Ionic liquid effects on mass transfer efficiency in extractive distillation of water–ethanol mixtures

The relatively high viscosities of ionic liquids could reduce the mass transfer efficiency of the extractive distillation process. The rate-based model was adopted to analyze this phenomenon since it predicted the performance of an extractive distillation pilot plant using ionic liquids as solvent. For the water–ethanol separation, three ionic liquids: 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium dicyanamide and the organic solvent ethylene glycol were used for the analysis. Simulations were conducted for sieve trays and Mellapak^® 250Y. The results indicate that relatively high viscosities affect the mass transfer efficiency. However, the improvements in relative volatilities obtained from the ionic liquids help to overcome this effect. However, with high solvent viscosities (>65 mPa s at T = 353.15 K) it was not possible to overcome the reductions. Additionally, at higher distillate rates high relative volatilities yielded negative effects on mass transfer efficiency because of a decrease in vapor velocity.     

Design and control of a middle-vessel batch distillation for separating DMC–EMC–DEC mixture

In this paper, the mixture of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate was separated by middle-vessel batch distillation with feeding in middle-vessel and process control characteristics were researched. The steady state simulation results in Aspen Plus were exported to Aspen Dynamics. Then control effect of liquid level control with HighSelector, composition control (structure1, structure2) and temperature control (proportional action, proportional integration action) were proposed. Composition control structure 2 and temperature control with PI action were investigated to achieve a good control effect.     

Screening of ionic liquids as entrainers for the separation of 1-propanol + water and 2-propanol + water mixtures using COSMO-RS model

The COSMO-RS model was used to screen potential ionic liquids for the separation of aqueous azeotropic mixtures 1-propanol?+?water and 2-propanol?+?water. A combination of 22 cations (involving imidazolium, pyridinium, pyrrolidinium, quinolinium, and ammonium) and 36 anions were investigated. The anions chloride [Cl] and dihydrogen phosphate [H₂O₄P] were found to strongly influence the vapor liquid equilibrium behavior, whereas the ammonium-based cations diethanol ammonium [(Et)₂AMM]⁺ and tetra methyl ammonium [M₄AMM]⁺ were the most promising cations. In addition, the study of mixing enthalpy and excess Gibbs free energy confirmed that the molecular interaction of ionic liquids with water was found to be much larger than that with alcohols 1-propanol and 2-propanol, indicating the presence of a strong hydrogen bonding between the ionic liquids and water. Further, the addition of ionic liquids to the alcohol–water mixture reduces the activity coefficient of water and increases the relative volatility of the mixture, facilitating easier separation. Ionic liquids [(Et)₂AMM][Cl], [(Et)₂AMM][H₂O₄P], [M₄AMM][Cl], and [M₄AMM][H₂O₄P] are expected to be effective entrainers for the separation of the industrially important 1-propanol?+?water and 2-propanol?+?water systems.     

Methyl acetate–methanol mixture separation by extractive distillation: Economic aspects

Methyl acetate is considered low toxicity volatile solvent produced either as a by-product during methanol carbonylation or via acetic acid esterification with methanol. In both cases, pure methyl acetate has to be isolated from the reaction mixture. Simulation of methyl acetate separation from its mixture with methanol by extraction distillation was carried out in ASPEN + software. In total three case studies were assumed using two different extraction solvents and two solvent regeneration strategies. In case A, novel extraction solvent 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid, was considered. Raw material separation was achieved in an extraction distillation column while the solvent regeneration was accomplished in a second distillation column in this case. In case study B, the same extraction solvent was used; however, its regeneration was carried out in a single-effect evaporator. Dimethyl sulfoxide was the second extraction solvent selected. Its use in methyl acetate-methanol separation is presented in case study C. As high purity of dimethyl sulfoxide was required for the methyl acetate-methanol azeotrope breaking, its regeneration was carried out in the second distillation column only. To simulate the ternary methyl acetate–methanol–extraction solvent mixtures separation, vapor–liquid equilibrium was predicted based on the NRTL equation. Further, unknown properties of the considered ionic liquid and variation of these properties with temperature were predicted and introduced into the ASPEN + components properties database. Based on these data, optimum operation parameters of the respective separation equipment were established. In all case studies, the same condition had to be fulfilled, namely minimum methyl acetate content in the distillate from the extraction distillation column of 99.5mol-%. Results of simulations using the respective optimum operation parameters were employed in the economic evaluation of the three separation unit designs studied. It was found that the least energy-demanding design corresponds to the case study B in terms of both capital as well as operation expenses.

Open image in new window

     

Effect of methylimidazolium-based ionic liquids on vapor–liquid equilibrium behavior of tert-butyl alcohol + water azeotropic mixture at 101.3 kPa

Three ionic liquids(ILs),1-ethyl-3-methylimidazolium bromine([EMIM]Br),1-butyl-3-methylimidazolium bromine([BMIM]Br),and 1-hexyl-3-methylimidazolium bromine([HMIM]Br),were used as the solvent for separation of {tert-butyl alcohol(TBA)+ water} azeotrope.Vapor–liquid equilibrium(VLE)data for {TBA + water + IL}ternary systems were measured at 101.3 k Pa.The results indicate that all the three ILs produce an obvious effect on the VLE behavior of {TBA + water} system and eliminate the azeotropy in the whole concentration range.[EMIM]Br is the best solvent for the separation of {TBA + water} system by extractive distillation among the three ILs.The experimental VLE data for the ternary systems are correlated with the NRTL model equation with good correlations.Explanations are given with activity coefficients of water and TBA,and the experimental VLE-temperature data for {TBA or water + IL} binary systems.     

Design,optimization and controllability of an alternative process based on extractive distillation for an ethane–carbon dioxide mixture

Alternative configurations based on cryogenic extractive distillation were proposed and simulated by using Aspen Plus 7.0^® coupled to a multi-objective stochastic optimization procedure (differential evolution, DE). The evaluation of the performances of the proposed configurations was focused on the ethane–carbon dioxide azeotrope separation considering different liquefied hydrocarbon fractions as entrainers. The design alternatives were compared to the conventional chemical absorption system.The proposed sequences were simultaneously Pareto optimized by minimizing the total annual cost (TAC) and maximizing the acid gas removal. Complementary studies regarding the theoretical control properties, the thermodynamic efficiency and the greenhouse gases generation were conducted for several representative operating conditions obtained from the Pareto optimized fronts. The proposed cryogenic extractive distillation sequences realized the higher carbon dioxide removal together with the lower TAC compared to the conventional chemical absorption system.     

Evaluation of the performance of heat pump-assisted distillation of an ethanol–water mixture

The process of separation of an ethanol–water mixture was simulated. A heat pump system was then implemented on the distillation column with the highest energy requirements in the process. Complete elimination of hot and cold utilities of the pretreatment column was obtained through an improved system by application of a heat pump at a compressor work of 406.6 kW. Installation of the heat pump system on the pretreatment column of the system results in a reduction of 10.7% of annual operating costs and 6.6% of the total annual costs (TAC). However, the capital costs of the process will enhance by 22.6%.     

Separation of water–isotopes mixture in continuous-flow thermal diffusion columns for recovery of deuterium

The present study deals with the estimation of deuterium recovery from the separation of water–isotopes mixture (H₂O–HDO–D₂O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H₂O–HDO–D₂O system were derived by following the same procedure performed in the previous work. The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D₂O and confirmed with the experimental results.     

Liquefaction of rice straw in sub- and supercritical 1,4-dioxane–water mixture

The critical liquefaction of rice straw in sub- and supercritical 1,4-dioxane–water mixture was investigated in a 500 mL autoclave at temperature of 260–340 °C, resistance time of 0–20 min, and volume ratios 0–100 vol.% (1,4-dioxane:mixture). The yields of oil and PA + A (preasphaltene and asphaltene) were in the range of 29.64–57.30 wt.% and 6.42–22.68 wt.%, depending on the temperature, resistance time and volume ratio. The synergistic capability of 1,4-dioxane–water mixture could allow the great decomposition of the tubular structure of lignocelluloses. It was shown by the results that the “oxygen-transfer” reaction, deoxygenation and decarboxylation may occur in the liquefaction of rice straw with 1,4-dioxane–water mixture, while deoxygenation and decarboxylation may be the main reaction. The oil and PA + A fractions obtained at different volume ratios were analyzed by FTIR and GC–MS to investigate the effect of the ratios on the type of the compounds in the liquid products. It is shown that the nucleophilic and hydrolytic functions of water might be weaken at the higher ratio of 1,4-dioxane runs, resulting the lower amount of phenolic, acidic, hydrocarbon and ester derivatives in the oil and PA + A fractions.     

Pervaporation separation of an azeotropic mixture of a tetrahydrofuran–water system with nanostructured polyhedral oligomeric silsesquioxane embedded poly(vinyl alcohol)

Cage - structured polyhedral oligomeric silsesquioxane (POSS) molecules were used as modifiers in the fabrication of poly(vinyl alcohol) (PVA) membrane for the separation of an azeotropic mixture of tetrahydrofuran (THF) and water system. Poly(ethylene glycol) and anionic octa(tetramethyl ammonium)-functionalized POSS were used for this study. The membranes exhibited excellent water selectivity and permeance because of their preferential interactions toward water molecules in the azeotropic THF–water mixture. In the presence of poly(ethylene glycol)–POSS and anionic octa(tetramethyl ammonium)–POSS, the PVA membrane exhibited a significant increase in selectivity. A modified Maxwell–Stefan equation was used for the computation of the theoretical flux, which was compared with the experimental values. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47060.     

Silver nanoparticles embedded in modified polyallylamine resin as efficient catalysts for alkyne–azide 1,3-dipolar cycloaddition in water

A silver nanoparticle composite based on modified polyallylamine has been synthesized by a simple chemical route and its catalytic activity has been tested for alkyne–azide cycloaddition reaction. This silver nanocomposite shows an excellent catalytic activity at 80 °C for the synthesis of 1,4-disubstituted 1,2,3-triazole by alkyne–azide cycloaddition. The solid silver nanocomposite catalyst was characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry and thermogravimetric analysis. The developed catalyst is stable in air, easy to prepare and can be recovered easily and reused ten times without a significant decrease in activity.     

Preparation of an oil shale suspension in a water–mazut emulsion as a raw material for gasification

The results of tests of the raw material preparation module of a laboratory setup for studying the gasification of a mixture of oil shale with oil residues are reported. It was shown that the equipment of the raw material preparation module makes it possible to obtain a stable water–hydrocarbon suspension of oil shale (with a solid-phase particle size of 1–100 μm). The viscosity ratio at 80°C was no higher than a required value (VR 16.0), which ensures its free pumping through the sprayers of a gasifier and a uniform distribution in the combustion chamber volume.     

Geminal Br?nsted Acid Ionic Liquids as Catalysts for the Mannich Reaction in Water

Quaternary ammonium geminal Brønsted acid ionic liquids (GBAILs) based on zwitterionic 1,2-bis[N-methyl-N-(3-sulfopropyl)-alkylammonium]ethane (where the carbon number of the alkyl chain is 4, 8, 10, 12, 14, 16, or 18) and p-toluenesulfonic acid monohydrate were synthesized. The catalytic ionic liquids were applied in three-component Mannich reactions with an aldehyde, ketone, and amine at 25 °C in water. The effects of the type and amount of catalyst and reaction time as well as the scope of the reaction were investigated. Results showed that GBAIL-C₁₄ has excellent catalytic activity and fair reusability. The catalytic procedure was simple, and the catalyst could be recycled seven times via a simple separation process without noticeable decreases in catalytic activity.     

Tetraalkylammonium Ionic Liquids as Dual Solvents–Catalysts for Direct Synthesis of Sugar Fatty Acid Esters

As nonionic surfactants derived from naturally renewable resources such as sugars and fatty acids, sugar fatty acid esters have been widely utilized in food, cosmetic and pharmaceutical industries. Our present study has demonstrated that the inexpensive and halogen-free tetraalkylammonium salts (e.g., [Bu₄N][Ac], [Et₄N][Ac] and [Me₄N][Ac]) can act as dual solvents–catalysts for regioselective acylation to produce glucose laurate. This non-enzymatic synthesis can proceed under mild conditions with high specificity, and the conversions obtained were superior to that when an enzyme catalyst (lipase, EC 3.1.1.3) was added. A higher yield was obtained in the ammonium salt with a longer alkyl chain on the cation, while no product was obtained in [Bu₄N][HSO₄] and [Bu₄P][Ac]. A reaction mechanism has been proposed, which is supported by phase-transfer catalysis and law of matching water affinity.     

Exclusive and fast water channels in zwitterionic graphene oxide membrane for efficient water–ethanol separation

Graphene oxide (GO) membranes have shown great prospects as the next-generation membranes to tackle many challenging separation issues. However, the employment of GO membranes remains difficult for the precise separation of molecules with strong coupling effect and small size discrepancy such as water–ethanol. Herein, a new strategy of constructing exclusive and fast water channels in GO membrane was proposed to achieve high-performance water–ethanol separation via the synergy between zwitterion-functionalized GO and hydrophilic polyelectrolyte. The as-formed ordered and stable channels possess high-density ionic hydrophilic groups, which benefit from inhibiting the strong coupling between water and ethanol, facilitating the fast permeation of water molecules while suppressing ethanol molecules. As a result, the ultrathin GO-based membrane acquires exceptionally high separation performance with a flux of 3.23 kg/m² h and water–ethanol separation factor of 2,248 when separating water–ethanol (10 wt%/90 wt%) mixture at 343 K. This work paves a feasible way to construct 2D channels for the high-efficiency separation of strong-coupling mixtures.     

Ionic Liquids as Exceedingly Convenient Solvents for the Friedel–Crafts Monoalkylation of Electron-Rich Arenes with Paraformaldehyde Using HCl as Catalyst

Friedel–Crafts hydroxyalkylation of 2-methoxynaphthalene, anisole and 2-methylfuran with paraformaldehyde has been carried out in N-ethyl-N-methylimidazolium chloride (1⁺Cl^-) or N-butyl-N-methylimidazolium hexafluorophosphate (2⁺PF^- ₆) or ethanol using concentrated aqueous HCl as catalyst. The results have shown an extraordinary activity and selectivity towards the formation of the corresponding hydroxymethyl derivative using 2⁺PF^- ₆ as solvent. This sharply contrasts with the case of the ethanol as solvent wherein the reaction is much slower and diarylation products are largely formed.     

Probability density functions for bubble size distribution in air–water systems in stirred tanks

Bubble size distribution (BSD) is relevant to the design of gas–liquid systems, as it determines the interfacial area available in heat and mass transfer processes. Although data on BSD in stirred aerated tanks are available, a systematic comparison of alternative modeling functions for these data is lacking. In this work, BSDs obtained in air–water dispersions in a stirred aerated tank with a Rushton turbine and BSDs available in the literature for similar systems were modeled by 14 empirical probability density functions (PDFs). It was found that both the distribution of Nukiyama–Tanasawa with three adjustable parameters and the Rosin–Rammler distribution with two adjustable parameters reasonably fit original and literature BSDs. It is also concluded that it is possible to correlate the PDF parameters with the power dissipated by the agitator in the liquid phase, allowing the BSD to be modeled with only two parameters in a range of dissipated power from 0.5 to 2.3?kW/m³. BSDs thus modeled provide good predictions of average bubble size.     

Nano Ca–Mg–Zn ferrites as tuneable photocatalyst for UV light-induced degradation of rhodamine B dye and antimicrobial behavior for water purification

We report the synthesis of Ca-doped Mg–Zn ferrite Mg_0.4Zn_(0.6-x)Ca_xFe₂O₄ nanomaterials with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 through citrate precursor approach and their structural, morphological, optical, photocatalytic, and antimicrobial properties were systematically studied. The prepared nanoferrites's cubic spinel structure with an average crystallite size of 15–38 nm was evaluated by the XRD examination. The spherical morphology of these ferrite nanoparticles was seen from scanning electron microscopy (SEM). The observed bands at 560 cm⁻¹ and 406 cm⁻¹ in the FTIR spectra confirmed the spinel structure of the synthesized nanoferrite. The optical study confirmed an optical band gap of 1.60 eV–1.86 eV. The photocatalysis was done for the degradation of rhodamine B dye solution under UV light. All the synthesized nano ferrites displayed a promising antimicrobial potential upon Candida albicans fungi. Mg_0.4Zn_0.1Ca_0.5Fe₂O₄ nanoparticles have a better photocatalytic response (99.5%) for the degradation of rhodamine B dye and show superior antimicrobial activity (96.1%) for the inhibition of Candida albicans fungi.