Comparison of solvent-based affinity separation processes using Cyrene and Sulfolane for aromatic/aliphatic separations

BACKGROUND: Vapor–liquid and liquid–liquid equilibria of unsaturated and saturated hydrocarbons with the bio-based solvent dihydrolevoglucosenone, trademarked as Cyrene, have been reported recently, aiming at the utilization of the solvent in liquid–liquid extraction (LLX) and extractive distillation (ED). In this work, for a model system comprised of methylcyclohexane (MCH) and toluene (TOL), both LLX-based and ED-based processes were compared over a wide range of compositions based on simulations in AspenPlus V10. An economic evaluation based on total annual costs was performed, and the processes using Cyrene were compared with equivalent processes using the industrial benchmark Sulfolane. RESULTS: In the absence of literature data for Sulfolane–MCH–TOL, additional liquid–liquid extractions were done to facilitate parameter estimation for simulation. The Cyrene-based ED process was found to be more efficient than the Sulfolane-based ED process, primarily at lower (<50 mol%) TOL feed concentration, but also higher TOL feed concentrations. For LLX purposes it was found that the Cyrene-based LLX process was economically the least attractive, primarily due to the larger miscibility region of Cyrene with the hydrocarbon mixture. CONCLUSIONS: The overall conclusion for this specific binary mixture is that LLX with Sulfolane is most economic at a TOL feed concentration of <30 mol%, while for >30 mol% the ED process with Cyrene is most economic. This process analysis showed that Cyrene is an appropriate bio-based alternative for Sulfolane as an entrainer for ED processes to separate aromatics and aliphatics.