Separation of toluene from heptane via liquid-liquid extraction in microtube contactor using triethylene glycol

A T-microtube contactor was used for the separation of toluene by liquid-liquid extraction using triethylene glycol (TEG). A full factorial design of experiments was applied with 3 levels and 2 blocks for 3 factors including extraction temperature (30-60 degrees C), contact time (2-10 s), and solvent-to-feed molar ratio (1:1-5:1). Statistical analysis revealed that, other than the main effects, the interaction between contact time and solvent-to-feed molar ratio was significant. The extraction efficiency increased with increasing temperature and/or increasing molar ratio. Within the range of contact time investigated, extraction with 2 s of contact time exhibited superior performance compared to longer contact times due to the micro-droplets of the disperse phase. Increasing the portion of solvent and/or decreasing the contact time resulted in rising pressure drop. The optimal conditions were 2 s of contact time, 60 degrees C and the TEG/feed molar ratio of 5:1 with the extraction efficiency of 58.36%. The overall volumetric mass transfer coefficient was in the range of 1.4 x 10(-1)-1.15 x 10(0) s(-1) for extraction at 30 degrees C. A regression model for the prediction of extraction efficiency was proposed in the form of quadratic model. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.