CO₂-Expanded Alkyl Acetates: Physicochemical and Molecular Modeling Study and Applications in Chemical Processes

Abstract

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Pressure and Temperature Tuning of Gas-Expanded Liquid Structure and Dynamics

“…This is due to the reduction of intermolecular interactions between octene–octene and nonanal–nonanal with increasing CO 2 pressure, as observed in the RDFs for both systems. A similar trend in viscosity has been observed experimentally for alkyl acetates, alcohols, acetonitrile, and cyclohexane when expanded by CO 2 . ,, Also, with increasing temperature, CO 2 -expanded 1-octene and nonanal show a decrease in the shear viscosity for a fixed pressure, consistent with the general behavior of neat liquids. Additionally, at a given temperature and CO 2 mole fraction, the viscosity of CO 2 -expanded nonanal is higher than that for CO 2 -expanded 1-octene.…”

“…To our knowledge, it has not been previously noted, though the viscosity has been calculated as a function of x CO 2 for a number of CXLs. 17,42,43 These results found a linear dependence of η s on x CO 2 for CO 2 -expanded cyclohexane, 42 acetonitrile, 17,42 and alkyl acetates 43 but quadratic dependence for methanol. 42 The data presented in ref 17 are sufficient to construct a plot of η s −1 versus V/V 0 for CO 2 -expanded acetonitrile, and for that system these two quantities are reasonably described as linearly related.…”

“…Previous studies have shown that CO 2 -expanded liquids exhibit two different dependencies of density with increasing CO 2 pressure (or, equivalently, mole fraction). − CXLs formed from alcohols (methanol, ethanol, propanol, butanol, isopropyl alcohol, and tert -butyl alcohol), acetonitrile, and cyclohexane show a (mass) density maximum as the mass increases at low x CO 2 but drops at higher CO 2 pressures. − On the other hand, CO 2 -expanded ethyl lactate shows a decrease of the mass density with increasing x CO 2 . The observed density maximum behavior has been attributed to CO 2 molecules first occupying the vacant space between the liquid molecules at low CO 2 pressures, whereas at higher CO 2 pressures, the more rapid volume increase (see Figure ) is associated with a greater displacement of the organic solvent molecules, leading to a density drop .…”

“…40−42 On the other hand, CO 2 -expanded ethyl lactate shows a decrease of the mass density with increasing x CO 2 . 43 The observed density maximum behavior has been attributed to CO 2 molecules first occupying the vacant space between the liquid molecules at low CO 2 pressures, whereas at higher CO 2 pressures, the more rapid volume increase (see Figure 5) is associated with a greater displacement of the organic solvent molecules, leading to a density drop. 42 The monotonically decreasing density with x CO 2 in the ethyl lactate CXL was attributed to the dilution of relatively dense ethyl lactate by CO 2 .…”

Palladium Nanoparticles in Glycerol/Ionic Liquid/Carbon Dioxide Medium as Hydrogenation Catalysts

“…Figure 3 collects the values of viscosity measured by using DCVJ at 60 °C and 80 °C. As reported in the literature for liquids in general, 13,[63][64][65] a monotonous decrease in viscosity of the DES (choline tosylalaninate/glycerol mixture with a 1/100 ratio) was expected by increasing CO2 pressure. However, we observed an increase in the viscosity at pressures lower than 50 bar and a viscosity decrease at higher pressures.…”