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3 pages, 191 KiB

Open AccessEditorial

Advances in Deep Eutectic Solvents: New Green Solvents

by Shuhang Ren, Tiancheng Mu and Weize Wu

Processes 2023, 11(7), 1920; https://doi.org/10.3390/pr11071920 - 26 Jun 2023

Cited by 8 | Viewed by 3033

Abstract

This Special Issue, entitled “Advances in deep eutectic solvents: New green solvents”, was organized to collect original research articles on the latest developments in the new green solvents, deep eutectic solvents (DESs), and their applications [...] Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

Research

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22 pages, 2750 KiB

Open AccessEditor’s ChoiceArticle

Technical and Economical Assessment of CO₂ Capture-Based Ammonia Aqueous

by Nela Slavu, Adrian Badea and Cristian Dinca

Processes 2022, 10(5), 859; https://doi.org/10.3390/pr10050859 - 26 Apr 2022

Cited by 14 | Viewed by 2801

Abstract

In the context of climate change and the reduction in CO₂ emissions from fossil fuel combustion, the integration of CO₂ capture technologies in steam power plants is a key solution. The aim of this study was to analyze the use of [...] Read more.

In the context of climate change and the reduction in CO₂ emissions from fossil fuel combustion, the integration of CO₂ capture technologies in steam power plants is a key solution. The aim of this study was to analyze the use of ammonia, at different mass concentrations, in capturing post-combustion CO₂ in a coal-fired power station and comparing it with the reference 30% MEA case. In this regard, a multi-criteria model was developed to establish the optimal solvent used, considering the least impact on technical performance, economic, and environmental indicators. As a result, the lowest CO₂ capture cost was obtained for the CO₂ capture process based on 7% NH₃, with 59.07 €/tCO₂. Integration of the CO₂ capture process is more economically viable when the CO₂ emissions tax is higher than 70 €/tCO₂ for 7% NH₃ and 15% NH₃, 80 €/tCO₂ for 5% NH₃ and 30% MEA, and 90 €/tCO₂ for 2% NH₃. Regarding the overall efficiency, the energy penalty associated with the CO₂ capture process integration varied between 15 and 35%, and the lowest value was obtained for 15% NH₃. The GWP indicator ranged between 113 and 149 kg_CO₂_eq/MWh for NH₃ compared to MEA 133 kg_CO₂_eq/MWh and the case with no CO₂ capture was 823 kg_CO₂_eq/MWh. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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20 pages, 9295 KiB

Open AccessArticle

Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with Extractive Distillation

by Fang Bai, Chao Hua, Yongzhi Bai and Mengying Ma

Processes 2021, 9(10), 1706; https://doi.org/10.3390/pr9101706 - 23 Sep 2021

Cited by 10 | Viewed by 2585

Abstract

Deep eutectic solvents (DESs) have properties that make them suitable candidates to be used as entrainers for extractive distillation. In the previous work, it was proven that DES(1:2) (tetrabutylammonium bromide: levulinic acid, 1:2, molar ratio) can break the cyclohexane-benzene azeotrope. In the present [...] Read more.

Deep eutectic solvents (DESs) have properties that make them suitable candidates to be used as entrainers for extractive distillation. In the previous work, it was proven that DES(1:2) (tetrabutylammonium bromide: levulinic acid, 1:2, molar ratio) can break the cyclohexane-benzene azeotrope. In the present work, the HBA and HBD ratio and molar concentration of DES were optimized to obtain a better constitute and condition of DES to be utilized in cyclohexane and benzene extractive distillation. The physical properties and structure of the prepared DESs were characterized. Vapor–liquid equilibrium data of the ternary system (benzene + cyclohexane + DESs) were also measured at atmospheric pressure. All experimental equilibrium data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models, from which the coefficient of determination (R2) of the three pseudo-ternary systems fitting was calculated. From the obtained results, the best HBA and HBD ratio in the DESs is elucidated as 1:2, the best molar concentration of DES is 0.1, and the NRTL model predicts the experimental data more accurately than the Wilson and UNIQUAC models. From the derived mechanism, the formation of stronger hydrogen bond and π–π bond interactions between DES and benzene is obtained when HBA and HBD ratio in DES is 1:2. In other conditions, the azeotrope cannot be broken, or the efficiency is low. The present work provides an environmentally friendly method to separate aromatic/aliphatic mixtures and act as a guide for further study of DESs in extractive distillation. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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10 pages, 272 KiB

Open AccessFeature PaperArticle

A Preliminary Assessment of the ‘Greenness’ of Halide-Free Ionic Liquids—An MCDA Based Approach

by Kranthi Kumar Maniam and Shiladitya Paul

Processes 2021, 9(9), 1524; https://doi.org/10.3390/pr9091524 - 27 Aug 2021

Cited by 1 | Viewed by 1722

Abstract

With the growing interests in non-aqueous media for diversified applications, ionic liquids (ILs) are frequently considered as green solvents. While the environmental, health, and safety assessments of the commercially developed ILs and their ‘greenness’ status are in debate, research focus is shifting towards [...] Read more.

With the growing interests in non-aqueous media for diversified applications, ionic liquids (ILs) are frequently considered as green solvents. While the environmental, health, and safety assessments of the commercially developed ILs and their ‘greenness’ status are in debate, research focus is shifting towards the application of halide-free ILs for diversified applications. To clarify the situation on their greenness, and to understand if they really possess safe characteristics, we performed an initial assessment of 193 halide free ionic liquids composed of four groups of cations (imidazolium, pyridinium, pyrrodilinium, piperidinum) and 5 groups of anions (acetate, propionate, butyrate, alkanesulfonates, alkylsulfates). The ‘Technique for Order of Preference by Similarity to Ideal Solutions’ (TOPSIS), a multi-criteria decision analysis (MCDA) tool that allows ranking many alternatives is applied by carrying out the assessment against 14 criteria that includes hazard statements, precautionary statements, biodegradability, and toxicity towards different organisms. The ranking results obtained against the set of criteria considered show that the halide free ILs placed between recommended polar solvents: methanol and ethanol can be considered to be safer alternatives in terms of ‘greenness’. The study in this work provides an initial assessment of the halide-free ionic liquids evaluated against 14 criteria in terms of their safety characteristics (“green character”) using the MCDA-TOPSIS approach. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

21 pages, 125387 KiB

Open AccessArticle

Mono-, Bi-, and Tri-Metallic DES Are Prepared from Nb, Zr, and Mo for n-Butane Selective Oxidation via VPO Catalyst

by Muhammad Faizan, Kifayat Ullah Khan Niazi, Hasnain Nawaz, Niaz Muhammad, Hao Li, Fei Dai, Ruirui Zhang, Ruixia Liu and Suojiang Zhang

Processes 2021, 9(9), 1487; https://doi.org/10.3390/pr9091487 - 24 Aug 2021

Cited by 13 | Viewed by 3511

Abstract

In recent work, deep eutectic solvents (DESs) as ionic liquid analogues have been abundantly used in catalysis. Herein, vanadium phosphorus oxide (VPO) catalysts were synthesized from mono-, bi-, and tri- metallic DES of Nb, Zr, and Mo metal dopants as structure-directing agents and [...] Read more.

In recent work, deep eutectic solvents (DESs) as ionic liquid analogues have been abundantly used in catalysis. Herein, vanadium phosphorus oxide (VPO) catalysts were synthesized from mono-, bi-, and tri- metallic DES of Nb, Zr, and Mo metal dopants as structure-directing agents and electronic promoters for n-butane selective oxidation towards maleic anhydride. Higher MA selectivity and larger n-butane conversion was successfully obtained using the newly developed catalysts, while oxidation by-product CO_x (CO, CO₂) was minimized. Characterization techniques including FTIR, DSC, XRD, TEM, SEM, EDS, Raman spectroscopy, TGA, XPS, and NH₃-TPD were employed to fully characterize the DESs, precursors and catalysts. This work led to an increase of 7.8% in MA mass yield with 16% more n-butane conversion as compared to an unpromoted VPO catalyst. Moreover, the utilization of a low-carbon alkane brought in a green impact on the chemical plant as well as the environment. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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15 pages, 1852 KiB

Open AccessFeature PaperArticle

Liquid-Liquid Equilibrium of Deep Eutectic Solvent-Aromatic-Aliphatic Ternary Systems: Experimental Study with COSMO Model Predictions

by Kyle McGaughy and M. Toufiq Reza

Processes 2021, 9(7), 1169; https://doi.org/10.3390/pr9071169 - 5 Jul 2021

Cited by 2 | Viewed by 2879

Abstract

Common solvents used for aromatic extraction from aliphatics typically degrade into toxic compounds, while green alternatives perform poorly compared to the state-of-the-art solvents. Deep eutectic solvents (DES) are a novel solvent type made of hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA). [...] Read more.

Common solvents used for aromatic extraction from aliphatics typically degrade into toxic compounds, while green alternatives perform poorly compared to the state-of-the-art solvents. Deep eutectic solvents (DES) are a novel solvent type made of hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA). DES have been applied in various applications, including advanced separations. In this study, DES were studied experimentally and using the Conductor-like Screening Model (COSMO) to separate benzene from cyclohexane as model compounds for an aromatic:aliphatic system. Both equilibrium and kinetic studies were performed to determine the liquid liquid equilibrium (LLE) and mass transfer rate for the DES-based separation. Selected HBAs including tetrabutylammonium bromide (N4444Br), tetrahexylammonium bromide (N6666Br), choline chloride (ChCl), and methyltriphenylphosphonium bromide (METPB) were paired with HBDs including ethylene glycol (EG) and glycerol (Gly). COSMO was used, with adjustments to reflect DES specific interactions, to predict the liquid-liquid equilibrium (LLE). COSMO results showed that ChCl and N6666Br-based DES extracted too little benzene or too much cyclohexane, respectively, to be considered for experimental evaluation. Overall, the COSMO model predictions for LLE of EG-based DES were very accurate, with root-mean-square deviations (RMSD) below 1% for both N4444Br:EG and METPB:EG. The glycerol systems were less accurately modeled, with RMSD’s of 4% for N4444Br:Gly and 6% for METPB:Gly. The lower accuracy of glycerol system predictions fmay be due to limitations in COSMO for handling glycerol’s influence on polarizability in the DES that is not seen in EG-based DES. Mass transfer kinetics were determined experimentally for DES and the results were fit to a first order kinetics model. METPB:Gly had the highest mass transfer coefficient at 0.180 min⁻¹, followed by N4444Br:EG at 0.143 min⁻¹. N4444Br:Gly and METPB:EG had the lowest mass transfer coefficients at 0.096 min⁻¹ and 0.084 min⁻¹, respectively. It was found that mass transfer rate was not directly related to maximum benzene solubility, as N4444Br:EG and METPB:Gly had the highest and lowest benzene removal, respectively, but had similar mass transfer coefficients. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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13 pages, 24465 KiB

Open AccessArticle

Separation of Benzene-Cyclohexane Azeotropes Via Extractive Distillation Using Deep Eutectic Solvents as Entrainers

by Fang Bai, Chao Hua and Jing Li

Processes 2021, 9(2), 336; https://doi.org/10.3390/pr9020336 - 12 Feb 2021

Cited by 13 | Viewed by 4002

Abstract

The separation of benzene and cyclohexane azeotrope is one of the most challenging processes in the petrochemical industry. In this paper, deep eutectic solvents (DES) were used as solvents for the separation of benzene and cyclohexane. DES1 (1:2 mix of tetrabutylammonium bromide (TBAB) [...] Read more.

The separation of benzene and cyclohexane azeotrope is one of the most challenging processes in the petrochemical industry. In this paper, deep eutectic solvents (DES) were used as solvents for the separation of benzene and cyclohexane. DES1 (1:2 mix of tetrabutylammonium bromide (TBAB) and levulinic acid (LA)), DES2 (1:2 mix of TBAB and ethylene glycol (EG)) and DES3 (1:2 mix of ChCl (choline chloride) and LA) were used as entrainers, and vapor-liquid equilibrium (VLE) measurements at atmospheric pressure revealed that a DES comprised of a 2:1 ratio of LA and TBAB could break this azeotrope with relative volatility (αij) up to 4.763. Correlation index suggested that the NRTL modelling approach fitted the experimental data very well. Mechanism of extractive distillation gained from FT-IR revealed that with hydrogen bonding and π–π bond interactions between levulinic acid and benzene could be responsible for the ability of this entrainer to break the azeotrope. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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Review

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27 pages, 2158 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Capture of Acidic Gases from Flue Gas by Deep Eutectic Solvents

by Yan Wang, Shuhang Ren, Yucui Hou and Weize Wu

Processes 2021, 9(8), 1268; https://doi.org/10.3390/pr9081268 - 22 Jul 2021

Cited by 24 | Viewed by 3570

Abstract

Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO₂, CO₂ and NO capture, are [...] Read more.

Up to now, many kinds of deep eutectic solvents (DESs) were investigated for the capture of acidic gases from flue gases. In this review, non-functionalized and functionalized DESs, including binary and ternary DESs, for SO₂, CO₂ and NO capture, are summarized based on the mechanism of absorption, physical interaction or chemical reaction. New strategies for improving the absorption capacity are introduced in this review. For example, a third component can be introduced to form a ternary DES to suppress the increase in viscosity and improve the CO₂ absorption capacity. DESs, synthesized with halogen salt hydrogen bond acceptors (HBAs) and functionalized hydrogen bond donors (HBDs), can be used for the absorption of SO₂ and NO with high absorption capacities and low viscosities after absorption, due to physicochemical interaction between gases and DESs. Emphasis is given to introducing the absorption capacities of acidic gases in these DESs, the mechanism of the absorption, and the ways to enhance the absorption capacity. Full article

(This article belongs to the Special Issue Advances in Deep Eutectic Solvents: New Green Solvents)

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