Nonlinear chemical reaction between Na2S2O3 and Peroxide compound

Kinetics of reaction between Na₂S₂0₃ and peroxide compound (H₂0₂ or Na₂S₂O₃) in a batch reactor and in a continuous stirring tank reactor (CSTR) were studied. Steady oscillations in uncatalyzed reactions in a CSTR were first discovered. In Na₂S₂0₃-H₂O₂-H₂S0₄ reaction system, Pt potential and pH of higher and lower flow rates beyond oscillation flow rates were in around the same extreme values. The reaction catalyzed by Cu²⁺ consists of the catalyzed oscillation process and the uncatalyzed osciliation one. On the basis of experiment, a reaction mechanism consisting of three stages was put forward. The three stages are H⁺ positive-feedback reactions, proton negative-feedback (uncatalyzed negative-feedback and catalyzed negative-feedback) reactions and transitional reactions. The mechanism is able to explain reasonably the nonlinear chemical phenomena appearing in the thiosulfate oxidation reaction by peroxide compounds. Project supported by the National Natural Science Foundation of China.     

Nonlinear chemical reaction between Na_2S_2O_3 and Peroxide compound

Kinetics of reaction between Na2S2O3 and peroxide compound ( H2O2 or Na2S2O8) in a batch reactor and in a continuous stirring tank reactor (CSTR) were studied.Steady oscillations in uncatalyzed reactions in a CSTR were first discovered.In Na2S2O3-H2O2-H2SO4 reaction system,Pt potential and pH of higher and lower flow rutes beyond oscillation flow rates were in around the same extreme values.The reaction catalyeed by Cu2+ corsist of the catalyzed oscillation process and the uncatalyzed osciliation one.On the basis of experiment,a reaction mechanism consisting of three stages was put forward.The three stages are H positive-feedback reactions,proton negative-feedba k (uncatalyzed negative-feedback and catalyzed negative-feedback) reactions and transitional reactions.The mechanism is able to explain reasonably the nonlinear chemical phenomena appearing in the thiosulfatc oxidation reaction by peroxide-compounds.     

非对称取代卟啉锌、镉的生成反应动力学及动力学盐效应研究

本文报道应用停流方法对非对称取代卟啉［5-(4-乙酰氨基苯基)-10,15,20-三(4-甲基苯基)卟啉］(H₂T(p-CH₃)₃(p-NHCOCH₃)PP)与Zn(Ⅱ)、Cd(Ⅱ)在丙酮中的生成反应动力学进行了研究,提出了反应机理,并用非线性拟合和线性拟合的方法求得了生成反应各基元步骤的动力学参数,同时还探讨了温度,溶剂效应、动力学盐效应对反应体系的影响,并对锌、镉两种卟啉在生成机理及生成反应速率上的差异给予了解释。     

Calcium Phosphate Coating on Titanium Plate

Abstract

Calcium phosphate films, obtained by electrophoresis and sputtering were studied by ESCA, IR and x-ray diffraction.     

3-硝基邻苯二甲酸锆的制备、热分解机理及非等温反应动力学

用3-硝基邻苯二甲酸、氢氧化钠和硝酸氧锆为原料,制备了3-硝基邻苯二甲酸锆,采用元素分析、X射线荧光衍射和FT-IR对其结构进行了表征.用TG-DTG以及变温固相原位反应池/傅里叶变换红外光谱(RSFT-IR)联用技术研究了3-硝基邻苯二甲酸锆的热分解机理,对主分解反应的DTG峰进行了数学处理,计算得到了动力学参数和动力学方程.结果表明,3-硝基邻苯二甲酸锆的分解反应总共有4个阶段,其中主分解反应发生在第2阶段,主分解反应的表观活化能Ea与指前因子A分别为158.84kJ·mol-1和109.85s-1,主分解阶段的反应机理服从一级Mample法则,主分解反应的动力学方程为dα/dt=109.85(1-α)e-1.91×104/T.     

低温条件下羰基硫催化水解反应本征动力学研究

 采用自行设计和安装的微反－色谱联用装置,在50～70℃,n（H2O）／n（COS）＝60～550的条件下,以TGH为催化剂,对羰基硫催化水解反应本征动力学进行了研究．利用不同的目标函数,采用非线性Marquart法对实验数据进行回归,所建立的本征动力学方程式为r（COS）＝－dXd（W／f（COS））＝1．82·1014p（COS）p－0．5（H2O）exp－758008．374T．并对其反应机理进行了探讨．     

The kinetic regularities, products, and mechanism of the thermal decomposition of dimethyldioxirane. The contribution of molecular and radical reaction channels

The products and kinetics of the thermal decomposition of dimethyldioxirane (DMDO) were studied. The reaction proceedsvia three parallel pathways: isomerization to methyl acetate, oxygen atom insertion into the C−H bond of a solvent molecule (acetone), and the solvent-induced homolysis of the O−O bond in the DMDO molecule. The contribution of the latter reaction channel isca. 23% at 56°C. The overall kinetic parameters of DMDO thermolysis in oxygen atmosphere were determined. The free radical-induced DMDO decomposition occurs in an inert atmosphere. The formal kinetics of this reaction was investigated. The mechanism of the DMDO thermolysis is discussed. Dedicated to Professor E. T. Denisov on the occasion of his 70th Birthday. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1344–1354, August, 2000.     

竹材非等温热解动力学

利用热重分析技术对竹材在高纯N2条件下,从室温至1273K进行了非等温热解分析,研究了升温速率(5、10、20和40K/min)对热解过程的影响,探讨了其热解机理。研究表明,竹材非等温热解过程主要分为失水干燥、快速热解和缓慢分解三个阶段组成,其中第二阶段是整个过程的主要阶段,析出大量挥发分造成明显失重。升温速率对热解过程有显著影响,随着升温速率的增加,最大热解速度增大,对应的峰值温度升高,热滞后现象加重,热解各阶段向高温侧移动。热解机理满足一维扩散Parabolic法则,反应机理函数为g(α)=α2。不同升温速率下活化能为75.32-82.99kJ.mol-1,指前因子为1.17×105-1.12×106min-1。     

反应NH~4ClO~4+Mg+K~2Cr~2O~7的非线性化学动力学2: 固相 振荡燃烧的化学模 型

建立了NH~4ClO~4+Mg+K~2Cr~2O~7固相振荡燃烧体系的非吸热三变量立方自催化化学模型,应用非线性数学分析方法,研究了固相振荡燃烧的非线性化学动力学机理,并对此进行了数值模拟,结果反映了这一振荡燃烧体系所具有的非线性化学动力学特性。     

3，5-二硝基水杨酸铈的制备﹑热分解机理及非等温反应动力学

用3,5-二硝基水杨酸和硝酸铈为原料,制备了3,5-二硝基水杨酸铈(CeDNS),采用元素分析、X射线荧光光谱和FTIR对其进行了表征。用TG和DSC以及变温固相原位反应池/傅立叶变换红外光谱(RS-FTIR)联用技术研究了3,5-二硝基水杨酸铈的热分解机理,对主放热反应的DSC峰进行了数学处理,计算得到了动力学参数和动力学方程。结果表明,3,5-二硝基水杨酸铈的分解反应共有3个阶段,其中包括一个脱水吸热过程和一个主放热过程,主分解反应发生在第2阶段,主分解反应的表观活化能E_a与指前因子A分别为：159.17 kJ·mol^-1 和10^11.33 s^-1,主分解阶段的反应机理服从Avrami-Erofeev方程(n=1/4),主分解反应的动力学方程为：dα/dt=10^11.33×4(1-α)[-ln(1-α)]^3/4e^-1.92×104/T。     

正丁烷脱氢制正丁烯催化剂*

综述了对正丁烷脱氢制备正丁烯的催化剂体系,包括有氧脱氢中钒基催化剂、钼酸盐系列和焦磷酸盐系列催化剂;催化脱氢中贵金属Pt系催化剂、以ZSM-5分子筛为载体的催化剂以及膜反应器。探讨了正丁烷脱氢动力学,并在Mars-van Krevlen和 Eley-Rideal机理模型动力学基础上归纳了正丁烷氧化脱氢及直接脱氢的机理。讨论了正丁烷催化剂的影响因素,比较了各类催化剂的特点并对其进行展望,认为ZSM-5分子筛将可能成为正丁烷脱氢制正丁烯的新的研究热点。     

卟啉铁与抗坏血酸均相电子转移反应的动力学和机理

采用电子吸收光谱和光谱－电化学方法研究了中位－四（邻硝基苯基）四苯并卟啉的Fe(Ⅲ）配合物与抗坏血酸在DMF溶液中的均相电子转移反应的动力学和机理。结果表明此电子转移反应来源于抗坏血酸与铁卟啉中心铁离子的轴向配位作用,并将一个电子转移至铁离子。反应速度对铁卟啉和抗坏血酸均为一级,并与抗坏血酸的离解有关。     

Model reactions of amine curing of glycidylamine epoxy resins: Homopolymerization of N-methylglycidylaniline

The kinetics of homopolymerization of the monofunctional epoxide N-methylglycidylaniline in the presence of a tertiary amine or an amino alcohol has been followed by reversed phase high performance liquid chromatography and size exclusion chromatography. The reaction products were identified by mass spectrometry using potassium ionization of desorbed species (K⁺IDS). 1,3-Di-N-methylanilino-2-propanol (P) was the main reaction product and low molecular weight oligomers with M_n > 600 were also formed. The molecular weight and fraction of oligomers decrease with increasing concentration of the initiator. The suggested complex reaction mechanism involves formation of four stable oligomeric series initiated by reaction of the epoxide with either an OH group of (a) the amino alcohol, (b) product P, (c) traces of water, or (d) the tertiary amine to form ionic species resulting in the ionic propagation. Regeneration of the initiator and formation of new initiating centers during the polymerization are the causes of low molecular weights of oligomers. © 1992 John Wiley & Sons, Inc.     

超细AgO粉末:制备及热分解非等温动力学

采用化学沉淀法,以臭氧为氧化剂制备了超细AgO粉末,并用XRD、XPS、SEM和粒度分析仪对制备的粉末进行了表征,借助热重分析法(TG)和线性升温理论对超细AgO粉末的热分解过程和非等温热分解动力学机理进行了研究。结果表明,制备的AgO属于单斜晶系,形貌为片状,其粒径分布在45～551nm之间,大部分在200nm左右;AgO的热分解分两步,158℃开始分解,放出氧气形成Ag2O,413℃进一步分解形成Ag;其热分解反应服从核生成和核成长为控制步骤的A2机理,热分解表观活化能为90.26kJ·mol-1,反应频率因子为1.64×108s-1。     

Microheterogeneous solvation for aminolysis reactions in AOT-based water-in-oil microemulsions

A kinetic study was carried out on the aminolysis of p-nitrophenyl acetate (NPA) by n-decylamine (DEC), piperazine (PIP) and sarcosine (SAR) in AOT/isooctane/water (w/o) microemulsions. By using the pseudophase model both the rate constants at the interface, k2i, and the water microdroplet, k2w, can be obtained. The obtained results show that k2i increases together with the water content of the microemulsion, whereas k2w increases as the water content of the system decreases. In the aqueous microdroplet the predominant interaction Na+...OH2 causes a decrease in the strength of the hydrogen bonds and therefore facilitates the desolvation of the reagents as W decreases. This desolvation of the reagents causes the increase of k2w as W decreases. In the interface of the microemulsion the predominant interaction SO3-...HOH causes an increase in the electronic density on the water molecules and the consequent decrease in their efficiency in the solvation of the partial negative charge, which develops on the carbonyl oxygen atom in the transition state of the reaction. This decrease in the solvation causes k2i to decrease together with the water content of the system.     

Kinetic model for reactivity in quaternary water-in-oil microemulsions

A study was carried out on the nitrosation of piperazine (PIP) and N-methylbenzylamine (MeBzAm) by N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in quaternary microemulsions of tetradecyltrimethylammonium bromide (TTABr)/isooctane/alcohol/water, varying the nature and the concentration of the following alcohols: 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol and 1-decanol keeping the [1-alcohol]/[TTABr] = 4 relationship constant. In addition a study was carried out on the influence of the alcohol concentration, working with molar relationships [1-hexanol]/[TTABr]=3, 4 and 5. On the basis of the molar volumes of the alcohol and surfactant and the concentration of alcohol at the interface it was possible to calculate the change in its volume with as varying compositions of the microemulsion. In order to interpret the experimental results a kinetic model was devised which takes into account the distribution of the reactants between the different pseudophases and the change in the volume of the interface. The rate constants at the interface of the microemulsion are lower than in pure water and are independent of the nature of the alcohol used as a cosurfactant and the molar relationship [alcohol]/[TTABr]. This independence indicates that the main role of the cosurfactant is to increase the volume of the interface with the consequent dilution of the reactants.