A Raman Spectroscopy Study of the Separation of Hydrofluorocarbons Using Zeolites
| Autor: | Richard R. Cavanagh, Kerwin D. Dobbs, Clare P. Grey, Nicholas Maliszewskyj, Terrence J. Udovic, Michael Crawford, John J. Rush, Robert J. Smalley, David R. Corbin |
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| Rok vydání: | 1999 |
| Předmět: |
education.field_of_study
Chemistry Population Analytical chemistry Ozone depletion Surfaces Coatings and Films symbols.namesake Adsorption Materials Chemistry symbols Physical chemistry Polar Physical and Theoretical Chemistry Zeolite education Raman spectroscopy Conformational isomerism Raman scattering |
| Zdroj: | The Journal of Physical Chemistry B. 103:431-434 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/jp9832903 |
| Popis: | Hydrofluorocarbons (HFCs), such as HFC-134a (CF3CFH2), are replacing chlorofluorocarbons (CFCs) in many applications because of their low ozone depletion potentials. The more complex chemical syntheses of HFCs, however, may not provide the molecular species desired with sufficient purity, leading to the need to separate reaction products. An important example is provided by the separation of the isomers HFC-134a and HFC-134 (CF2HCF2H) over the faujisitic zeolite NaX (Na86Al86Si106O384). An understanding of the fundamental mechanism controlling this separation involves the unusual aspect that HFC-134 can exist as either a trans or gauche conformer; a key factor is that the trans conformer is nonpolar whereas the gauche conformer is highly polar. Here we report the results of a Raman scattering study which show the trans-gauche population ratio for HFC-134 adsorbed on NaX is decreased as much as 20-fold compared to the gas phase. Furthermore, the conformational ratio changes with HFC loading, the polar gauc... |
| Databáze: | OpenAIRE |
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