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Physisorption of Hydrogen in A, X and ZSM-5 Types of Zeolites at Moderately High Pressures
Xiao-ming Du,Er-dong Wu*
Author NameAffiliationE-mail
Xiao-ming Du Shenyang National Laboratory for Materials Sciences, Institute of Metal Research, Chinese Academy of Science, Shenyang 110016, China  
Er-dong Wu* Shenyang National Laboratory for Materials Sciences, Institute of Metal Research, Chinese Academy of Science, Shenyang 110016, China ewu@imr.ac.cn 
Abstract:
The hydrogen adsorption properties and uptake capacities of the A, X and ZSM-5 types of zeolites were investigated at temperatures of 77, 195 and 293 K and pressures up to 7MPa, using a conventional volumetric adsorption apparatus. All hydrogen adsorption isotherms were basically type I, but the maximum in isotherm,a unique feature of supercritical adsorption, was observed at high pressures of 2-5 MPa at 77 K. The isosteric heats of adsorption were determined from the isotherms and the factors that influence their variations were discussed. Different types of zeolites exhibited remarkably different hydrogen uptake, based on both the framework structure and the nature of the cations present. The highest gravimetric storage capacity of 2.55wt% was obtained for NaX-type zeolite at 4 MPa and 77 K. In CaA, NaX and ZSM-5 types of zeolites,hydrogen uptakes were proportional to the specific surface areas, which were associated with the available void volumes of the zeolites. A threshold in hydrogen adsorption observed in NaA and KA was attributed to a pore blocking effect by large cations in KA. A ratio of the kinetic diameter of adsorbate to the effective opening diameter of zeolite was used to judge the blocking effect for physisorption.
Key words:  Zeolite, Hydrogen storage, Hydrogen adsorption, Adsorption isotherm
FundProject:
氢在A、X及ZSM-5型沸石上的高压物理吸附
杜晓明    ,吴尔冬*
摘要:
采用常规体积吸附装置测定了77、195、293 K和7 MPa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77 K,压力为2~5 MPa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77 K/4 MPa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.该实验将吸附质分子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塞效应.
关键词:  沸石  储氢  氢吸附  吸附等温线
DOI:10.1360/cjcp2006.19(5).457.6
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