酯化法合成氯乙酸甲酯的动力学研究

在反应精馏制备氯乙酸甲酯的生产过程中,反应动力学研究对该工艺具有非常重要的意义。反应动力学研究是在不同温度下,反应物的转化率随时间的变化曲线,经过合理的数据处理得到反应活化能、反应速率常数等动力学参数,进而得到反应动力学模型。文中主要研究了在间歇反应釜中,甲醇与氯乙酸直接酯化反应制备氯乙酸甲酯的本征反应动力学。通过比较验证,动力学模型计算值与实验值吻合良好,可为反应精馏过程的模拟提供动力学数据。     

阳离子交换树脂催化合成月桂酸甲酯的动力学研究

通过对以Amberlyst 39树脂为催化剂合成月桂酸甲酯的实验研究,计算得到该反应动力学数据,为月桂酸甲酯化反应的工业化设计提供数据和理论的参考。采用PH、E-R、LHHW三种不同的动力学模型对该反应进行拟合,结果表明E-R和LHHW模型的计算值与实验值吻合度都较高,说明在该过程中水的吸附和脱附过程的动力学可忽略,因此E-R模型最适用于表达该反应过程。     

改性双马来酰亚胺树脂的固化特性

本文采用差示扫描量热（DSC）法研究了QYS91—Ⅱ改性双马树脂的固化反应动力学，利用Kissinger方程和Crane方程分别得到了该树脂固化反应表观活化能E、表观频率因子A和反应级数n，进而提出了该树脂固化成型过程的动力学模型，通过固化反应动力学模型对固化反应特性进行了预测，为改性双马树脂实际应用中固化工艺参数的进一步优化提供了一定的理论参考依据。     

多元硅醇固化缩聚动力学

固化是有机硅树脂涂层制备过程的一个重要步骤,其本质是多元硅醇在非溶液体系中的交联缩聚反应。采用FTIR对有机硅树脂固化进行分析,并建立了固化过程中的多元硅醇缩聚反应动力学模型,该动力学模型能描述固化过程的反应动力学。通过研究得到无固化剂以及分别采用2-乙基-4-甲基咪唑、碳酸胍或乙酸胍固化剂时的一系列动力学参数,如反应程度、反应速率常数、反应活化能等。在不同温度下,固化剂可以促进多元硅醇的固化缩聚,并使最终反应程度增加。     

乙苯液相过氧化反应自由基动力学模型的应用研究

利用乙苯液相过氧化反应的自由基动力学模型得到的计算值和实验数据十分接近,说明该模型符合反应实际。利用该模型可以进行多段降温过程的工艺优化模拟计算,从而达到同时兼顾反应速率和选择性的目的。     

环氧树脂/胺基酰亚胺潜伏性固化体系非等温固化动力学研究

分别采用Kissinger模型和Flnn-Wall-Ozawa(FWO)模型研究了E-51型环氧树脂/胺基酰亚胺潜伏性固化体系的非等温固化动力学,得到了该体系在这2种模型下的固化反应活化能.分析了不同动力学模型对该体系固化反应动力学研究的影响.结果表明,由2种模型得到的固化动力学参数基本相近.E-51/胺基酰亚胺体系的固化反应具有变活化能特征,固化反应起始阶段的活化能较高,约为103～112 kJ/mol;当固化度为0.9时,活化能约为63～82 kJ/mol.     

SAPO-34催化剂上甲醇制烯烃反应——催化反应失活动力学

甲醇制烯烃(MTO)催化剂SAPO-34在反应过程中存在失活现象,为了合理设计MTO反应器,需要了解该反应的本征动力学以及催化剂的失活规律,为此在固定床等温积分反应器内进行了甲醇制烯烃反应失活动力学的研究。通过测定不同催化反应时间下反应物和各产物的浓度,考察了催化剂不同使用时间后的催化活性,研究了SAPO-34催化剂的失活规律,建立了5集总反应和失活动力学模型,该模型充分考虑到水和积炭对反应过程的影响。根据实验测定的动力学数据拟合得到了失活反应的动力学常数,该动力学模型预测得到的SAPO-34催化剂上MTO反应产物组成随反应时间的变化规律与实验值吻合很好,说明了获得的动力学模型的可靠性。     

RTM用双马树脂的化学流变性与固化动力学

对适用于RTM工艺的QY8911-Ⅳ双马树脂的化学流变性和固化动力学进行了研究。基于粘度测试数据,利用双Arrhenius公式建立了该树脂的化学流变学方程,该模型方程与实测值吻合较好,利用该模型可以选择合适的注射工艺。采用非等温DSC和等温DSC研究了树脂的固化过程,得到了反应活化能与转化率的关系,基于Kamal模型得到了相应的反应级数。     

低温液相甲醇合成反应动力学模型与参数估计

由低温液相甲醇合成的反应机理出发 ,考虑了均相和多相催化剂的不同作用及不同的吸附方式 ,导出了两步法低温液相甲醇合成的动力学模型 .结合搅拌釜中测得的动力学数据 ,对动力学模型进行了筛选和参数回归 .结果表明氢气为分子吸附 ,反应为双位吸附反应 ,甲醇脱附为反应控制步骤的反应动力学模型能较好地拟合实验数据 .由此得到了低温液相甲醇合成反应动力学模型方程 ,模型满足F检验 ,且参数符合各自的物理意义 .该动力学模型由于是对两步反应综合起来进行动力学分析 ,因而结果可在反应器数学模型中应用     

异佛尔酮二胺/环氧树脂非等温固化动力学研究

采用差示扫描量热法(DSC)对异佛尔酮二胺和环氧树脂体系的固化反应动力学进行了研究。分别通过n级反应法和Málek的最大概然机理函数法确定固化反应机理函数,求出固化反应动力学参数,得到相应的固化反应动力学模型。结果表明,通过Kissinger,Crane方法求解动力学参数所得到的n级反应模型与实验值差别较大;而采用Málek方法判别机理,表明该固化反应按照自催化反应机理进行,由esták-Berggren(S-B)自催化模型计算所得到的曲线与实验得到的数据曲线较吻合,能较好地描述该体系的固化反应过程。     

葡萄糖催化加氢制山梨醇的动力学研究

本文进行了葡萄糖在拉内镍(Raney nickel)存在下的加氢反应动力学研究,反应温度383～413K,反应压力2.0～6.OMPa.根据实验结果筛选出一个合适的反应模型,即为吸附在催化剂表面上的葡萄糖分子和氢分子间进行的反应,产物山梨醇的脱附为速度控制步骤.本征动力学方程为;r=kK_Gc_GaK_Hp_H/(1+K_Gc_G+aK_Hp_H)     

Enhancing thermostability of -mannanase by protective additives

The effects of some sugars (glucose, mannose, fructose, sucrose and chitosan) and polyols (glycol, glycerol and sorbitol) as protective additive on the thermostability of ?-mannanase were studied. The optimal reaction temperatures of ?-mannanase and the thermodynamics and the deactivation kinetics with or without additives were also investigated. The experimental results show that sucrose, chitosan and sorbitol could apparently improve the thermal stability of ?-mannanase when their concentration was kept at 2 g/L. The optimal combination additive proportion was sucrose: chitosan : sorbitol = 1 : 2 : 2 (molar ratio) using the orthogonal experimental design. The sucrose, chitosan, glycerol, sorbitol and the combination additive might increase the optimal reaction temperature from 50°C to about 60°C due to their good protection effect. The thermal deactivation curves of ?-mannanase accorded with the kinetic rules of first order reaction, and the corresponding kinetic and thermodynamic parameters were calculated. Meanwhile, the protective mechanism of the additives against deactivation of enzyme was also discussed.     

Preparation of sorbitol fatty acid polyesters,potential fat substitutes: Optimization of reaction conditions by response surface methodology

Effects of the reaction temperature, reaction time, mole ratio of fatty acid methyl esters (FAME) to sorbitol, and mole ratio of fatty acid sodium soaps (FASS) to sorbitol on yields of sorbitol fatty acid polyester (SFPE) were examined with a response surface methodology. The optimum reaction conditions selected with response surface analysis were as follows: reaction temperature, 144°C; reaction time, 6.65 h; mole ratio of FAME to sorbitol, 10.7∶1; and mole ratio of FASS to sorbitol, 0.77∶1. Under these reaction conditions, the experimental yield of sorbitol fatty acid polyester (mean value: 92% range: 89–94%) obtained from seven replications was close to the predicted value (94%) calculated from the polynomial response surface model equation. The response surface methodology approach used in this study was able to predict the reaction conditions necessary for a high yield of sorbitol fatty acid polyester.     

邻苯二酚与甲代烯丙基氯的醚化反应动力学

呋喃酚（2,3-二氢-2,2-二甲基-7-苯并呋喃酚）是制造杀虫剂呋喃丹（克百威）的重要中间体．呋喃酚的工业生产主要有邻硝基酚法、环已酮法和邻苯二酚法．同其他生产工艺比较,邻苯二酚法具有生产简单、收率高等优点．因此,目前工业上主要采用邻苯二酚法．     

山梨醇衍生物对聚乙烯结晶行为的影响

分别以山梨醇与对甲基苯甲醛、对乙基苯甲醛、3,4-二甲基苯甲醛为原料,利用缩醛反应机理,合成出3种不同的山梨醇衍生物——1,3-2,4-二亚(对甲基)苄基山梨醇(MDBS)、1,3-2,4-二亚(对乙基)苄基山梨醇(EDBS)、二(3,4-二甲基二苄叉)山梨醇(DMDBS)。使用溶液沉淀法制备含DMDBS、EDBS、MDBS质量分数分别为0.3%的3种粉末聚乙烯(PE)样品;采用X衍射仪、红外光谱仪、偏光显微镜、差示扫描量热仪对其进行了结晶结构及性质考察;用Avrami模型、Kissinger方程计算了各PE样品的结晶动力学参数。结果表明,山梨醇衍生物没有改变PE的晶体结构,保持了PE晶体的稳定性,提高了成核密度,使PE球晶尺寸由65μm平均降至53μm。动力学数据表明,山梨醇衍生物能提高PE的结晶速率,降低结晶活化能,PE的Avrami指数由4减小至3~3.6。在添加量相同的条件下,DMDBS、EDBS和MDBS可分别令PE结晶度提高4.83%、4.42%、1.25%。DMDBS对PE的改性效果最明显,EDBS次之,MDBS最小。     

Enhancing thermostability of β-mannanase by protective additives

The effects of some sugars (glucose, mannose, fructose, sucrose and chitosan) and polyols (glycol, glycerol and sorbitol) as protective additive on the thermostability of β-mannanase were studied. The optimal reaction temperatures of β-mannanase and the thermodynamics and the deactivation kinetics with or without additives were also investigated. The experimental results show that sucrose, chitosan and sorbitol could apparently improve the thermal stability of β-mannanase when their concentration was kept at 2 g/L. The optimal combination additive proportion was sucrose: chitosan : sorbitol = 1 : 2 : 2 (molar ratio) using the orthogonal experimental design. The sucrose, chitosan, glycerol, sorbitol and the combination additive might increase the optimal reaction temperature from 50°C to about 60°C due to their good protection effect. The thermal deactivationcurves of β-mannanase accorded with the kinetic rules of first order reaction, and the corresponding kinetic and thermodynamic parameters were calculated. Meanwhile, the protective mechanism of the additives against deactivation of enzyme was also discussed. __________ Translated from Journal of Tianjin University, 2007, 41(1): 114–118 [译自: 天津大学学报]     

基于Monte Carlo方法的聚苯硫醚聚合反应动力学建模

根据聚苯硫醚（PPS）聚合机理及过程分析并通过合理假设,提出了基于Monte Carlo方法的PPS聚合反应动力学模型。利用文献数据对模型参数进行了拟合回归,结果表明动力学模型计算值与相应的实验数据符合良好,并且模型外推预测与相同条件的实验接近,两者偏差小于2%;通过模型对反应物配比的影响进行模拟计算,结果与文献值相符合。最后,通过建立工业PPS聚合反应器模型对工业生产过程进行了模拟计算,结果表明PPS生产过程宜采用多釜串联的方式。相关研究结果可对PPS聚合反应动力学建模和工业过程的设计和优化提供理论依据。     

Optimization of lipase-catalyzed sorbitol monoester synthesis in organic medium

The influence of acid/polyol molar ratio and reaction time on lipase-catalyzed esterification of oleic acid (OA) and sorbitol was studied to determine optimal conditions for monoester synthesis. A simple mathematical model was developed to determine relationships between various parameters of technical and/or economical importance. A direct relationship. independent of OA initial concentration and reaction time, was shown between the percentage of monoester in total esters, monoester concentration (the maximum was 25–30 mM for 70–80% monoester), and sorbitol conversion rate. A high sorbitol conversion was always associated with a low percentage of monoester in total ester. No absolute optimum could be found, so that compromises should be chosen, with the help of the results presented herein, depending on the constraints on the process. Two possible optima are proposed. In both examples, monoester (25–30 mM) is 80% pure. In the first case, productivity is maximized (15 mmol·L⁻¹·h⁻¹), but OA and sorbitol conversions are only 40 and 60%, respectively. In the second case, a high OA conversion (>99%) is favored at the expense of monoester productivity (1.8 mmol·L⁻¹·h⁻¹), 60% of the sorbitol being converted. It was shown that, although sorbitol monoester has better surface properties than diester, the addition of 20% diester did not modify the interfacial activity of monoester and slightly increased its surface activity.     

Hydrocracking: An improved Kinetic Model and Reactor Modeling

Stangeland's kinetic model for predicting hydrocracker yields was modified to explicitly account for the mass balance closure in each individual hydrocracking reaction and for the effect of hydrogen partial pressure on the hydrocracking reaction rate. This improved kinetic model has two additional parameters. The model was applied to the modeling of a fixed bed reactor for mild hydrocracking of vacuum gas oils in the framework of the Aspen Plus® process simulator. The kinetic parameters were regressed using the algorithm of Levenberg-Marquardt such that the mass balance in each individual hydrocracking reaction is satisfied. The reactor model assumed gas-liquid equilibrium and was used to quantify the effect upon conversion of the operating variables--liquid hourly spatial velocity, reactor pressure, and hydrogen-to-feed ratio--showing that both the kinetic and reactor models predict the appropriate trends compared to the reference data. The practical implications of explicitly introducing the mass balance closure for each hydrocracking reaction in the kinetic model are discussed.     

A nonisothermal differential scanning calorimetry study of the curing kinetics of an unsaturated polyester system

Nonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.