Self-diffusion measurements of methanol and 1-decanol in supercritical CO{sub 2} by {sup 13}C pulsed field gradient NMR

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A small amount of a highly polar compound, such as methanol, is frequently added to supercritical fluid (SCF) carbon dioxide to enhance its ability to dissolve polar molecules in SCF separation technology. Few diffusion coefficients in SCF mixtures have been reported in the literature. The pulsed field gradient spin-echo technique (PGSE) has been used extensively to measure self-diffusion in neat monohydric alcohols under pressure. Hurle et al. and Luedemann et al. showed that the experimental diffusion coefficients of methanol may be explained by a rough hard-sphere model (RHS) with a roughness parameter, A. In this paper, diffusion measurements are reported ... continued below

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17 p.

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Bai, S.; Mayne, C.L.; Grant, D.M. & Taylor, C.M.V. October 1, 1997.

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A small amount of a highly polar compound, such as methanol, is frequently added to supercritical fluid (SCF) carbon dioxide to enhance its ability to dissolve polar molecules in SCF separation technology. Few diffusion coefficients in SCF mixtures have been reported in the literature. The pulsed field gradient spin-echo technique (PGSE) has been used extensively to measure self-diffusion in neat monohydric alcohols under pressure. Hurle et al. and Luedemann et al. showed that the experimental diffusion coefficients of methanol may be explained by a rough hard-sphere model (RHS) with a roughness parameter, A. In this paper, diffusion measurements are reported for CO{sub 2}-methanol and CO{sub 2}-decanol mixtures in supercritical fluids. Since methanol in CO{sub 2} is primarily monomeric at low concentration, the RHS model, that is accurate for most simple, non-associated liquids, should apply. Previous nuclear spin-lattice relaxation studies in SCF CO{sub 2} suggest a large local solvent density enhancement, or solvent clustering, near a alcohol solute molecule under SCF conditions. If solvent clustering occurs in the vicinity of alcohol solute molecules, it should affect the diffusion coefficients. The authors have made the requisite measurements and found that they corroborate their previous spin-relaxation data.

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17 p.

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OSTI as DE97008161

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  • 13. symposium on thermophysical properties, Boulder, CO (United States), 22-27 Jun 1997

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  • Other: DE97008161
  • Report No.: LA-UR--97-1869
  • Report No.: CONF-970629--2
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 563976
  • Archival Resource Key: ark:/67531/metadc691677

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  • October 1, 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • Feb. 26, 2016, 4:36 p.m.

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Bai, S.; Mayne, C.L.; Grant, D.M. & Taylor, C.M.V. Self-diffusion measurements of methanol and 1-decanol in supercritical CO{sub 2} by {sup 13}C pulsed field gradient NMR, article, October 1, 1997; New Mexico. (digital.library.unt.edu/ark:/67531/metadc691677/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.