苯与甲苯及C8芳烃体系固液相平衡计算

针对对二甲苯结晶体系中由苯与甲苯及C₈芳烃组成的二元、三元及多元体系,选取了固液相平衡计算模型—Van′t Hoff方程简式,利用该模型计算二元、三元及多元体系的低共熔点温度及对应的低共熔点组成,并绘制三元体系固液相平衡相图。结果表明：由Van′t Hoff方程简式得到的苯-对二甲苯二元体系固液相平衡计算结果与文献数据吻合较好,表明所选固液相平衡计算模型适合于由苯与甲苯及C₈芳烃组成的体系固液相平衡计算;利用Van′t Hoff方程简式计算得到了由苯与甲苯及C₈芳烃组成的二元、三元、四元、五元和六元体系的低共熔点温度及组成,并预测了苯-甲苯和苯-乙苯二元体系的液相摩尔分数,利用这些数据绘制了对二甲苯-甲苯-苯、对二甲苯-乙苯-苯、苯-乙苯-甲苯3个三元体系的固液相平衡相图,这些数据和相图未见文献报道,可为PX结晶相关的苯与甲苯及C₈芳烃组成的体系固液相平衡研究提供理论指导和依据。     

2,6-DIPN与2,7-DIPN二元体系固液相图的测定和关联

绘制了2,6-二异丙基萘(2,6-DIPN)与2,7-二异丙基萘(2,7-DIPN)二元体系的固液相图,测定了2,6-DIPN和2,7-DIPN二元混合物体系的低共熔点,并用理想溶液模型进行了关联。结果表明,2,6-DIPN与2,7-DIPN二元体系固液平衡相图为简单低共熔混合物相图,低共熔点温度为-19.5℃,组成为2,7-DIPN12.2%(质量分数,下同),2,6-DIPN87.8%,由试验数据拟合得到2,6-DIPN的熔化焓为4.878kJ/mol。     

邻碘苯胺与对碘苯胺固液相图测定及数据关联

用步冷曲线法测定了邻碘苯胺与对碘苯胺二元混合物体系不同组成的凝固点,得到了邻碘苯胺与对碘苯胺二元系固液平衡相图,用理想固液平衡模型对实验数据进行了关联。结果表明:邻碘苯胺与对碘苯胺二元系固液平衡相图为简单低共熔固液相图,其低共熔点温度为298.56 K,共熔点的邻碘苯胺的摩尔分数为0.497 6。理想溶液模型计算值与实验值的平均相对偏差是0.17%,最大相对偏差是0.58%,说明该物系符合理想溶液模型。用该模型计算的邻碘苯胺的熔化焓为1.976 1 k J/mol,对碘苯胺的熔化焓为1.579 5 k J/mol。     

甲苯和二甲苯体系固液平衡相图及其低共熔点对比

针对对二甲苯结晶相关由甲苯和二甲苯组成的二元和三元体系,选取固液相平衡计算模型—Van′t Hoff方程简式计算了由甲苯和二甲苯组成的二元和三元体系的液相摩尔分数与低共熔点温度及组成,并绘制了与甲苯有关的对二甲苯-甲苯-邻二甲苯、邻二甲苯-甲苯-间二甲苯、对二甲苯-甲苯-间二甲苯等3个三元体系的固液相平衡相图,对比分析...     

苯和二甲苯体系固液相平衡的数据预测与相图

针对对二甲苯装置结晶单元中由苯和二甲苯组成的相关体系,选取了固液相平衡计算模型—Van′t Hoff方程简式,利用与苯和二甲苯有关的二元和三元体系固液相平衡文献数据对该模型进行考察,利用该模型预测由苯和二甲苯组成的二元和三元体系的固液相平衡数据,并绘制三元体系的固液相平衡相图。结果表明：采用Van′t Hoff方程简式计算,苯和二甲苯有关体系的液相摩尔分数的平均相对偏差为2.69%,低共熔点温度的偏差最高为0.59℃,最低为0.01℃,表明所选模型适用于由苯和二甲苯组成的体系固液相平衡计算;利用该模型预测苯-间二甲苯、苯-邻二甲苯二元体系及对二甲苯-间二甲苯-苯、对二甲苯-邻二甲苯-苯、间二甲苯-邻二甲苯-苯三元体系的固液相平衡数据,绘制了对二甲苯-间二甲苯-苯三元体系的固液相平衡相图,这些新的相平衡数据和相图均未见有文献报道,可为对二甲苯结晶相关体系的固液相平衡研究提供理论指导和依据。     

Na~+,K~+//Br~-,B_4O_7~(2-)-H_2O交互四元体系348K相平衡研究

采用等温溶解平衡法研究了348 K时交互四元体系Na+,K+//Br-,B4O27--H2O的相平衡及平衡液相,测定了平衡液相的溶解度以及密度,补充了该体系在348 K下的溶解度和密度数据。研究结果发现,该体系属于简单共饱和体系,无复盐和固溶体生成。根据实验数据绘制了相应的相图、密度-质量分数图和含水量图,相图中有2个共饱点,5条单变量曲线,4个结晶区。4个结晶区的平衡固相分别为:Na2B4O7.5H2O,K2B4O7.4H2O,KBr和NaBr。从相图上可以看出,该体系在348 K时Na2B4O7.5H2O的结晶区最大,NaBr的结晶区最小。     

三元体系LiBr-Li2SO4-H2O 298 K相平衡

为了获取地下卤水中的锂盐的溶解和析盐规律,进一步指导开发宝贵的液态锂资源,文中采用等温溶解平衡法研究了三元体系LiBr-Li_2SO_4-H_2O在298 K时的固液稳定相平衡关系,测定了平衡溶液的饱和溶解度和密度,并根据饱和液相组成、湿固相组成和对应的平衡固相绘制了等温溶解度图和密度-组成图。结果表明:三元体系在298 K时的相图为简单共饱和型相图,平衡固相中无复盐和固溶体形成;该体系的相图由一个共饱点E,2条单变量溶解度曲线AE和BE,2个单盐结晶区组成,其中结晶区分别对应于二水溴化锂和一水硫酸锂;在三元体系中,溴化锂对硫酸锂有明显的盐析作用,且一水硫酸锂的结晶区远大于二水溴化锂。平衡液相对应的饱和固相由湿渣法和XRD确定。     

四元体系NaCl-KCl-SrCl_2-H_2O 373 K固液相平衡

采用等温溶解平衡法进行了373K时四元体系NaCl-KCl-SrCl_2-H_2O的相平衡研究。根据平衡液相组成和平衡固相组成绘制了该四元体系相图和水图,并确定了共饱点的液相组成及对应的平衡固相。实验结果表明:四元体系NaCl-KCl-SrCl_2-H_2O在373K条件下属于简单共饱型,无复盐及固溶体生成,相图由1个共饱点,3条单变量曲线和3个固相结晶区构成,结晶区分别对应为NaCl,KCl和SrCl_2·2H_2O。同时还对该四元体系在373K与之前文献中报道的323,333,343,348,353K时的溶解度数据进行了比较和分析。     

KH_2PO_4-KNO_3-H_2O三元水盐体系在313.15 K条件下相图的测定和研究

采用等温溶解平衡法测定KH_2PO_4-KNO_3-H_2O三元水盐体系在313.15 K条件下的溶解度,并利用湿渣法和XRD对平衡固相进行分析和验证。根据实验数据绘制相图,相图结果表明,KH_2PO_4-KNO_3-H_2O体系的溶解度等温线有一个三元共饱和点,两条分支,将相图划分为4个区域:不饱和区、KH_2PO_4结晶区、KNO_3结晶区和KH_2PO_4-KNO_3的混合结晶区。313.15 K下的共饱和点组成为w(KH_2PO_4)7.76%、w(KNO_3)33.24%。同时,测定溶液的密度,画出三元体系溶液密度与KNO_3含量的关系图,并将实验测定的密度值与密度模型计算的密度值进行比较,验证了该密度模型的可靠性。     

298K时(NH_4)_2S_2O_3-(NH_4)_2SO_4-H_2O三元体系相平衡研究

通过改良合成复体法对(NH4)2S2O3-(NH4)2SO4-H2O三元体系在298 K下的溶液相平衡进行研究。利用X-射线粉末衍射法(XRD)表征平衡固相组成。结果证实:该方法能很好地用于(NH4)2S2O3-(NH4)2SO4-H2O三元体系平衡固相组成的分析。依据水、硫酸铵及硫代硫酸铵组成的饱和溶液各组分的质量分数绘制了(NH4)2S2O3-(NH4)2SO4-H2O在298 K下的三元体系相图。依据三元体系相图,结果显示:硫代硫酸铵的结晶区远远大于硫酸铵的结晶区,同时在该温度下,硫代硫酸铵、硫酸铵及水形成简单三元体系,体系中没有水合物形成。     

二氧化碳协助强化对二甲苯氧化的连续过程实验与模拟

利用连续实验装置考察了气相CO₂浓度和反应温度对PX氧化反应的影响,并通过反应器建模对连续实验过程进行了模拟计算。研究结果表明,当气相CO₂浓度介于40%～60%时,CO₂能显著提高反应器出口PX转化率以及主产物收率,并且可以降低液相中主要杂质的含量;温度高于192℃后对反应器出口指标的影响比低温时明显。本文建立的全混流反应器模型能够预测气相CO₂含量以及温度等不同反应条件下氧化反应器出口的PX转化率、主产物收率以及液相主要杂质随停留时间的变化。相关研究结果可为当前工业PX氧化过程效率提高以及节能降耗提供新的思路。     

合成二芳基乙烷新工艺的研究

研究了合成二芳基乙烷的新工艺,即以固体超强酸SO2-4/Fe2O3为催化剂,取代了浓硫酸催化工艺。同时考察了影响合成反应的因素。结果表明,原料苯乙烯与二甲苯之比为1∶7.5,催化剂用量为1%(总投料质量百分比),反应时间为3h,反应温度为140°C是最适宜的反应条件,产率可达85%,比浓硫酸催化产率提高了15%左右。为实现二芳基乙烷的绿色生产技术提供了依据。     

PTA与PX价格相关性的浅析

对PTA与PX价格相关性进行简要分析,通过对PTA/PX价格系数的计算以及利用生产利润走势图,确定两者价格系数均衡点,目的是为企业生产管理服务,促进企业健康发展。     

对二甲苯富氧氧化的研究及工业化试验

研究了以Co-Mn-Br为催化剂,对二甲苯(PX)液相氧化下不同氧浓度(质量分数21％~31％)和不同空速对对苯二甲酸(TA)产率、中间产物含量、PX消耗速率和尾气中二氧化碳含量等的影响。结果表明:提高进气中氧浓度,尾气中氧浓度相应提高,有利于加快PX的氧化和TA的生成速率,且未加剧醋酸深度氧化生成二氧化碳。在PX处理量一定时,提高进气氧浓度可大大降低气体空速。工业化富氧(氧气质量分数23％)条件下的氧化反应安全可行,不影响产品质量。     

SKI-400型二甲苯异构化催化剂的工业应用

介绍了镇海炼化芳烃PX装置异构化单元所采用的SKI- 4 0 0型催化剂的技术指标、反应性能、首次装填、预处理、投料试车及六个月来的运行情况 ,并对该催化剂的应用进行特性分析 ,指出了SKI - 4 0 0型催化剂完全适用于缺少歧化的芳烃联合装置 ,具有高活性、高乙苯转化率的特点。     

低纯度PX对PTA装置氧化残渣系统的影响

阐述了使用低纯度对二甲苯(PX)对PTA装置氧化残渣系统工艺参数、技术指标的影响。当PX纯度由99.7％降至99.25％时,固体残渣粘性强,系统易堵塞,回收液中催化剂浓度降低,醋酸质量分数上升至5％,系统进料负荷降低至5.6t/h。通过优化改进工艺,PX纯度大于99.5％时,残渣系统运转稳定,并维持高负荷运转。     

Multi-objective optimization of p-xylene oxidation process using an improved self-adaptive differential evolution algorithm

The rise in the use of global polyester fiber contributed to strong demand of the Terephthalic acid (TPA). The liquid-phase catalytic oxidation of p-xylene (PX) to TPA is regarded as a critical and efficient chemical process in industry [1]. PX oxidation reaction involves many complex side reactions, among which acetic acid combustion and PX combustion are the most important. As the target product of this oxidation process, the quality and yield of TPA are of great concern. However, the improvement of the qualified product yield can bring about the high energy consumption, which means that the economic objectives of this process cannot be achieved simulta-neously because the two objectives are in conflict with each other. In this paper, an improved self-adaptive multi-objective differential evolution algorithm was proposed to handle the multi-objective optimization prob-lems. The immune concept is introduced to the self-adaptive multi-objective differential evolution algorithm (SADE) to strengthen the local search ability and optimization accuracy. The proposed algorithm is successfully tested on several benchmark test problems, and the performance measures such as convergence and divergence metrics are calculated. Subsequently, the multi-objective optimization of an industrial PX oxidation process is carried out using the proposed immune self-adaptive multi-objective differential evolution algorithm (ISADE). Optimization results indicate that application of ISADE can greatly improve the yield of TPA with low combustion loss without degenerating TA quality.     

CoBr2-MnBr2 containing catalysts for catalytic oxidation of p-xylene to terephthalic acid

Catalytic oxidation of p-xylene (PX) to terephthalic acid (TA) was studied with catalysts containing cobalt acetate, manganese acetate, CoBr₂ and MnBr₂. The catalysts contain neither highly corrosive hydrogen bromide nor other metal ions, and have the advantage of easy catalyst recovery. The effects of Br/Co atomic ratio, reaction time and temperature, PX concentration, oxygen pressure, and catalyst concentration on PX conversion and product/intermediate yields were investigated. The catalyst system had a suitable reaction temperature of 100 °C, which was much lower than the commercial process temperature (175–225 °C). The maximum product (TA) yield was 93.5%, obtained at a Br/Co atomic ratio of three. Higher Br concentration resulted in the lower TA yield, which was ascribed to the benzylic bromide formation. The synthesis of TA could be adequately described as four reaction steps in series (PX → p-tolualdehyde → p-toluic acid → 4-carboxybenzaldehyde → TA), with a pseudo-first-order rate equation for each step, and the third step was rate-limiting. The rate constant ratios (k_j/k₃, j = 1 → 4) obtained at 100 °C were similar to the k_j/k₃ values reported earlier for cobalt acetate/manganese acetate/HBr catalysts in a range of 185–191 °C.     

The Solid–Liquid Phase Diagram of Binary Mixtures Dissolved in an Inert Oil: Application to Ternary Blends that Can Form Organogels

A simple generalization of the Hildebrand equation is presented for the prediction of the solid–liquid phase diagram of a binary mixture of structuring agents dissolved in an inert liquid. The model is a thermodynamic interpolation between three well-known limits: (1) the freezing depression curve of liquid A under influence of the addition of the solvent, (2) the freezing depression curve of liquid B under influence of the addition of the solvent, and (3) the binary solid–liquid phase diagram of substances A and B. The theory is shown to be valid as long as the freezing temperature of the liquid is well below the freezing temperatures of the structurants. The theory is compared to literature data for three different mixtures: (1) stearyl alcohol and stearic acid dissolved in sunflower oil, (2) hentriacontane+melissic acid in safflower oil, and (3) lauric acid + behenic acid in canola oil. The agreement between the thermodynamic calculation and experimental data is good. The solid–liquid phase behavior of glyceryl tristearate + stearic acid in edible oil is also studied. The location of the eutectic point of the latter system is predicted to shift toward an axis with zero tristearate concentration as the structurant concentration decreases from 50% to 5% (w/w).     

Room-Temperature Freeze Casting for Ceramics with Nonaqueous Sublimable Vehicles in the Naphthalene–Camphor Eutectic System

Freeze casting for Al₂O₃ was accomplished at room temperature with nonaqueous sublimable vehicles in the naphthalene–camphor eutectic system with a eutectic temperature of 31°C. A fully dense sintered body (>99.5% of theoretical density (T.D.)) was obtained with a eutectic composition vehicle, whereas at most 90% T.D. was obtained with an off-eutectic (i.e., hypo- or hypereutectic) composition vehicle due to formation of large uniquely shaped voids. Microstructural observation suggested that growing pro-eutectic crystals rejected the suspended Al₂O₃ particles to form large voids during the solidification process. At the eutectic composition, formation of fine lamellar microstructure in a solidified vehicle is considered to inhibit particle rejection resulting in large voids.