximum for both geometries. The effect of solid–fluid parameters on the pore diameter for the maximum isosteric heat of adsorption is determined for any system described by a Lennard–Jones potential. Constant relationships between the pore diameters for the maximum isosteric heat of adsorption and the specific solid–fluid parameters are found for cylindrical nanopores, spherical nanocavities, and parallel-wall slit-shaped pores. Surface mean curvature has a significant influence on the isosteric heat of adsorption.     

Experimental study and artificial neural network simulation of methane adsorption on activated carbon

The adsorption of methane on two activated carbons with different physical properties was measured. Adsorption isotherms were obtained by static volumetric method at different temperatures and pressures. The experimental results sow the best gas storage capacity was 113.5 V/V at temperature 280 K and pressure 8.5MPa on an activated carbon with surface area 1,060 m²/gr. An artificial neural network (ANN) based on genetic algorithm (GA) was used to predict amount of adsorption. The experimental data including input pressure, temperature and surface area of adsorbents as input parameters were used to create a GA-ANN simulation. The simulation results were compared with the experimental data and a good agreement was observed. The simulation was applied to calculate isosteric heat of adsorption by using the Clausius-Clapeyron equation. Comparison of the calculated adsorption heat showed different surface heterogeneity of the adsorbents.     

乙醇在MIL-101上的吸附相平衡及其吸附机理

主要研究了MIL-101材料对乙醇的吸附性能和吸附机理。采用水热合成法制备了MIL-101(Cr),并分别应用N₂静态吸附、X射线粉末衍射(PXRD)、傅里叶红外光谱(FTIR)等分析手段对MIL-101晶形结构、孔隙结构参数进行分析表征。应用静态吸附法测定乙醇和水蒸气在不同温度下的吸附等温线,并讨论乙醇吸附在MIL-101(Cr) 4种吸附位的机理,根据吸附等温线估算出乙醇和水蒸气在MIL-101上的等量吸附热,并测试了乙醇在MIL-101上的吸附循环性能。研究表明,在298 K下,MIL-101的乙醇吸附容量为20.3 mmol·g^-1,远高于传统吸附材料。在低压下MIL-101对乙醇的吸附量高于水蒸气的吸附量,这是由于乙醇的偶极矩和分子动力学直径均比水大,使得乙醇分子在孔道中受到更大吸附力场作用;在低吸附量范围,乙醇在MIL-101上的等量吸附热要高于水蒸气的等量吸附热。在较高吸附压力条件下,主要发生多层吸附或孔填充,受吸附剂的孔容限制效应,尺寸越大的分子被吸附的物质的量会越少,由于乙醇的动力学直径(0.45 nm)大于水分子的动力学直径(0.268 nm),所以在较高吸附压力下乙醇在MIL-101上吸附量要小于水蒸气的吸附量。多次吸附脱附等温线测试显示MIL-101具有良好的乙醇吸附循环性能。     

Synthesis of graphene-like nanosheets and their hydrogen adsorption capacity

Graphene-like nanosheets have been synthesized by the reduction of a colloidal suspension of exfoliated graphite oxide. The morphology and structure of the graphene powder sample was studied using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The graphene sheets are found to be in a highly agglomerated state, with many wrinkles. The sample has a BET surface area of 640 m²/g as measured by nitrogen adsorption at 77 K. Hydrogen adsorption-desorption isotherms were measured in the temperature range 77-298 K and at pressures of up to 10 bar. This gives hydrogen adsorption capacities of about 1.2 wt.% and 0.1 wt.% at 77 K and 298 K, respectively. The isosteric heat of adsorption is in the range of 5.9-4 kJ/mol, indicating a favourable interaction between hydrogen and surface of the graphene sheets. The estimated room temperature H₂ uptake capacity of 0.72 wt.% at 100 bar and the isosteric heat of adsorption of our sample are comparable to those of high surface area activated carbons, however significantly better than the recently reported values for graphene and a range of other carbon and nanoporous materials; single and multi walled carbon nanotubes, nanofibers, graphites and zeolites.     

Effects of Adsorbent Characteristics on Adiabatic Vacuum Swing Adsorption Processes for Solvent Vapor Recovery

The effects of the adsorbent characteristics on the performance parameters and periodic state behavior of the vacuum swing adsorption (VSA) solvent vapor recovery (SVR) processes are examined and optimized. The adsorbent characteristics studied were the adsorbent particle's porosity, density, radius and heat capacity, the packed bed void fraction, the isosteric heat of adsorption, the monolayer saturation limit of the solvent molecules on the adsorbent, the adsorbent's affinity to adsorb the solvent molecules and the mass transfer coefficient for the adsorption of the solvent molecules. It was found that the best VSA‐SVR process performances can be obtained using adsorbents characterized by the minimum possible packed bed void fraction and particle porosity, with the maximum possible adsorbent heat capacity and density, adsorption monolayer saturation capacity and mass transfer coefficient, and at intermediate adsorption affinity and isosteric heat of adsorption of the solvent molecules.     

Material design using molecular modeling for hydrogen storage

Using grand canonical Monte‐Carlo simulations, the adsorption capacities and isosteric heats of hydrogen on activated carbons, graphite nanofibers, and bundles of carbon nanotubes are estimated for identical thermodynamic states. These computations allow a systematic, meaningful, and unbiased comparison of the adsorption properties of hydrogen in such porous materials. The comparison shows that the hydrogen storage capacity can be optimized, but only to a limited extent, in adjusting the material pore sizes and functionalizing a part of the adsorption sites. Therefore, at room temperature and up to 70.0 MPa, for the three models of carbonaceous adsorbents, the hydrogen maximal excess adsorption is of the order of 2% of the adsorbent mass. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Adsorption characteristics of benzene on electrospun‐derived porous carbon nanofibers

The adsorption properties of polyacrylonitrile (PAN) carbon nanofibers fabricated by using an electrospinning route were assessed for their applicability as a novel alternative adsorbent. Commercial fiber, A–10, was chosen for comparison. Nitrogen adsorption/desorption isotherms and gravimetric techniques were used to examine the porous structure, adsorption equilibrium, kinetics, and the energetic heterogeneity of the prepared adsorbent. The nitrogen adsorption and desorption isotherms showed that PAN carbon nanofibers are highly microporous with small amounts of mesoporous regions. The equilibrium data of benzene was obtained at three different temperatures (343.15, 383.15, and 423.15) K with pressures up to 4 kPa. The data correlated successfully with the Toth isotherm equation. In addition, by using this isotherm model, the adsorption affinity and isosteric enthalpy of adsorption were determined. The results of the isosteric enthalpy of adsorption and adsorption energy distribution tests/equations revealed that although PAN carbon nanofibers have a heterogeneous surface, they seem to be more homogeneous than commercial carbon fibers. Moreover, the mass transfer and thermal desorption results showed that shallow pores contained within PAN carbon nanofibers may be effective adsorbents for removing toxic compounds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2454–2462, 2006     

吸附制冷用复合吸附剂的吸附等温线推算

用真空重力法测定了水和乙醇在自制复合吸附剂上的吸附等温线。采用由微孔填充理论导出的吸附平衡方程对所测得的等温线进行了拟合,计算相应的吸附热;对用Clausius Clapeyron方程推算吸附等温线的方法进行了讨论,并推算有关吸附等温线。结果表明:水在自制复合吸附剂M1 0001和M1 9906上平衡吸附量的推算值与实测值之间的相对误差<10%;乙醇在自制复合吸附剂上的推算误差<15%。给出了推算等温线和获得等压线的简便方法。