共查询到20条相似文献,搜索用时 203 毫秒
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LiNaY沸石经SiCl4气相同晶脱铝补硅后制得系列高硅铝比,高结晶度的Y沸石,用低温氮吸附法,救是样品对N2的吸附--脱附等温线,从而计算其比表面和孔体积,并采用BJH模型计算孔径分布。用真空重量法测定了四种C6化合物(正己烷,2,3-二甲基丁烷、苯、环己烷)的吸附等温线,探讨吸附量与吸附物的性能(极性、几何构型),吸附量一吸附剂脱铝深度的关系,从而得到,经SiCl4同晶取代后Y沸石的孔结构和表 相似文献
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考察了以拟薄水铝石为铝源、固体硅胶为硅源、四乙基氢氧化铵为模板剂时不同晶化混合液SiO2/Al2O3比和不同晶化温度对β沸石合成的影响。XRD、TGA、ICP及SEM研究结果表明,在晶化混合液SiO2/Al2O3比为20至50之间、晶化温度为140℃~160℃范围内能合成出高结晶度的β沸石,且β沸石硅铝比与晶化混合液硅铝比呈良好的线性关系:TGA总失重量随β沸石硅铝比增加而增加,晶化温度对β沸石的晶粒度没有明显影响。此外,所制备的Hβ沸石对甲苯与C9芳烃歧化和烷基转移反应具有良好的催化性能。 相似文献
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考察了不同浓度的盐酸、柠檬酸、酒石酸、草酸和磺基水杨酸溶\r\n液对Hβ沸石的脱铝效果.结果表明,酸处理可以明显提高β沸石的硅\r\n铝比,但沸石的相对结晶度显著降低.然而,低浓度柠檬酸溶液处理不\r\n仅可以提高β沸石的硅铝比,而且可以提高沸石的相对结晶度及水热稳\r\n定性.在引入外来硅源的情况下,考察了低浓度柠檬酸溶液对β沸石的\r\n脱铝补硅作用,提出了一种既可有效提高β沸石硅铝比,又可使β沸石\r\n具有较高结晶保留度的脱铝补硅方法.采用该方法改性的催化剂,对丙\r\n烯水合醚化反应连续运转720h,丙烯转化率由56.6%仅降为52%,表\r\n明催化剂稳定性得到明显改善. 相似文献
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沸石是天然和合成水合钠 (钾、钙、钡 )铝硅酸盐矿物的通称。合成沸石基于铝硅酸盐外配位层和沸石分子中碱 (碱土 )金属、铝、硅之间摩尔比的不同以及合成条件的差异 ,而有多种型号。其中常用的Na Al Si结构框架的就有 4A、 13X、Y、丝光沸石等类型[1] ,而 4A沸石经KCl或CaCl2 部分交换处理后 ,生成 3A (K Na Al Si)或 5A (Ca Na Al Si)沸石 ;13X型 (Na Al Si)经CaCl2 交换后生成10X (Ca Na Al Si)沸石。因此 ,Na Al Si型合成沸石是制取其它合成沸石的基础。本文介绍的合成沸… 相似文献
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丝光沸石是优良的吸附剂和工业生产对二甲苯的实用催化剂。脱铝是使丝光沸石改性的有效方法。Chen报道了脱铝丝光沸石对环己烷的吸附量在硅铝比为15~50范围内随硅铝比增加而减少,而在50~90范围内变化很小。张红浪等用高温水蒸气处理结合酸洗的方法脱铝,得到不同硅铝比的丝光沸石,并研究了脱铝对其结构、酸性和催化性能的影响。本 相似文献
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用低温氮物理吸附法研究了化学法和水热法相结合制备的两个系列Y沸石的孔结构性质。研究结果表明, 用不同化学试剂处理Y沸石形成的孔结构有明显差别。但是, 当把由此得到的Y沸石在相同条件下交替进行水热处理和化学处理时, 孔结构却呈现类似的变化趋势, 即总比表面积、微孔比表面积和微孔体积是先下降后上升, 经第二次水热和化学处理是再次下降再次回升。而过程中产生的“二次孔”比表面积却呈现先上升后下降, 又回升又下降的相反的变化趋势。这种变化趋势, 可能与水热处理和化学处理过程中非骨架铝物种的形成与消失有关。 相似文献
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Daniel Morel Fritz Stoeckli Francis Krhenbühl Laurent Misteli Paulin Munyazikwiye 《Helvetica chimica acta》1985,68(7):1844-1847
Nitrogen adsorption isotherms at 77K and enthalpies of immersion into water at 293K have been measured for a series of artificial and natural calcium carbonates. It appears that the external surface area and the micropore system can be fully characterized if a non-porous sample, present in the series, is used as an internal reference. Data are given for the reference isotherm. Owing to high specific interactions, immersion into water only provides information on the total surface area of the samples. 相似文献
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M. Jaroniec A. W. Marczewski W. D. Einicke H. Herden R. Schöllner 《Monatshefte für Chemie / Chemical Monthly》1983,114(8-9):857-873
The influence of heterogeneity parameters on the shape of excess adsorption isotherms has been discussed. These isotherms have been calculated according to the equations corresponding to different energy distributions. Next, the isotherm equations have been applied to examine the experimental excess isotherms for 1-tetradecene/dodecane mixture adsorption on different types ofX-zeolites at 293 K, 313 K and 333 K. The zeolite samples have been prepared from NaX-zeolite by exchanging the sodium ions for ions of alkalines and calcium group. Analysis of the above adsorption data by means of different isotherm equations showed that the parameters of aDubinin-Radushkevich-type equation change correctly with temperature and the contents of alkalines in the zeolite samples. 相似文献
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G. W. Chądzyński P. Staszczuk D. Sternik M. Błachnio 《Journal of Thermal Analysis and Calorimetry》2008,94(3):623-626
Properties relating to porosity of solids (fractal dimensions, surface roughness parameters) were evaluated from atomic force
microscopy (AFM) and nitrogen adsorption-desorption isotherms measured at 77 K for selected high-temperature [(RE) Ba2Cu3O7−x, RE=Y, Sm] superconductors. Adsorption capacity, specific surface area, fractal dimensions were determined from adsorption-desorption
isotherms. The adsorption isotherms of all samples were S-shaped and belong to type II according to the IUPAC classification.
A linear relationship was demonstrated between the fractal coefficients calculated by using the two methods and values of
adsorption capacity of monolayer. 相似文献
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Sylwester Furmaniak Piotr A. Gauden Maria Leaska Radosaw Mikiewicz Anna Bajet-Kosicka Piotr Kowalczyk 《Molecules (Basel, Switzerland)》2021,26(6)
The finite pore volume Guggenheim–Anderson–de Boer (fpv-GAB) adsorption isotherm model has been considered as a simple tool which not only enables us to analyze the shape of isotherms theoretically, but also provides information about pore diameter. The proposed methodology is based on the geometrical considerations and the division of the adsorption space into two parts: the monolayer and the multilayer space. The ratio of the volumes of these two spaces is unambiguously related to the pore diameter. This ratio can be simply determined from the N2 adsorption isotherm by its fitting with the use of fpv-GAB model. The volume ratio is equal to the ratio of the adsorption capacities in the monolayer and the multilayer—two of the best-fit parameters. The suggested approach has been verified using a series of isotherms simulated inside ideal carbon nanotubes. The adsorption data for some real adsorbents has also been used during tests. The studies performed have proven that diameters estimated with the use of the proposed method are comparable with the geometrical sizes or diameters published by others and based on the application of more sophisticated methods. For pores wider than 3 nm, the relative error does not exceed a few percent. The approach based on the fpv-GAB model reflects well the differences in pore sizes for the series of materials. Therefore, it can be treated as a convenient tool to compare various samples. 相似文献
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Behaviour of organic pollutants in paper and board samples intended to be in contact with food 总被引:1,自引:0,他引:1
This paper deals with the study of volatile compounds present in a set of three paper and board (P&B) samples of different composition, surface treatment, grammage and thickness. The volatile compounds released by the packaging material (P&B) can be trapped on the food and may then affect the safety and health of consumers. To evaluate if the recycled P&B could be used as food packaging material, adsorption studies have been performed with a selection of chemical substances. The adsorption isotherms are provided. Partition coefficients between paper and air have been calculated for a series of volatile compounds used as model compounds to represent different families of contaminants commonly present in P&B. Values from 4 to 3243 were obtained at different temperatures. The analysis of volatile compounds have been carried out by automatic headspace coupled on-line with GC/MS in SIM mode. The results obtained are shown and discussed. 相似文献
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The problem of diffusion controlled adsorption kinetics is solved by orthogonal collocation for the Henry and the Langmuir isotherms. The dependence of the surface concentration of a surfactant on time is described by explicit formulae for the whole range of time. The results are compared with those obtained by power series expansions and finite difference methods and have a high accuracy for any time value. The method of orthogonal collocation has been shown to be very effective. It is suitable for applications to similar problems. 相似文献