Ionic liquids for the separation of benzene and cyclohexane – COSMO-RS screening and experimental validation

The separation of benzene and cyclohexane from their mixture is difficult to perform via conventional distillation because of their close boiling points. In this work, liquid-liquid extraction using ionic liquids (ILs) is suggested for this purpose and 16 cations and 13 anions were selected to form 208 possible ILs screened with the Conductor-like Screening Model for Real Solvents (COSMO-RS) module. The screening result was experimentally validated by liquid–liquid extraction using four of the top ranked ILs, namely 1-ethyl-3-methylimidazolium acetate ([C2mim][Ac]), 1-ethyl-3-methylimidazolium dicyanamide ([C2mim][N(CN)2]), 1-ethyl-3-methylimidazolium thiocyanate ([C2mim][SCN]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][Tf2N]). The ternary liquid–liquid equilibria for these ILs with benzene and cyclohexane were investigated at 25 °C and 1 atm with feed concentration of benzene ranging from 10 to 60 wt%. Good agreement was achieved between the tie-lines obtained from the COSMO-RS model and those obtained experimentally. The performance of ILs used in this study was compared with organic solvents, other ILs, and deep eutectic solvents reported in literature. The results of selectivity and distribution ratio confirmed that COSMO-RS was a reliable method for solvent screening and demonstrated the suitability of the selected ILs as extracting solvents. In all ternary systems, no IL was detected in the cyclohexane layer and the concentration of cyclohexane in the IL layer was very low. This observation indicated that there was minimum cross-contamination between the phases and therefore less energy will be required for the solvent recovery

Separation of Benzene and Cyclohexane Using Eutectic Solvents with Aromatic Structure

The separation of benzene and cyclohexane is a challenging process in the petrochemical industry, mainly because of their close boiling points. Extractive separation of the benzene-cyclohexane mixture has been shown to be feasible, but it is important to find solvents with good extractive performance. In this work, 23 eutectic solvents (ESs) containing aromatic components were screened using the predictive COSMO-RS and their respective performance was compared with other solvents. The screening results were validated with experimental work in which the liquid–liquid equilibria of the three preselected ESs were studied with benzene and cyclohexane at 298.5 K and 101.325 kPa, with benzene concentrations in the feed ranging from 10 to 60 wt%. The performance of the ESs studied was compared with organic solvents, ionic liquids, and other ESs reported in the literature. This work demonstrates the potential for improved extractive separation of the benzene-cyclohexane mixture by using ESs with aromatic moieties

Extractive separation of benzene and cyclohexane using binary mixtures of ionic liquids

The separation of benzene and cyclohexane is a challenging process in petrochemical industry due to their close boiling points. Solvent mixing is a useful technique to enhance the extraction performance of liquid–liquid extraction process. In this work, the performance of solvent mixtures involving two organic solvents (N,N-dimethylformamide and ethylene glycol) and four ionic liquids (ILs), namely, 1-ethyl-3-methylimidazolium thiocyanate (C2mimSCN), 1-ethyl-3-methylimidazolium dicyanamide (C2mimN(CN)2), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimTf2N) and 1-ethyl-3-methylimidazolium acetate (C2mimAc) was investigated for the extractive separation of benzene and cyclohexane. The mixing ratios of the binary solvents were optimized using the ideal mixing calculation and validated experimentally through liquid–liquid extraction process. Six new quaternary liquid–liquid equilibria for the mixed solvents with benzene and cyclohexane were investigated at 25 °C and 1 atm, with feed concentrations of benzene ranging from 10 to 50 wt%. Ethylene glycol was discovered a good solvent pair with C2mimTf2N that could lead to potential cost savings. At the optimized mixing fraction, the {C2mimTf2N + C2mimSCN} mixture demonstrated the highest extraction performance, which was superior to that of sulfolane. Additionally, the {C2mimSCN + C2mimN(CN)2} and {C2mimN(CN)2 + C2mimAc} mixtures were found to increase the selectivity while maintaining the benzene distribution ratio in relation to sulfolane. The ILs were not present in the raffinate layer of any of the systems, indicating the reliable performance of the ILs in terms of avoiding solvent cross-contamination. This work demonstrated the use of binary solvent mixtures as a new efficient and versatile method to enhance extraction performance. © 2019 Elsevier B.V

Extraction of nitrogen compounds from model fuel using 1-ethyl-3-methylimidazolium methanesulfonate

Removal of nitrogen compounds is an essential process in the fuel processing industry. In this work, the extraction performance of 1-ethyl-3-methylimidazolium methanesulfonate ([Emim][MeSO3]) ionic liquid in removing pyrrole, indoline, pyridine and quinoline from cyclohexane is investigated. The ternary liquid-liquid equilibria for four systems containing [Emim][MeSO3] + pyrrole/indoline/pyridine/quinoline + cyclohexane were predicted using COSMO-RS and validated experimentally at 298.15 K under atmospheric pressure, with feed concentrations of nitrogen compounds ranging from 5 to 50 wt%. Othmer-Tobias and Hand correlations confirmed the consistency of the experimental data. The tie-lines obtained experimentally and predicted with COSMO-RS were in good agreement. Additionally, the non-random two-liquid (NRTL) model was successfully employed to correlate the experimental tie-lines. The effects of basicity of nitrogen compounds toward extraction efficiency were also investigated. The selectivity and distribution ratio results demonstrated the suitability of [Emim][MeSO3] as an extraction solvent for removing nitrogen compounds from fuel. Finally, the multicomponent extraction confirmed the performance of [Emim][MeSO3] for extractive denitrogenation. In all ternary systems investigated in this work, the concentration of cyclohexane in the extract phase was very small and the presence of the IL in the raffinate phase was negligible indicating minimum cross contamination between the extract and raffinate phases

Indole Derivatives Efficacy and Kinetics for Inhibiting Carbon Steel Corrosion in Sulfuric Acid Media

The global prevalence of metal corrosion is a significant challenge due to its detrimental effect. Environmentally friendly and non-hazardous alternatives for harmful and poisonous synthetic corrosion inhibitors are urgently necessary due to increasing environmental concerns and regulations prohibiting their application. In this study, indole molecules were employed as carbon steel corrosion inhibitors in acidic conditions. Gravimetrical and scanning electronic microscope (SEM) analysis was used in a preliminary investigation of indole as an organic inhibitor. The results revealed that adding indole to carbon steel before exposing it to sulfuric acid slowed and induced resistance to corrosion. The indole affixed themselves to the steel carbon surfaces, producing a barrier/protection for carbon steel. The efficacy of the indole in preventing corrosion was determined through the weight loss method. Temperature and inhibitory concentration effects on inhibition effectiveness under varying parameters were also reported. The temperatures employed were between 298 K and 328 K, while the inhibitor concentrations ranged from 1.2 × 10−3 M to 7.6 × 10−3 M, and both parameters significantly influenced corrosion inhibition effectiveness. The inhibitory mixture attained optimum efficacy in inhibiting corrosion, at 81 %, when the lowest and highest respective temperature and concentration were applied. The kinetic analysis was conducted under a range of temperatures to determine the reaction mechanisms of the inhibitor. The thermal adsorption isotherm of the inhibitor indicated that the surface adhered to Langmuir's adsorption isotherm. Additionally, investigations on corrosion and inhibition using the electrochemical impedance spectroscopy method (EIS) were conducted. This study can provide in-depth knowledge for advancing inhibitory science and engineering to enhance corrosion resistance in acidic media

Development of novel API-based deep eutectic solvents for esterification of high free fatty acid

Low-value feedstocks containing high free fatty acid (FFA) content are incompatible with direct alkali-catalysed transesterification, and require a deacidification step through esterification to reduce its FFA level. Herein, innovative acid catalysts were developed based on deep eutectic solvents (DESs) to pretreat low-quality palm oil (12.43 % FFA). DESs were formed using Brønsted acids (5-sulfosalicyclic acid and benzenesulfonic acid) and an active pharmaceutical ingredient (paracetamol) at a 3:1 M ratio. The DESs were characterized using ATR-FTIR and Hammett acidity function (H0). DES catalyst dosage, methanol requirement, reaction time and temperature parameters were optimized, and its recyclability was evaluated. The FFA contents were reduced to below the limit of < 2 % using acidic DESs at optimized conditions. Reaction kinetics revealed that DES-catalysed reactions followed the pseudo first order rate of reaction and required the lowest activation energy of 40.91 kJ/mol. Through the Eyring-Polanyi thermodynamic study, the DES-catalysed esterification reactions were endothermic (ΔH° > 0), non-spontaneous (ΔS° < 0 and ΔG° > 0) and endergonic. COSMO-RS computational calculations reveal the viable formation of the DESs based on its moieties, and supports the good solubility of the DESs in methanol. This study demonstrates the feasible valorisation of low-value feedstocks using innovative catalysts in enabling biodiesel production

Characterization of tetraethylene glycol-based deep eutectic solvents and their potential application for dissolving unsaturated fatty acids

Deep eutectic solvents (DESs) are credible alternatives for ionic liquids. Most DESs have favourable properties such as lower production cost, biodegradability and are environmental friendly. In this work, tetraethylene glycol (TTEG)-based DESs were successfully prepared by mixing TTEG and choline chloride at different molar ratios. The physicochemical properties such as conductivity, freezing point, density, surface tension and viscosity were measured at temperatures between 298.15 K and 353.15 K. It was found that the molar ratio of both compounds affected the physicochemical properties. As the solubility of unsaturated fatty acids, such as oleic acid and linoleic acid, in these DESs are industrially significant, this property became an important consideration. Computer simulations using the COSMO-RS program which is based on the interpretation of the σ-profiles, as well as the evaluation of Gibbs energy change of mixing were in excellent agreement with the experimental results. To the best of our knowledge, this is the first report on TTEG-based DESs which were used to dissolve unsaturated fatty acids. This work could introduce a new perspective in lipids chemistry, biofuel production, food processing and vegetable oil extraction

Ultrasonic assisted extraction of oil from argan seeds using ionic liquids as novel co‑solvent

In this study, the extraction of oil from argan seeds using ultrasonic assisted extraction was investigated using n-decane as the extraction solvent and ionic liquids as the novel co-solvents. The extraction process was assessed based on the mass ratio of solvent to seed and extraction time, alongside the exploration of different ionic liquids as co-solvents. The results showed that in the absence of ionic liquid, the optimum oil yield of 35.2% was achieved at mass ratio of solvent to seed of 6:1 at 60 °C and 30 min. The extraction process adhered to pseudo-second-order kinetic model, with a rate constant of 0.0127%−1 min−1. When ionic liquid 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C3mim][NTf2]) was utilized as a co-solvent alongside n-decane, the oil yield showed an improvement ranging from 0.4 to 4.0%, even when the mass of n-decane used remained similar. However, ionic liquid alone cannot serve as a substitute for n-decane as the extraction solvent. The experimental results were also compared with COSMO-RS analysis. The study demonstrates that ionic liquids can slightly enhance the oil yield by working synergistically with n-decane to improve the dissolution of lignocelluloses present on the seeds. This, in turn, facilitates better penetration of solvent into the seed matrix and enhancing the oil extraction

New route for preparing palmitic acid imidazole from free fatty acid using imidazole

In this study, imidazole was used for the first time in esterification of free fatty acid (FFA) from acidic oil and for palmitic acid imidazole production. The FFA content in jatropha oil mixed with crude palm oil (CPO) was significantly reduced from 10.57% to 1.73% under the following optimum conditions (25% imidazole dosage, 30 mins of reaction time, reaction temperature at 60 °C and methanol to oil molar ratio of 20:1). This research opens up new possibilities for utilizing imidazole as a catalyst in various esterification processes, offering a promising and eco-friendly pathway for industrial applications