Phosphonium-based Deep Eutectic Solvents Research Articles

Performance and Mechanism Study on Functionalized Phosphonium-Based Deep Eutectic Solvents for CO2 Absorption

Performance and Mechanism Study on Functionalized Phosphonium-Based Deep Eutectic Solvents for CO2 Absorption

Tunable and functional phosphonium-based deep eutectic solvents for synthesizing of cyclic carbonates from CO2 and epoxides under mild conditions

Carbon dioxide (CO2) conversion into carbonates is one of the important ways to reduce carbon emissions. In this study, several phosphonium-based functional deep eutectic solvents (DESs) were prepared as catalysts for the synthesis of cyclic carbonates under mild conditions. The research showed that under mild conditions (60 °C, 0.8 MPa, 4 h, and 3.5 mol% catalyst loading), 1-ethylamine-3-butylphosphine bromide−diethylene glycol ([P4,4,4,2NH2][Br]-DEG) DES catalyst can achieve 96% propylene carbonate (PC) yield. In addition, the DES catalyst can be recovered by simple solvent extraction, and the PC yield does not decrease significantly after five cycles. Finally, in situ FT-IR and density functional theory (DFT) were used to provide a potential reaction mechanism for the cycloaddition reaction. Mechanism studies show that synergistic catalysis between quaternary phosphine ionic liquids (ILs) and ethylene glycol (EG)/DEG promotes CO2 conversion to cyclic carbonate.

Phosphonium-based deep eutectic solvents: Physicochemical properties and application in Zn-air battery

Electrolytes play a significant role in metal-air batteries and influence the battery's performance. Deep eutectic solvents (DESs) are viable and attractive candidates as high-performance electrolytes in batteries. This study investigated the temperature-dependent physicochemical properties of several phosphonium-based DESs such as the freezing point, density, viscosity, surface tension, and conductivity. The viscosity of the DES electrolyte is correlated as a function of molar conductivity using Walden's rule. Subsequently, the electrochemical characterizations of a Zn-air battery with the DES electrolyte, such as the cell voltage, power density, and current limit are studied. The electrochemical and physicochemical profiles of the phosphonium-based DESs possess dependence on the salt-to-hydrogen bond donor (HBD) molar ratio and appear viable for further exploration in metal-air battery applications. To the best of our knowledge, this is the first study that investigates the efficacy of the phosphonium-based DESs as the electrolyte in Zn-air batteries.

Gas-free alkoxycarbonylation of aryl iodides in a phosphonium-based deep eutectic solvent with Mo(CO)6 as a solid CO source.

Pd-catalyzed alkoxycarbonylation of aryl iodides has been explored, for the first time, in phosphonium-based deep eutectic solvents under gas-free conditions, by using Mo(CO)6 as the CO source. The method allows the preparation of ethylene glycol and glycerol esters in high yields (up to 99%), short reaction times and under mild reaction conditions with a very low catalyst loading (0.5 mol%).

Chemical structure-based models for prediction of density of ammonium and phosphonium-based deep eutectic solvents

In this work, linear and nonlinear quantitative structure–property relationship (QSPR) models are proposed to predict the density of deep eutectic solvents (DESs). A large experimental database of 2005 density data belonging to chloride and bromide-based DESs with ammonium and phosphonium-based cations and various hydrogen bond donors (HBDs) was collected from literatures. Using a modified particle swarm optimization (MPSO) variable-selection approach, subsets of relevant descriptors were selected to relate the density of DESs to their corresponding cation and HBD structures. To develop the nonlinear models, an adaptive neuro-fuzzy inference system (ANFIS) method was used with the same inputs and outputs of linear models. The squared correlation coefficient (R2) of linear models for chloride and bromide-based DESs are 0.897 and 0.960, while the density of DESs with anion part of chloride and bromide is predicted by ANFIS with the R2 of 0.956 and 0.980, respectively. The internal and external validations of the proposed models indicate that these models can be used for prediction of DESs densities with high accuracy and reliability.

Highly efficient and reversible low-concentration SO2 absorption in flue gas using novel phosphonium-based deep eutectic solvents with different substituents

Four hydrogen bond acceptors (HBAs) with different carbon chain length substituents, including methyl-triphenyl phosphonium bromide (MTPB), ethyl-triphenyl phosphonium bromide (ETPB), propyl-triphenyl phosphonium bromide (PTPB), and butyl-triphenyl phosphonium bromide (BTPB), combined with ethylene glycol (EG) were developed to synthesize four low-viscosity deep eutectic solvents (DESs). In this study, the effect of different substituents in DESs on low-concentration SO2 absorption was systematically studied at 30–70 °C. Experimental results show that the EG-MTPB DES has a higher SO2 absorption capacity and a lower viscosity than other DESs. The reason for the higher SO2 absorption capacity of EG-MTPB DES was described by viscosity experiments and quantum chemical calculations. It was shown that the strong polarization ability of the CH3 group promotes the absorption of SO2 by DESs. 1H NMR and FTIR results indicated that chemical interactions primarily exist between the S of SO2 and Br, and the O of SO2 and the H atom of EG form hydrogen bonds. The density functional theory (DFT) results also confirm that the charge of the Br atom migrated to the S atom. Also, thermostability and regeneration experiments showed that the EG-MTPB DES exhibits good stability and can thus be used for industrial flue gas desulfurization.

Predicting the heat capacities of ammonium- and phosphonium-based deep eutectic solvents using artificial neural network

Deep eutectic solvents (DESs) are more environment-friendly and sustainable solvents than ionic liquids (ILs). Determining their physical properties is vital prior to their application. However, it is not practical to experimentally determine the physical properties of all DESs. Therefore, developing models to estimate their physical properties is necessary. In this study, a generalized model using artificial neural network (ANN) was developed to predict the heat capacities of ammonium- and phosphonium-based DESs over the temperature range of 278.15 – 353.15 K at atmospheric pressure. The best ANN model developed from the training and optimization process has an architecture with two hidden layers of 7 and 6 neurons, respectively. The overall average absolute relative deviation of the proposed model from the data was 0.57%. Qualitative analyses suggest a promising predicting capability of the proposed model. The calculated values of the statistical descriptors are close to their ideal values. Therefore, the proposed model can be used to reliably predict the heat capacities of other ammonium- and phosphonium-based two-component DESs.

Ternary glycerol-based deep eutectic solvents: Physicochemical properties and enzymatic activity

The present study investigates deep eutectic solvents (DESs) as potential media for enzymatic hydrolysis. A series of ternary ammonium and phosphonium-based DESs were prepared at different molar ratios by mixing with aqueous glycerol (85%). The physicochemical properties including surface tension, conductivity, density, and viscosity were measured at a temperature range of 298.15 K – 363.15 K. The eutectic points were highly influenced by the variation of temperature. The eutectic point of the choline chloride: glycerol: water (ratio of 1: 2.55: 2.28) and methyltriphenylphosphonium bromide:glycerol:water (ratio of 1: 4.25: 3.75) is 213.4 K and 255.8 K, respectively. The stability of the lipase enzyme isolated from porcine pancreas (PPL) and Rhizopus niveus (RNL) toward hydrolysis in ternary DESs medium was investigated. The PPL showed higher activity compared to the RNL in DESs. Molecular docking simulation of the selected DES with the substrate (p-nitrophenyl palmitate) toward PPL was also reported. It is worth noting that ternary DES systems would be viable lipase activators in hydrolysis reactions.

Optimization of Nazarov Cyclization of 2,4-Dimethyl-1,5-diphenylpenta-1,4-dien-3-one in Deep Eutectic Solvents by a Design of Experiments Approach.

The unprecedented Nazarov cyclization of a model divinyl ketone using phosphonium-based Deep Eutectic Solvents as sustainable non-innocent reaction media is described. A two-level full factorial Design of Experiments was conducted for elucidating the effect of the components of the eutectic mixture and optimizing the reaction conditions in terms of temperature, time, and substrate concentration. In the presence of the Deep Eutectic Solvent (DES) triphenylmethylphosphonium bromide/ethylene glycol, it was possible to convert more than 80% of the 2,4-dimethyl-1,5-diphenylpenta-1,4-dien-3-one, with a specific conversion, into the cyclopentenone Nazarov derivative of 62% (16 h, 60 °C). For the reactions conducted in the DES triphenylmethylphosphonium bromide/acetic acid, quantitative conversions were obtained with percentages of the Nazarov product above 95% even at 25 °C. Surface Responding Analysis of the optimized data furnished a useful tool to determine the best operating conditions leading to quantitative conversion of the starting material, with complete suppression of undesired side-reactions, high yields and selectivity. After optimization, it was possible to convert more than 90% of the model substrate into the desired cyclopentenone with cis percentages up to 77%. Experimental validation of the implemented model confirmed the robustness and the suitability of the procedure, leading to possible further extension to this specific combination of experimental designs to other substrates or even to other synthetic processes of industrial interest.

Prediction of Electrical Conductivity of Deep Eutectic Solvents Using COSMO-RS Sigma Profiles as Molecular Descriptors: A Quantitative Structure–Property Relationship Study

This work presents the development of molecular-based mathematical models for the prediction of electrical conductivity of deep eutectic solvents (DESs). Two new quantitative structure–property relationship (QSPR) models based on conductor-like screening model for real solvent (COSMO-RS) molecular charge density distributions (Sσ-profiles) were developed using the data obtained from the literature. The data comprise 236 experimental electrical conductivity measurements for 21 ammonium- and phosphonium-based DESs, covering a wide range of temperatures and molar ratios. First, the hydrogen-bond acceptors (HBAs) and hydrogen-bond donors (HBDs) of each DES were successfully modeled using COSMO-RS. Then, the calculated Sσ-profiles were used as molecular descriptors. The relation between the conductivity and the descriptors in both models has been expressed via multiple linear regression. The first model accounted for the structure of the HBA, the HBD, the molar ratio, and temperature, whereas the second model additionally incorporated the interactions between the molecular descriptors. The results showed that by accounting for the interactions, the regression coefficient (R2) of the predictive model can be increased from 0.801 to 0.985. Additionally, the scope and reliability of the models were further assessed using the applicability domain analysis. The findings showed that QSPR models based on Sσ-profiles as molecular descriptors are excellent at describing the properties of DESs. Accordingly, the obtained model in this work can be used as a useful guideline in selecting DESs with the desired electrical conductivity for industrial applications.

Extraction of pyridine from n-alkane mixtures using methyltriphenylphosphonium bromide-based deep eutectic solvents as extractive denitrogenation agents

In our previous work, we showed that phosphonium-based deep eutectic solvents (DESs) are good candidates for the extractive denitrogenation of oil fuels. In particular, pyridine was successfully extracted from n-hexane and n-heptane via liquid-liquid extraction. The extraction using ‘methyltriphenylphosphonium bromide and ethylene glycol’ DES yielded high distribution ratios and selectivities of pyridine. In this work, two phosphonium-based DESs were prepared, the first one was a “binary DES” composed of methyltriphenylphosphonium bromide and glycerol and the second one was a “ternary DES” composed of methyltriphenylphosphonium bromide, glycerol, and ethylene glycol. One objective was to assess the extraction properties of the DESs for pyridine from n-alkanes. Another objective of this work was to study the influence of n-alkane chain length on the extraction performance. Thus, the oil models selected were n-hexane/pyridine, n-heptane/pyridine, and n-octane/pyridine. First, the prepared DESs were characterized for their water content, density, viscosity, and the degradation temperatures. Then the solubility of n-hexane, n-heptane, n-octane, and pyridine in the DESs was measured at 298.2 K and 1.01 bar. Afterward, the liquid-liquid equilibrium (LLE) data of the pseudo-ternary systems {n-alkane + pyridine + DES} were determined at a temperature of 298.2 K and a pressure of 1.01 bar. The consideration of a pseudo-ternary system was validated by showing that none of the DES constituents appears in the n-alkane-rich phase “the raffinate”.The solute distribution ratios and the selectivities were calculated from the experimental LLE data and compared to our previous work and some relevant literature. Furthermore, the LLE data were correlated with the non-random two-liquid (NRTL) model using ASPEN Plus. There was good agreement between the calculated experimental results. Finally, the COnductor like Screening MOdel for Real Solvents (COSMO-RS) model was used to predict the ternary tie lines for the studied systems. Based on the good distribution ratios and selectivities obtained, the studied DESs can be considered as potential solvents for extractive denitrogenation processes.

Comment on the paper of Hosein Ghaedi et al. entitled “Measurement and correlation of physicochemical properties of phosphonium-based deep eutectic solvents at several temperatures (293.15 K–343.15 K) for CO2 capture”

The usability and correctness of the internal pressure values as calculated by Ghaedi et al. (2017) are critically discussed. The comparison with the data based on thermodynamic relationships shows that their results are misleading.

Investigation of various process parameters on the solubility of carbon dioxide in phosphonium-based deep eutectic solvents and their aqueous mixtures: Experimental and modeling

This research presents the application of predictive regression model such as quadratic regression for estimation of CO2 solubility in deep eutectic solvents namely allyltriphenylphosphonium bromide-triethylene glycol (ATPPB-TEG) into different molar ratios and their aqueous solutions. In doing so, a design of experiment (DOE) was applied based on Taguchi L18 orthogonal array method. Four factors, namely pressure, temperature, molar ratio and water/DES concentration in mixture were selected as input parameters of model. The output parameter of model was the CO2 solubility in terms of mole fraction of CO2 (XCO2). A quadratic regression model was developed after validation and confirmation through several strong approaches. The results disclose that the prediction of developed quadratic regression model is in acceptable agreement with experimental solubility data. The overall R-squared (R2) and absolute relative error (ARE) values of proposed quadratic regression model were 0.9966 and 0.0725, respectively. Moreover, analysis of variance (ANOVA) indicates that pressure is the most significant factor influencing the XCO2. Finally, the signal to noise (S/N) ratio shows that the highest levels for pressure, concentration of DES in mixture, and molar ratio, and lowest level for temperature are the optimal levels of input parameters to obtain the highest CO2 solubility in this system. The developed quadratic regression model and correlation are effective and provide quick, reliable and accurate predictions of CO2 solubility in DESs without carrying out any time consuming, difficult and expensive experimental measurements. To the best of our knowledge, this is the first time a regression model was developed for prediction of CO2 solubility in DESs and their aqueous solutions.

Thermal stability analysis, experimental conductivity and pH of phosphonium-based deep eutectic solvents and their prediction by a new empirical equation

Deep eutectic solvents (DESs) are derived from two or more salts as the hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). Because of many unique features, DESs can be a versatile alternative to ionic liquids and traditional solvents. In this work, DESs were prepared namely allyltriphenylphosphonium bromide-diethylene glycol (ATPPB-DEG) and allyltriphenylphosphonium bromide-triethylene glycol (ATPPB-TEG) into three mole ratios 1:4, 1:10, and 1:16 salt to HBDs. The thermal stability was comprehensively analysed under the temperature range of (30–800)°C. The conductivity and pH values were determined within the temperature range of 293.15K–343.15K. The results revealed that the amount and type of HBDs have an effect on these properties. Moreover, the effect of temperature was studied on these properties. As the temperature increases, the conductivity values increase while the pH values decrease. Finally, a new empirical equation was applied to correlate the experimental conductivity and pH data. It was found that this equation is powerful and reliable to correlate these properties of DESs.

CO2 capture with the help of Phosphonium-based deep eutectic solvents

Deep eutectic solvents (DESs) are derived from the concomitant reaction of two or more salts i.e. between hydrogen bond acceptor (HBA) and hydrogen bond donors (HBD) components. In this work, DESs were prepared namely allyltriphenyl phosphonium bromide-diethylene glycol (ATPPB-DEG) and allyltriphenyl phosphonium bromide-triethylene glycol (ATPPB-TEG) into three molar ratios 1:4, 1:10, and 1:16 salt to HBDs. The carbon dioxide solubility in DESs at temperature of 303.15K and pressure up to 2MPa were determined and reported in terms of mole fraction, CO2 loading and Henry's law constants. Krichevsky–Kasarnovsky equation was used to correlate the solubility data and obtain Henry's law constants at 303.15K. Finally, the effects of hydrogen bonding within DESs, molar ratio, molar volume, free volume, ether group and alkyl chain length were investigated based on CO2 solubility in DESs. To the best of our knowledge, this is the first time CO2 solubility in these DESs was studied.

Thermal stability and FT-IR analysis of Phosphonium-based deep eutectic solvents with different hydrogen bond donors

Recently, deep eutectic solvent (DES), a relatively new type of solvent, has received a considerable amount of attention from researchers in different fields of research. DESs have a high potential to be an alternative to ionic liquids (ILs) and traditional solvents. It is important the knowledge of thermal stability and interaction of functional groups on both salt as a hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) in order to use of DESs as alternative solvents for numerous industrial applications. In this work, four DESs have been selected with the same salt but four different HBDs. Salt was allyltriphenyl phosphonium bromide (ATPPB) and HBDs were glycerol (GL), ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG). DESs were prepared easily into the same molar ratio of 1:4 salt to HBDs. Fourier transform infrared spectroscopy (FT-IR) as an effective technique was conducted to gain information about hydrogen-bonding and vibration modes as well as investigate the functional groups of DESs. Finally, the thermal stability of DESs was studied under nitrogen at a temperature range of 30 to 800°C.

The study on temperature dependence of viscosity and surface tension of several Phosphonium-based deep eutectic solvents

Deep eutectic solvents (DESs) are derived from two or more salts as the hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). In this work, six deep eutectic solvents (DESs) were prepared namely allyltriphenyl phosphonium bromide- diethylene glycol (ATPPB-DEG) and allyltriphenyl phosphonium bromide - triethylene glycol (ATPPB-TEG) using three molar ratios of 1:4, 1:10 and 1:16 salt to HBDs. The temperature range for experimental viscosity was from 293.15 to 343.15K and that of the experimental surface tension was between 298.15 and 343.15K. The results disclosed that hydrogen bonding in DESs has a great effect on the properties. Among all DESs with the same components, the DESs with the strong hydrogen bonding in their structures had the higher viscosity and surface tension. Besides, by increasing the temperature and quantity of HBDs in DESs, both of these properties experienced a decreasing trend in the amount. It was found that the molecular weight of DESs with the same component has an effect on the properties. The higher molecular weight caused the higher viscosity and surface tension. Further, ATPPB-TEG DESs had the higher viscosity and lower surface tension than ATPPB-DEG DESs because of the higher alkyl chain in their structures. Several models and a new empirical equation were used to correlate the experimental viscosity data. It was found that there is a well agreement between theoretical and experimental values especially when the new empirical equation is used. In addition, the activation parameters for all DESs were calculated using the experimental viscosity data and application of Eyring's absolute rate theory. The experimental surface tension was employed to predict the critical temperature, surface entropy and internal surface energy of DESs. Finally, two empirical equations were used for relating the experimental surface tension to the experimental viscosity of DESs.

Measurement and correlation of physicochemical properties of phosphonium-based deep eutectic solvents at several temperatures (293.15 K–343.15 K) for CO2 capture

Recently, deep eutectic solvents (DESs) as the new solvents have received considerable amount of attention between researchers in different research fields and are under investigation so find out their potential to become a versatile alternative to ionic liquids (ILs) and traditional solvents. DESs are derived from two or more salts as the hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). Six DESs were synthesized namely allyltriphenylphosphonium bromide- diethylene glycol (ATPPB-DEG) and allyltriphenylphosphonium bromide- triethylene glycol (ATPPB-TEG) using three mole ratios of 1:4, 1:10 and 1:16 salt to HBDs. In this work, we report physicochemical properties of these DESs, which include density, molar volume, isobaric thermal expansion, refractive index, specific refraction, molar refraction, free molar volume, electronic polarization and internal pressure at several temperatures from 293.15K to 343.15K. Most of these properties are fitted to a linear equation by the method of least-squares using the Levenberg-Marquardt algorithm to derive the corresponding parameters and estimate the root mean square error (RMSE) and least squared correlation coefficient (R2).

Toxicity of Several Potassium Carbonate and Phosphonium-Based DeepEutectic Solvents towards Escherichia coli and Listeria monocytogenesBacteria

Deep eutectic solvents (DESs) and ternary deep eutectic solvents (TDESs) and are derived from two or more salts as the hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). In this work, the several DESs and a TDES were prepared. Allyltriphenyl phosphonium bromide and potassium carbonated were selected as HBAs to mix with various HBDs such as glycerol (GL), ethylene glycol (EG), diethylene glycol (DEG) and triethylene glycol (TEG) into different molar ratios. Two different groups of bacteria were selected for investigation of toxicity of species, namely Escherichia coli (EC) as a Gram negative bacterium and Listeria monocytogenes (LM) as a Gram positive bacterium. The results revealed that by increasing alkyl chain length on HBD, the toxicity of DESs increases towards EC bacterium. However, there appears to have no direct relationship between effect of alkyl chain length and toxicity DESs towards LM bacterium. Moreover, by studying the effect of molar ratio the toxicity of DESs, it was observed that there is no direct relationship between them. Furthermore, it was found that the type of HBD has a dominant effect on the toxicity of DESs compared to type of salt. By comparing the toxicity of DESs in this work with that of ILs in literature, it was found that DESs are less toxic than ILs. The last interesting result of this work is that TDES exhibited the lowest toxicity on EC and LM bacteria compared with DESs.

Synthesis and thermo-physical properties of deep eutectic solvent-based graphene nanofluids

This study introduces a new class of heat transfer fluids by dispersing functionalised graphene oxide nanoparticles (GNPs) in ammonium and phosphonium-based deep eutectic solvents (DESs) without the aid of a surfactant. Different molar ratios of salts and hydrogen bond donors (HBD) were used to synthesise DESs for the preparation of different concentrations of graphene nanofluids (GNFs). The concentrations of GNPs were 0.01 wt%, 0.02 wt% and 0.05 wt %. Homogeneous and stable suspensions of nanofluids were obtained by high speed homogenisation and an ultrasonication process. The stability of the GNFs was determined through visual observation for 4 weeks followed by a centrifugal process (5000–20 000 rpm) for 30 min in addition to zeta potential studies. Dispersion of the GNPs in DES was observed using an optical microscope. The synthesised DES-based GNFs showed no particle agglomeration and formation of sediments in the nanofluids. Thermo-physical properties such as thermal conductivity and specific heat of the nanofluids were also investigated in this research. The highest thermal conductivity enhancement of 177% was observed. The findings of this research provide a new class of engineered fluid for heat transfer applications as a function of temperature, type and composition DESs as well as the GNPs concentration.