共查询到19条相似文献,搜索用时 203 毫秒
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氢在A、X及ZSM-5型沸石上的高压物理吸附 总被引:1,自引:0,他引:1
采用常规体积吸附装置测定了77、195、293K和7MPa的条件下氢在A、X及ZSM-5沸石上的吸附特性和吸附容量.所有的氢吸附等温线基本符合Ⅰ型等温线,但在77K,压力为2-5MPa的等温线上观察到了超临界高压吸附所特有的最大吸附量.从等温线确定了等量吸附热并讨论了其影响因素.根据骨架结构和所含阳离子类型的差异,各种沸石表现出不同的氢吸附量.其中NaX沸石在77K/4MPa下的重量储氢分数为2.55%,是该实验中所测得的最高吸附量.CaA、NaX和ZSM-5沸石的氢吸附量与其比表面积成正比,这与沸石中的可用空穴容积有关.然而NaA和KA沸石不存在这种线性关系.实验中还观察到,NaA与KA沸石间出现氢吸附量的临界值是由KA沸石中较大的阳离子堵塞效应引起的.该实验将吸附质分了的动力学直径与沸石主晶孔的有效直径之比用于判断物理吸附中的堵塞效应. 相似文献
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通过碱沉淀法制备了Ce,Al,Ni,Cu的水合氧化物,研究了它们的Langmuir吸附等温线,并利用BET法通过吸附-脱附氮气测定了其比表面积,同时对其吸附氟离子前后的变化进行了IR谱图的表征.结果表明不同水合金属氧化物具有不同的比表面积,其孔径分布也不尽相同,吸附量与比表面积之间没有直接相关的正比关系.吸附等温线均符... 相似文献
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报道了直接测定楔压等温线的方法,研究了阳离子表面活性剂TTAB在浓度大于CMC时,液膜的平衡厚度与楔压的关系,以及膜表面张力与溶液表面张力之间的差别。结果显示,在低楔压时,膜厚随楔压增加而变薄,在高楔压时,随着楔压的增加,膜厚变化很小。由楔压等温线得出的膜表面张力的结果说明了一般黑膜的表面张力数值与溶液的表面张力并没有明显的差别。 相似文献
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对范德瓦耳斯方程吸引项修正后, 分析了两种经验状态方程的等温线, 并与范德瓦耳斯方程作了比较 相似文献
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用温度场论方法计算了F-L模型在有限温度和密度下的状态方程,分析了压强对净重子数密度的等温线.结果表明,在平均场近似下,F-L模型所给出的退禁闭相变为一级相变. 相似文献
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M. Konstantakou Th.A. Steriotis G.K. Papadopoulos E.S. Kikkinides 《Applied Surface Science》2007,253(13):5715-5720
The Monte Carlo method in its grand ensemble variant (GCMC) is used in combination with experimental data in order to characterize microporous carbons and obtain the optimal pore size distribution (PSD). In particular, the method is applied in the case of AX-21 carbon. Adsorption isotherms of CO2 (253 and 298 K) and H2 (77 K) up to 20 bar have been measured, while the computed isotherms resulted from the GCMC simulations for several pore widths up to 3.0 nm. For the case of H2 at 77 K quantum corrections were introduced with the application of the Feynman-Hibbs (FH) effective potential. The adsorption isotherms were used either individually or in a combined manner in order to deduce PSDs and their reliability was examined by the ability to predict the experimental adsorption isotherms. The combined approach was found to be capable of reproducing more accurately all the available experimental isotherms. 相似文献
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Numerical values of reduced second and third virial coefficients and their temperature derivatives are reported for a two-dimensional gas, for use in interpreting adsorption isotherms of monolayers on isoenergetic substrates. Correct values of the third virial coefficient have not been available before. Examples of earlier treatments of adsorption data are given to demonstrate that values of the higher virial coefficients are essential for adequate discussions of adsorption isotherms. When these are used the high-temperature adsorption isotherms of argon on graphitized carbon black in the monolayer region are completely described in terms of the unperturbed bulk-gas parameters. 相似文献
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We present simultaneous measurements of adsorption isotherms and dielectric isotherms for krypton and xenon on boron nitride. Dielectric measurements give a good characterization of monolayer formation and completion, and provide new information on the dielectric properties evolution from a two-dimensional system towards the bulk. 相似文献
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By implementing the J-walking formalism within the test particle method, adsorption isotherms for various Lennard-Jones systems were constructed. The method decreases the uncertainties in the average thermodynamic values by approximately one order of magnitude and substantially increases the percentage insertion of the ghost particle. The adsorption isotherms showed that at low temperatures the amount of adsorbed material seems to be independent of the vapour pressure of the gas if attractive forces dominate the system. On the other hand, systems dominated by repulsive forces show the usual type B behaviour for adsorption isotherms. The equation of state is used to confirm these results. 相似文献
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A. Magnus G. Carvalho A. A. Coelho S. Gama F. C.G. Gandra P. J. von Ranke N. A. de Oliveira 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):67-72
We have explored a simple Landau model to calculate magnetization isotherms considering magnetic hysteresis. The model parameters
have been chosen to fit the magnetic and magnetocaloric data of MnAs compound. Experimental data show that there is a great
difference between the isothermal variation of the entropy (ST) obtained from isotherms measured increasing and decreasing magnetic field. This great difference is reproduced theoretically.
From the experimental and phenomenological isotherms, we calculated the ST. From the theoretical entropy, we also obtained ST, which does not present the colossal peak. 相似文献
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We have extensively studied the nonequilibrium behavior of atactic polystyrenes in a broad range of temperatures. Depending on the conditions of the initial temperature (To) and the aging temperature (T), the shapes of isotherms plotted in the form of total fractional free volume (viz., δ) versus logarithmic aging time can be linear or nonlinear. At a T in the vicinity of Tg , the isotherms converge together. When the Tis lowered, the isotherms become increasingly nonlinear; eventually, these isotherms intersect one another at various points, forming a newly discovered crossing phenomenon. Differences in volume contraction persist throughout further aging, regardless of the equality in δ right at the moment of crossing. In a further case, the nonlinear isotherms between the two polystyrenes may be superposable by a simple δ shift, despite their substantial differences in δ. As none of these phenomena can be justified by kinetic arguments, this study seriously questions the validity of the existing kinetic theories as well as the existence of the extrapolated underlying equilibrium state. 相似文献
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The isothermal adsorption of nicotine from an aqueous solution onto zeolite type USY was investigated. The adsorption isotherms of nicotine onto the zeolite at different temperatures ranging from 298 to 322 K were determined. It was found that the adsorption isotherms can be described by the model of Freundlich adsorption isotherm. Based on the adsorption isotherms the changes of adsorption heat, free energy and entropy with adsorption degree were determined. The determined decrease of adsorption heat with adsorption degree can be explained by the presence of the adsorption centers of different energy and concentration on interface of zeolite-nicotine solution. It was found that the probability function of density distribution of the heat of adsorption (DDF) has exponential form. It was concluded that the possibility of fitting the adsorption isotherms of nicotine onto the zeolite by Freundlich adsorption isotherm was a direct consequence of that. The determined increase in entropy with the increase in adsorption degree can be explained with the change of phase state of adsorbed nicotine. 相似文献
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《Applied Surface Science》2007,253(13):5616-5621