{"title":"用x射线衍射和氮吸附新方法测定脱铝铝石的结晶度","authors":"A.P. Carvalho, M. Brotas de Carvalho, J. Pires","doi":"10.1016/S0144-2449(97)00101-2","DOIUrl":null,"url":null,"abstract":"<div><p>Samples obtained from thermal dealumination (in the presence and absence of water vapour) of three offretite zeolites with, respectively, 4.4, 3.4, and 2.9 aluminium atoms per unit cell, were investigated by i.r. spectroscopy. X-ray diffraction, and nitrogen adsorption. The <em>percentage of crystallinity</em> was then evaluated by two different methods: the standard XRD technique and a new method based on nitrogen adsorption data analysed through the <em>α</em><sub>s</sub>-method. In this case the volume of the ultramicropores (width less than 0.7 nm) was considered. Differences between the two estimates, as well as the loss of crystallinity during dealumination, which is expressed by the representation of both crystallinity evaluations, C<sub>XRD</sub> or C<sub>ADS</sub>, versus ν<sub>1</sub> (the frequency of the stretching asymmetric T-O band), were analysed for self-steamed and steamed samples. The results obtained agree within 20%, and often better. For self-steamed samples the crystallinity evaluated from XRD patterns is always smaller than that estimated from adsorption data, whereas for steamed samples the opposite situation is generally observed.</p></div>","PeriodicalId":23983,"journal":{"name":"Zeolites","volume":"19 5","pages":"Pages 382-386"},"PeriodicalIF":0.0000,"publicationDate":"1997-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S0144-2449(97)00101-2","citationCount":"13","resultStr":"{\"title\":\"Degree of crystallinity of dealuminated offretites determined by X-ray diffraction and by a new method based on nitrogen adsorption\",\"authors\":\"A.P. Carvalho, M. Brotas de Carvalho, J. Pires\",\"doi\":\"10.1016/S0144-2449(97)00101-2\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Samples obtained from thermal dealumination (in the presence and absence of water vapour) of three offretite zeolites with, respectively, 4.4, 3.4, and 2.9 aluminium atoms per unit cell, were investigated by i.r. spectroscopy. X-ray diffraction, and nitrogen adsorption. The <em>percentage of crystallinity</em> was then evaluated by two different methods: the standard XRD technique and a new method based on nitrogen adsorption data analysed through the <em>α</em><sub>s</sub>-method. In this case the volume of the ultramicropores (width less than 0.7 nm) was considered. Differences between the two estimates, as well as the loss of crystallinity during dealumination, which is expressed by the representation of both crystallinity evaluations, C<sub>XRD</sub> or C<sub>ADS</sub>, versus ν<sub>1</sub> (the frequency of the stretching asymmetric T-O band), were analysed for self-steamed and steamed samples. The results obtained agree within 20%, and often better. For self-steamed samples the crystallinity evaluated from XRD patterns is always smaller than that estimated from adsorption data, whereas for steamed samples the opposite situation is generally observed.</p></div>\",\"PeriodicalId\":23983,\"journal\":{\"name\":\"Zeolites\",\"volume\":\"19 5\",\"pages\":\"Pages 382-386\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"1997-11-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://sci-hub-pdf.com/10.1016/S0144-2449(97)00101-2\",\"citationCount\":\"13\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Zeolites\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0144244997001012\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Zeolites","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0144244997001012","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
Degree of crystallinity of dealuminated offretites determined by X-ray diffraction and by a new method based on nitrogen adsorption
Samples obtained from thermal dealumination (in the presence and absence of water vapour) of three offretite zeolites with, respectively, 4.4, 3.4, and 2.9 aluminium atoms per unit cell, were investigated by i.r. spectroscopy. X-ray diffraction, and nitrogen adsorption. The percentage of crystallinity was then evaluated by two different methods: the standard XRD technique and a new method based on nitrogen adsorption data analysed through the αs-method. In this case the volume of the ultramicropores (width less than 0.7 nm) was considered. Differences between the two estimates, as well as the loss of crystallinity during dealumination, which is expressed by the representation of both crystallinity evaluations, CXRD or CADS, versus ν1 (the frequency of the stretching asymmetric T-O band), were analysed for self-steamed and steamed samples. The results obtained agree within 20%, and often better. For self-steamed samples the crystallinity evaluated from XRD patterns is always smaller than that estimated from adsorption data, whereas for steamed samples the opposite situation is generally observed.