[Show abstract][Hide abstract] ABSTRACT: In this work, three kinds of novel functionalized ionic liquids (ILs) [NEt2C2Py][SCN], [C4OPy][SCN] and [C4CNPy][SCN] were developed by introducing a tertiary amino group, ether group and nitrile group on the pyridinium cation to improve SO2 absorption performances. Among the investigated ILs, [NEt2C2Py][SCN] showed the highest absorption capacity of 1.06 gSO2•gIL-1 under ambient conditions due to a combination of the chemical and physical absorption. By contrast, the enhancement in SO2 capacity by [C4CNPy][SCN] and [C4OPy][SCN] is mainly ascribed to the stronger physical interaction between ILs and SO2 than the conventional IL [C4Py][SCN]. Meanwhile, higher SO2/CO2 selectivity was also obtained using these functionalized ILs, which was increased up to 41% comparing with that of [C4Py][SCN]. Moreover, the effect of water on SO2 capacity and the absorption mechanism were studied. The results indicated that the presence of water caused a slight decrease in SO2 capacity of [C4CNPy][SCN] and [C4OPy][SCN] because of physical absorption, whereas a slight increase in SO2 capacity by [NEt2C2Py][SCN] due to the formation of hydrogen sulfite salts through chemical absorption. In addition, three kinds of cation-functionalized ILs could remain the stable absorption performance after five cycles of absorption and desorption, implying these ILs show great potentials for SO2 capture.
[Show abstract][Hide abstract] ABSTRACT: Mastery over the morphology of nanomaterials usually enables control of their properties and enhancement of their usefulness for a given application. Herein, we report a seed-mediated approach for the fabrication of bimetallic copper–platinum (CuPt) alloy nanoparticles with different morphologies. This strategy involves the first synthesis of Cu seed particles with multiple twins, and subsequent nucleation and growth of Pt metal. Then upon the Cu/Pt molar ratios in the synthesis, the rapid interdiffusion of Cu and Pt atoms results in the formation of bimetallic CuPt alloy nanoparticles with polyhedral, stellated, or dendritic morphologies. It has been found that both the morphology and electronic coupling effect between Cu and Pt components have significant effect on the electrochemical property of the alloy particles. In particular, the dendritic CuPt alloy nanoparticles display the highest specific activity for methanol oxidation reaction (MOR) due to their abundant atomic steps, edges, and corner atoms in the dendritic structure, while the polyhedral CuPt alloy particles show best carbon monoxide (CO) tolerant behavior due to the strong electronic donation effect from Cu to Pt atoms.
Journal of Power Sources 07/2015; 286. DOI:10.1016/j.jpowsour.2015.04.003 · 6.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Because of their many distinct advantages, the application of ionic liquids (ILs) for the synthesis and tailoring of nanoscale metal catalysts represents a burgeoning direction in materials chemistry. We herein depict the using of ammonium dibutyl phosphate ([AD]PO4), an organic soluble ionic liquid as an additive for the synthesis of Pt-based nanoparticles at elevated temperature in oleylamine. The experimental results reveal that not only the size/morphology, but also the electrocatalytic property of the platinum (Pt)-based bimetallic nanoparticles could be significantly tuned by a small amount of ionic liquid added in the reaction systems. For the silver (Ag)-Pt bimetallic system, core–shell Ag–Pt nanoparticles with dense or dendritic Pt shells are obtained at IL/oleylamine volume ratio of 0.25/10 and 0.5/10, while for gold (Au)-Pt bimetalic system, although the tuning of IL on the size/morphology of the particles are not apparent, the core–shell Au-Pt nanoparticles synthesized at IL/oleylamine volume ratio of 0.5/20 exhibit superior catalytic activity and durability for methanol oxidation reaction (MOR), compared to those prepared at other volume ratios.
Colloids and Surfaces A Physicochemical and Engineering Aspects 07/2015; 482(386):393. DOI:10.1016/j.colsurfa.2015.06.053 · 2.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is challenging to produce methyl methacrylate with high yield using direct oxidative esterification of methacrolein with methanol under oxygen atmosphere, and the key factor is the development of high-efficient and long-life supported Pd catalyst. In order to get the excellent catalyst, the effect of main influencing factors, such as promoters, supports, Pd precursors and reduction agents, on the catalyst structure and the catalytic performance were systematically studied. The results of the analysis indicated that the addition of promoters Pb to Pd crystallites catalyst, made the formation of new active bimetallic Pd3Pb crystallites, which could improve the catalytic activity; supports with different components and physico-chemical properties had great influence on the size of bimetallic Pd3Pb crystallites; different Pd precursors had different adsorption mechanism on the support which affected the dispersion of Pd; reductant and reduction temperature affected the size of Pd3Pb crystallites. These studies are important clues for developing the new and cheap catalyst for this kind of direct oxidative esterification reactions.
Chemical Engineering Science 05/2015; DOI:10.1016/j.ces.2015.05.038 · 2.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: High viscosity of ionic liquids (ILs) is one of the bottlenecks for its application in industry. Understanding the relationship between structure and viscosity is a key issue for directional designing ILs with low viscosity. In this work, the microstructures and interactions of three representative imidazolium-based ILs were studied by quantum chemistry calculations and molecular dynamics simulations in order to investigate the origin of different viscosity. An all-atom force field for difluorophosphate ([PO2F2]) anion was developed. The sandwich structures of hydrogen bond network were observed. The relationship between the number/energy of hydrogen bond and viscosity was proposed. The sequence of interaction energy is consistent with the trend of experimental viscosity. The simulation studies suggest that the hydrogen bond and interaction energy play important roles in determination of the viscosity of ILs.
[Show abstract][Hide abstract] ABSTRACT: Indole is an important industrial substance derived from wash oil, and the traditional alkali fusion method causes serious environmental problems. In this research, imidazolium-based ionic liquids (IBILs) were developed as new extraction agents to separate indole from wash oil with extraction efficiencies more than 90%. The influence of the structure of IBILs was explored. The extraction efficiency and the distribution coefficient of indole were used as the indexes to evaluate the IBILs extraction ability. The key experimental parameters such as initial indole concentration, extraction time, extraction temperature, and volume ratio of IBILs-to-model wash oil were investigated to obtain the optimum condition. The separation mechanism was studied by analyzing the chemical bonds using spectrographic analysis and molecular simulation. IBILs were recycled by back-extraction and exhibited good recycling properties with no obvious reduction and high extraction efficiency. Finally, the optimal process was conducted based on the process simulation.
Green Chemistry 03/2015; 17(7). DOI:10.1039/C5GC00081E · 8.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Utilization of CO2 (carbon dioxide) to synthesize useful organic compounds has attracted much attentions from the academia and industry. Recently, the fixation of CO2 catalyzed by using four hydroxyl-functionalized ionic liquids (ILs) has been successfully achieved. However, the detailed mechanism is still ambiguous. We performed a theoretical study on the mechanism of the fixation of CO2 catalyzed by 2-hydroxyl-ethyl-triethylammonium bromide (HETEAB) using the DFT method. The structural and energetic information for each possible route were obtained. Furthermore, the similarities and differences of two different catalysts, HETEAB and 2-hydroxyl-ethyl-tributylammonium bromide (HETBAB), were discussed in detail. In addition, the result shows that the OH functional group is one essential factor to improve the catalyst ability. Except that, including active H atom in the IL is the other major factor to refine the catalytic performance.
International Journal of CO2 Utilization 03/2015; 10. DOI:10.1016/j.jcou.2015.02.006 · 3.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ionic liquids (ILs) have been used in an enormous number of chemical and biological processes. In recent years, self-assembly of ILs into the micelles has attracted much attention and proved to be the key feature in interpreting many physical phenomena and have influence on fluids transport. Micelles or aggregates are mostly reported to be quasi-spherical objects with the alkyl tails forming the core and the imidazolium headgroups exposed to water. In this work, the formation and structure of rodlike micelle in [C12mim]Br aqueous solution was studied by molecular dynamics simulations based on the united-atom force field. Several separate simulations were performed using both liquid droplet and random-like starting conditions, and self-assembly of cations into the rodlike micelle was observed, which is consistent with the TEM result. A more detailed analysis and comparison between the solution and neat IL using radial distribution functions demonstrate the influencing factors of the micelles, the structure, and interaction between ions and water. Besides, the intermolecular energy and hydrogen-bond number and pattern were also analyzed to further reveal the nature of the micelles.
[Show abstract][Hide abstract] ABSTRACT: Phenolic compounds are widely used in chemical industrial applications. The traditional method of extracting phenolic compounds, which uses strong alkaline and acid, is harmful to the environment. In this research, amide and its homologues were developed as new extraction agents. And they could form deep eutectic solvent (DES) with phenols, and this DES was immiscible with oil. Formation mechanism of the DES was investigated using a Fourier transform infrared spectrometer (FT-IR). Hydrogen bond (H-bond) between acylamino and phenolic hydroxyl groups was observed. Different experimental conditions, such as different substituents of amide compounds, reaction temperature, reaction time, and mole ratio of extraction agent to phenols were studied. The influence rules of different experimental conditions were obtained, so did the optimized conditions. The extraction agent was recycled through back extraction, and exhibited good recycling properity and high extraction efficiency. Based on above experimental results, a separation process was proposed.
[Show abstract][Hide abstract] ABSTRACT: Carbon-supported palladium nanoparticles (NPs) with hollow interiors (hPdNPs/C) are fabricated via a facile approach. In this strategy, core-shell NPs with an Ag core and an Ag-Pd alloy shell (Ag@Ag-Pd) are firstly synthesized in oleylamine by galvanic replacement reaction between Ag seed particles and Pd2+ ion precursors. Then the core-shell Ag@Ag-Pd NPs are loaded on the XC-72 carbon supports and refluxed in acetic acid to remove the original organic surfactant. The carbon-supported core-shell Ag@Ag-Pd NPs are subsequently agitated in saturated Na2S or NaCl solution for 24 h to eliminate the Ag component from the core and shell regions, leading to the formation of hPdNPs/C. In specific, the hPdNPs/C generated by NaCl treatment exhibit superior catalytic activity and durability for formic acid oxidation reaction (FAOR) and oxygen reduction reaction (ORR), compared with the commercial Pd/C catalysts from Johnson Matthey, mainly due to the high electrochemically active surface areas (ECSAs) of the hollow structure, whereas the hPdNPs/C obtained by Na2S treatment display very poor catalytic performance due to the serious poisoning induced by S2- adsorption.
[Show abstract][Hide abstract] ABSTRACT: In this work, the interactions between a representative pyridinium-based ionic liquid (IL) with cyano-functionalized anion ([C4Py][SCN]) and dimethyl sulfoxide (DMSO) were investigated in detail using attenuated total reflection infrared spectroscopy (ATR-FTIR), hydrogen nuclear magnetic resonance (1H NMR), and density functional theory (DFT) calculations. It was found that H-bonds are universally involved and play important role for the miscibility of DMSO with [C4Py][SCN] IL and maintain the stability of this system. ATR-FTIR and excess spectroscopy analysis indicated that the H-bonds involving the alkyl C-Hs and C≡N are strengthened with the addition of DMSO, while the H-bonds involving pyridinium ring C-Hs as well as the H-bonds formed between the [C4Py]+ and [SCN]− are weakened. The addition of [C4Py][SCN] IL led to the H-bonds involving the C-Hs in DMSO weakened comparing with the associated H-bonds in the pure DMSO system. The results of DFT calculations indicated that the DMSO molecules cannot disrupt the strong Coulombic interaction between the [C4Py]+ and [SCN]−. Natural bond orbital (NBO) analysis further confirmed that the interaction mechanisms of DMSO molecule with the anion and cation are different in nature. These studies will shed light on exploring the applications of ILs as reaction or separation media.
Chemical Engineering Science 01/2015; 121:169-179. DOI:10.1016/j.ces.2014.07.024 · 2.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hollow Palladium (hPd) nanoparticles (NPs) are prepared via a simple and mild successive method. Firstly, core-shell NPs with silver (Ag) cores and silver-palladium (Ag-Pd) alloy shells are synthesized in aqueous phase by galvanic replacement reaction (GRR) between Ag NPs and Pd2+ ion precursors. Saturated aqueous sodium chloride (NaCl) solution was then employed to remove the Ag component from the core and shell regions of core-shell Ag@Ag-Pd NPs, resulting in the formation of hPd NPs with shrunk sizes in comparison with their core-shell parents. Specifically, the hPd NPs exhibit superior catalytic activity and durability for catalyzing the oxidation of formic acid, compared with the Pd NPs reduced by NaBH4 in aqueous solution and commercial Pd/C catalyst from Johnson Matthey, mainly due to the large electrochemically active surface areas of the hollow particles. In addition, The Ag component in core-shell Ag@Ag-Pd NPs has an unfavorable influence on catalytic activity of NPs for formic acid oxidation. However, the durability could be improved due to the electron donating effect from Ag to Pd atoms in the core-shell NPs.
Journal of Power Sources 12/2014; 272:152–159. DOI:10.1016/j.jpowsour.2014.08.059 · 6.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The synthesis of noble metal nanoparticles (NMNPs) using, or in the presence of, ionic liquids (ILs) represents a burgeoning direction in materials chemistry. Processing these nanomaterials synthesized in ILs would be drastically simplified if they could be routinely dispersed into a wide variety of polar/nonpolar solvents. We herein demonstrate the phase transfer of the as-prepared nanoparticles from ILs to an organic or aqueous medium. The protocol involves first mixing the noble metal sols in ILs and an ethanolic or a methanolic solution of transfer agent and then extracting the transfer-agent-stabilized NMNPs into toluene or aqueous phase. Electron micrographs reveal that the particles are fully dispersed after transfer, and the size/morphology of the NMNPs could be significantly tuned by the ILs. In particular, electrochemical measurements of the Pt nanoparticles upon methanol oxidation reaction demonstrate that the particles are dominated by low-index crystal planes.
[Show abstract][Hide abstract] ABSTRACT: The FeCl3-containing Lewis-acidic ionic liquids (ILs) [C6mim]Cl/FeCl3(1:1.5), [C6mim]Cl/FeCl3(1:2), [C8mim]Cl/FeCl3(1:1.5), and [C8mim]Cl/FeCl3(1:2) were used as extractants for desulfurization of model fuel and gasoline fuel, respectively. The results demonstrate that these ILs are effective for the removal of sulfur compounds from model fuel under different mass ratio of IL to model fuel (1:1, 1:3, 1:5, 1:10) at 25°C. The extractive performance of ILs increased as the molar ratio of FeCl3 to [Cnmim]Cl(n = 6, 8) varied from 1:1 to 1:2. The selectivity of sulfur compounds by extraction process followed the order of dibenzothiophene (DBT)>benzothiophene (BT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT). The sulfur removal of gasoline fuel containing sulfur content of 440.3 ppmw could be up to 85.8%; that is to say that the sulfur content of gasoline fuel varied from 440.3 ppmw to 62.4 ppmw after one extraction stage. Moreover, the [C6mim]Cl/FeCl3(1:2) can be recycled for at least 4 times with a little decrease in the desulfurization activity.
[Show abstract][Hide abstract] ABSTRACT: The mechanism of cycloaddition reaction between carbon dioxide and epoxide, catalyzed by HEMIMC (1-(2-hydroxyl-ethyl)-3-methylimidazolium chloride), was investigated using the DFT (density functional theory) method. In the presence of HEMIMC, the reaction mechanism changed from single-step to multipath. Seven reaction pathways are reported here, including two steps, epoxide ring-opening and ring-closure of cyclic carbonate, or three main steps, epoxide ring-opening, carbon dioxide insertion, and ring-closure of cyclic carbonate. The catalytic activity of HEMIMC was studied, and the catalytic mechanism was elucidated. The nucleophilic attack of anion and hydrogen bond are two of the most important factors to promote the cycloaddition reaction, especially the OH functional group in HEMIMC. Finally, the influence of different anions on the catalytic activity was investigated.
[Show abstract][Hide abstract] ABSTRACT: Biodegradable ionic liquids (bio-ILs) have attracted intensive attention due to toxicological and ecological reasons. It is critically important to understand the structural properties of bio-ILs at the molecular level. In this work, the interactions between four biodegradable naphthenate ionic liquids were investigated by density functional theory. The results indicate that multiple hydrogen bonds (H-bonds) are the major intermolecular structural feature between the cation and anion. These H-bonds were analyzed by natural bond orbital (NBO), quantum theory of atoms in molecules (AIM) and reduced density gradient (RDG) function. The influence of anionic structure on the interaction energy was studied. Based on the canonical orbital analysis, it is found that the sigma-type orbital overlap and the partial charges transfer between the anion and cation, finally, result in the decrease of the energy and rationalize the location of the anion. Additionally, linear relationships between second-order interaction energies and the increment of electron density, as well as the interaction energies and the sum of the electron density at bond critical points for all studied [Ch][NA] ion pairs were found.
[Show abstract][Hide abstract] ABSTRACT: Series of 1-allyl-3-methylimidazolium halometallate ionic liquids (ILs) were synthesized and used to degrade poly(ethylene terephthalate) (PET) as catalysts in the solvent of ethylene glycol. One important feature of these new IL catalysts is that most of them, especially [amim][CoCl3] and [amim][ZnCl3], exhibit higher catalytic activity under mild reaction condition, compared to the traditional catalysts [e.g., Zn(Ac)2], the conventional IL catalysts (e.g., [bmim]Cl), Fe-containing magnetic IL catalysts (e.g., [bmim][FeCl4]), and metallic acetate IL catalysts (e.g., [Deim][Zn(OAc)3]). For example, using [amim][ZnCl3] as catalyst, the conversion of PET and the selectivity of bis(hydroxyethyl) terephthalate (BHET) reach up to 100% and 80.1%, respectively, under atmospheric pressure at 175 degrees C for only 1.25 h. Another important feature is that BHET can be easily separated from the catalyst and has a high purity. Finally, based on the experimental phenomena, in -situ infrared spectra, and experimental results, the possible mechanism of degradation with synthesized IL is proposed. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
[Show abstract][Hide abstract] ABSTRACT: Nursing and teaching are considered risk professions with high levels of stress and burnout. Dual-qualification nursing teachers (DQNT) are nurses who both teach and practise. These nurses face additional stress. This study explored the stressors of DQNT in the Chengdu-Chongqing Economic Zone of China. This qualitative study used in-depth, open-ended interviews. The interview responses were analysed using a grounded theory approach. The participants in this study included 21 DQNT from 5 teaching hospitals in the Chengdu-Chongqing Economic Zone of China. The results indicated that heavy workload, personal safety, inadequate pay, role overload, and poor working environment are stressors of DQNT. Furthermore, Chinese DQNT face violence from patients and students. The study provides a theoretical basis to help DQNT to cope with stress.