Influence of particle size distribution on thermokinetics of ilmenite with sulphuric acid reaction

The knowledge about kinetics of the reaction titanium raw materials with sulphuric acid is very important from the reason of influence of initial conditions of reaction on efficiency, quality and safety. One of the very important parameter, which influence on kinetics of this reaction is distribution of particles sizes of raw material. Presented results of investigation of reaction thermokinetics of ilmenite with different particles sizes, obtained in special construction of calorimeter, demonstrated very great influence of this parameter on rate of reaction with sulphuric acid. On the base of experimental investigation the kinetic model of this reaction was elaborated which takes into account density of particles sizes distribution described by the function of Rosin–Rammler. Presented model was tested on the base of experimental data of ilmenite with sulphuric acid reaction.     

Reaction kinetics of glycidyl trimethyl ammonium chloride and chitosan in 1-allyl-3-methylimidazolium chloride

The modification of chitosan in ionic liquids through homogeneous reactions has advantages including shorter time and simple post-treatment and the generated chitosan derivatives have high degrees of subsititution and good reproducibility. In this paper, we studied the reaction kinetics of glycidyl trimethyl ammonium chloride and chitosan in 1-allyl-3-methylimidazolium chloride. Chitosan concentration, temperature, and reaction time were studied to determine their influence on reaction kinetics. The results indicated that reaction rate increased with increases of both chitosan concentration and temperature. A first-order kinetics equation was generated, where the relationship between reaction rate constant and temperature was determined.     

Quantitative Evaluation of the Influence of Physicochemical Properties of Solvents on the Kinetics of Formation of Phosphorus-Containing Semicarbazides

The kinetics of the reaction of diphenylphosphinic acid hydrazide with phenyl isocyanate in various solvents at 25°C was studied. The results can be quantitatively correlated with the physicochemical characteristics of solvents using the four-parameter Koppel-Palm equation. This relationship allows quantitative analysis of the solvation effects. The decisive influence on the reaction rate is exerted by the basicity and polarity of solvents. The reaction mechanism is discussed, and the possible scheme of solvation is suggested.     

Investigation of the Influence of Diffusion Control on the Curing Reaction Using DSC and Temperature Modulated DSC

The curing reaction of a thermosetting system is investigated by DSC and temperature modulated DSC (TMDSC). When the material vitrifies during curing, the reaction becomes diffusion controlled. The phase shift signal measured by TMDSC includes direct information on the reaction kinetics. For long periods the phase shift is approximately proportional to the partial temperature derivative of the reaction rate. This signal is very sensitive for changes in the reaction kinetics. In the present paper an approach to determine the diffusion control influence on the reaction kinetics from the measured phase shift is developed. The results are compared with experimental data. Further applications of this method for other reactions are proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

硫酸存在时N-溴代苯二甲酰亚胺对甘露糖的胶束催化氧化

The kinetics of micellar-catalyzed oxidation of mannose by N-bromophthalimide was studied in the presence of sulfuric acid at 313 K. The orders of reaction with respect to [mannose], [oxidant], and [H+] were found to be fractional, first, and negative fractional order, respectively. Anionic micelles of sodiumdodecyl sulfate showed a partial inhibitory effect, while cationic micelles of cetyltrimethylammonium bromide increased the reaction rate with the same kinetic behavior. The reaction was catalyzed by cationic micelles, because of favorable electrostatic/thermodynamic/hydrophobic/hydrogen bonding between reactants and cationic micelles. Their catalytic roles are best explained by Berezin’s model. A variation of [phthalimide] showed that the rate of reaction decreased with increasing [phthalimide]. It was observed that, an increase of [mercuric acetate] had no effect on reaction velocity. The influence of salts on the reaction rate was also studied. The rate constant (kW ), binding constants (KS+KO), and corresponding activation parameters (Ea, ⊿H#, ⊿S#, and ⊿G#) were determined. A detailed mechanism with associated reaction kinetics is presented and discussed.     

离子交换树脂吸附乙酰丙酸的动力学研究

研究了大孔弱碱性树脂D310对乙酰丙酸的静态吸附动力学特征.采用批式离子交换法,考察了树脂粒径、溶液浓度、搅拌速率、温度对交换过程的影响,并用动边界模型对乙酰丙酸的离子交换过程进行了描述..结果表明,离子交换过程的控制步骤为颗粒扩散控制,搅拌速率和反应温度对交换速率无显著影响,吸附速率随乙酰丙酸初始浓度的增加而升高.交换过程的反应速率常数k0为0.8315,反应级数n为0.5313,表观活化能Ea为9.504kJ/mol,并得到了动力学总方程式.     

聚偏氟乙烯中空纤维膜器对钐传质性能的影响

以Ｐ５０７－煤油ＨＣｌ－Ｓｍ为实验体系,在两种聚偏氟乙烯中空纤维膜器中研究了溶胀性能、反萃酸度对基于水相的总传质系数及中空纤维膜孔径的影响,考察了料液酸度、萃取剂浓度、钐离子浓度与萃取速率的关系。获得了相应的反应级数。根据界面反应动力学,得到了速率常数值和动力学方程。     

D_4/N-β-氨乙基-γ-氨丙基甲基二甲氧基硅烷本体共聚反应聚合度变化的Monte Carlo模拟

用MonteCarlo方法模拟八甲基环四硅氧烷 (D4 )与N β 氨乙基 γ 氨丙基甲基二甲氧基硅烷(APAEDMS)的本体开环共聚动力学 .模拟过程采用自由体积理论简化处理扩散效应并与本征反应动力学耦合 .本征动力学常数通过模拟主要共聚基元反应得到 ,基于优化的动力学常数通过模拟从分子水平揭示D4 APAEDMS本体开环共聚反应过程主要表现为活性阴离子聚合行为 ,同时又伴有部分逐步聚合特征 .     

Electrochemical study of the degradation kinetics of polyaniline powder in sulfuric and hydrochloric acid media

Investigation of the degradation kinetics of polyaniline (PANi) powder has been performed with a cavity microelectrode in sulfuric and hydrochloric acid electrolytes using cyclic voltammetry. It was shown that the overall degradation mechanism is limited by first-order reaction kinetics. The rate constant of the polymer hydrolysis was found to be lower than the one determined for thin films. The influence of the electrolyte concentration was also investigated and compared with our previous work on the use of PANi as a battery material. Electronic Publication     

Kinetics of the acidic hydrolysis of fenuron in the aqueous and micellar media

The kinetics of the hydrolysis of fenuron by hydrochloric acid in aqueous methanol solution was studied spectrophotometrically. The influence of cationic micelles of cetyltrimethylammonium bromide and anionic micelles of sodium lauryl sulfate on the rate of hydrolysis of fenuron have also been studied. The anionic micelles increased the rate of reaction, while the cationic micelles decreased the rate of hydrolysis. The reaction followed first-order kinetics in [fenuron]. The rate of reaction was increased with increase in [HCl] in lower range, but become constant at higher concentration in aqueous and micellar pseudophases. The reaction starts with the protonation of amino group of fenuron followed by rate-determining attack of water. The results in micellar media are accounted for on the basis of distribution of substrate into micellar and aqueous pseudophases.     

Effect of ozone on poly(vinyl chloride) degradation

The influence of ozone on the kinetics and mechanisms of poly(vinyl chloride) degradation has been studied. The rate constants for reaction of ozone with saturated and unsaturated units of macromolecules have been measured. The products of the reaction of ozone with double bonds are inactive and do not influence the subsequent thermal dehydrochlorination of the polymer. The products of reaction of ozone with saturated units greatly increase dehydrochlorination.     

In situ Fourier transform infrared spectroscopy as an efficient tool for determination of reaction kinetics

The performance of new FTIR-based monitoring technology to representatively determine reaction kinetics has been demonstrated on an example of homogeneously catalyzed liquid-phase sucrose hydrolysis to fructose and glucose. The reaction kinetics were investigated by using the ReactIR 1000 reaction analysis system, which enables determination of the component concentration from its characteristic FTIR spectrum. During the sucrose inversion, the ReactIR 1000 instrument connected to a computer controlled standard glass batch reactor provided the required operating conditions and information about the component concentration in real-time. We have studied the influence of hydrogen ion concentration, temperature and initial concentration of sucrose on the sucrose disappearance rate. It was found out that the inversion of sucrose is an irreversible reaction, which is not affected by the formation of fructose and glucose in the liquid-phase. Then, the parameters of the kinetic model (i.e., reaction rate constant and activation energy) were calculated. A comparison of the model output and the measured data showed that the kinetics of the sucrose inversion could be well described by means of the pseudo first-order kinetic model. Finally, the method of determining the kinetic model by FTIR spectroscopy was verified by comparing the results obtained in the batch reactor with the results obtained in the continuously stirred tank reactor.     

Catalytic syntheses of poly cyclic compounds based on norbornadiene-2,5 in the presence of nickel complexes: III. Cyclic dimerization of norbornadiene-2,5 in the presence of organophosphorus additives

The cyclodimerization of norbornadiene-2,5 (NBD) catalyzed by the systems formed on the basis of bis(ηy³-allyl)nickel and organophosphorus compounds and the process kinetics are studied. The formation rate of all products follows the overall second-order rate law: first order with respect to the catalyst and NBD. The addition of phosphines and phosphites substantially decreases the reaction rate compared to that in nickel systems containing no organophosphorus additives. The influence of the phosphine ligand structure and temperature on the ratio of the reaction products is studied. The blocking of one coordination site on the nickel atom changes the process kinetics. The loss of two vacancies results in the loss of the catalytic activity of the system. A mechanism explaining the stoichiometry and composition of the reaction products is proposed.     

Kinetics and Mechanism of Catalytic Reduction of U(VI) with Hydrazine on Platinum Catalysts in Nitric Acid Media

The kinetics of U(IV) produced by hydrazine reduction of U(VI) with platinum as a catalyst in nitric acid media was studied to reveal the reaction mechanism and optimize the reaction process. Electron spin resonance (ESR) was used to determine the influence of nitric acid oxidation. The effects of nitric acid, hydrazine, U(VI) concentration, catalyst dosage and temperature on the reaction rate were also studied. In addition, the simulation of the reaction process was performed using density functional theory. The results show that the influence of oxidation on the main reaction is limited when the concentration of nitric acid is below 0.5 mol/L. The reaction kinetics equation below the concentration of 0.5 mol/L is found as: -dc(UO₂²⁺)/dt)=kc^0.5323(UO₂²⁺)c^0.2074(N₂H₅⁺)c^-0.2009(H⁺). When the temperature is 50 ℃, and the solid/liquid ratio r is 0.0667 g/mL, the reaction kinetics constant is k=0.00199 (mol/L)^0.4712/min. Between 20 ℃ and 80 ℃, the reaction rate gradually increases with the increase of temperature, and changes from chemically controlled to diffusion-controlled. The simulations of density functional theory give further insight into the influence of various factors on the reaction process, with which the reaction mechanisms are determined according to the reaction kinetics and the simulation results.     

铁－芳烃络合物光引发剂的吸收光谱研究

铁－芳烃络合物光引发剂的吸收光谱研究陈旭东，黄新华陈用烈，梁兆熙（西南师范大学化学系重庆，６３０７１５）（中山大学高分子研究所广州）关键词铁－芳烃络合物，光引发剂，吸收光谱，光解铁－芳烃络合物作为环氧化物阳离子聚合光引发剂已引起人们关注［１，２］．我...     

Kinetics of Hydroxyethylation of Dimethylamine

The kinetics of hydroxyethylation of dimethylamine with oxirane was studied in the temperature interval 20-50°C at the oxirane : dimethylamine molar ratio of 1 : 3. The influence exerted on the reaction rate by the reaction product, dimethylethanolamine, was examined.     

溶液电导率法对碳酸钙结晶动力学的研究

溶液电导率法对碳酸钙结晶动力学的研究;结垢;电导率     

The influence of a medium on the rate of the reaction between N,N′-dioctylurea and <Emphasis Type="Italic">n</Emphasis>-octanol

The kinetics and mechanism of alcoholysis of symmetrical dioctylurea in inert solvents were studied. The reaction was found to follow two parallel pathways, one involving the destruction of initial urea and the other, bimolecular interaction. For the reaction series under consideration, the influence of the nature of solvents on the rate of the reaction was studied.