Encapsulated deep eutectic solvent for esterification of free fatty acid

A novel encapsulated deep eutectic solvent (DES) was introduced for biodiesel production via a two-step process. The DES was encapsulated in medical capsules and were used to reduce the free fatty acid (FFA) content of acidic crude palm oil (ACPO) to the minimum acceptable level (< 1%). The DES was synthesized from methyltriphenylphosphonium bromide (MTPB) and p-toluenesulfonic acid (PTSA). The effects pertaining to different operating conditions such as capsule dosage, reaction time, molar ratio, and reaction temperature were optimized. The FFA content of ACPO was reduced from existing 9.61% to less than 1% under optimum operating conditions. This indicated that encapsulated MTPB-DES performed high catalytic activity in FFA esterification reaction and showed considerable activity even after four consecutive recycling runs. The produced biodiesel after acid esterification and alkaline transesterification met the EN14214 international biodiesel standard specifications. To our best knowledge, this is the first study to introduce an acidic catalyst in capsule form. This method presents a new route for the safe storage of new materials to be used for biofuel production. Conductor-like screening model for real solvents (COSMO-RS) representation of the DES using σ-profile and σ-potential graphs indicated that MTPB and PTSA is a compatible combination due to the balanced presence and affinity towards hydrogen bond donor and hydrogen bond acceptor in each constituent

Selection of ionic liquids and deep eutectic solvents via quantum chemical methods and liquid-liquid equilibria involved in the extractive denitrogenation of diesel / Hanee Farzana Hizaddin

The removal of nitrogen compounds from transportation fuel is proven to enhance the efficiency of desulfurization process, which aims to meet the rigorous regulations regarding zero-emissions. Ionic liquids (ILs) and deep eutectic solvents (DESs) were screened for this purpose using quantum chemical methods. Geometry optimization was performed for all involved species at Hartree-Fock level and 6-31G* basis set. Generation of cosmo files using Density Functional Theory and Triple zeta valence potential basis set was carried out at single point calculation. The cosmo files were used to obtain σ-profiles and σ-potentials for qualitative screening of ILs and DESs. (i) The screening of ILs revealed that cations with an aromatic ring have better capacity as hydrogen bond donors (HBDs) than do non-aromatic cations, whereas the acetate anion appeared to have better affinity towards HBD than did ethylsulfate and methanesulfonate anions. The σ-profile and σ-potential analysis confirmed that there is an interaction between nitrogen compounds and cations via CH-π interaction along with between nitrogen compounds and anions via hydrogen bonding. Moreover, a detailed quantum chemical calculation was performed to investigate the interaction between ILs and nitrogen compounds at molecular level, in which optimized geometry was used to obtain the orbital energies, global scalar properties, interaction energies and partial charges. The calculations indicated that cations with an aromatic ring, that is, imidazolium and pyridinium, combined with either ethylsulfate or methanesulfonate anion have favorable interaction with nitrogen compounds in comparison to cations without an aromatic ring. (ii) The screening of DESs showed that the interaction between nitrogen compounds and DESs is based on hydrogen bonding. Altogether, 94 DESs were examined quantitatively by predicting the values of the activity coefficients at infinite dilution of nitrogen compounds and diesel in the DESs. These were then used to estimate selectivity, capacity and iv performance index at infinite dilution as the basis of the screening process taking into account the cation, anion and HBD choices as well as the salt:HBD molar ratio. Based on the screening results, 22 ternary liquid-liquid equilibria (LLE) experiments were carried out at room temperature and atmospheric pressure to test three ILs – namely 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylpyridinium ethylsulfate, and 1-ethyl-3-methylimidazolium methanesulfonate, and two DESs – namely tetrabutylammonium bromide/ethylene glycol (1:2) and tetrabutylphosphonium bromide/ethylene glycol (1:2). The aim was to remove non-basic and basic nitrogen compounds from n-hexadecane as a model diesel compound. NMR spectroscopy was used for the compositional analysis. Consistency tests were performed to ascertain the reliability of all experimental data. All ternary systems reported distribution ratios and selectivity values greater than unity with minimal cross-contamination between the extract and raffinate phases. The ternary LLE data were correlated with NRTL model and compared with COSMO-RS predictions, both of which were in excellent agreement with the experimental tie-lines. In conclusion, the quantum chemical screening of ILs and DESs explained the interaction between ILs/DESs and nitrogen compounds at molecular level, which facilitates solvent selection for the denitrogenation process. The ternary LLE experiments with the selected ILs and DESs confirmed that these solvents have high potential for industrial extractive denitrogenation

Mechanistic insights into carbon dioxide utilization by superoxide ion generated electrochemically in ionic liquid electrolyte

Understanding the reaction mechanism that controls the one-electron electrochemical reduction of oxygen is essential for sustainable use of the superoxide ion (O2-) during CO2 conversion. Here, stable generation of O2- in butyltrimethylammonium bis(trifluoromethylsulfonyl)imide [BMAmm+][TFSI-] ionic liquid (IL) was first detected at -0.823 V vs. Ag/AgCl using cyclic voltammetry (CV). The charge transfer coefficient associated with the process was ∼0.503. It was determined that [BMAmm+][TFSI-] is a task-specific IL with a large negative isovalue surface density accrued from the [BMAmm+] cation with negatively charged C(sp2) and C(sp3). Consequently, [BMAmm+][TFSI-] is less susceptible to the nucleophilic effect of O2- because only 8.4% O2- decay was recorded from 3 h long-term stability analysis. The CV analysis also detected that O2- mediated CO2 conversion in [BMAmm+][TFSI-] at -0.806 V vs. Ag/AgCl as seen by the disappearance of the oxidative faradaic current of O2-. Electrochemical impedance spectroscopy (EIS) detected the mechanism of O2- generation and CO2 conversion in [BMAmm+][TFSI-] for the first time. The EIS parameters in O2 saturated [BMAmm+][TFSI-] were different from those detected in O2/CO2 saturated [BMAmm+][TFSI-] or CO2 saturated [BMAmm+][TFSI-]. This was rationalized to be due to the formation of a [BMAmm+][TFSI-] film on the GC electrode, creating a 2.031 × 10-9 μF cm-2 double-layer capacitance (CDL). Therefore, during the O2- generation and CO2 utilization in [BMAmm+][TFSI-], the CDL increased to 5.897 μF cm-2 and 7.763 μF cm-2, respectively. The CO2 in [BMAmm+][TFSI-] was found to be highly unlikely to be electrochemically converted due to the high charge transfer resistance of 6.86 × 1018 kΩ. Subsequently, O2- directly mediated the CO2 conversion through a nucleophilic addition reaction pathway. These results offer new and sustainable opportunities for utilizing CO2 by reactive oxygen species in ionic liquid media

In Situ Electrosynthesis of Peroxydicarbonate Anion in Ionic Liquid Media Using Carbon Dioxide/Superoxide System

Climate engineering solutions with emphasis on CO2 removal remain a global open challenge to balancing atmospheric CO2 equilibrium levels. As a result, warnings of impending climate disasters are growing every day in urgency. Beyond ordinary CO2 removal through natural CO2 sinks such as oceans and forest vegetation, direct CO2 conversion into valuable intermediaries is necessary. Here, a direct electrosynthesis of the peroxydicarbonate anion (C2O62–) was investigated by the reaction of CO2 with the superoxide ion (O2·–), electrochemically generated from O2 reduction in bis(trifluoromethylsulfonyl)imide [TFSI–] anion derived ionic liquid (IL) media. This is the first time that the IL media were employed successfully for CO2 conversion into C2O62–. Moreover, the charge transfer coefficient for the O2·– generation process in the ILs was less than 0.5, indicating that the process was irreversible. Voltammetry experiments coupled with global electrophilicity index analysis revealed that, when CO2/O2 was contacted simultaneously in the IL medium, O2·– was generated in situ first at a potential of approximately −1.0 V. Also, CO2 was more susceptible to attack by O2·– before any possible interaction with the IL except for [PMIm+][TFSI–]. This was because CO2 has a higher global electrophilicity index (ωCO2 = 0.489 eV) than those for the [EDMPAmm+][TFSI–] and [MOEMMor+][TFSI–]. By further COSMO-RS modeling, CO2 absorption was proven feasible at the COSMO-surface of the [TFSI–] IL-anion where the charge densities were σ = −1.100 and 1.1097 e/nm2. Therefore, the susceptible competitiveness of either IL cations or CO2 to the nucleophilic effects of O2·– was a function of their positive character as estimated by their electrophilicity indices. As determined by experimental attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and DFT-FTIR computation, the reaction yielded C2O62– in the ILs. Consequently, the presence of O=O symmetric stretching FTIR vibrational mode at ∼844 cm–1 coupled with the disappearance of the oxidative cyclic voltammetry waves when sparging CO2 and O2 confirmed the presence of C2O62–. Moreover, based on DFT/B3LYP/6-31G, pure C2O62– has symmetric O=O stretching at ∼805 and ∼844 cm–1 when it is in association with the IL-cation. This was the first spectroscopic observation of C2O62– in ILs, and the O=O symmetric stretching vibration has peculiarity for identifying C2O62– in ILs. This will open new doors to utilize CO2 in industrial applications with the aid of reactive oxygen species

Coupling the capabilities of different complexing agents into deep eutectic solvents to enhance the separation of aromatics from aliphatics

(Liquid + liquid) extraction of ethylbenzene from n-octane by using tetrabutylammonium bromide-based deep eutectic solvents (DESs) containing pyridine, ethylene glycol, or a mixture of both complexing agents was investigated at 25 degrees C and atmospheric pressure. The performance of each DES was determined from the distribution ratio and selectivity values calculated using experimental (liquid + liquid) equilibrium data of the ternary systems ethylbenzene + n-octane + DESs. The DES with only ethylene glycol had a high selectivity but a low distribution ratio, whereas the DES with only pyridine had a high distribution ratio but a low selectivity. For the other DESs, adding pyridine increased the distribution ratio, and increasing the molar ratio of ethylene glycol increased the selectivity. Generally, whenever the selectivity increased, the distribution ratio decreased, and vice versa. The nonrandom two-liquid model was used to correlate the experimental data, and the average root mean square deviation (RMSD) between correlated and experimental tie lines was 1.4. Moreover, the Conductor-like Screening Model for Real Solvents was successfully used to predict the ternary tie lines for the studied systems with an average RMSD of 3.7. (C) 2015 Elsevier Ltd. All rights reserved

Evaluation of Molecular Interaction in Binary Mixture of Ionic Liquids + Heterocyclic Nitrogen Compounds: Ab Initio Method and COSMO-RS Model

Ab initio method was applied to investigate the interaction between six heterocyclic nitrogen compounds with 18 ionic liquids. Important quantum chemical descriptors like orbital energy values, orbital energy gap, and global scalar properties including hardness, softness, electronegativity, and electrophilicity index were calculated for each individual species, ionic liquid complexes, and complexes of ionic liquid with heterocyclic nitrogen compounds. The effect of interaction energy and partial charge transfer were also investigated for the ion pair and their complexes. COSMO-RS model is used for qualitative screening of the ionic liquids via σ-profile and σ-potential. Comparison between experimental and COSMO-RS predicted ternary tie-lines were done to validate computational method; good agreement was achieved with average RMSD less than 5%. From the results, ILs based on aromatic ring cations combined with either [EtSO₄] or [Ac] anion are recommended as solvent for extractive denitrification of liquid fuels, with [EPY]­[EtSO₄] being the most favorable IL for removal of heterocyclic nitrogen compounds from liquid fuels at 298.15 K

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

Liquid-liquid separation of azeotropic mixtures of ethanol/alkanes using deep eutectic solvents: COSMO-RS prediction and experimental validation

Separation of azeotropic mixtures is a topic of great industrial interest. In this work, liquid-liquid extraction using deep eutectic solvents (DESs) is explored to separate binary azeotropic mixtures of ethanol and n-hexane, n-heptane or n-octane. Ten DESs were screened using the COSMO-RS approach by predicting the activity coefficient at infinite dilution, γ∞ of ethanol and n-alkanes in each DES. Then, three DESs were selected for experimental validation where Tetrabutylammonium bromide/Levulinic acid (TBAB/LA) with a molar ratio (1:2) gave the best extractive performance for all systems. Ternary liquid-liquid extraction experiments were conducted at room temperature with this DES. It was found that the tie-lines of all systems have positive slopes, indicating that a small amount of solvent is required to extract ethanol. Moreover, the distribution ratio and selectivity values are all greater than unity and the DES was not detected in the raffinate phase which indicate minimal cross-contamination between extract and raffinate phases. Finally, COSMO-RS predictions of the ternary tie-lines were in excellent agreement with experimental data, with an average RMSD value of 1.65%. The experimental data were also successfully correlated with NRTL model with an average RMSD value of 1.50%

Performance of p-Toluenesulfonic Acid–Based Deep Eutectic Solvent in Denitrogenation: Computational Screening and Experimental Validation

Deep eutectic solvents (DESs) are green solvents developed as an alternative to conventional organic solvents and ionic liquids to extract nitrogen compounds from fuel oil. DESs based on p-toluenesulfonic acid (PTSA) are a new solvent class still under investigation for extraction/separation. This study investigated a new DES formed from a combination of tetrabutylphosphonium bromide (TBPBr) and PTSA at a 1:1 molar ratio. Two sets of ternary liquid&ndash;liquid equilibrium experiments were performed with different feed concentrations of nitrogen compounds ranging up to 20 mol% in gasoline and diesel model fuel oils. More than 99% of quinoline was extracted from heptane and pentadecane using the DES, leaving the minutest amount of the contaminant. Selectivity was up to 11,000 for the heptane system and up to 24,000 for the pentadecane system at room temperature. The raffinate phase&rsquo;s proton nuclear magnetic resonance (1H-NMR) spectroscopy and GC analysis identified a significantly small amount of quinoline. The selectivity toward quinoline was significantly high at low solute concentrations. The root-mean-square deviation between experimental data and the non-random two-liquid (NRTL) model was 1.12% and 0.31% with heptane and pentadecane, respectively. The results showed that the TBPBr/PTSADES is considerably efficient in eliminating nitrogen compounds from fuel oil