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Highlights • The entrainers p -xylene, butyl propionate and isobutyl acetate were selected. • The VLE data for (DMC + entrainers) and (ethanol + isobutyl acetate) were measured. • The measured VLE data were correlated by the NRTL, UNIQUAC and Wilson models. • The extractive distillation process for separating DMC and ethanol was proposed. Abstract Dimethyl carbonate and ethanol can form an azeotrope with the minimum boiling point. To separate the azeotrope (dimethyl carbonate + ethanol) by extractive distillation, p -xylene, butyl propionate, and isobutyl acetate were chosen as entrainers, and the isobaric vapour-liquid equilibrium (VLE) data for the binary systems of (dimethyl carbonate + p -xylene), (dimethyl carbonate + butyl propionate), (dimethyl carbonate + isobutyl acetate) and (ethanol + isobutyl acetate) were measured at 101.3 kPa using a modified Rose type recirculating still. The thermodynamic consistency of the VLE experimental data for the four binary mixtures was tested by the Herington and van Ness methods. Furthermore, the measured VLE data were correlated by the NRTL, UNIQUAC and Wilson thermodynamic models and the binary interaction parameters of the three models were regressed. Based above, an extractive distillation process with the entrainer of p -xylene was proposed and simulated to separate the azeotrope (dimethyl carbonate + ethanol). [ABSTRACT FROM AUTHOR]

• Energy-saving separation of methyl alcohol - methyl ethyl ketone – tert -butanol azeotropic system is studied. • A few extractive distillation processes with ionic liquid are proposed and parametrically optimized. • The best one greatly reduces energy consumption, investment and CO 2 emission. • An efficient simulated annealing based optimization strategy is designed. Several new extractive distillation configurations using green and highly selective ionic liquid (IL) as extractant are proposed as an alternative to the conventional extractive distillation (CED) and conventional extractive dividing wall column (CEDWC) configuration to separate methyl alcohol (MeOH)-methyl ethyl ketone (MEK)-tert butyl alcohol (TBA) azeotropic mixture, including direct and indirect extractive distillation (direct-ED, indirect-ED), azeotropic extractive distillation (AED), and extractive dividing wall column (EDWC). These schemes are optimized with the objective of total annual costs (TAC) by simulated annealing based optimization method. Among these schemes, EDWC is undoubtedly the best due to the benefits of IL and dividing wall column. As compared with the CED process, it can reduce TAC by 22.19%, total capital cost by 31.47%, total operating cost by 8.35%, CO 2 emission by 7.7%. In addition, the computation shows that the used optimization method is very practical for the optimal design of complex distillation systems with the advantages of direct, efficient, robust and global optimal. [ABSTRACT FROM AUTHOR]

• Efficient triple-side-stream quaternary extractive distillation is developed. • A computing-efficient simulated annealing optimization strategy is used. • The best one among side-stream flow control schemes is identified. • Side-stream flows dynamic responses to feed disturbances are examined. Dynamic control of extractive distillation process with multiple liquid side-streams is challenging although it has an energy-saving potential. In this work, the optimal design and control of a high-efficient triple-side-stream quaternary extractive distillation process (TSQED) is presented for separating acetone/methanol/butanone/tert‑butanol. All operating parameters are optimized by a simulated annealing based systematic method, resulting in the reduction of total annual costs by 9.37%, energy consumption by 18.76%, and CO2 emissions by 33.17% as compared with conventional extractive distillation process. Subsequently, three control structures (CS1, CS2, and CS3) are proposed and demonstrated according to different side-stream flowrate control strategy. In the CS1, the side-stream flowrate is proportional to feed flow. In the CS2, the side-stream flowrate is proportional to reboiler vapor flow. In the CS3, and temperature-sensitive plate in distillation column is identified and cascaded by side-stream flowrate. By contrast, CS3 is far better than CS1 and CS2 in terms of dynamic responses and integral performance criteria. This attributes to the virtuous effect of the inferential temperature control on side-stream flowrate in the whole process control of TSQED. Finally, the feedforward control of QR/F is added in the CS4 to further improve the effectiveness of CS3. [Display omitted] [ABSTRACT FROM AUTHOR]