Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum-boiling azeotropes and no systematic approaches for entrainer screening have been presented. A systematic approach to design of two-column extractive distillation for separating azeotropes with heavy entrainers has been proposed. A thermodynamic feasibility analysis for azeotropes with potential heavy entrainers was first conducted. Then, five important properties are selected for entrainer evaluation. Fuzzy logic and develop membership functions to calculate attribute values of selected properties have been used. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, the top five entrainers from the ranking list have been selected and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone-chloroform azeotropes with five potential entrainers.

A multicriteria decision-making methodology for the sustainability prioritization of industrial systems is proposed. The methodology incorporates a fuzzy Analytic Hierarchy Process method that allows the users to assess the soft criteria using linguistic terms. A fuzzy Analytic Network Process method is used to calculate the weights of each criterion, which can tackle the interdependencies and interactions among the criteria. The Preference Ranking Organization Method for Enrichment Evaluation approach is used to prioritize the sustainability sequence of the alternative systems. Moreover, a sensitivity analysis method was developed to investigate the most critical and sensitive criteria. The developed methodology was illustrated by a case study to rank the sustainability of five alternative hydrogen production technologies. The advantages of the developed methodology over the previous approaches were demonstrated by comparing the results determined by the proposed framework with those determined using the pervious approaches.

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The production of p-xylene has received more and more attention since it is widely used in chemical synthetic resins, pharmaceutical, chemical fiber, and pesticides industries. The p-xylene production through toluene alkylation is considered to be more promising due to high selectivity of p-xylene and little environmental impact compared to other methods. Although the existing p-xylene production process through toluene alkylation could achieve high selectivity of p-xylene, the methanol conversion is still as low as 70.0 %, requiring methanol recovery and recycle system and resulting in additional loss of toluene in the downstream separation of light component, methanol and toluene. Based on these findings, an intensified p-xylene production process through toluene alkylation with complete methanol conversion is proposed and simulated using Aspen Plus V8.4 ®. The optimal operating conditions for the alkylation reactor are obtained using the sensitivity analysis tool and sequential quadratic programming (SQP) optimization solver in Aspen Plus V8.4 ®. It is found that the methanol conversion could reach 98.0 % with p-xylene selectivity of 92.0 % through increasing reaction temperature to 442.5 ᵒ C and pressure to 4.0 bar compared to the existing process, resulting in the removal of methanol recovery and recycle system and less toluene loss in the downstream separation. The comparative evaluations demonstrate that the

To the best of our knowledge, very few efforts have been investigated for separating heterogeneous mixtures methanol/toluene/water with multiazeotropes using extractive dividing-wall column (EDWC). In this work, we propose a systematic approach for the energy-efficient EDWC to achieve less capital cost and operating cost in separating heterogeneous multiazeotropes mixtures, which involves thermodynamic feasible insights via residue curve maps to find separation constraints, global optimization based on a proposed CPOM model, and a dynamic control through Aspen Dynamics simulator to better maintain product purities. An energy-saving EDWC with heat integration (HI-EDWC) flowsheet is then proposed to achieve the minimum total annualized cost (TAC). The computational results show that the TAC of the proposed HI-EDWC is significantly reduced by 15.14% compared with the optimal double-column extractive distillation with an additional decanter. Furthermore, an effective control strategy CS3 with a fixed reboiler duty-to-feed ratio and temperature/(S/F) cascade is proposed to better handle the methanol, toluene, and water product purities than basic control structures CS1 and CS2 while feed flow rate and composition disturbances are introduced in the proposed HI-EDWC process.

The separation of the ternary nonideal system ethyl acetate (EtAC)/ethanol (EtOH)/water with multiazeotropes is very important since they are always generated in the production process of n-butanol synthesis from ethanol, which is much more difficult due to the formation of the multiazeotrope and distillation boundary. Herein, a systematic conceptual design, optimization, and control approach for ternary extractive distillation of multiazeotrope mixtures EtAC/EtOH/water is proposed. The procedure involves entrainer screening, conceptual design, global optimization, process evaluation, and a robust control strategy. The optimization results demonstrate that the total annual cost, exergy loss, and carbon dioxide emissions of the proposed triple-column extractive distillation are significantly reduced compared with those of the existing process. Dynamic performances illustrate that the improved dual temperature and feedforward control strategy can well handle the three product purities, while two kinds of disturbances (i.e., feed flow rate and composition) are introduced.

In this study, an integrated vector-based three-dimensional (3D) methodology for the life cycle sustainability assessment (LCSA) of chemical process alternatives is proposed. In the methodology, a 3D criteria assessment system is first established by using the life cycle assessment, the life cycle costing, and the social life cycle assessment to determine the criteria from the environmental, economic, and social pillars, respectively. The methodology incorporates the analytic hierarchy process (AHP) method to convert experts' judgments on the soft criteria into quantitative data and realize a unitary scale for both quantified soft criteria and normalized hard criteria. After assigning appropriate weights to each pillar and criterion by using the AHP method, the sustainability of the alternative processes can be prioritized by employing a novel vector-based algorithm, which combines the absolute sustainability performance and the relative sustainability deviation of the investigated processes. A case study on the sustainability assessment of three alternative ammonia production processes demonstrates that the proposed methodology is able to serve as a comprehensive and rigorous tool for the stakeholders to rank and identify the most sustainable chemical process alternatives.

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