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Extractive Distillation with Ionic Liquids As Solvents : Selection and Conceptual Process Design

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Extractive Distillation with Ionic Liquids As Solvents : Selection and Conceptual Process Design Extractive distillation with ionic liquids as solvents : selection and conceptual process design Citation for published version (APA): Gutierrez Hernandez, J. P. (2013). Extractive distillation with ionic liquids as solvents : selection and conceptual process design. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR751728 DOI: 10.6100/IR751728 Document status and date: Published: 01/01/2013 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. 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Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Download date: 02. Oct. 2021 Extractive distillation with ionic liquids as solvents: selection and conceptual process design Juan P. Gutiérrez H. Doctoral committee Chairman Prof.dr.ir. Hans Kuipers Eindhoven University of Technology Promoter Prof.dr.ir. André B. de Haan Eindhoven University of Technology Co-promoter Dr.ir. G. Wytze Meindersma Eindhoven University of Technology Examiners Prof.dr. Geert-Jan Witkamp Delft University of Technology Prof.dr. Henk van den Berg University of Twente Prof.dr. Dieter Vogt Eindhoven University of Technology Prof.dr. Kai Leonhard RWTH Aachen University Dr. ir. Anton A. Kiss AkzoNobel B.V. RD&I. This project was financially supported by AgentschapNL, formerly SenterNovem, project number EOSLT06016 (Energie Onderzoek Subsidie, Lange Termijn). A catalogue record is available from the Eindhoven University of Technology Library. Extractive distillation with ionic liquids as solvents: selection and conceptual process design Gutiérrez H., J.P. ISBN: 978-90-386-3356-5 Cover designed by Juan P. Gutiérrez H. Printed by Gildeprint, Enschede, The Netherlands. Copyright © Gutierrez, J.P. The Netherlands, 2013. All rights reserved. Extractive distillation with ionic liquids as solvents: selection and conceptual process design PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Technische Universiteit Eindhoven, op gezag van de rector magnificus, prof.dr.ir. C.J. van Duijn, voor een commissie aangewezen door het College voor Promoties in het openbaar te verdedigen op dinsdag 2 april 2013 om 16.00 uur door Juan Pablo Gutiérrez Hernández geboren te Manizales, Colombia Dit proefschrift is goedgekeurd door de promotor: prof.dr.ir. A.B. de Haan Copromotor: dr.ir. G.W. Meindersma Summary Extractive distillation technology is widely used in the chemical and petrochemical industries for separating azeotropic, close-boiling and low relative volatility mixtures. It uses an additional solvent in order to interact with the components of different chemical structure within the mixture. The activity coefficients are modified in such a way that the relative volatility is increased. Therefore, the choice of the solvent determines the effectiveness of this process. Several solvent selection methodologies had been developed in the literature. They are based on one-way interaction parameters, meaning interactions of the components to be separated with the solvent. It has been widely accepted to consider as a promising solvent the one which is able to increase the relative volatility the most. However, the total annual cost (TAC) and the energy demand influence the final selection. Ionic liquids (ILs) are promising replacements of existing volatile solvents in extractive distillation. However, at this moment insufficient knowledge exists on the optimal properties for ionic liquids to be employed and their implementation in actual process systems. The main goal of this research was to analyze the selection and performance of ionic liquids in extractive distillation processes for three separation cases which differ from each other in polarity and chemical structures: 1-hexene/n-hexane, methylcyclohexane/toluene and water/ethanol. Theoretical ionic liquid design and selection for each mixture is done using COSMOtherm software (version C2.1, release 01.11a) by predicting activity coefficients at infinite dilution. Experimental selectivities and relative volatilities of real solutions were measured in order to choose the most suitable ionic liquids. At last, different extractive distillation processes using ionic liquids were proposed and analyzed. 1-Hexene/n-hexane separation Olefins are important base chemicals used for the manufacture of poly(olefins), plasticizers, etc. and according to Sasol, the projected demand for 2012 of C6-C8 olefins is around 0.85x106 ton. Due to the small differences in boiling temperatures and to the low relative volatility of the system, the separation of olefins and paraffins is energy intensive, meaning that all the commercially available processes for the production of olefins use several fractional distillation columns. In this work, 1-hexene and n-hexane were chosen as representative olefin and paraffin components. Extractive distillation using N-methyl-2-pyrrolidone (NMP) has been used to separate this mixture. COSMOtherm activity coefficients at infinite dilution were used to select suitable ionic liquids for this case study. Non-cyclic, cyclic and aromatic-like cations were tested in this software in combination with 27 different anions. According to the i activity coefficients predicted with COSMOtherm, the solubility and selectivity of ionic liquids in 1-hexene and n-hexane is very low. This was confirmed experimentally for the selected ionic liquids using vapor – liquid equilibrium data. None of the ILs studied in this work is able to significantly increase the relative volatility in comparison with the conventional solvent NMP. Only the ionic liquid 1- hexyl-3-methyl-imidazolium tetracyanoborate [HMIM][TCB] reached a slightly higher relative volatility (1.63) than the conventional solvent NMP (1.55). However, the increase is not large enough to consider this solvent as a suitable replacement. Besides this, the ionic liquids have solubility constraints which force the use of large solvent to feed ratios to avoid the formation of two liquid phases. Methylcyclohexane/toluene separation Aromatics are among the most important chemical raw materials for the manufacture of plastics, synthetic rubber and synthetic fiber. The total production in 2009 in Western Europe of benzene, toluene and p-xylene was about 7.2x106, 1.6x106 and 1.7x106 tons, respectively. Because of the low relative volatility, external agents are used to increase the economic feasibility of the distillation units, e.g. N-methyl-2-pyrrolidone, sulfolane. The activity coefficients at infinite dilution for the mixture methylcyclohexane (MCH) and toluene with ionic liquids predicted with COSMOtherm showed a clear compromise between selectivity (easiness of separation) and solubility. Aromatic- like cations in combination with bis((trifluoromethyl)sulfonyl)imide (BTI) and tetracyanoborate (TCB) anions were selected and experimentally investigated. The relative volatility of the mixture MCH + toluene increased when any of the selected solvents (including the conventional solvent NMP) was added. The results showed that the TCB anion performed better than BTI. Therefore, the ILs 1-hexyl-3-methyl imidazolium tetracyanoborate [HMIM][TCB] and 1-butyl-3-methyl imidazolium tetracyanoborate [BMIM][TCB] seem to be the most promising replacements of NMP in the extractive distillation of methylcyclohexane and toluene. Binary and ternary liquid-liquid experimental data for the systems methylcyclohexane + toluene + [HMIM][TCB] and [BMIM][TCB] were collected and correlated with the NRTL and UNIQUAC thermodynamic models. The binary correlations were less satisfactory than ternary correlations. The results showed that UNIQUAC represented the experimental data better than the NRTL model, with a root mean square error below 0.02. The parameters obtained from the regressions of liquid-liquid equilibrium data were used to predict the vapor-liquid equilibrium (VLE). These were compared with experimental data taken by a headspace technique which showed that UNIQUAC and its parameters are able to predict the VLE of the ternary
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