Separations of dispersions formed by mixing immiscible organic roomtemperature ionic liquids (IL)/hydrocarbon/and aqueous systems using a centrifugal solvent-extraction contactor have been successfully demonstrated in proof-ofconcept testing. This accomplishment is significant in that physical property factors that are typical of ionic liquid systems (e.g., similar densities of the bulk phases, low interfacial tensions, and high viscosities) are typically unfavorable for dispersion separation, particularly in continuous processes. Efficient separation of dispersions containing ionic liquid solvents is essential for utilization of these compounds in liquid-liquid extraction applications to maximize both solute transfer efficiency and solvent recovery. Efficient solvent recovery is of particular concern in IL applications because of the high cost of most IL solvents. This paper presents the results of initial experiments with three hydrophobic ionic liquids to determine how their physical properties affect phase mixing and phase disengagement in contact with an aqueous solution using a centrifugal contactor. While the results of the reported work are promising, additional work is needed to optimize existing mathematical models of contactor hydraulics to address special considerations involved in IL-based processes and to optimize the equipment itself for IL applications.
The kinetics of the transesterification of soybean oil has been investigated in a centrifugal contactor reactor/ separator at temperatures from 45 to 80 °C and pressures up to 2.6 bar. The high shear force and turbulent mixing achieved in the contactor minimized the effect of diffusion on the apparent reaction rate, and hence it could be assumed that the transesterification rate was limited by the reaction kinetics. The yields of product methyl esters were quantified using gas chromatography flame ionization detection (GC-FID), infrared (IR) spectroscopy, proton nuclear magnetic resonance (H 1 NMR), and viscosity measurements and typically were found to achieve 90% of complete conversion within 2 min. However, to meet American Society for Testing and Materials (ASTM) specifications with one pass through the reactor, a minimum 22-min residence time at 80 °C was needed. Performance was improved by stepwise processing, allowing separation of byproduct glycerine and injection of additional small aliquots of methanol at each step. The chemical kinetics was successfully modeled using a three-step mechanism of reversible reactions, and employing activation energies from the literature, with some modification in pre-exponential factors. The mechanism correctly predicted the exponential decline in reaction rate as increasing methyl ester and glycerine concentrations allow reverse reactions to occur at significant rates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.