D. Hartanto
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1
To achieve this objective, a multi-stage entrainer selection methodology was developed, integrating initial screening, predictive modelling, experimental validation, and process performance comparison. In Chapter 2, potential greener entrainers were screened using an initial screening phase, which identified potential greener entrainers based on high boiling temperatures, favorable solvency, and compliance with green chemistry principles. Subsequently, key separation metrics, such as selectivity and capacity at infinite dilution, and performance index, were predicted using quantum chemical calculations (COSMO-RS). In addition, relative volatility was predicted using both COSMO-RS and group contribution methods (UNIFAC and modified UNIFAC Dortmund). Promising candidates were then evaluated experimentally through miscibility tests and relative volatility measurements. Selected greener entrainer candidates, along with benchmark entrainer NMP in both mixtures, were examined for their vapor-liquid equilibrium (VLE) data. Chapters 3 and 4 focus on generating reliable VLE data for both mixtures in the presence of each selected greener entrainer at various entrainer-to-feed ratios (E/F) and operating pressures. The experimental data were examined through thermodynamic consistency tests. Moreover, the data were regressed using activity coefficient models (NRTL and UNIQUAC) to obtain the optimum binary interaction parameters. In Chapter 5, these parameters were implemented in Aspen Plus V.12 for ED process simulations. Greener entrainers were evaluated according their performance compared to NMP using economic indicator (total annual cost) and sustainability metrics, such as energy requirements, water consumption, and CO2 emissions. In addition, the use and limits of predictive tools for ED entrainer screening were evaluated.
The screening results in Chapter 2 identify promising greening entrainers. For the methylcyclohexane–toluene mixture, gamma-valerolactone (GVL), n-butyl-2-pyrrolidone (NBP), and dimethyl isosorbide (DMI) were selected for VLE data experimental evaluation, while NBP, DMI, and guaiacol were selected for the n-hexane–ethanol mixture. Some NADESs and other biobased and greener organic entrainers exhibited favorable predicted selectivity but showed immiscibility issues in the investigated mixtures and were therefore excluded from further evaluation. In Chapters 3 and 4, the measured VLE data for both mixtures containing each entrainer passed the thermodynamic consistency test, indicating the reliability of the data. The VLE data confirmed that the selected greener entrainers significantly increase the relative volatility of the mixtures and effectively remove close-boiling and azeotropic behavior. Process simulations discussed in Chapter 5 indicate that for the separation of methylcyclohexane-toluene, GVL reduces total annual cost (TAC) by 5.6% compared to NMP, while also having a lower energy intensity of 6.1%. In contrast, DMI and NBP exhibit slightly higher TAC values of 6.2% and 15.2%, respectively, along with slightly higher energy intensity of 3.0% and 18.2%. For CO2 emissions and water consumption, GVL remains comparable to NMP, with both exhibiting values of 0.04-0.05 kgCO2/kgproducts and 0.05 m3water/kgproducts. For the n-hexane-ethanol mixture, NBP shows a comparable TAC, with 1.6% slightly higher than that of NMP, with a 3.1% increase in energy intensity. Meanwhile, guaiacol and DMI demonstrate increasing TAC by 10.9% and 14.0%, respectively, along with energy intensity that are 12.5% and 18.8% higher. In addition, CO2 emissions for these options remain comparable at around 0.05-0.06 kgCO2/kgproducts and water consumption is similar at approximately 0.05-0.07 m3water/kgproducts. Importantly, these greener entrainers have significantly lower toxicity profiles than NMP. Furthermore, the TAC deviation threshold of 32% from predictive models compared to the experimental-based NRTL model makes them suitable for early-stage entrainer screening. However, experimental validation remains necessary for detailed process design.
Overall, this thesis provides a systematic and experimentally validated framework for selecting greener entrainers in extractive distillation. The work delivers new and reliable VLE data along with optimum binary interaction parameters and a comparison of process-level performance. The findings demonstrate that replacing conventional entrainers, such as NMP, with greener alternatives is technically feasible, economically viable, and environmentally sustainable. This supports the transition toward more eco-efficient extractive distillation processes.
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To achieve this objective, a multi-stage entrainer selection methodology was developed, integrating initial screening, predictive modelling, experimental validation, and process performance comparison. In Chapter 2, potential greener entrainers were screened using an initial screening phase, which identified potential greener entrainers based on high boiling temperatures, favorable solvency, and compliance with green chemistry principles. Subsequently, key separation metrics, such as selectivity and capacity at infinite dilution, and performance index, were predicted using quantum chemical calculations (COSMO-RS). In addition, relative volatility was predicted using both COSMO-RS and group contribution methods (UNIFAC and modified UNIFAC Dortmund). Promising candidates were then evaluated experimentally through miscibility tests and relative volatility measurements. Selected greener entrainer candidates, along with benchmark entrainer NMP in both mixtures, were examined for their vapor-liquid equilibrium (VLE) data. Chapters 3 and 4 focus on generating reliable VLE data for both mixtures in the presence of each selected greener entrainer at various entrainer-to-feed ratios (E/F) and operating pressures. The experimental data were examined through thermodynamic consistency tests. Moreover, the data were regressed using activity coefficient models (NRTL and UNIQUAC) to obtain the optimum binary interaction parameters. In Chapter 5, these parameters were implemented in Aspen Plus V.12 for ED process simulations. Greener entrainers were evaluated according their performance compared to NMP using economic indicator (total annual cost) and sustainability metrics, such as energy requirements, water consumption, and CO2 emissions. In addition, the use and limits of predictive tools for ED entrainer screening were evaluated.
The screening results in Chapter 2 identify promising greening entrainers. For the methylcyclohexane–toluene mixture, gamma-valerolactone (GVL), n-butyl-2-pyrrolidone (NBP), and dimethyl isosorbide (DMI) were selected for VLE data experimental evaluation, while NBP, DMI, and guaiacol were selected for the n-hexane–ethanol mixture. Some NADESs and other biobased and greener organic entrainers exhibited favorable predicted selectivity but showed immiscibility issues in the investigated mixtures and were therefore excluded from further evaluation. In Chapters 3 and 4, the measured VLE data for both mixtures containing each entrainer passed the thermodynamic consistency test, indicating the reliability of the data. The VLE data confirmed that the selected greener entrainers significantly increase the relative volatility of the mixtures and effectively remove close-boiling and azeotropic behavior. Process simulations discussed in Chapter 5 indicate that for the separation of methylcyclohexane-toluene, GVL reduces total annual cost (TAC) by 5.6% compared to NMP, while also having a lower energy intensity of 6.1%. In contrast, DMI and NBP exhibit slightly higher TAC values of 6.2% and 15.2%, respectively, along with slightly higher energy intensity of 3.0% and 18.2%. For CO2 emissions and water consumption, GVL remains comparable to NMP, with both exhibiting values of 0.04-0.05 kgCO2/kgproducts and 0.05 m3water/kgproducts. For the n-hexane-ethanol mixture, NBP shows a comparable TAC, with 1.6% slightly higher than that of NMP, with a 3.1% increase in energy intensity. Meanwhile, guaiacol and DMI demonstrate increasing TAC by 10.9% and 14.0%, respectively, along with energy intensity that are 12.5% and 18.8% higher. In addition, CO2 emissions for these options remain comparable at around 0.05-0.06 kgCO2/kgproducts and water consumption is similar at approximately 0.05-0.07 m3water/kgproducts. Importantly, these greener entrainers have significantly lower toxicity profiles than NMP. Furthermore, the TAC deviation threshold of 32% from predictive models compared to the experimental-based NRTL model makes them suitable for early-stage entrainer screening. However, experimental validation remains necessary for detailed process design.
Overall, this thesis provides a systematic and experimentally validated framework for selecting greener entrainers in extractive distillation. The work delivers new and reliable VLE data along with optimum binary interaction parameters and a comparison of process-level performance. The findings demonstrate that replacing conventional entrainers, such as NMP, with greener alternatives is technically feasible, economically viable, and environmentally sustainable. This supports the transition toward more eco-efficient extractive distillation processes.
Green solvents have emerged as promising green entrainers to substitute conventional entrainers in extractive distillation to separate azeotropic mixtures. However, the limited availability of thermodynamic data for green-solvent-containing mixtures continues to hinder their practical implementation in this process. This study is the first to report experimental vapor–liquid equilibrium (VLE) data for the n-hexane + ethanol azeotropic system containing the greener entrainer 1-butylpyrrolidin-2-one (NBP) alongside the benchmark entrainer 1-methylpyrrolidin-2-one (NMP). Using a Fischer Labodest VLE602 ebulliometer, VLE measurements were performed at pressures of 50.0 and 100.0 kPa and various entrainer-to-feed ratios (E/F). The reliability of the reported VLE data was tested and confirmed using the Van Ness thermodynamic consistency test. The results show that NBP enhances relative volatility and effectively eliminates the azeotrope, performing comparably to the benchmark entrainer NMP. The nonrandom-two-liquid (NRTL) model was utilized to regress the investigated VLE data and determine the optimum binary interaction parameters (BIPs). As a result, the NRTL model demonstrates good agreement with the experimental data. This thermodynamic modeling confirms the data’s reliability and suitability for process design, highlighting NBP’s potential as an environmentally friendly alternative entrainer in extractive distillation.
In this work, dimethyl isosorbide (DMI) and 1-butylpyrrolidin-2-one (NBP), as biobased and greener organic solvents, were used for the first time as entrainers in extractive distillation to separate a close-boiling mixture of methylcyclohexane and toluene. Vapor–liquid equilibrium (VLE) data were collected for pseudoternary mixtures consisting of methylcyclohexane and toluene in the presence of DMI and NBP at various entrainer-to-feed ratios (E/F) and pressures. The VLE measurements were conducted by using a Fischer Labodest VLE602 ebulliometer, and the thermodynamic consistency of the data was verified by using the Van Ness test. Both DMI and NBP were found to increase the relative volatility of methylcyclohexane to toluene, successfully eliminating close-boiling behavior. Compared to benchmark entrainers, both outperformed 1-methylpyrrolidin-2-one (NMP) and sulfolane under certain conditions. In comparison with other green entrainers, DMI and NBP showed similar performance to gamma-valerolactone (GVL) and Cyrene under specific conditions. The VLE data were accurately correlated by using the nonrandom two-liquid (NRTL) model.