CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation

Abstract

A sapphire high-pressure NMR cell, capable of independently controlling sample pressure, temperature, and concentration, is used to measure 13 C spin-lattice relaxation times for carbons 1, 5, and 9 of 1-decanol in dense carbon dioxide at pressure between 80 and 200 atm. These NMR experiments, carried out along four isotherms between 288 and 348 K, provide relaxation data for 1-decanol in liquid and supercritical fluid CO 2 . The nuclear spin-lattice relaxation mechanisms for carbons 1, 5, and 9 of 1-decanol as well as for the carbon nucleus in carbon dioxide of this mixture are discussed. The relaxation data are analyzed using a modified Stokes-Einstein-Debye equation, together with an AK model, that postulates the formation of CO 2 clusters with the 1-decanol molecule in CO 2 -decanol mixture at supercritical and near-critical liquid densities. Such CO 2 cluster formation with methanol molecules was also detected in earlier relaxation measurements in CO 2 -methanol mixtures at the comparable densities. Possible solvent clustering gradients along the aliphatic chain in 1-decanol in dense CO 2 are also suggested.

Comparative study of digestive enzymes of squid (Todarodes pacificus) viscera after supercritical carbon dioxide and organic solvent extraction

“…Due to the increase in pressure, the density of the SCO 2 was increased and hence the solvating power. The effect of pressure can be attributed to the increase in solvent power and by the strengthening of intermolecular physical interactions [16][17][18]. Similar results were found in the extraction of oil from green coffee [19] and boiled anchovy [8].…”

Characterization of the Yellow Croaker Larimichthys polyactis muscle Oil Extracted with Supercritical Carbon Dioxide and an Organic Solvent

“…The solvating power of supercritical fluids decreases with a rise in temperature because the density decreases dramatically as the temperature increases at low pressures. The effect of pressure can be attributed to the increase in solvating power and the strengthening of intermolecular interactions (Morita and Kajimoto, 1990;Bai et al, 1997;Bulgarevich et al, 2002). Similar results were found in the extraction of oil from green fied at 250 bar and 35ºC.…”

Supercritical CO2 recovery of caffeine from green coffee oil: new experimental solubility data and modeling

“…This tendency can also be associated to an increase in the magnitude of the physical intermolecular interactions between the solvent and solute molecules, since these are short range forces that strengthen as the distance decreases. [13][14][15] The temperature effect on the solubility shows the occurrence of a retrograde behavior at pressures lower than 19.3 MPa. Below this level of pressure, known as crossover pressure, the caffeine solubility decreases as temperature increases.…”