Microporous Materials最新文献_第5页

Rietveld refinement of the calcined form of SAPO-40 SAPO-40煅烧形态的Rietveld细化

Microporous Materials Pub Date : 1997-10-01 DOI: 10.1016/S0927-6513(97)00034-5

Anton Meden, Christian Baerlocher, Lynne B. McCusker

{"title":"Rietveld refinement of the calcined form of SAPO-40","authors":"Anton Meden, Christian Baerlocher, Lynne B. McCusker","doi":"10.1016/S0927-6513(97)00034-5","DOIUrl":"10.1016/S0927-6513(97)00034-5","url":null,"abstract":"<div>In contrast to many aluminophosphate-based molecular sieves, calcined SAPO-40 ([Si7Al29P28O128]) appears to be remarkably stable at high temperatures in both dry and humid atmospheres. To investigate the structural basis for this unusual stability, a structure refinement of calcined SAPO-40 (Pccn, a = 22.2638(5), b = 13.7788(2), c = 14.1137(2)Å) using the Rietveld method was performed (Rwp = 0.080, Rexp = 0.043 and RF = 0.043). Comparison of the framework structure before and after calcination indicates that the unit cell expansion (1.5% along x and 0.6% along y) is due to small shifts in the positions of all atoms in the framework rather than by any local distortion involving only a few atoms. Diffuse electron density was found in the pores although several different calcination procedures were tried. This may indicate that the calcination was incomplete, but is more likely to be caused by the presence of silica and/or alumina species resulting from a reorganization of the framework during the calcination. The extra-framework material was described by including three additional oxygen positions in the structural model and refining their population parameters. The scattering power corresponds to about 90 electrons per unit cell.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"11 5","pages":"Pages 247-251"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00034-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88573274","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: 2

Nature and strength of acid sites in HY zeolites: a multitechnical approach HY沸石中酸位的性质和强度:一种多技术方法

Microporous Materials Pub Date : 1997-10-01 DOI: 10.1016/S0927-6513(97)00047-3

A. Boréave , A. Auroux , C. Guimon

{"title":"Nature and strength of acid sites in HY zeolites: a multitechnical approach","authors":"A. Boréave , A. Auroux , C. Guimon","doi":"10.1016/S0927-6513(97)00047-3","DOIUrl":"10.1016/S0927-6513(97)00047-3","url":null,"abstract":"<div>The combination of several physico-chemical techniques such as temperature programmed desorption, microcalorimetry, infrared spectroscopy and photoelectron spectroscopy, together with structural data (by XRD and NMR), has allowed a detailed study of the acidity of commercial HY faujasites, both non-dealuminated and dealuminated by hydrothermal treatment. These techniques have been used with different basic probe molecules such as ammonia, pyridine and 2,6-lutidine (2,6-dimethylpyridine). They have demonstrated the existence of three different regions of acid strength. The weak sites associated to NH3 adsorption heats between 70 and 130 kJ mol−1 are of Lewis and Brönsted types, the former being predominent in the dealuminated zeolites. The sites of intermediary strength are essentially the framework bridged hydroxyl groups (heats between 130 and 150 kJ mol−1). The strong sites (heats above 160 kJ mol−1) contain a significant number of extra-framework Lewis-type sites, but also Brönsted sites. The strength of these sites seems to be due to mutual interactions between Lewis and Brönsted sites. The use of 2,6-lutidine has furthermore allowed us to differentiate between two different populations of Lewis sites.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"11 5","pages":"Pages 275-291"},"PeriodicalIF":0.0,"publicationDate":"1997-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00047-3","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75349039","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: 93

Synthesis of aluminophosphate-based layered compounds using Al(OH)3 用Al(OH)3合成磷酸铝基层状化合物

Microporous Materials Pub Date : 1997-10-01 DOI: 10.1016/S0927-6513(97)00038-2

Yun-Jo Lee, Hakze Chon

引用次数: 8

Synthesis and characterization of a new microporous aluminophosphate with levyne structure in the presence of HF 在HF存在下，一种新型醋酸结构微孔磷酸铝的合成与表征

Microporous Materials Pub Date : 1997-10-01 DOI: 10.1016/S0927-6513(97)00045-X

Guangshan Zhu , Feng-Shou Xiao , Shilun Qiu , Pang-Cho Hun , Ruren Xu , Shujie Ma , Osamu Terasaki

引用次数: 18

Conversion of 4-methylpentan-2-ol over alkali–metal ion-exchanged X and Y zeolites: a microcalorimetric and catalytic investigation 碱金属离子交换的X和Y沸石上4-甲基戊烷-2-醇的转化:微热法和催化研究

Microporous Materials Pub Date : 1997-09-01 DOI: 10.1016/S0927-6513(97)00030-8

A Auroux , P Artizzu , I Ferino , R Monaci , E Rombi , V Solinas

{"title":"Conversion of 4-methylpentan-2-ol over alkali–metal ion-exchanged X and Y zeolites: a microcalorimetric and catalytic investigation","authors":"A Auroux , P Artizzu , I Ferino , R Monaci , E Rombi , V Solinas","doi":"10.1016/S0927-6513(97)00030-8","DOIUrl":"10.1016/S0927-6513(97)00030-8","url":null,"abstract":"<div>The acid-base properties of alkali–metal ion-exchanged X and Y zeolites were investigated by ammonia and sulfur dioxide adsorption microcalorimetry, in parallel with a catalytic reaction, viz. 4-methylpentan-2-ol conversion. Li and Na zeolites present much higher heats of NH3 adsorption and greater coverage at the same pressure than the other zeolites. The acidic strength of X differs by only a few kilojoules per mole from the corresponding Y zeolites. The amounts of SO2 adsorbed are very similar for all the Y zeolites except for LiY, on which the amount is smaller. X zeolites adsorb higher amounts than Y zeolites. Most of the samples have centres possessing significant basicity (Q>150kJmol−1). The main product from 4-methylpentan-2-ol, for both X and Y catalysts, was 4-methylpent-2-ene; on Y zeolites, which exhibited the higher catalytic activity, a larger amount of other types of isomer was generally formed. In the case of Cs-exchanged X, excess cesium oxide was also added by impregnation with Cs acetate. Microcalorimetric measurements indicated that the extra framework cesium oxide provided even stronger basic adsorption sites; the catalytic runs showed that a significant amount of 4-methylpentan-2-one was produced only on CsX containing excess Cs oxide.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"11 3","pages":"Pages 117-126"},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00030-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84590746","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: 20

Synthesis of VPI-8 VPI-8的合成

Microporous Materials Pub Date : 1997-09-01 DOI: 10.1016/S0927-6513(97)00031-X

M Yoshikawa , S.I Zones , M.E Davis

引用次数: 14

A computational investigation of the sorption of methane into zeolitic structures 沸石结构中甲烷吸附的计算研究

Microporous Materials Pub Date : 1997-09-01 DOI: 10.1016/S0927-6513(97)00018-7

A.R George, C.R.A Catlow, J.M Thomas

引用次数: 8

Growth of silicalite-1 films on gold substrates 硅-1薄膜在金衬底上的生长

Microporous Materials Pub Date : 1997-09-01 DOI: 10.1016/S0927-6513(97)00037-0

S. Mintova , V. Valtchev , V. Engström , B.J. Schoeman , J. Sterte

引用次数: 40

Zr-exchanged and pillared beidellite: preparation and characterization by chemical analysis, XRD and Zr K EXAFS 锆交换柱状贝德尔石的制备及其化学分析、XRD和Zr K EXAFS表征

Microporous Materials Pub Date : 1997-09-01 DOI: 10.1016/S0927-6513(97)00041-2

J Miehé-Brendlé , L Khouchaf , J Baron , R Le Dred , M.-H Tuilier

{"title":"Zr-exchanged and pillared beidellite: preparation and characterization by chemical analysis, XRD and Zr K EXAFS","authors":"J Miehé-Brendlé , L Khouchaf , J Baron , R Le Dred , M.-H Tuilier","doi":"10.1016/S0927-6513(97)00041-2","DOIUrl":"10.1016/S0927-6513(97)00041-2","url":null,"abstract":"<div>Zirconia-pillared clays (with synthetic beidellite as host material) were prepared by replacing the sodium interlayer cations by zirconium hydroxy polycations, and then heating to stabilize the structure. The pillaring solution was an aqueous zirconyl chloride solution. The process was first optimized in order to decrease the volume of solution and the reaction time. From the XRD results, the interlayer spacing was found to be near 9  Å) after calcination. The B.E.T. surface area equals 174 g−1. In order to follow the pillaring process, an EXAFS study at the Zr K edge was carried out on crystalline zirconyl oxychloride, the pillaring solution, ion-exchanged and pillared beidellite. There is no difference between the nearest and next-nearest-neighbour environments of Zr in solid zirconyl oxychloride and the pillaring solution. Furthermore, it is found that the Zr environment of the zirconyl polycation is preserved in the pillaring process. Although the mean Zr–O and Zr–Zr distances are shortened from 2.21 and 3.59Å, respectively, in exchanged beidellite to 2.17 and 3.38Å, respectively, in the calcined material, the nearly square frame of the Zr4 zirconyl units is also preserved after the calcination process. The results are consistent with the intercalation of zirconyl pillars made of isolated zirconyl polycations normal to the (001) planes of the beidellite layers. From the charge deduced from chemical analysis, one polycation cancels the charge of four unit cells of the beidellite.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"11 3","pages":"Pages 171-183"},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00041-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88745090","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: 27

Characteristics and combustion/decomposition activities of CuO/mordenite 氧化铜/丝光沸石的特性及燃烧/分解活性

Microporous Materials Pub Date : 1997-09-01 DOI: 10.1016/S0927-6513(97)00052-7

Chang-Yong Lee , Kyoung-Heum Han , Baik-Hyon Ha

{"title":"Characteristics and combustion/decomposition activities of CuO/mordenite","authors":"Chang-Yong Lee , Kyoung-Heum Han , Baik-Hyon Ha","doi":"10.1016/S0927-6513(97)00052-7","DOIUrl":"10.1016/S0927-6513(97)00052-7","url":null,"abstract":"<div>Various amounts of copper oxide were loaded by impregnation of copper salt solution on dealuminated mordenites and redox-treated at 500°C and 750°C. The catalysts were characterized by XRD, ESR, H2-TPR and O2-TPD, and tested for the combustion of methane, acetone, benzene and 1-hexene, and NO decomposition. The redox-treatment induced most of the copper to exist as a CuO crystallite on the mordenite and its reducibility decreased as the temperature increased. Redox-treatment at 750°C reduced the crystallinity of the mordenite and increased the size of the CuO crystallite, especially for the samples with a higher CuO content. The optimum amount of copper for the combustion was 3–5 wt.%. However, the activity of the NO decomposition increased with the amount of CuO present. Maximum activities were observed for both the combustion and the NO decomposition when the ratio of silica/alumina was 20∼30. These results suggest that forming CuO crystallites, including clusters and ion exchanged Cu2+ ions, on dealuminated mordenite by the impregnation of copper salt is desirable for the preparation of the catalysts for combustion/NO decomposition.</div>","PeriodicalId":100926,"journal":{"name":"Microporous Materials","volume":"11 3","pages":"Pages 227-235"},"PeriodicalIF":0.0,"publicationDate":"1997-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0927-6513(97)00052-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91420978","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: 8