Following ¹⁸O uptake in scCO₂-H₂O mixtures with Raman spectroscopy

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• 作者：Charles F. Windisch Jr. ; ^{cf.windisch@pnl.gov} ; Herbert T. Schaef ; Paul F. Martin ; Antoinette T. Owen ; B. Peter McGrail
• 关键词：Raman spectroscopy ; Vibrational spectroscopy ; Supercritical CO2 ; CO2&ndash ; H2O mixtures ; Isotope exchange ; 18O labeling
• 刊名：Spectrochimica Acta Part A ; Molecular and Biomolecular Spectroscopy
• 出版年：2012
• 期刊代码：99_13861425
• 类别：ch
• 出版时间：August, 2012
• 卷：94
• 期：Complete
• 页码：186-191
• 文件大小：757 K

摘要

The uptake of ¹⁸O by scC¹⁶O₂ in mixtures containing liquid H₂¹⁸O was followed with Raman spectroscopy using a specially designed high-pressure optical cell. Characteristic bands from the C¹⁶O¹⁸O and C¹⁸O₂ molecules were identified in the supercritical phase and measured in the spectra as a function of time after introducing the liquid H₂¹⁸O into the scC¹⁶O₂. Temporal dependence indicated the process was diffusion-limited in our cell for both C¹⁶O¹⁸O and C¹⁸O₂. The ratio of concentrations of the ¹⁸O-labeled CO₂ molecules, C¹⁸O₂/C¹⁶O¹⁸O, was much higher than a random distribution of the isotopes for the system expected at equilibrium. The results are consistent with previous studies showing both rapid kinetics for oxygen exchange in aqueous solutions and the role of CO₂ transport at liquid water interfaces. More importantly, they demonstrate the potential for using Raman spectroscopy with ¹⁸O isotopic labeling in scCO₂ reaction studies with the recently determined frequency and intensity characteristics of the Fermi dyad peaks from ¹⁸O-containing CO₂ molecules.