Propriétés physico-chimiques et thermodynamiques du système binaire hexamethylphotriamide + eau

Densities, dielectric constants, refractive indices, excess volumes enthalpies of mixing and excess free energies of hexamethylphosphotriamide (HMPT) + water mixtures are reported. The excess thermodynamic functions are negative and show their greatest deviation from ideality near 0,3 mole fraction of HMPT. These data indicate strong interaction between HMPT and water and suggest the existence of complexes of the type: HMPT – n H₂O.     

Mechanical properties of mixtures of two compatible polymers

The properties of mixtures of poly(2, 6-dimethyl p-phenylene oxide) and poly(styrene) have been measured by DSC, density gradient, dynamic mechanical response, and tensile testing. The mixtures are found to have single glass trasitions that vary continuously with the composition. They also have small negative excess volumes of mixing, indicative of strong polymerpolymer interaction. The dynamic mechanical response of the mixtures shows that the low temperature secondary relaxations are suppressed whereas those at high temperatures are enhanced. These observations imply that mixing on the segmental levc l has occurred. A plot of tensile strength vs composition at different strain rates reveals two regions of failure behavior. The high PS, high strain rate region is brittle, and the high PM₂PO, low strain rate region is ductile. When the tensile yield data are treated according to the Ree-Eyring equation, the addition of PS to PM₂PO is found to reduce the flow volum, e of the mixture. The overall effect on mechanical properties of adding small amounts of one component to the other is similar to that of anti-plasticization. Our experimental observations are consistent with the shifting of the relaxation mechanisms to longer times due to the negative excess volume of mixing.     

Aggregation Behavior of Task-Specific Acidic Ionic Liquid N-Methyl-2-Pyrrolidinium Dihydrogen Phosphate [NMP][H2PO4] in Aqueous and Aqueous Salt Solutions

The effect of alkali salt (NaCl, NaBr, and KCl) addition on aggregate formation of N-methyl-2-pyrrolidinium dihydrogen phosphate [NMP][H₂PO₄] ionic liquid in aqueous solution was determined using surface tension at 298.15K and conductance from 288.15 to 308.15K. The surface parameters such as critical aggregation concentration (CAC), adsorption efficiency, surface pressure, surface tension at CAC, minimum surface cover by a single molecule, and maximum area excess concentration were calculated from surface tension measurements with and without salts. The results show that [NMP][H₂PO₄] forms aggregates at lower concentrations and is more surface active than classical cationic surfactants.     

Effect of coal soluble constituents on caking property of coal

Three cokemaking bituminous coals were extracted by the CS₂/NMP mixed solvents with different content of NMP, and the effect of the amount and the component of coal soluble constituents on the caking property of the extracted residues of coals were investigated in this study. The CS₂/NMP mixed solvent (1:1 by volume) was found to give the maximal extraction yields for the three coals, and the fat coal gave the highest extraction yield of 78.6% (daf) corresponding to its highest caking index of 101. It was found that for coking coal, when the extraction yield got to the maximum of 25.3% in the 1:1 by volume of CS₂/NMP mixed solvent, the residue extracted still had caking property with the caking index of 19. This means parts of the caking constituents of coal are un-extractible because of covalent bonding or strong associative cross-links. The soluble components extracted by the CS₂/NMP mixed solvent and their effects on the caking indexes of the residues at a similar extraction yield quite differed depending on the NMP content in the mixed solvent. The coal solubles extracted by the CS₂/NMP mixed solvent with NMP less than 50% contained less light constituents with less of oxygen groups. This may lead to the decrease in the caking indexes for the residues obtained at the similar extraction yields compared to those of the CS₂/NMP mixed solvent with NMP more than 50%.     

Sorption and transport of gases in miscible poly(methyl acrylate)/poly(epichlorohydrin) blends

The sorption and the transport of He, Ar, N₂, CH₄, and CO₂ in miscible poly(methyl acrylate)(PMA)/poly(epichlorohydrin)(PECH) blends from 1 to 20 atm at 35°C are reported. For He, Ar, N₂, and CH₄, the permeabilities and the diffusion time lags are independent of the upstream pressure, if the compaction effect resulting from compression of the polymer membrane onto the supporting medium is eliminated. The permeability of CO₂ increases with upstream pressure but solubility follows a simple Henry's law behavior. For all five gases, the dependence of solubility, diffusion coefficient, and permeability on blend composition are compared with theoretical mixing rules with the conclusion that both the interaction energy density and the excess activation energy for gas diffusion in the blends are near zero. The fact that the specific volumes of the blends exactly follow linear additivity also confirms that only very weak interactions exist between PMA and PECH.     

Pore structure of lightweight clay aggregate incorporate with non-metallic products coming from aluminium scrap recycling industry

This paper deals with the non-waste utilisation of aluminium recycling waste called non-metallic products (NMP) and their reprocessing into environmentally friendly material. In the present studies, lightweight expanded clay aggregates were produced from natural plastic clay and NMP. They were obtained recovering Al metal from black dross by using conventional metallurgical process. Based on the results obtained from chemical and mineralogical investigations of NMP, heat treatment in the temperature range from 1150 °C to 1280 °C was selected as an appropriate method to eliminate impurities of residues, such as aluminium nitride (AlN), iron sulphite (FeSO₃), aluminium chloride (AlCl₃). Emissions of gases during high-temperature treatment of NMP act as initiators to create extra porous structure of sintered ceramic bodies. The effect of raw material composition, previous treatment of NMP and sintering temperatures on the aggregate's properties were evaluated. Physical and microstructural properties of sintered aggregates were determined.     

Examination of the role of CS2 in the CS2/NMP mixed solvents to coal extraction

The roles of CS₂ in the CS₂/NMP mixed solvent to coal extraction and solubilization were investigated in this study. There was little effect of removing of CS₂ from the solutions on the solubilities of UF coal extract and pyridine insoluble (PI) of the extract in the NMP/CS₂ mixed solvent, suggesting that NMP has high enough solubilities to the UF coal extract and PI. Six Argonne different rank coals were extracted with the CS₂/NMP mixed solvent and NMP, respectively. It was found that the extraction yield difference between NMP and CS₂/NMP mixed solvent for UF coal is largely deviated from the curve obtained for the other 5 coals, suggesting that the pre-swelling of CS₂ in the mixed solvent may be one of important roles for high extraction yield of UF coal in the CS₂/NMP mixed solvent. FTIR indicated that there was a strong interaction between CS₂ and NMP in the CS₂/NMP mixed solvent of 1 : 1 volume ratio, which made the strong absorbance at 2156 cm^− 1 in the FTIR spectra, and this interaction may disrupt the dipole based association of NMP thus making the CS₂/NMP mixed solvent lower viscosity, to penetrate more quickly into the network structure of coal, resulting in the larger solvent partner (NMP) to enter and break the stronger coal–coal interactions.     

Excess volume and excess enthalpy of binary mixtures composed of 1,2-dichloropropane and 1-alkanol (C5-C8)

The excess molar volumes and excess molar enthalpies at T=298.15 K and atmospheric pressure for the binary systems {CH₃CHClCH₂Cl (1)+CH₃(CH₂) _n?1OH (2)} (n=5 to 8) have been determined over the whole range of composition from the density and heat flux measurements using a digital vibrating-tube densimeter and an isothermal calorimeter, respectively. The measured excess molar volumes of all binary mixtures showed positive symmetrical trend with values increasing with chain length of 1-alkanol. Similarly, excess enthalpy values of all binary mixtures showed skewed endothermic behavior with values increasing with chain length of 1-alkanol. The maxima of excess molar enthalpy values were observed around x₁=0.65 with excess enthalpy value ranging from 1,356.8 J/mol (1-pentanol) to 1,543.4 J/mol (1-octanol). The experimental results of both H _m ^E and V _m ^E are fitted to a modified version of Redlich-Kister equation using the Padé approximant to correlate the composition dependence. The experimental H _m ^E data were also fitted to three local-composition models (Wilson, NRTL, and UNIQUAC). The correlation of excess enthalpy data in these binary systems using UNIQUAC model provides the most appropriate results.     

USING EXCESS VOLUME OF MIXING TO CORRELATE DIFFUSIVITIES IN LIQUIDS

It has been postulated in the past that diffusivities in liquids can be correlated with the excess volume or mixing. A system has been examined in which the diffusivities and excess volumes of mixing vary in a nonlinear manner with changes in concentration; however, the diffusivity is always a linear function of the excess volume of mixing.     

Molar volumes of aqueous acetic acid-ammonium salt solutions

The mean apparent molar volumes φ_v of the CH₃COOHNH₄X(X  Cl, Br, NO₃) solutions have been determined at 40° from precise density measurements. The modified Young's rule for electrolyte-nonelectrolyte mixtures has been used to predict mean apparent molar volume, φ_v, from the pure water data. The modified Young's rule was found to be applicable for the CH₃COOHNH₄X systems to some extent. The deviations from the Young's rule approximation are studied as excess volumes of mixing of CH₃COOH and NH₄X solutions.     

Measurement and correlation of excess enthalpies for water+ethanol+1-buthyl 3-methylimidaozolium tetrafluoroborate system

It is difficult to find physical properties data for systems containing ionic liquids, excess molar enthalpies, binary interaction parameter, etc. In this study, the excess molar enthalpies were measured for water+ethanol+ionic liquid system using a isothermal microcalorimeter at 298.15 K. The ionic liquid used was 1-butyl 3-methyl imidazolium tetrafluoroborate, [BMIM] [BF₄]. The isothermal microcalorimeter (IMC) is a flow-type calorimeter that measures the heat of mixing directly, using specific mixing cell. By employing NRTL, electrolyte-NRTL and UNIQUAC models, binary interaction parameters were determined and investigated for the correlation with vapor liquid equilibrium (VLE). The e-NRTL model with the partial dissociation was employed to correlate the ionic liquid system. The binary data of VLE system were used from literatures. Specifically, UNIQUAC volume and surface area parameters were determined using Bondi radius.     

VLE calculation of carbon dioxide+n-alkanes binary mixtures with MHV2 mixing rule

Vapor-liquid equilibria for binary and asymetric systems include carbon dioxide+C₁-C₈, C₁₀ are calculated by using the Peng-Robinson-Stryjek-Vera equation of state coupled with the modified MHV2 mixing rule. The modified UNIFAC model is used for determining activity coefficient and excess Gibbs free energy. Calculated equilibrium pressures and mole fractions in vapor phase are compared with the experimental data. The average absolute deviation percent (AAD%)s indicates that the error involved in the application of the MHV2 mixing rule by optimized q₁ and q₂ is less than WS and PRSK mixing rules in most cases.     

1-丁基-3-甲基咪唑磷酸二丁酯+甲醇/乙醇+水三元工质溶液混合焓的测量及预测

采用绝热量热法测量了由离子液体1-丁基-3-甲基咪唑磷酸二丁酯([bmim][DBP])分别与CH₃OH、C₂H₅OH和H₂O所组成的3个二元工质溶液体系[bmim][DBP](1)+ CH₃OH(2)/C₂H₅OH(2)/H₂O(2),以及2个三元工质溶液体系[bmim][DBP](1)+ CH₃OH(2)/C₂H₅OH(2)+ H₂O(3)在298.15 K和常压下的摩尔混合焓H_m^E。利用Gibbs-Helmholtz方程和NRTL活度系数模型,对每个二元溶液体系摩尔混合焓的实验数据进行关联,获得模型方程中的组分作用参数。摩尔混合焓的模型拟合值与实验值的平均相对偏差分别为1.81%、1.44%和0.72%。在此基础上预测了2个三元工质溶液体系的摩尔混合焓。结果表明:三元工质溶液体系的摩尔混合焓在实验浓度范围内均为负值,混合为放热过程。表明三元工质溶液具有成为吸收制冷循环新工质溶液的基本特征;采用NRTL模型预测2个三元溶液体系摩尔混合焓的计算值与实验值的平均相对误差分别为2.31%、2.49%。     

Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.     

Kinetic and Mechanistic Studies on Reactions of Pyrrolidone Derivatives with Ozone

Reactions of various pyrrolidone derivatives (NRPs = 2-pyrrolidone (2P), N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), N-iso-butyl-2-pyrrolidone (NiBP), N-n-pentyl-2-pyrrolidone (NPP), N-neopentyl-2-pyrrolidone (NNPP), N-dimethylpropyl-2-pyrrolidone (NDPP), N-cyclohexyl-2-pyrrolidone (NCP)) with O₃ have been studied under pseudo–first-order conditions with excess O₃ in aqueous solution of pH 2.0 at various temperatures (278–298 K). It was found that the reaction rates is expressed as –d[NRPs]/dt = k[NRP][O₃], that the second-order rate constants (k) slightly increase with increasing the effective charges in order of NMP, NEP, NProP, NBP and NPP, and that the k values of NBP and NPP are larger than those of more bulky NiBP and more bulky NNPP and NDPP, respectively. In these reactions, the ΔH^? values are consistent with each other, while the ΔS^? values decrease with decreasing length of alkyl groups. Furthermore, it was found that reactions of NRPs (NMP, NEP, NProP, NBP, and NPP) with O₃ show the linear relationship between the obtained ΔS^? values and the softness of NRPs. From these results, it was proposed that the reactions of NRPs with O₃ proceed through the interaction between O₃ and N atom of NRPs. The analyses of products in the reactions of NRPs with O₃ were also carried out by ¹³C-NMR and GC/MS measurements, and indicated that N-alkylsuccinimide and N-acyl-2-pyrrolidone are produced through intramolecular side-chain oxidations of α-carbon of NRPs. From these results, it is proposed that the reactions of NRPs with O₃ proceed through the mechanism with the selective attacks of O₃ to N atom of NRPs.     

The effects of residual polymerization solvent on the physical properties of poly(2‐cyano‐p‐phenylene terephthalamide)

Poly(2‐cyano‐p‐phenylene terephthalamide) (CY‐PPTA) was obtained by the polycondensation of terephthaloyl dichloride and 2‐cyano‐p‐phenylene diamine in the mixture of N‐methyl‐2‐pyrrolidone (NMP) and calcium chloride (CaCl₂). Washing the polymerized product with water and drying at the elevated temperature inevitably left a small amount of polymerization residues which could be eliminated only by additional washing with acetone. The thermogravimetric and ¹H‐/¹³C‐NMR analyses revealed that the residues were largely composed of NMP which existed as a complex with the polymer. The complex was broken up between 200 and 300 °C and evolved 5 wt % of gaseous products, which had an adverse effect on the physical properties of as‐spun CY‐PPTA fibers obtained by dry jet‐wet spinning. The heat treatment of the as‐spun fibers including residual NMP exhibited some porous morphology on the fiber surface due to the evolved gases. However, the existence of the residual NMP had little effect on the intrinsic viscosity and liquid crystalline phase behavior of the polymer. Both rheological and optical properties exhibited the critical concentration at 3 wt % with the clear schlieren texture of nematic liquid crystalline phase. The inclusion of residual NMP decreased dynamic viscosity and yield stress. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43672.     

Understanding chemical reactions between carbons and NaOH and KOH: An insight into the chemical activation mechanism

Direct mixing of an anthracite with hydroxides (KOH or NaOH) and heat treatment up to 730 °C has shown to be a very good activation procedure to obtain activated carbons with very high surface areas and high micropore volumes. The reactions involved during the heat treatment of these hydroxide/anthracite mixtures have been analysed to deep into the fundamental of the knowledge of this chemical activation process, that has not been studied before. For this purpose, the present paper analyses the drying process, the atmosphere during the carbonisation, the chemical state of the activating agents (NaOH, KOH and Na₂CO₃) and the chemical reactions occurring during the heat treatment which have been followed by FTIR and TPD. The analysis of our results allows us to conclude that steam is a good atmosphere for the carbonisation process, alone or joined with nitrogen, but not as good as pure nitrogen. On the other hand, during the activation process, the presence of CO₂ should be avoided because it does not develop porosity. The reactions, and chemical changes, involved during this chemical process are discussed both from a thermodynamical point of view as well as identifying the reaction products (H₂ by TPD and Na₂CO₃ by FTIR). As a result, this paper helps to cover the present lack of understanding of the fundamentals of the reactions of an anthracite with hydroxides which are necessary to understand the activation of the material.     

Pervaporation removal of water from ionic liquid solutions using Nafion membranes

We report a pervaporation process to remove water from a solution containing ionic liquid (IL) + solvent + water. Specifically, Nafion-based membranes were employed for the separation, and tributylmethylammonium dimethylphosphate and N-methyl-2-pyrrolidone (NMP) were the IL and solvent, respectively. Membrane swelling in contact with the IL–NMP–H₂O solution was accommodated by judicious use of gaskets and membrane supports. The pervaporation fluxes of water and NMP increased with temperature and flow rate of the permeate sweep gas. Among the membranes examined, a commercially available Nafion membrane (XL, Ion Power) provided the highest water (10 mg h^?1 cm^?2) and NMP (182 mg h^?1 cm^?2) fluxes. The results show that pervaporation separation is a technologically feasible method to decrease the water content of an IL–NMP–H₂O solution from 1 to 0.5 wt%.     

Co-dispersion behavior and interactions of nano-ZrB2 and nano-SiC in a non-aqueous solvent

The co-dispersion behavior and interactions of nano-ZrB₂ and nano-SiC in a non-aqueous solvent were investigated. Polyvinylidene fluoride (PVDF) and oleic acid were adopted as dispersants to study the stable co-dispersion mechanism in a non-aqueous solvent. Because N-methyl-2-pyrrolidone (NMP) has a relatively high dielectric constant among non-aqueous solvents, NMP was introduced; NMP was found to exhibit a good affinity with dispersants. ZrB₂ and SiC were mixed in NMP with or without dispersants. ZrB₂ and SiC in a paste without dispersants aggregated due to the poor repulsion force by a double-layer overlapping. The paste with PVDF was more homogeneous than the paste with oleic acid. The steric hindrance effect of PVDF was evaluated using SEM image analysis. FT-IR analysis results show that PVDF and oleic acid were chemically adsorbed onto the particle surface.     

Factors determining glass transition temperature and relaxation time of poly(vinyl chloride)

Glass transition properties were obtained by measurements of the dilatometric glass transition temperature T_g at elevated pressure by isobaric cooling at a constant rate. The properties include the pressure-volume-temperature (P-V-T) relations of the liquid, the specific heat capacity and the dielectric properties for a single sample of poly(vinyl chloride). From the experimental results, various thermodynamic excess quantities such as the free volumes and the configurational entropy and energies were evaluated as factors determining T_g and the relaxation time τ. Some empirical rules concerning T_g, which have been proposed by Simha and Boyer, and Wunderlich, are also examined. The main conclusions are as follows: (1) the free volume is not an essential factor determining T_g and τ; (2) the Adam-Gibbs parameter is slightly superior to the other excess entropy and energies defined as the difference of the entropy and energies between the liquid and the hypothetical crystal whose thermal expansivity and compressibility are the same as those of the corresponding glasses; and (3) the glass transition may not be treated as a quasi-equilibrium thermodynamic transition to which one of the Ehrenfest relations applies.