{"title":"Calorimetric determination of the superficial acidity and active sites in Ziegler-Natta catalysts","authors":"A. Auroux ∗, K. Bujadoux, J.C. Jannel, D. Lalart","doi":"10.1016/0168-7336(89)80008-7","DOIUrl":null,"url":null,"abstract":"<div><p>The surface acidity and active sites of Ziegler-Natta catalysts (TiCl<sub>3</sub>, <span><math><mtext>1</mtext><mtext>3</mtext></math></span>AlCl<sub>3</sub>-MgCl<sub>2</sub>) before and after allevlation have been characterized by measuring the differential heats of adsorption of various probe molecules in the vapour phase.</p><p>The surface acidity was measured by the adsorption of acetonitrile. This probe molecule appeared to be adsorbed by all metallic sites on the surface, and the order in energetic distribution of these sites showed three populations of sites of decreasing strength which have been proposed as Al > Ti > Mg.</p><p>Characterization of the sites active in polymerization was done using various olefins with different steric hindrance but all inactive towards polymerization such as isobutene, <em>trans</em>-2-hexene and cyclohexene.</p></div>","PeriodicalId":101061,"journal":{"name":"Reactivity of Solids","volume":"7 1","pages":"Pages 67-74"},"PeriodicalIF":0.0000,"publicationDate":"1989-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0168-7336(89)80008-7","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Reactivity of Solids","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0168733689800087","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
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Abstract
The surface acidity and active sites of Ziegler-Natta catalysts (TiCl3, AlCl3-MgCl2) before and after allevlation have been characterized by measuring the differential heats of adsorption of various probe molecules in the vapour phase.
The surface acidity was measured by the adsorption of acetonitrile. This probe molecule appeared to be adsorbed by all metallic sites on the surface, and the order in energetic distribution of these sites showed three populations of sites of decreasing strength which have been proposed as Al > Ti > Mg.
Characterization of the sites active in polymerization was done using various olefins with different steric hindrance but all inactive towards polymerization such as isobutene, trans-2-hexene and cyclohexene.
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