Experimental phase equilibria studies of the PbO–SiO2 system

Phase equilibria of the PbO–SiO₂ system have been established for a wide range of compositions: (i) liquid in equilibrium with silica polymorphs (quartz, tridymite, and cristobalite) between 740°C and 1580°C, at 60‐90 mol% SiO₂; (ii) with lead silicates (PbSiO₃, Pb₂SiO₄, and Pb₁₁Si₃O₁₇) and lead oxide (PbO) between 700°C and 810°C. A high‐temperature equilibration/quenching/electron probe X‐ray microanalysis (EPMA) technique has been used to accurately determine the compositions of the phases in equilibrium in the system. Significantly, no liquid immiscibility has been found in the high‐silica range, and the liquidus in this high‐silica region has been accurately measured. The phase equilibria information in the PbO–SiO₂ system is of practical importance for the improvement of the existing thermodynamic database of lead‐containing slag systems (Pb–Zn–Fe–Cu–Si–Ca–Al–Mg–O).     

水盐体系相平衡研究进展

水盐体系相平衡与相图是无机盐化工的理论基础,对水盐体系相平衡的研究可为盐湖盐类资源的综合开发利用提供理论支持。从水盐体系相平衡实验和理论研究两个方面,综述了近期国内外相关研究进展及研究方法。重点介绍了稳定相平衡和介稳相平衡体系相图测定方法及特点,概述了相区间和结晶类型变化的影响因素;从热力学模型法、统计力学理论和分子模拟3 个方面介绍了水盐体系相平衡的理论研究思路及基于液-固化学势平衡的研究现状,并讨论了3 类方法在相平衡研究上的可能发展方向。最后总结了该领域的一些研究热点,并对水盐体系相平衡的研究趋势作了展望。     

Partitioning behaviour of cephalexin and 7‐aminodeacetoxicephalosporanic acid in PEG/ammonium sulfate aqueous two‐phase systems

In order to develop an aqueous two‐phase system (ATPS) for cephalexin synthesis with extractive bioconversion, the partitioning behaviour of cephalexin and 7‐aminodeacetoxicephalosporanic acid (7‐ADCA) in poly(ethylene glycol) (PEG)/salt ATPS were examined. Parameters such as PEG size, salt type and tie line length were investigated to find a primary extraction system. In PEG400/ammonium sulfate and PEG400/magnesium sulfate systems, the partition coefficient of cephalexin (K_C) was larger than 1 while that of 7‐ADCA (K_A) deviated about 1.5. Addition of neutral salts, surfactants and water‐miscible solvents were also investigated in the primary ATPS in order to improve the separation efficiency. K_C greatly increased when neutral salts and surfactants were added to the PEG400/ammonium sulfate primary systems whereas K_A was only slightly higher than that of the additive‐free ATPS. In an improved ATPS for extractive bioconversion, consisting of PEG400 (20% w/w), ammonium sulfate (17.5% w/w), methanol (5% w/w) and NaCl (3% w/w), a K_C value of up to 15.2 was achieved; K_A was 1.8; K_P (partition coefficient of phenylglycine methyl ester) was 1.2 and the recovery yield of cephalexin was 94.2%. The results obtained from the extractive bioconversion of cephalexin in the improved ATPS showed that it is feasible to perform such an enzymatic process in an ATPS and the system offers the potential as a model for enzymatic synthesis of some water soluble products. © 2001 Society of Chemical Industry     

Molecular thermodynamics approach on phase equilibria of dendritic polymer systems

We suggest a molecular thermodynamic framework to describe the phase behavior of dendritic polymer systems. The proposed model, which is based on the lattice cluster theory, contains correlations of molecular structure and specific interactions such as hydrogen bonding to the phase equilibria of branch-structured polymer systems. We examine liquid-liquid equilibria (LLE) of hyperbranched polymer solutions and vapor-liquid equilibria (VLE) of dendrimer solutions in the viewpoints of effects of a branched structure and specific interaction formations among endgroups of dendritic polymer and solvent molecules. We investigate VLE of dendrimer/solvent (Benzyl Ether Dendrimer/Toluene) systems by the combination of a new lattice-based model and atomistic simulation technique. The interaction energy parameters are obtained by the pairs method [Baschnagel et al., 1991] including Monte Carlo simulation with excluded volume constraint. In the pairs method [Baschnagel et al., 1991], we do not simulate the whole molecule as in molecular dynamics or molecular mechanics, but only monomer segments interacting with solvent molecules. The proposed model shows improvements in prediction for both phase equilibria (VLE and LLE) due to the branched structure and specific interaction due to endgroups at periphery of dendritic polymer molecule. Atomic simulation technique gives good result in prediction without fitting variables. Our results show that the specific interactions between the endgroup and the solvent molecule play an important role in phase behavior of the given systems.     

厌氧氨氧化影响因素实验研究

研究了水力停留时间(HRT)、温度、pH和进水m(NH_4~+-N)∶m(NO_2~- -N)对厌氧氨氧化脱氮性能的影响.实验结果表明,厌氧氨氧化的最佳HRT、温度、pH、进水m(NH_4~+-N)∶m(NO_2~- -N)分别为12 h、30～35℃、7.02～8.36、0.95～1.2.在最佳反应条件下,当进水TN质量浓度为365.5～432.4 mg/L时,对NH_4~+-N、NO_2~--N、TN的平均去除率分别为96.8%、97.8%、92.4%.     

Calculation of phase equilibria in systems containing water and supercritical components

The Redlich-Kwong equation of state was used in both the liquid and vapour phases to calculate vapour-liquid equilibria in binary and ternary systems c     

磷酸二氢铵-磷酸氢二铵-聚磷酸铵-水四元体系相平衡的实验与计算

利用Schreinemaker湿渣法,通过离子色谱和质量守恒方程联立得到各组分在饱和液相和湿渣相中的分布,从而得到25℃下磷酸二氢铵-磷酸氢二铵-聚磷酸铵-水四元空间相图,解释了聚磷酸铵水溶液结晶、沉淀的问题,对聚磷酸铵作为高效水溶肥料使用、储存具有指导意义.同时为快速获得聚磷酸铵其他体系相图,引入电解质溶液局部组成模...     

磷石膏和碳酸氢铵制备硫铵复合肥工艺研究

利用磷石膏和碳酸氢铵制备市场价值较高的硫铵复合肥,探讨了磷石膏和碳酸氢铵体系的反应历程,研究了反应温度、反应时间、反应介质体积和质量分数对反应产物硫铵质量分数的影响。结果表明:当反应温度为45℃,反应时间为2h,反应介质体积和质量分数分别为180mL和10%时,反应产物硫铵的质量分数最高,约为43.72%。利用BK-POL型偏光显微镜观察产物硫铵溶液的自然结晶体,观察的结果为菱形柱状结晶。     

Direct observation of water uptake and release in individual submicrometer sized ammonium sulfate and ammonium sulfate/adipic acid particles using X-ray microspectroscopy

Scanning transmission X-ray microscopy (STXM), a microscopy method which allows imaging with a spatial resolution of 40 nm, and X-ray absorption spectroscopy were used to follow in situ the water uptake and release in submicrometer sized particles on a substrate enclosed in a microreactor. Oxygen K-edge near edge X-ray absorption fine structure (NEXAFS) spectra from supported ammonium sulfate particles in their dry salt, saturated solution and supersaturated solution states were obtained for the first time. The variations at the oxygen edge were related to the water content as a function of relative humidity (RH), consistent with mass growth measurements done on larger samples or suspended particle ensembles. Investigations on morphological changes upon water uptake were performed in mixed ammonium sulfate-adipic acid particles using STXM images and NEXAFS spectra taken at the oxygen and the carbon absorption edges, confirming the two phase structure suspected from previous hygroscopicity studies, where adipic acid forms a separate phase of complex morphology partially enclosed by the ammonium sulfate solution at high RH. This example emphasizes the combination of chemical resolution provided via NEXAFS, spatial resolution via STXM and the in situ capability provided by the novel microreactor to obtain information about the microstructure of mixed organic/inorganic particles under close to ambient conditions.     

电解锰生产用硫酸锰、镁、铵复盐体系结晶的研究

在电解锰浸出液中,Mn⁽²⁺⁾、Mg(2+)、Mg⁽²⁺⁾、NH(2+)、NH⁺_4初始浓度分别为28,20,30 g/L时,研究结晶温度、蒸发瓶转速、结晶时间、有无晶种对复盐体系结晶的影响。结果表明,随着结晶温度的提高,锰、镁、铵结晶率呈快速上升趋势;随着转速和结晶时间的提高,锰、镁、铵结晶率整体呈缓慢上升趋势;相较无晶种添加,添加8%晶种时,可小幅提高体系结晶率。复盐体系锰、镁、铵结晶的最佳工艺条件为:结晶温度为55℃,转速为90 r/min,结晶时间为60 min,添加8%晶种,此时,复盐体系锰、镁、铵结晶率分别为68.05%,97.59%,94.81%,效果较好。     

燃煤烟气脱硝副产物硫酸氢铵/硫酸铵沉积与分解特性研究

搭建模拟空预器多段控温实验台,研究不同SO₃浓度、SO₃/NH₃比、不同温度下硫酸氢铵（ABS）与硫酸铵（AS）的生成、沉积与分解特性。在高温条件下发生的初始沉积部位,沉积物均为液态ABS,其失重特性与纯ABS基本一致。而在低温条件下,则根据SO₃/NH₃比的不同沉积物特性有所变化。SO₃/NH₃比为2∶1时,沉积物为H₂O、H₂SO₄与少量ABS的混合物,以密集液滴形态存在,呈多段分解特性;SO₃/NH₃比为1∶1与1∶2时,沉积物为分散性较强的干AS粉末,分解特性与纯AS基本一致。研究结果可为ABS防控提供指导。     

High-pressure phase equilibria of systems carbon dioxide + n-eicosane and propane + n-eicosane

In this work we investigated the phase equilibrium behavior of the binary asymmetric systems propane (C3) + n-eicosane (C20) and carbon dioxide (CO₂) + n-eicosane (C20). We used a variable-volume view cell for obtaining fluid–fluid equilibrium (FFE), solid–fluid equilibrium (SFE) and solid–fluid–fluid equilibrium (SFFE) experimental data. We modeled the phase equilibria of both systems using the Peng–Robinson Equation of State for describing the fluid phases and an expression for the fugacity of pure solid n-eicosane with parameters fit to reproduce the pure n-eicosane melting line. We performed the phase equilibrium calculations by implementing path-following methods for tracking entire solid–fluid (SF) and solid–fluid–fluid (SFF) equilibrium curves for binary asymmetric mixtures. This made it possible to obtain complete isoplethic lines or complete three-phase equilibrium lines in single runs. Although the model is relatively simple, it is able to grasp the complex observed behavior for the systems studied here.     

Phase behavior and morphological studies of polyimide/PVP/solvent/water systems by phase inversion

The solubility gaps for poly(vinyl pyrrolidone) (PVP) in four polyimide solutions (NMP, DMF, GBL, DMSO) were determined by cloud point measurement and correlated with χ_PI/Solvent and Δδ_PVP/Solvent. Membranes prepared with NMP and DMF systems showed a tendency of suppressing fingerlike structure with addition of PVP. On the other hand, membranes prepared with GBL and DMSO systems showed an inclination toward inducing macrovoid formation. These effects of PVP on the membrane morphology were explained by means of miscibility gap, viscosity of the polymer solution, polymer–polymer phase separation, and overall porosity. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3481–3488, 2001     

Toluene degradation by a water/silicone oil mixture for the design of two phase partitioning bioreactors

Toluene degradation performances were studied in a 10 L Two-Phase Partitioning Bioreactor (TPPB).The liquid phase consisted of a mixture of water and PDMS 50 (PolyDiMethylSiloxane,i.e.silicone oil,viscosity of 46 maa·s) in the volume ratio of 75％/25％.Two series of experiments were carried out:in the first,the reactor was sequentially supplied with toluene whereas in the second,toluene was continuously supplied.Activated sludge from the wastewater treatment plant of Beaurade (Rennes,France) was used at an initial concentration of 0.5 dry mass g· (mixture L)-1.The elimination capacity (EC) was investigated as well as the change in biomass concentration over time.Toluene biodegradation was very efficient (removal efficiency,RE =100％) for toluene flows ranging from 0.2 to 1.2 ml· h-1,corresponding to elimination capacities of up to 104 g· m-3· h-1.For a toluene flow of 1.2 ml·h-1,the biomass concentration measured at the end of the experiment was 4.7 dry mass g.(mixture L)-1.The oxygen concentration in the liquid phase was clearly not a limiting factor in these operating conditions.Based on these results,an extrapolation leading to the design of a large-scale pilot TPPB can now be considered to study toluene degradation performances in industrial conditions.     

Ternary phase equilibrium studies of furfural-water-solvent systems

Phase equilibrium and tie line data determined at 298 K for the ternary system comprising furfural, water and organic solvents (benzene, cyclohexane, pentan-1-ol, cyclohexanol and benzyl alcohol) are presented. The tie-line data for the systems have been correlated by Hand's method. Among the five solvents studied, cyclohexane showed the highest selectivity followed by benzene, benzyl alcohol, pentan-1-ol and cyclohexan-1-ol, in that order.     

Supercritical fluid extraction from Priprioca: Extraction yield and mathematical modeling based on phase equilibria between solid and supercritical phases

This study aimed to investigate the supercritical carbon dioxide extraction of Cyperus articulatus L. (Priprioca). Before the experiments were performed, the raw material was cleaned, vacuum packed and maintained at −5 °C. The moisture content of the material was determined using an oven with forced air circulation operating at 105 °C. The material was then ground, and the mean diameter of the resulting particles was determined using a set of standard sieves. Extraction was performed at pressures of 100–300 bar, temperatures of 40–50 °C, and extraction times up to 240 min using supercritical carbon dioxide as the solvent. For each load, approximately 50 g of Priprioca was packed into the extractor. According to the experimental results, the yields of extraction were significantly influenced by pressure and temperature. Additionally, this paper provides a mathematical model of the supercritical extraction of Priprioca. The employed mathematical model was based on the mass conservation law, which included two partial differential equations for the solute concentration in the solid and fluid phases. By applying a novel method, the distribution coefficient of the extract between supercritical fluid and solid phases was obtained using the criterion of equal fugacity at equilibrium. The model-predicted extraction yield was then compared with the corresponding experimental data. Additionally, the reasons for the deviations between the model and the experimental data under certain operational conditions are discussed.     

酸度对硫酸亚铁/硫酸亚铁铵溶液稳定性影响

采用重铬酸钾法,对酸性介质中硫酸亚铁、硫酸亚铁铵溶液中二价铁离子含量进行了测定,通过计算得出二价铁离子被氧化的损耗量,研究了不同pH值条件下的二价铁离子被氧化的损耗量,做出了量化曲线,发现在pH=3.5～5.5时,其氧化程度是相对稳定的,且硫酸亚铁铵比硫酸亚铁要稳定一些。     

己内酰胺在硫酸铵晶体表面吸附特性

引言己内酰胺(caprolactam,CPL)受热时发生聚合反应,可作为尼龙-6纤维、工程塑料、聚酰胺等单体的原料,是一种重要的石油化工产品[1-2].硫酸铵是己内酰胺工艺的重要副产物,如意大利SNIA甲苯法工艺每生产1t己内酰胺副产硫酸铵约4.2 t[3].     

Experimental study and mathematical simulation of the crystallization of ammonium sulfate in a forced circulation crystallizer

The growth mechanism of ammonium sulfate crystals is studied. A mathematical model for the process of continuous crystallization in an experimental FC-crystallizer based on the previously reported model of crystal attrition is developed. A mathematical model for the mass crystallization of ammonium sulfate in an industrial crystallizer with forced circulation by an axial three-blade propeller pump, which takes into account the impact of crystals onto its blades, is developed as well. Optimal operating conditions for an industrial crystallizer, the parameters of an axial propeller pump, and its operating conditions for producing crystals of a given size at minimal power consumption are chosen.