Inas M. AlNashef

Superoxide Ion: Generation and Chemical Implications

Superoxide ion (O2(•-)) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2(•-) is rather scarce. In addition, numerous studies on O2(•-) were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2(•-) reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2(•-) so as to enable researchers to venture into future research. It comprises the main characteristics of O2(•-) followed by generation methods. The reaction types of O2(•-) are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2(•-) environmental chemistry is also discussed. The detection methods of O2(•-) are categorized and elaborated. Special attention is given to the feasibility of using ionic liquids as media for O2(•-), addressing the latest progress of generation and applications. The effect of electrodes on the O2(•-) electrochemical generation is reviewed. Finally, some remarks and future perspectives are concluded.

Potential applications of deep eutectic solvents in natural gas sweetening for CO2 capture

Abstract Novel solvents named deep eutectic solvents (DESs) have been intensively investigated in recent years. Their non-toxicity, biodegradability, low volatility, easy preparation and low cost make them promising green solvents for several industrial processes. This article provides a status review of the possible applications of DESs in natural gas (NG) sweetening by carbon dioxide (CO2) capturing. Investigations on preparation and chemical structures of DESs were reported. In addition, very recent physiochemical properties and applications of DESs were well discussed. Mainly, experimental and predicted solubilities of CO2 in DESs were reported and compared in this work. It was deduced that DESs offer some potential advantages over the conventional solvents, i.e. alkanolamines, in terms of absorption efficiency, easy preparation and low economic cost. It is expected that in coming decades, DESs will offer potential use in NG technology. Further investigations are highly required to highlight more about these neoteric solvents.

The Effect of Temperature on Kinetics and Diffusion Coefficients of Metallocene Derivatives in Polyol-Based Deep Eutectic Solvents.

The temperature dependence of the density, dynamic viscosity and ionic conductivity of several deep eutectic solvents (DESs) containing ammonium-based salts and hydrogen bond donvnors (polyol type) are investigated. The temperature-dependent electrolyte viscosity as a function of molar conductivity is correlated by means of Walden’s rule. The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) at different temperatures are studied by cyclic voltammetry and potential-step chronoamperometry in DESs. For most DESs, chronoamperometric transients are demonstrated to fit an Arrhenius-type relation to give activation energies for the diffusion of redox couples at different temperatures. The temperature dependence of the measured conductivities of DES1 and DES2 are better correlated with the Vogel-Tamman-Fulcher equation. The kinetics of the Fc/Fc+ and Cc+/Cc electrochemical systems have been investigated over a temperature range from 298 to 338 K. The heterogeneous electron transfer rate constant is then calculated at different temperatures by means of a logarithmic analysis. The glycerol-based DES (DES5) appears suitable for further testing in electrochemical energy storage devices.

Adsorptive removal of residual catalyst from palm biodiesel: application of response surface methodology

In this work, the residual potassium hydroxide catalyst was removed from palm oil-based methyl esters using an adsorption technique. The produced biodiesel was initially purified through a water washing process. To produce a biodiesel with a better quality and also to meet standard specifications (EN 14214 and ASTM D6751), batch adsorption on palm shell activated carbon was used for further catalyst removal. The Central Composite Design (CCD) of the Response Surface Methodology (RSM) was used to study the influence of adsorbent amount, time and temperature on the adsorption of potassium species. The maximum catalyst removal was achieved at 40°C using 0.9 g activated carbon for 20 h adsorption time. The results from the Response Surface Methodology are in a good agreement with the measured values. The absolute error in prediction at the optimum condition was 3.7%, which is reasonably accurate. This study proves that adsorption post-treatment techniques can be successfully employed to improve the quality of biodiesel fuel for its effective use on diesel engines and to minimize the usage of water.

RETRACTED: Neoteric FT-IR investigation on the functional groups of phosphonium-based deep eutectic solvents

Deep eutectic solvents (DESs) are novel solvent media that are currently under investigation as an alternative to ionic liquids and conventional solvents. The physical properties of DESs as well as their mild environmental footprint and potentially critical industrial application necessitate understanding the interaction of functional groups on both the salt and hydrogen bond donor (HBD). In this study, four DESs were prepared by mixing triethylenglycol, diethylenglycol, ethylenglycol, and glycerol as HBDs with methyltriphenylphosphonium bromide as a salt at a molar ratio of 1:4. Fourier transform infrared spectroscopy was conducted to highlight the chemical structure and mechanism of the combination of the four DESs. New spectra illustrating the combination of the functional groups of the HBDs and salt were observed and interpreted. This study is the first to investigate the properties of neoteric phosphonium-based DESs.

Computational investigation of the microstructural characteristics and physical properties of glycerol-based deep eutectic solvents

Recently, there has been significant interest in the possibility of using deep eutectic solvents (DESs) as novel green media and alternatives to conventional solvents and ionic liquids (ILs) in many applications. Due to their attractive properties, such as their biodegradability, low cost, easy preparation, and nontoxicity, DESs appear to be very promising solvents for use in the field of green chemistry. This computational study investigated six glycerol-based DESs: DES1 (glycerol:methyl triphenyl phosphonium bromide), DES2 (glycerol:benzyl triphenyl phosphonium chloride), DES3 (glycerol:allyl triphenyl phosphonium bromide), DES4 (glycerol:choline chloride), DES5 (glycerol:N,N-diethylethanolammonium chloride), and DES6 (glycerol:tetra-n-butylammonium bromide). The chemical structures and combination mechanisms as well as the sigma profiles and sigma potentials of the studied DESs were explored in detail. Moreover, density, viscosity, vapor pressure, and IR analytical data were predicted and compared with the corresponding experimental values reported in the literature for these DESs. To achieve these goals, the conductor-like screening model for realistic solvents (COSMO-RS) and the Amsterdam Density Functional (ADF) software package were used. The predicted results were found to be in good agreement with the corresponding experimental values reported in the literature. Further theoretical investigations are needed to confirm the experimental results—regarding both properties and applications—reported for these DESs.

Desulfurization of liquid fuel via extraction with imidazole-containing deep eutectic solvent

Abstract The desulfurization of liquid fuels with deep eutectic solvent (DES) newly synthesized from inexpensive constituents of imidazole and tetrabutylammonium bromide salt was conducted via liquid-liquid extraction. The aim of the work is to lower the sulfur content of liquid fuels to below the environmental regulation using DES in a process with low energy requirement. A simulated fuel containing dibenzothiophene (DBT) and thiophene as representative refractory sulfur compounds and a commercial-grade diesel fuel were used for this work. Quantitative monitoring of sulfur compounds in the raffinate phase of the fuels was performed using high-performance liquid chromatography and energy-dispersive X-ray fluorescence techniques. The results of sulfur extraction showed that DBT and thiophene extraction efficiencies of 70% and 47%, respectively, could be achieved from the simulated fuel in a single run extraction. Similarly, 47% total sulfur removal from the commercial-grade diesel fuel was achieved with the solvent. The deep desulfurizations of the fuels were successfully achieved in four and five successive stages with the simulated fuel and the diesel fuel, respectively. The solvent was effectively regenerated after the extraction process with both fuels, thus allowing for its repetitive usage.

Efficient non-catalytic oxidative and extractive desulfurization of liquid fuels using ionic liquids

Oxidative desulfurization (ODS) is one of the promising alternative and heavily researched desulfurization technologies. This is partly due to its ability to preferentially oxidize and ease the removal of refractory sulfur compounds with the aid of a suitable solvent. Despite its long list of advantages, challenges in different research areas within ODS technology still exist. In this work, an effort was made to bridge the gap that exists in terms of the selection of suitable oxidant and strategy. A preliminary kinetic modeling of the experimental data showed that the non-catalytic conversion of dibenzothiophene (DBT) and benzothiophene (BT) to their corresponding sulfones using the electrophilic meta-chloroperoxybenzoic acid (mCPBA) can be considered a bimolecular and a trimolecular reaction respectively. Using an ionic liquid (IL) as an extraction solvent in a simultaneous oxidation and extraction setup (EODS), >78% BT was removed at optimum experimental conditions. Using the post-oxidation extractive desulfurization setup (OEDS), 99% removal of BT was achieved at milder optimum experimental conditions. Also using the OEDS strategy, >99% of DBT removal was achieved after only 15 min at 60 °C, with a mass fraction of ≥0.5 and O/S of 3/1 for all the ILs tested. Finally, the sulfur content of a commercial diesel fuel was reduced to 15.6 ppm using the OEDS strategy with tetrabutylphosphonium methanesulfonate as a suitable extraction solvent, which can be readily regenerated.

Neoteric FT-IR Investigation on the Functional Groups of Phosphonium-Based Deep Eutectic Solvents

Deep eutectic solvents (DESs) are novel solvent media that are currently under investigation as an alternative to ionic liquids and conventional solvents. The physical properties of DESs as well as their mild environmental footprint and potentially critical industrial application necessitate understanding the interaction of functional groups on both the salt and hydrogen bond donor (HBD). In this study, four DESs were prepared by mixing triethylenglycol, diethylenglycol, ethylenglycol, and glycerol as HBDs with methyltriphenyl phosphonium bromide as a salt at a molar ratio of 1:4. Fourier transform infrared spectroscopy was conducted to highlight the chemical structure and mechanism of the combination of the four DESs. New spectra illustrating the combination of the functional groups of the HBDs and salt were observed and interpreted. This study is the first to investigate the properties of neoteric FT-IR for phosphonium-based DESs in addition to (MTPB:TEG) which was reported previously.