N-methyl-2-pyrrolidinone Research Articles

Molecular Composition of Soxhlet N-Methyl-2-pyrrolidinone Extracts from a Lignite

N-Methyl-2-pyrrolidinone (NMP) is a capable solvent which could extract more substance from coals than any other solvents. However, the molecular composition of the extract was still unclear. In this study, a lignite was subjected to Soxhlet extraction using pyridine followed by NMP. The NMP extract and its hydrolyzed product were characterized by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The results showed that the NMP extract and its hydrolyzed product had very high nitrogen contents and NxOy class species with multiple nitrogen and oxygen atoms dominant in the detected species. Relative abundance of 15N isotope and the molecular composition of extracts obtained from different extraction conditions indicated that the NMP involved into the extracts. Both self-polymerization of NMP and chemical reactions between NMP and coals occurred in the thermal extraction.

Toward Understanding the Efficient Exfoliation of Layered Materials by Water-Assisted Cosolvent Liquid-Phase Exfoliation

Preparation of two-dimensional layered materials (2DLM) nanosheets is critical for both fundamental studies and applications. Here we present a systematic study to explore the fundamental factors to control the exfoliation of graphite and MoS2 in aqueous N-methylpyrrolidinone (NMP) using water as the cosolvent. Detailed materials characterizations suggested that the cosolvency significantly influences the yield and the stability of exfoliated nanosheets. The dependence of exfoliation on cosolvency was examined by fundamental factors including solid–liquid interfacial parameters, Hansen Solubility Parameter (HSP), and intermolecular-interaction-sensitive physical parameters of the water–NMP mixed solvent system. Fourier transform infrared spectroscopy (FTIR) study revealed that the water–NMP heteroassociated molecular structures, formed with the addition of water to NMP, could play an important role in the liquid exfoliation of layered materials. Our work provides a guide to rational design of a solvent sy...

Synthesis and properties of novel soluble aromatic polyamides containing 4-aryl-2,6-diphenylpyridine moieties and pendant fluorinated phenoxy groups

Three diamine monomers containing pyridine groups were prepared via the modified Chichibabin reaction of aromatic aldehydes with 4′-nitroacetophenone, followed by reduction with hydrazine hydrate in the presence of Pd/C. Novel aromatic polyamides containing 4-aryl-2,6-diphenylpyridine moieties and pendant fluorinated phenoxy groups were synthesized from these diamines and two fluorinated isophthaloyl dichlorides by the low temperature solution polycondensation in N,N-dimethylacetamide (DMAc). All the polymers are amorphous and readily soluble in strong polar organic solvents such as DMAc, N-methyl-2-pyrrolidinone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) at room temperature. The resulting polymers showed glass transition temperatures between 270 and 314 °C and 5 % weight loss temperatures ranging from 442 °C to 475 °C, and char yields at 800 °C higher than 53 % in nitrogen. These polyamides could be cast into transparent, flexible and strong films from DMAc solution with tensile strengths of 72.5–87.3 MPa, tensile moduli of 2.35–2.87 GPa, and elongations at break of 5.3–9.5 %. The polyamide films exhibited low dielectric constants of 3.21–3.54 (1 MHz), low water uptakes in the range of 1.17–1.38 %, and high transparency with an ultraviolet-visible absorption cut-off wavelength in the 380–391 nm range.

Optical evidence for chemical interaction of the polyaniline/fullerene composites with N-methyl-2-pyrrolidinone

Surface enhanced Raman scattering (SERS) spectroscopic studies reveal a particular chemical interaction of the polyaniline/fullerene (PANI/C60) composite with N-methyl-2-pyrrolidinone (NMP). The chemical polymerization of aniline in the presence of sulfuric acid, potassium dichromate and fullerene has been used for the preparation of the PANI/C60 composite. The polymerization reaction involves a doping of PANI with C60 anion radicals. The interaction of the composite with NMP leads to a de-doping of PANI that involves a transformation of leucoemeraldine salt (LS) repeating units into leucoemeraldine base (LB). Additionally, a gradual increasing in the intensity of the Raman line at 1452 cm−1 associated to the Ag(2) pentagonal pinch mode of fullerene and a decrease in the intensity of the Raman lines of PANI are reported. This change arises from the formation of a charge-transfer complex C60-NMP. The subsequent chemical treatment of PANI-LB with FeCl3 leads to the formation PANI-emeraldine salt. An inhibition of the transformation of PANI doped with C60 anion radicals into a PANI-LB and the C60-NMP charge transfer complex in the presence of CdS particles dispersed in NMP is demonstrated by SERS spectroscopy.

Nanostructured Si Alloys Via Ethanol Delithiation

Introduction Si-based alloys are potential candidates as high energy density negative electrodes in Li-ion batteries. Such alloys have high theoretical capacity but also have high volume expansion, which can lead to cell fade. It has been shown previously that amorphous Si (a-Si) synthesized by chemical or physical deposition has improved cycling performance compared to crystalline Si (cr-Si) [1, 2]. Typically, a-Si is made by ball milling or atomic deposition techniques. Templating methods have also been employed to make nanostructured Si alloys that include void space in which the Si can expand [3, 4]. Such alloys can perform well as negative electrodes in Li cells. An inexpensive route for synthesizing bulk quantities of a-Si or nanostructured Si alloys is desirable. In this study, a new chemical delithiation method employing ethanol as an oxidizing agent was applied to prepare bulk quantities of a-Si from Li-Si compounds. The a-Si formed was found to have a unique exfoliated layered structure, which has lower volume expansion than cr-Si and improved cycling characteristics. C-Si and Fe-Si alloys were also synthesized by the delithiation of C-Li-Si and Fe-Li-Si alloys using this chemical delithiation method. When tested as negative electrodes in Li cells, the C-Si and Fe-Si alloys showed superior electrochemical characteristics and lower volume expansion than cr-Si. Experimental Li12Si7, Li7Si3, Li13Si4 or Li22Si5 compounds were first prepared in an arc furnace from the elements. Ethanol was then used to delithiate the Li-Si compounds under an Ar atmosphere. After the resulting slurry was washed with distilled water, a-Si was recovered with a 70% yield. C-Li-Si and Fe-Li-Si precursors with serial C: Si or Fe: Si stoichiometric ratios were prepared by ball milling. Ethanol was then used to delithiate the C-Li-Si or Fe-Li-Si alloys under an Ar atmosphere. After the resulting products were washed with distilled water, C-Si and Fe-Si alloys were recovered with 79% and 70% yields, respectively. Electrode slurries were prepared by mixing active materials (a-Si, C-Si or Fe-Si), carbon black and polyimide in a volume ratio of 62.5/18/19.5 in N-methyl pyrrolidinone. Electrode disks were punched from the coating foil and heated in a tube furnace for 3h at 300 °C under an Ar flow. 2325 coin-type cells were assembled in an Ar-filled glovebox with a Li counter/reference electrode. All cells were cycled between 5~900 mV with a Maccor Series 4000 Automated Test System. Results a-Si prepared from ethanol delithiation of Li12Si7, Li7Si3, Li13Si4, and Li22Si5 resulted in layered products, except in the case of Li22Si5, which was composed of dense particles. Figure 1 shows an SEM image of a-Si prepared from ethanol delithiation of Li12Si7. a-Si prepared from ethanol delithiation of Li12Si7 had the most orderly layered structure, with the layers being highly exfoliated. All a-Si samples had superior cycling performance and lower volume expansion compared to cr-Si. Figure 2 shows the cycling performance of an a-Si electrode prepared from ethanol delithiation of Li12Si7 and a cr-Si electrode. It is thought that the porous layered structure of these delithiated materials can accommodate the Si volume expansion during lithiation, resulting in low overall particle expansion and improved cycling performance. Remarkably, C-Si and Fe-Si alloys made by the delithiation of ball milled C-Li-Si or Fe-Li-Si alloys contained very low silicide or carbide content. Instead the alloys were primarily composed of a nano-composite of elemental C and Si or Fe metal and Si. This was confirmed by X-ray diffraction and Mössbauer spectroscopy. These alloys have a completely different nanostructure than conventional ball milled Si-based alloys, in which carbon and Fe are typically completely reacted to form carbides and silicides. Conclusions The alcohol delithiation method represents an effective means of producing Si-based alloys as negative electrode materials for Li cells. The unique nanostructures of these alloys and their electrochemical performance will be discussed.

Fabrication of cost effective iron ore slime ceramic membrane for the recovery of organic solvent used in coke production

Improvement of coking properties of sub-bituminous coal (A) and bituminous coal (B) was done using blended organic solvents, namely, n-methyl-2-pyrrolidinone (NMP) and ethylenediamine (EDA). Various solvent blends were employed for the coal extraction under the total reflux condition. A low-cost ceramic membrane was fabricated using industrial waste iron ore slime of M/s TATA steel R&D, Jamshedpur (India) to separate out the dissolved coking fraction from the solvent-coal mixture. Membrane separations were carried out in a batch cell, and around 75 % recovered NMP was reused. The fractionated coal properties were determined using proximate and ultimate analyses. In the case of bituminous coal, the ash and sulfur contents were decreased by 99.3 % and 79.2 %, respectively, whereas, the carbon content was increased by 23.9 % in the separated coal fraction. Three different cleaning agents, namely deionized water, sodium dodecyl sulphate and NMP were used to regain the original membrane permeability for the reusing.

Protein chemical synthesis by α-ketoacid-hydroxylamine ligation.

Total chemical synthesis of proteins allows researchers to custom design proteins without the complex molecular biology that is required to insert non-natural amino acids or the biocontamination that arises from methods relying on overexpression in cells. We describe a detailed procedure for the chemical synthesis of proteins with the α-ketoacid-hydroxylamine (KAHA ligation), using (S)-5-oxaproline (Opr) as a key building block. This protocol comprises two main parts: (i) the synthesis of peptide fragments by standard fluorenylmethoxycarbonyl (Fmoc) chemistry and (ii) the KAHA ligation between fragments containing Opr and a C-terminal peptide α-ketoacid. This procedure provides an alternative to native chemical ligation (NCL) that could be valuable for the synthesis of proteins, particularly targets that do not contain cysteine residues. The ligation conditions-acidic DMSO/H2O or N-methyl-2-pyrrolidinone (NMP)/H2O-are ideally suited for solubilizing peptide segments, including many hydrophobic examples. The utility and efficiency of the protocol is demonstrated by the total chemical synthesis of the mature betatrophin (also called ANGPTL8), a 177-residue protein that contains no cysteine residues. With this protocol, the total synthesis of the betatrophin protein has been achieved in around 35 working days on a multimilligram scale.

Thermodynamic, excess and optical studies on the intermolecular interactions of binary liquid mixtures of imidazolium based ILs

The densities, ρ, speeds of sound, u and refractive indices, nD of binary mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide {[Bmim][NTf2]} and N-methyl-2-pyrrolidinone (NMP), including those of pure liquids, over the entire composition range were measured at temperatures (298.15, 303.15, 308.15, 313.15, 318.15 and 323.15)K and atmospheric pressure. From the experimental values, the excess molar volumes, VmE, excess isentropic compressibilities, κsE, excess speeds of sound, uE, deviations in refractive index, ΔϕnD and deviations in molar refraction, ΔRM have been calculated. The partial molar volumes, V¯m,1 and V¯m,2 and excess partial molar volumes, V¯m,1E and V¯m,2E over the whole composition range and the partial molar volumes, V¯m,1° and V¯m,2° and excess partial molar volumes, V¯m,1°E and V¯m,2°E of the components at infinite dilution have also been calculated. The variations of these parameters with composition and temperature have been discussed in terms of intermolecular interactions prevailing in these mixtures.

ChemInform Abstract: Nickel—Copper‐Catalyzed C(sp2)—N Cross‐Coupling of Cyclic and Bridged Amides: An Access to Cyclic Enamides and Alkenyl Vince Lactams.

An efficient C(sp2)N cross-coupling of styrenyl and vinyl halides with cyclic and bridged amides catalyzed by nickel acetonylacetonate [Ni(acac)2] and copper(I) iodide (CuI) in the absence of any ligand has been developed. The reaction conditions are optimized to give the maximum yield of products using cesium carbonate (Cs2CO3) (2.0 equiv.) in N-methyl-2-pyrrolidinone (NMP) at 110 °C under argon in the presence of Ni(acac)2/CuI (10 mol% each). A series of alkenyl derivatives of Vince lactams (bridged amides) and cyclic amides are obtained by this procedure. Halogen-containing styrenyl bromides also underwent coupling with amides to provide the products. The coupling is highly chemoselective as during the reactions the halogens (Br, Cl, F) on the aromatic ring remained intact and these can be used for further functionalization to make these enamides more useful. Although the (E)-styrenyl halides produced the corresponding (E)-styrenyl enamides, reactions with (Z)-styrenyl halides produced 1,3-di-ynes instead of (Z)-styrenyl enamides. This may be explained by the possibility of E2 type elimination of (Z)-styrenyl halides in the presence of a strong base like cesium carbonate followed by homocoupling. This catalyst system works efficiently for the N-arylation too along with N-styrenylation and vinylation. The bridged as well as cyclic amides successfully coupled with substituted aryl halides to provide the corresponding products. In general, the reactions are clean and high yielding. The operations are very simple and the products are obtained pure by standard column chromatography. The reaction is compatible with variety of amides and alkenyl bromides. The roles of nickel acetonylacetonate and copper(I) iodide in this reaction have been established and a possible reaction pathway has been outlined. The significant feature of this protocol is the alkenylation of Vince lactams via C(sp2)N cross-coupling, which has not been reported so far and these products may have much potential in the pharmaceutical industry.

N-Butylpyrrolidinone as a dipolar aprotic solvent for organic synthesis

N-Butylpyrrolidinone (NBP) has been demonstrated as a suitable safer replacement solvent for N-Methylpyrrolidinone (NMP) in selected organic syntheses.

Nickel–Copper‐Catalyzed C(sp2)N Cross‐Coupling of Cyclic and Bridged Amides: An Access to Cyclic Enamides and Alkenyl Vince Lactams

AbstractAn efficient C(sp2)N cross‐coupling of styrenyl and vinyl halides with cyclic and bridged amides catalyzed by nickel acetonylacetonate [Ni(acac)2] and copper(I) iodide (CuI) in the absence of any ligand has been developed. The reaction conditions are optimized to give the maximum yield of products using cesium carbonate (Cs2CO3) (2.0 equiv.) in N‐methyl‐2‐pyrrolidinone (NMP) at 110 °C under argon in the presence of Ni(acac)2/CuI (10 mol% each). A series of alkenyl derivatives of Vince lactams (bridged amides) and cyclic amides are obtained by this procedure. Halogen‐containing styrenyl bromides also underwent coupling with amides to provide the products. The coupling is highly chemoselective as during the reactions the halogens (Br, Cl, F) on the aromatic ring remained intact and these can be used for further functionalization to make these enamides more useful. Although the (E)‐styrenyl halides produced the corresponding (E)‐styrenyl enamides, reactions with (Z)‐styrenyl halides produced 1,3‐di‐ynes instead of (Z)‐styrenyl enamides. This may be explained by the possibility of E2 type elimination of (Z)‐styrenyl halides in the presence of a strong base like cesium carbonate followed by homocoupling. This catalyst system works efficiently for the N‐arylation too along with N‐styrenylation and vinylation. The bridged as well as cyclic amides successfully coupled with substituted aryl halides to provide the corresponding products. In general, the reactions are clean and high yielding. The operations are very simple and the products are obtained pure by standard column chromatography. The reaction is compatible with variety of amides and alkenyl bromides. The roles of nickel acetonylacetonate and copper(I) iodide in this reaction have been established and a possible reaction pathway has been outlined. The significant feature of this protocol is the alkenylation of Vince lactams via C(sp2)N cross‐coupling, which has not been reported so far and these products may have much potential in the pharmaceutical industry.magnified image

Measurements of activity coefficients at infinite dilution of organic solutes and water on polar imidazolium-based ionic liquids

The activity coefficients at infinite dilution, γ13∞, of 55 organic solutes and water in three ionic liquids with the common cation 1-butyl-3-methylimidazolium and the polar anions Cl−, [CH3SO3]− and [(CH3)2PO4]−, were determined by (gas+liquid) chromatography at four temperatures in the range (358.15 to 388.15)K for alcohols and water, and T=(398.15 to 428.15)K for the other organic solutes including alkanes, cycloalkanes, alkenes, cycloalkenes, alkynes, ketones, ethers, cyclic ethers, aromatic hydrocarbons, esters, butyraldehyde, acetonitrile, pyridine, 1-nitropropane and thiophene. From the experimental γ13∞ values, the partial molar excess Gibbs free energy, G‾mE,∞, enthalpy H‾mE,∞, and entropy S‾mE,∞, at infinite dilution, were estimated in order to provide more information about the interactions between the solutes and the ILs. Moreover, densities were measured and (gas+liquid) partition coefficients (KL) calculated. Selectivities at infinite dilution for some separation problems such as octane/benzene, cyclohexane/benzene and cyclohexane/thiophene were calculated using the measured γ13∞, and compared with literature values for N-methyl-2-pyrrolidinone (NMP), sulfolane, and other ionic liquids with a common cation or anion of the ILs here studied. From the obtained infinite dilution selectivities and capacities, it can be concluded that the ILs studied may replace conventional entrainers applied for the separation processes of aliphatic/aromatic hydrocarbons.

Solution properties of polyaniline/carbon particle composites

Abstract This study reports on the synthesis of polymer polyaniline, a conductive polymer by nature, and the preparation of polyaniline/carbon particle (PANI/CP) composites by in situ polymerization. The solution properties and conductivities in solution of synthesized PANI and PANI/CP materials were analyzed. The viscosity of PANI and PANI/CP composite materials in N-methylpyrrolidinone (NMP) solvent at different temperatures was measured to examine their behavior in solution. Initially, the viscosity-molecular weight of PANI polymer was measured and calculated to be 78,521. The viscosities of PANI and PANI/CP composite materials decreased as the temperature increased. However, the viscosities of PANI/CP composite materials increased as the percent CP content in the composites increased. The ionic conductivities and pH changes in NMP solvent, measured at different concentrations of PANI and PANI/CP composite materials, and prepared in different ratios, were measured to investigate their behavior in solution. The ionic conductivities of PANI/CP composite materials increased as the percent CP content in the composites increased. Changes in the pH of PANI/CP composite materials decreased as the percent CP content in the composites increased. The conductivity of PANI/10% CP composite material in solution was greater than that of neat PANI polymer in solution; this indicated that CPs in PANI/10% CP composite materials made important positive contributions to the conductivities.

Enhanced Cycleability of LiNi0.5Mn1.5O4 Cathode with Zn Substitution

Introduction In the last decade, lithium-ion batteries are expected to be applied in electric vehicles. High voltage or capacity cathode materials are required to achieve high energy batteries. Spinel LiNi0.5Mn1.5O4 draws much attention owning to a voltage plateau as high as 4.7 V vs. Li/Li+, accepted capacity, excellent rate capability and good safety.[1] However, high voltage plateau brings side reactions between the cathode and the electrolyte at high voltage which cause capacity fade of spinel LiNi0.5Mn1.5O4.[2] Partial substitution of Mn or Ni by metal elements such as Al, Cr, Fe, Co etc.[3] has been proven to be successful to enhance its cycleability. Series substitutions of Mg instead of Ni are achieved to modify the spinel. The cycleability has been much improved by Mg substitution even charged to 5.1 V. Experimental LiZn x Ni0.5-x Mn1.5O4 was prepared via a sol–gel method assisted by citric acid as chelating agents. Citric acid was firstly dissolved in distilled water. Stoichiometric LiNO3, Zn(NO3)2•6H2O， Ni(NO3)2•6H2O and Mn(NO3)2•4H2O were added to the solution above with continuous stirring. The final solution was evaporated at 80 ºC until a gel was obtained and then dried at 140 ºC for 10 h. The powders was preheated at 400 ºC for 10 h and then calcined at 850 ºC for 24 h in air. The structure and morphology of the samples were studied by X-ray diffraction (XRD). Electrochemical measurements were carried out with CR2032 coin cells. The obtained materials were mixed with C-black and PVDF (80:10:10 wt %) in N-methyl pyrrolidinone solvent. After coating the above slurries on Al foils, the electrodes were dried at 80 ºC in vacuum. In the coin-cell tests, metallic lithium foil was used as the counter and reference electrodes; the electrolyte was 1 M LiPF6in a 1:1 solvent mixture of ethylene carbon (EC)/dimethyl carbonate (DMC). Results and Discussion Figure 1 displays XRD patterns for LiZn x Ni0.5-x Mn1.5O4 (x=0, 0.02, 0.04, 0.08, 0.25, 0.5) powders. The powders all show cubic structure. Rocksalt impurity phase Ni1-x O can be found in the samples of x=0 and 0.02. Impurity Ni1-x O, Li1-x Ni x O, or Ni6MnO8 as a well-known secondary phase in samples of LiZn x Ni0.5-x Mn1.5O4 can be observed at around 37.6˚ and 45.7˚[1–3] when x=0 and 0.02. The impurity intensity decreases with increasing Zn content and the x=0.04 and 0.08 samples show pure spinel phase. While x=0.25 and 0.5, a new impurity phase ZnMn2O4 emerges. In spinel structure, Zn ions prefer occupying tetrahedral sites (8a), such as ZnFe2O4 and ZnAl2O4. As a result, Zn ions are supposed to exist in tetrahedral sites (8a) instead of Li ions. Cycling performance for the electrodes made of LiZn x Ni0.5-x Mn1.5O4 (x=0, 0.02, 0.04, 0.08) at 0.5 C between 3.5–4.9 V is shown in Figure 2. The capacity mainly origin from Ni2+/Ni3+ and Ni3+/Ni4+ redox couples for the spinel LiNi0.5Mn1.5O4. As a result, the capacity decreased with increasing Zn substitution content instead of Ni. However, the cycleability has been much improved by Zn substitution especially when x = 0.08. Only 65 % capacity retention was obtained for the bare electrode. Compared to the pristine electrode, the LiZn0.08Ni0.42Mn1.5O4 electrode delivers 98 mAh/g for the first cycle with remarkable capacity retention of 95 % after 100 cycles. XPS data reveals that a Li-permeable SEI layer formed on the surface of the electrode which protects the electrolyte from oxidation at high voltage[4]. In conclusion, LiZn x Ni0.5-x Mn1.5O4 spinels (x=0, 0.02, 0.04, 0.08, 0.25, 0.5) have been successfully prepared by sol-gel method. Zn substitution significantly improved the cycleability of the spinels. A plausible explanation is that a Li-permeable SEI layer formed on the surface of the Zn substitution electrode which protects the electrolyte from oxidation at high voltage. Figure 1

Real time optical and mechano-optical studies during drying and uniaxial stretching of Polyetherimide films from solution

In order to have a fundamental understanding of the temporal evolution of physical characteristics of Polyetherimide (PEI) film and processing parameters, real time measurements are essential. Because drying and stretching processes of solvent-cast polymer film are complex, off line measurements are unable to reveal the temporally varying detailed information, especially for fast “transient events”. To solve the problem, two measurement systems, one for drying that tracks real time thickness, weight, surface temperature, in-plane and out-of-plane birefringence of solution casting film, and another for uniaxial stretching that tracks real time true stress, true strain and birefringence of stretched film are used. By using these systems, we are able to systematic investigate the development of optical anisotropy through in and out of plane birefringence monitoring drying of solution cast films and their mechano-optical behavior during stretching, and quantify the influence of solvent N-methyl-2-pyrrolidinone (NMP) on these relationships.

Application of DSC to study the promoting effect of a small amount of high donor number solvent on the solvent swelling of kerogen with non-covalent cross-links in non-polar solvents

This paper investigates the effect of a small amount of a strong electron-donating solvent (or high electron donor number solvent) on the solvent swelling of covalently and non-covalently cross-linked Kukersite oil shale kerogen in non-polar solvents. The non-polar (or non-specifically interacting) solvents used in the study were benzene, o-xylene and tetralin. The specifically interacting (or swelling promoting), high donor number solvent added was N-methyl-2-pyrrolidinone (NMP). The changes in solvent uptake of the samples caused by the specifically interacting solvent, previously in equilibrium with respect to a non-specifically interacting solvent, were studied using a Differential Scanning Calorimeter (DSC). The specifically interacting solvent was added in small amounts, up to roughly 2mmol of NMP per gram of kerogen (that is, 0.208, 0.416, 0.624, 0.831, 1.039 and 2.07mmol of NMP per gram of kerogen). The experiments indicated an increase up to about two times in the swelling ratio by adding a strong electron donor solvent at 0.8mmol per gram of kerogen. The effect was most pronounced in the case of tetralin, the solvent with the lowest initial swelling ratio and the largest molar volume. From solvent melting point depression and gas chromatography (GC) experiments, it could be stated that up to 0.8mmolNMP/gkerogen most of the high electron donor solvent was absorbed by the Kukersite kerogen. The value 0.8mmol NMP per gram of kerogen is specific to Kukersite oil shale kerogen. The DSC-based method applied can be considered quantitative up to this limiting value of 0.8mmol NMP per gram of kerogen, and above this value the results indicate characteristic trends.

A facile synthesis of copper sulfides composite with lithium-storage properties

Copper sulfides are synthesized by heating a mixture of copper and sulfur powders in different stoichiometries in N-methyl-2-pyrrolidinone (NMP) solvent. All the electrodes show excellent electrochemical performance, especially ‘copper excess’ copper sulfides electrodes. These electrodes can be charged and discharged at high rate, with good capacity retention. The electrochemical reaction mechanism of copper sulfides during discharge–charge process is investigated. It is most likely that all of S element in the copper excess electrode would transfer into a crystal of Cu2S during charge–discharge cycles, which corresponded to a single electrochemical reaction and showed excellent cycling and rate performance. These encouraging results indicate that copper-excess copper sulfides could be a promising anode material for lithium batteries with high rate capability.

Separation of benzene and thiophene with a mixture of N-methyl-2-pyrrolidinone (NMP) and ionic liquid as the entrainer

In this study, a mixture of N-methyl-2-pyrrolidinone (NMP) and ionic liquid (IL) was proposed as the entrainer for the separation of benzene and thiophene by extractive distillation. [EMIM]+[BF4]− might be a suitable IL for investigating the selectivity and capacity together using the COSMO-RS model. The experimental vapor–liquid equilibrium (VLE) results indicated that the addition of IL did not obviously improve the relative volatility of benzene to thiophene; however, the content of NMP in the vapor phase could be significantly reduced using the combination of NMP and [EMIM]+[BF4]− in comparison to the benchmark solvent NMP. Moreover, the UNIFAC model was extended and the corresponding interaction parameters were obtained by correlating the ternary (benzene+thiophene+NMP) and quaternary (benzene+thiophene+NMP+[EMIM]+[BF4]−) VLE equilibrium data obtained in this work at ambient pressure.

Excellent electrochemical performance of homogeneous polypyrrole/graphene composites as electrode material for supercapacitors

Polypyrrole (PPy) was synthesized on graphene (GN) sheets which was reduced from graphene oxide by microwave irradiation in N-methyl-2-pyrrolidinone (NMP) and dispersed very well in β-naphthalene sulfonic acid solution. Homogeneous polypyrrole/graphene (PGN) composites had been successfully prepared via an in situ emulsion polymerization method and showed better electrochemical performance including high specific capacitance, rate characteristic and cycling stability compared with polypyrrole/graphene oxide (PGO) composites. The NMP molecules entered into GN which was helpful for PPy deposition on the GN sheets evenly. The supercapacitive behaviors of the corresponding electrodes were estimated with cyclic voltammetry and galvanostatic charge/discharge measurements in 1 M KCl electrolyte and the results showed that the specific capacitance of PGN composites was up to 906 F g−1 at the current density of 0.2 A g−1, much higher than that of the PGO (704 F g−1) and PPy (430 F g−1). Its specific capacitance retains more than 91 % of its initial capacitance after 1,000 cycles at a high current density of 5 A g−1. The good electrochemical performance of PGN composites is mainly attributed to its uniform structure, the N doping, and the synergistic effects between the two components.

Effects of selected size of graphene nanosheets on the mechanical properties of polyacrylonitrile polymer

Mechanical properties of polyacrylonitrile (PAN) polymer can be significantly improved by the incorporation of graphene nano-sheets of different sizes. The graphite was exfoliated to graphene using sonic tip in the presence of N-methyl pyrrolidinone (NMP) as a solvent. Exfoliated graphene was separated from unexfoliated graphitic crystallites using selected speed (rpm) of centrifuge for specific time. The exfoliated graphene nano-sheets were classified into two different groups on the basis of flake size, (i.e. 1 μm and 3.5 μm). Then these graphene sheets were incorporated into PAN to study the effects of their flake size on mechanical properties. Different mechanical properties such as Young’s modulus, ultimate tensile strength (UTS) and elongation at break (dL at break) were studied. Young’s modulus and UTS improved more than 45 % and 25 %, for 3.5 μm graphene flake size respectively. While more than 40 % and 21 %, improvement in modulus and UTS for 1 μm graphene sheet were observed respectively.