Abstract
Aromatic/aliphatic separation stands as a challenge for both industry and academia. More and more efforts are being made to improve energy-demanding technologies based on liquid–liquid extraction or extractive distillation processes. Recently, ionic liquid-based technologies devoted to separating benzene, toluene, and xylene from pyrolysis gasoline have been evaluated, and extractive distillation showed more potential than liquid–liquid extraction in terms of separation performance and global energy requirements. In this work, extractive distillation with ionic liquids is completely evaluated from solvent selection to rate-based process design and compared with the Morphylane benchmark process. The ILUAM database is explored through a validated COSMO/Aspen methodology to understand the impact of the ionic liquid nature on the extractive distillation operation. A parametric study focused on the extractive distillation column (EDC) is conducted for preliminary set initial guesses to design task. The final issue is centered on rigorously designing the ionic liquid-based and Morphylane processes at commercial specifications. Two different ionic liquid-based process configurations are evaluated based on the opportunities that the use of ionic liquids enables. The new process configuration working with [emim][TCM] reduces the energy costs and capital expenditures associated with the Morphylane process by 67 and 63%, respectively, along with a reduction in the solvent costs, confirming it as a cleaner alternative. In addition, a parametrization of the Cubic Plus Association equation of state (CPA EoS) obtained from the regression of experimental vapor–liquid–liquid equilibrium data is also used to simulate the EDC in equilibrium and rate-based mode. Both models provide similar results, confirming the ability of the conductor-like screening model–segment activity coefficient model as an a priori tool and the reliability of the CPA EoS as a regressive alternative to describe these kinds of complex multicomponent systems.
Highlights
Petroleum refining gives rise to mixtures where aromatic and nonaromatic hydrocarbons coexist.[1]
COSMO-SAC code 1 was revealed as the best option to scan the ILUAM database for the separation of aromatics from aliphatics because the LLE and VLE are described with more accuracy than with COSMO-SAC code 2 and 3, standing the three equations as good qualitative descriptors of the experimental data
The aromatic selectivity of the ionic liquid is confirmed as the key property for the separation of the binary mixtures {n-octane + benzene} independent of the operating conditions in the column
Summary
Petroleum refining gives rise to mixtures where aromatic and nonaromatic hydrocarbons coexist.[1]. It was found that selectivity plays a dominant role in maximizing the aliphatic/ aromatic relative volatility, but an eye must be kept on the distribution ratio to avoid two liquid phases in equilibrium.[24−26] Tricyanomethanide-based ionic liquids, which have balanced extractive properties, turned out as the best mass agents.[27] the vapor−liquid and vapor−liquid−liquid equilibria (VLE/ VLLE) of several binary {aliphatic or aromatic + ionic liquid} and ternary systems {aliphatic + aromatic + ionic liquid} were determined in a wide range of temperatures and solvent-to-feed (S/F) ratios All these data were modeled with the Cubic Plus Association equation of state (CPA EoS).[28−30]. Both CPA and COSMO-SAC models describe the extractive distillation process, confirming the COSMO-SAC model as a reliable a priori tool and setting the CPA EoS as an alternative approach obtained from the regression of experimental VLE/VLLE data to describe these kinds of complex multicomponent systems
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