Microporous Materials最新文献_第2页

Separation of alcohol/water mixtures by pervaporation through zeolite A membranes 沸石A膜渗透蒸发分离酒精/水混合物

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00080-1

Jalal J. Jafar, Peter M. Budd

引用次数: 100

Cation location in dehydrated zeolite NaY revisited: SI position is displaced from the center of the hexagonal prism 脱水沸石NaY中的阳离子位置重访:SI位置从六角形棱镜的中心移位

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00069-2

Günter Engelhardt

引用次数: 17

The influence of gel properties on the kinetics of crystallization and particulate properties of MFI-type zeolities. I. The influence of time and temperature of gel ageing on the particulate properties of silicalite-1 microcrystals 凝胶性质对mfi型沸石结晶动力学和颗粒性质的影响。1 .凝胶老化时间和温度对硅石-1微晶颗粒性能的影响

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00075-8

Ankica Čižmek , Boris Subotica , Damir Kralj , Vesna Babić-Ivančić , Anton Tonejc

{"title":"The influence of gel properties on the kinetics of crystallization and particulate properties of MFI-type zeolities. I. The influence of time and temperature of gel ageing on the particulate properties of silicalite-1 microcrystals","authors":"Ankica Čižmek , Boris Subotica , Damir Kralj , Vesna Babić-Ivančić , Anton Tonejc","doi":"10.1016/S0927-6513(97)00075-8","DOIUrl":"10.1016/S0927-6513(97)00075-8","url":null,"abstract":"<div>The influence of time and temperature of ageing of the amorphous gel precursor (2.5Na2O-8TPABr-60SiO2-800H2O) on the particulate properties (particle size distribution, particle shape, number of particles) of silicalite-1 synthesized at 170°C were studied by different experimental methods such as X-ray diffractometry (XRD), differential thermogravimetric analysis (TGA), particle size analysis, FT infra-red spectroscopy and scanning-electron microscopy (SEM). In spite of negligible changes in the crystal morphology, ageing of the gel considerably affects the number and size of silicalite-1 crystals in the crystalline end products. The observed effects were discussed in terms of the formation of specific ordered subunits between silicate species and TPA+ ions (germ nuclei) and their role in the nucleation and crystal growth of silicalite-1 crystals.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"12 4","pages":"Pages 267-280"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00075-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75610061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 28

Thermal and hydrothermal stability of framework-substituted MCM-41 mesoporous materials 骨架取代MCM-41介孔材料的热稳定性和水热稳定性

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00079-5

L.Y. Chen, S. Jaenicke, G.K. Chuah

引用次数: 112

Zeolites P1 and L as precursors for the preparation of alkaline-earth zeolites 沸石P1和L作为制备碱土沸石的前驱体

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00083-7

Shervin Khodabandeh, Mark E. Davis

引用次数: 14

Rh/SiO2 catalysts prepared by the sol-gel method 溶胶-凝胶法制备Rh/SiO2催化剂

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00025-4

C.K. Lambert, R.D. Gonzalez

{"title":"Rh/SiO2 catalysts prepared by the sol-gel method","authors":"C.K. Lambert, R.D. Gonzalez","doi":"10.1016/S0927-6513(97)00025-4","DOIUrl":"10.1016/S0927-6513(97)00025-4","url":null,"abstract":"<div>A series of Rh/SiO2 catalysts were prepared by the sol-gel method. The precursors used were tetraethoxysilane (TEOS) dissolved in ethanol and rhodium(III) acetylacetonate dissolved in acetone. Preparative variables include the amount of water added to the sol and the gelation temperature. Typical BET surface areas were 550–700 m2 g−1 with very narrow pore size distributions centered at approximately 4 nm. Sample characterization studies were performed using TGA-DTA-MS to determine the effect of O2 pretreatment and 29Si solid-state NMR to determine the extent to which silica was condensed. Sintering studies of Rh/SiO2 catalysts for which there was a reasonable match between metal particle size and pore diameter were performed. Catalysts prepared by ion-exchange having comparable dispersions to those prepared by the sol-gel method also showed considerable resistance to sintering in O2. Following heat treatment in O2 at 650°C, the particle size distribution of catalysts prepared by ion-exchange appear to broaden to a greater extent than catalysts prepared by the sol-gel method. This suggests that the sol-gel preparation is more effective in retaining the metal particles within the narrow pores of the support.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"12 4","pages":"Pages 179-188"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00025-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88795324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 12

FER membrane synthesized by a vapor-phase transport method: its structure and separation characteristics 气相输运法合成的FER膜:结构与分离特性

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00076-X

Norikazu Nishiyama , Takaaki Matsufuji , Korekazu Ueyama , Masahiko Matsukata

{"title":"FER membrane synthesized by a vapor-phase transport method: its structure and separation characteristics","authors":"Norikazu Nishiyama , Takaaki Matsufuji , Korekazu Ueyama , Masahiko Matsukata","doi":"10.1016/S0927-6513(97)00076-X","DOIUrl":"10.1016/S0927-6513(97)00076-X","url":null,"abstract":"<div>The mechanism of formation of ferrierite (FER) membrane on an alumina support by a vapor-phase transport (VPT) method was studied using XRD, SEM, FE-SEM and EDX. The XRD measurement for a FER membrane after the removal of FER particles formed on the support showed that FER was formed in the pores of the alumina support, namely, a FER-alumina composite layer was formed. The FE-SEM image for the cross-sectional view of the FER-alumina composite layer showed that FER nanocrystals of about 50 nm diameter grew in the pores of the alumina support. Pervaporation tests for benzene/p-xylene mixtures were performed at 303 K. Even when the concentration of benzene in the feed solution was extremely small (0.5 mol%), the flux of benzene through the FER membrane was still greater than that of p-xylene. Therefore, a separation factor as high as 600 was obtained in the low feed concentration of benzene. Such a high selectivity for the benzene/p-xylene mixture suggested that the selectivity for the benzene/p-xylene mixture appears at the pore mouths of FER on the feed side of the FER-alumina composite layer.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"12 4","pages":"Pages 293-303"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00076-X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87277387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 52

Sn-MFI molecular sieves: synthesis methods, 29Si liquid and solid MAS-NMR, 119Sn static and MAS NMR studies Sn-MFI分子筛:合成方法，29Si液体和固体核磁共振，119Sn静态和核磁共振研究

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00081-3

N.K. Mal, V. Ramaswamy, P.R. Rajamohanan, A.V. Ramaswamy

{"title":"Sn-MFI molecular sieves: synthesis methods, 29Si liquid and solid MAS-NMR, 119Sn static and MAS NMR studies","authors":"N.K. Mal, V. Ramaswamy, P.R. Rajamohanan, A.V. Ramaswamy","doi":"10.1016/S0927-6513(97)00081-3","DOIUrl":"10.1016/S0927-6513(97)00081-3","url":null,"abstract":"<div>Four different methods of the hydrothermal synthesis of Sn-sil-1 (MFI structure) (Si/Sn > 15) molecular sieves are described. Three of the methods are in a basic medium (pH = 12.4) and the last is in a fluoride medium (pH = 6.4). The procedure in which SnCl4.5H2O is dissolved first in Si(OC2H5)4 (TEOS) before hydrolysis by tetrapropyl ammonium hydroxide (method A) seems to be the most suitable in terms of the crystallinity of the resulting material and its activity in the hydroxylation of phenol by aqueous H2O2 (72% efficiency for H2O2). The course of hydrolysis of TEOS and SnCl4 is studied systematically by 29Si liquid NMR spectroscopy. It is inferred that as soon as SnCl4 is partially hydrolysed, it combines with monomeric Si(OH)4 (Q0) species. This combination leads to the formation of Q1, Q2 and Q3 species and a clear solution. The liquid NMR data provide direct evidence for the interaction of Sn species with silicate species in the synthesis mixture. Further, 29Si MAS NMR and 119Sn static and MAS NMR spectral studies of the crystalline product indicate that the Sn4+ ions are probably attached to the defect silanol groups in a tetrahedral coordination, but tend to assume five- or six-fold coordination very easily due to their large size.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"12 4","pages":"Pages 331-340"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00081-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80008578","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 54

Simulation of the isomerization of an ortho-diethylbenzene on zeolites using a continuum approach and different diffusion models 用连续介质方法和不同扩散模型模拟邻二乙苯在沸石上的异构化

Microporous Materials Pub Date : 1997-12-01 DOI: 10.1016/S0927-6513(97)00077-1

Elias Klemm, Gerhard Emig

{"title":"Simulation of the isomerization of an ortho-diethylbenzene on zeolites using a continuum approach and different diffusion models","authors":"Elias Klemm, Gerhard Emig","doi":"10.1016/S0927-6513(97)00077-1","DOIUrl":"10.1016/S0927-6513(97)00077-1","url":null,"abstract":"<div>The overall kinetics of the isomerization of the dialkylbenzenes on zeolites such as ZSM-5 are affected by the intrinsic kinetics and, in many cases, additionally by configurational diffusion inside the microporous zeolite. Simulation studies on the basis of a continuum model allow a deeper insight into this complex situation. It has been shown that both a reactant diffusion limitation and product shape selectivity (different diffusion rates of the products) may influence the overall kinetics (conversion/selectivity). Calculating concentration profiles inside the crystallite gives additional details about the interrelation of diffusion and reaction. Due to the strong interaction between the diffusing molecules themselves, as well as between diffusing molecule and zeolite surface, various diffusion models have been implemented. Depending on the diffusion model used, it could be shown that at high occupancies, differences occurred only in the calculated conversions, but not in the calculated selectivities. On the basis of the simulation results a recommendation is given concerning the determination of diffusion coefficients from measured overall kinetics. Furthermore, it was found that selectivity strongly depends on the chosen type of reactor, e.g. a plug flow reactor or an ideally mixed reactor. This is important for a comparison of data measured in different experimental set-ups.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"12 4","pages":"Pages 281-291"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00077-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87715324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Determination of ion-exchanged Co2+ cation in Co-ZSM-5 by temperature-programmed desorption 程序升温解吸法测定Co-ZSM-5中离子交换的Co2+阳离子

Microporous Materials Pub Date : 1997-11-01 DOI: 10.1016/S0927-6513(97)00055-2

Chul Wee Lee , Paul Joe Chong , Young Chul Lee , Chong Shik Chin , Larry Kevan

引用次数: 8