用于催化裂解小试装置的流化床反应器

通过分析催化裂解反应中传统型的固定流化床小试反应器的缺点,提出改善固定流化床小试反应器的设计方案,即改变进料方式为反应器底部进料,使用三段可控加热夹套对反应器进行加热,反应器底部采用进料气体分布板。改进后的设计克服了由于反应温度高而造成反应物在反应器中结焦的问题,消除了反应器内温度分布不均匀。应用实验表明,将该反应器应用于以石脑油为原料催化裂解制备乙烯和丙烯的小试反应,操作效果良好,并具有较宽的应用范围。     

液液硝化反应器的分散特性和放大研究

根据界面化学反应速率和传质速率的动态平衡理论 ,在五个几何相似的具有双排蛇管的模拟硝化反应器中 ,测定了不同工况下液液湍流搅拌分散系统的Sauter直径。提出了计算Sauter直径的经验公式 ,并通过实验测定了有关参数。实验结果表明 ,该硝化反应器在进行放大时有一最佳中试容积 ,从而得到了放大的依据。     

Diffusion model of an airlift three-phase catalytic reactor and scale-up

A model of an airlift three-phase catalytic reactor is developed for cases of interphase mass transfer between the gas and the liquid in an airlift pipe and a catalytic reaction at the interface between the liquid and catalyst particles. The model equations give the vertical distribution of the average concentration of the active gaseous component (oxygen) in the gas and liquid phases and the average concentration of the active liquid component (alcohol) using the average velocities in the airlift and drain pipes. The model proposed solves the problem of the scale effect. A hierarchical approach is proposed to determine the model parameters from experimental data.     

The temperature scanning reactor: A kinetics instrument

The application of temperature scanning methods of kinetic experimentation is explained, documented, and illustrated with two examples. The experimental procedures involved as well as an outline of the required methods of data handling are presented and the advantages of this technique brought out. There is reason to expect that, even without the fitting of rate expressions, TSR data will make it possible to test catalysts rapidly and over broad ranges of reaction conditions, in hours rather than months. It is also expected that the implementation of TS methods for kinetic data gathering will make it possible for fitted kinetic rate expressions to play an important role in guiding mechanistic studies of chemical reactions.     

Modeling and scale-up simulation of U-tube ozone oxidation reactor for treating drinking water

In the present study, we developed a novel simulation model of the U-tube reactor for treating drinking water, which is composed of a coaxial inner tube serving as an efficient concurrent down-flow ozone dissolver and an outer column carrying out reactions between ozone and organic substances including odorous materials (2-methylisoborneol: 2-MIB) dissolved in the raw water. We assume that the U-tube is composed of a plug flow section (inner tube) followed by a tanks-in-series section (outer bubble column) and take into account the effect of the hydrostatic pressurization on the flow and absorption equilibrium for the gaseous components including ozone and other inactive species in developing the mass balance models. An algorithm is constructed of the differential multiple mass balance equations for the inner tube sections and multiple difference mass balance equations in the series tanks in the outer column section to enable the scale-up from a pilot plant to a full-scale plant. The gas holdup and gas-liquid mass transfer coefficient were measured in a model reactor and correlated for the use of the simulation calculation. Available literature data and correlations on the rates of reactions between ozone and organic substances including odorous material 2-MIB, gas-liquid equilibrium for active and inactive gases and axial fluid mixing properties are also incorporated in the simulation calculation. The simulation results well explained the available data of the ozone absorption efficiency and the removal efficiency of the odorous material in a pilot U-tube reactor. The simulation procedure was also successfully extended to verify the performance of a full-scale U-tube reactor. It is shown that the ozone absorption is practically a single function of the gas/liquid ratio while the removal efficiency of the odorous material is a single function of the ozone dose for a specified U-tube configuration.     

A scale-up strategy for low-temperature methanol synthesis in a circulating slurry bubble reactor

Slurry bubble column reactors are being increasingly utilized in the large-scale conversion of coal or natural gas to liquid hydrocarbons and alcohols. A new suite of tools for developing low-temperature methanol synthesis in circulating slurry bubble reactors is explored in this study. The scale-up strategy consisting of hydrodynamics in cold flow units, catalyst performance evaluation in an autoclave, and process investigation in a pilot-scaled circulating slurry bubble reactor is presented. This methodology should be helpful for designing and scaling-up the low-temperature methanol synthesis and other related processes in slurry bubble column reactors, which will enhance and speed them towards commercial application.     

A cross-flow reactor: Theoretical model for first order kinetics

The-phase reactions (gas, liquid, solid catalyst) have traditionally been carried out in slurry, fluid-bed, and trickle-bed reactors. In this paper a cross-flow reactor has been modeled in which liquid flows through channels in one direction and fills the catalytic porous walls, while gas flows at right angles in alternate channels. The walls are considered as idealized pores with reactant gas at one end and liquid reactant at the other. Flow through the channels is laminar and concentration profiles are given by the Leveque or Graetz solutions. Coupling of the pore and channel equations occurs at the walls, where different boundary conditions are examined. Operation of the reactor at total liquid recycle is treated and the concentration of reactant as a function of time is presented at a value of the Thiele modulus, initial reactant ratio, and Peclet number representative of experiments for the hydrogenation of nitrobenzoic acid.     

Dissolution kinetics of Ca-maleate crystals: Evaluation for biotransformation reactor design

In order to develop a bioreactor for solid to solid conversions the biocatalytic conversion of solid Ca-maleate to solid Ca-D -malate is studied. The dissolution of Ca-maleate is the first step in this process and is described here. A kinetic model, based on the interfacial-barrier theory and the diffusion-layer theory, was developed which describes the increase in Ca-maleate concentration due to dissolution with the help of the time-dependent parameters. According to the model two processes contribute to the dissolution of Ca-maleate·H₂O crystals: (1) the dissolution (and dissociation) reaction of Ca-maleate at the solid–liquid interface, characterized by a time-independent reaction rate coefficient, and (2) the transport of Ca²⁺ and maleate²⁻ across a boundary liquid film, characterized by a time-dependent mass-transfer rate coefficient. In addition, the surface of a crystal and the driving force are time-dependent variables. Since Ca-maleate·H₂O crystals are not uniform, a crystal-size distribution was also used in the model. The effects of stirring speed, temperature, pH, and initial Ca²⁺ concentration on the dissolution rate of Ca-maleate·H₂O crystals were determined experimentally in order to evaluate the model. The model fitted the data well (R²>0·97). In order to determine whether the overall dissolution process was reaction or transport controlled, a method based on overall reaction and transport rates (per unit of driving force) was developed. This showed that the dissolution of Ca-maleate was reaction controlled. Temperature influenced the reaction rate coefficient the most; it ranged from 5·7×10⁻⁶ m s⁻¹ at 10°C to 67×10⁻⁶ m s⁻¹ at 60°C. The reaction rate coefficient was also influenced by the pH and the initial Ca²⁺ concentration, but, as expected, hardly by the stirring speed. Simplifying the model by omitting the time-dependent mass-transfer rate coefficient and by assuming uniform crystals, resulted in only slightly worse fits of the data with R² being at most 0·004 smaller. © 1988 Society of Chemical Industry     

Polymer reaction engineering: From reaction kinetics to polymer reactor control

Polymer reaction engineering is a relatively “young”, very broad, multidisciplinary, rapidly developing field. It is the combination of polymer science, chemistry and technology with process engineering principles. The outcome of this high degree of synergism has evolved over the last fifteen or so years towards an area that includes any or all of the following: polymerization and post-polymerization (chemical modification) reaction kinetics; mathematical modelling and process simulation; polymer reactor design and scale-up; sensor development and process monitoring; and polymer reactor optimization, state estimation and computer control. This article will attempt to give an overview of the results obtained in our laboratory over the last seven years from systematic studies of polymer reaction engineering and polymer production technology problems. These problems cover all aspects of polymer reaction engineering mentioned above. Going from fundamentals to practice, the basic premise of the article is that only by adopting a holistic approach can one devise effective strategies in order to achieve the final objective of more efficient polymer reactor design and control, and hence improved production systems of polymeric materials.     

Continuous production of biodiesel with supercritical methanol: Optimization of a scale-up plug flow reactor by response surface methodology

A scale-up plug flow reactor was evaluated for the continuous production of biodiesel from refined palm kernel oil (PKO) with supercritical methanol and optimized by response surface methodology. The effects of the operating temperature (270–350 °C), pressure (15.0–20.0 MPa) and methanol:PKO molar ratio (20:1–42:1) were evaluated at a constant residence time of 20 ± 2 min by using a central composite design. Analysis of variance demonstrated that a modified quadratic regression model gave the best coefficient of determination (R² = 0.9615) and adjusted coefficient of determination (Adj. R² = 0.9273). The interaction terms in the regression model illustrated small synergistic effects of both temperature–pressure and temperature–methanol:PKO molar ratio. The optimal conditions were 325 ± 5 °C, 18.0 ± 0.5 MPa and a methanol:PKO molar ratio of 42 ± 2:1, attaining a maximum production rate of 18.0 ± 1.5 g biodiesel/min with a fatty acid methyl ester content of 93.7 ± 2.1%. The product obtained from the optimal conditions had high cetane number, and could be considered as a fuel additive for cetane number enhancement.     

Reaction kinetics of carboxymethylation of cornstarch

Reaction kinetics of carboxymethylation of cornstarch in the reaction media of ethanol was studied in this article by determining the changes of NaOH concentration and degree of substitute of reacting matter in the reaction process at different temperature. The equation of reaction rate has been set up and proved to be corresponding with the second‐order reaction. The main and side reaction rate constants at different temperature and the main and the side reaction activation energy have been obtained, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

丙酸甲酯水解反应动力学研究

为了给工业中水解丙酸甲酯提供动力学支持,文中研究了以NKC-9型阳离子交换树脂为催化剂水解丙酸甲酯的动力学过程。在消除内外扩散的影响下,考察了转速、催化剂用量、反应温度以及水酯摩尔比等因素对丙酸甲酯转化率的影响,得出较优实验条件为转速400 r/min、催化剂用量为溶液总质量的7%,反应温度为343.15 K,水酯摩尔比5∶1。通过对328.15—343.15 K下的实验数据进行拟合,得到丙酸甲酯水解的动力学方程。通过实验与计算值的比较验证,此反应动力学方程合理,可用于模拟计算。     

Reaction kinetics of isopropyl palmitate synthesis

In this study, the kinetics of isopropyl palmitate synthesis including the reaction mechanism was studied based on the two-step noncatalytic method. The liquid-phase diffusion effect on the reaction process was eliminated by adjusting the stirring rate. The results showed that the two-step reaction followed a tetrahedral mechanism and conformed to second-order reaction kinetics. Nucleophilic attack on the carbonyl carbon afforded an intermedi-ate, containing a tetrahedral carbon center. The intermediate ultimately decomposed by elimination of the leav-ing group, affording isopropyl palmitate. The experimental data were analyzed at different temperatures by the integral method. The kinetic equations of the each step were deduced, and the activation energy and frequency factor were obtained. Experiments were performed to verify the feasibility of kinetic equations, and the result showed that the kinetic equations were reliable. This study could be very significant to both industrial application and determining the continuous production of isopropyl palmitate.     

油酸甲酯合成反应动力学研究

油酸甲酯是一种重要的化工原料,因现行生产工艺存在污染环境、腐蚀设备、反应转化率较低等问题,使其生产受到了一定制约,为此,提出了一种无催化"两步法"合成油酸甲酯的工艺路线。文中在"两步法"工艺路线的基础上进一步研究了油酸甲酯合成反应动力学。采用积分法分析了在293,298,303,308,313 K下的实验数据,结果表明二步反应均符合二级反应特征,反应遵循四面体机理,并得到了不同温度下的动力学方程式。根据得到的不同温度下的反应速率常数确定了二步反应的活化能分别为121.6 kJ/mol和115.2 kJ/mol,频率因子为2.76×1019和4.03×1018。在实验293—313 K温度范围内,通过实验对得到的动力学方程进行验证,得到的实验值与动力学方程计算值相符合,说明得到的动力学方程是可靠的,为"两步法"合成油酸甲酯的工业放大提供了理论依据。     

微反应器内叔丁醇氢溴化反应动力学研究

将叔丁醇氢溴化反应在微通道反应器内进行动力学研究。结果表明,温度与正、逆反应速率常数成正相关,与平衡常数成反相关;正、逆反应活化能分别为7 821.9和124 234.2 J/mol,反应级数均为一级,动力学方程为rC=2.399e-940.6/T(1-XA)-1.8×1017e-14 942.3/TX1A/2(6.75+XA)1/2。根据浓度和温度效应,分析得到了最优操作温度曲线方程,为今后研究工作中的设计和操作计算提供了理论依据与参考。     

Biological degradation of EDTA: Reaction kinetics and technical approach

The microbial mineralization of EDTA in waste water by a mixed culture was studied with suspended and immobilized cells. Efficient degradation of EDTA could be achieved, though the chelator is stated not to be biodegradable. A complete set of kinetic parameters was determined that enables the modelling of EDTA degradation and, related to this, bacterial growth, ammonium release, maintenance requirement as well as oxygen uptake. In order to obtain important technical scale-up parameters, the microorganisms were immobilized on different carrier particles and employed in continuously operated three-phase airlift-loop reactors. The reactors could be operated at a dilution rate up to D=1·2 h⁻¹ (D≪μ_max) that, at an EDTA concentration of 450 mg dm⁻³, led to EDTA degradation rates up to 12·8 kg m⁻³ day⁻¹. The extent of EDTA deg-radation remained constant at 95–99% with increasing values of D. Achieved kinetic parameters of the biofilm systems were compared with those which were obtained from experiments with suspended cells. © 1998 Society of Chemical Industry     

Fluidized-bed coal combustion: In-bed sorbent sulfation model

A model is developed to account for sulfur capture within the sorbent bed of a fluidized-bed coal combustor. The model is expressed in an analytical form that contains two sorbent specific parameters. The sorbent parameters, which describe the kinetics of the sulfation reaction are obtained from thermogravimetric analysis data on the SO₂-sorbent reaction. Various hydrodynamic and mass transfer properties in relation to the bubbling phenomena are taken into consideration in the model. The predictions of the model which are made without arbitrary parameters, compare favorably with the experimental data on sorbent performance from large scale experimental fluidized-bed coal combustors.     

Viscosity buildup in condensation reactions: Reaction conditions and reactor size effects

The viscosity of sulfonated melamine-formaldehyde resins prepared in batch receptors of different sizes is shown to be a function of the reaction time, temperature, and pH. A formula relating these variables to viscosity buildup is presented. It shows that the pH is more influential than the temperature in increasing viscosity. The reactor mixing patterns are also shown to have a profound influence on resin viscosity. The agitator geometry, and not its tip speed, was found to affect considerably the viscosity buildup. Implications of these observations on the scale-up of condensation reactions are discussed.     

Reaction kinetics determination based on microfluidic technology

Microfluidic technology has been successfully applied to determine the reaction kinetics relying on its great characteristics including narrow residence time distribution,fast mixing,high mass and heat trans-fer rates and very low consumption of materials.In this review,the recent progresses about the reaction kinetics measured in microreactors are comprehensively organized,and the kinetic modeling thoughts,determination methods and essential kinetic regularities contained in these studies are summarized according to the reaction types involving nitration,oxidation,hydrogenation,photochemical reaction,polymerization and other reactions.Besides,the significant advances in the innovation of micro-platform are also covered.The novel reactor configuration methods were established mainly to achieve rapid and efficient data collection and analysis.Finally,the advantages of microfluidic technology for the kinetic measurement are summarized,and a perspective for the future development is provided.