Acetaldehyde dimethylacetal synthesis with Smopex 101 fibres as catalyst/adsorbent

The synthesis of dimethylacetal using acetaldehyde and methanol as raw material in the presence of Smopex 101 fibres as catalyst and adsorbent in batch reactor and in a fixed bed adsorptive reactor, respectively, was studied. In the batch reactor the determination of thermodynamic and reaction kinetics data for acetalization reaction was presented. A kinetic model based on a pseudo-homogeneous rate expression using activities was proposed to describe the experimental kinetic results. The dynamic binary adsorption experiments were carried out in the absence of reaction at 293.15 K in a laboratory scale column. The experimental results of the adsorption of binary non-reactive mixtures are reported and used to obtain multi-component adsorption equilibrium isotherms of Langmuir type. The mathematical model was proposed to describe the adsorptive reactor dynamic behaviour. The experimental results obtained for the reaction and regeneration experiments were compared with the model proposed. Model equations were solved by orthogonal collocation on finite elements (OCFE) implemented by the PDECOL package, using the measured model parameters and was validated for both reaction and regeneration steps.     

吸附-光催化法用于降解室内VOC的研究进展

吸附-光催化法因其高效、便捷、无污染等特点,在室内挥发性有机物(VOC)治理领域拥有着广阔的应用前景。本文介绍了吸附-光催化降解VOC机理;总结了近年来常用的固定化TiO₂的制备方法,以及各自的工艺流程、适用范围和存在的问题;综述了反应环境(风速、初始浓度、温度、相对湿度)对吸附-光催化降解率的影响。分析表明,在选择TiO₂固定化工艺时,应当根据吸附剂基材的表面基团、孔隙结构和亲疏水性等特征合理经济地确定制备方法;在探讨反应环境对室内VOC降解率的影响规律时,应综合考虑VOC自身特性和反应器类型等实验条件以得到不同条件下的最佳环境参数。最后指出,低温成膜的制备方法以及对反应环境如何影响低浓度多组分VOC降解的研究将成为今后的发展趋势。     

Direct production of crystalline boric acid through heterogeneous reaction of solid borax with propionic acid: Operation and simulation

The production of boric acid through reaction of borax crystals with propionic acid was investigated in batch mode. It was found that the product boric acid precipitates on the solid borax reactant. An increase in the coefficient of variation of feed crystals resulted in an increase in the time of completion of the reaction. A sharp interface model with variable bulk fluid concentration of liquid reactant was developed for simulation of the process. The analytical solution of the series of rate equations involving liquid film, solid boric acid layer and chemical reaction resistances was obtained, and a new method for simultaneous determination of kinetic parameters was established. The chemical reaction and diffusion through the solid layer of boric acid were the rate controlling mechanisms. A numerical algorithm was also developed for predicting the fractional conversion of multisize borax crystals using the mono size kinetic parameters determined according to the proposed analytical method.     

Study on the enzymatic hydrolysis of racemic methyl ibuprofen ester

The hydrolysis of racemic methyl ibuprofen ester in the presence of lipase from Candida rugosa was investigated in shake flasks. Experiments were performed to study the effect of temperature, pH and shaking speed on the reaction rate. Different hydrophobic co‐solvents were screened for the highest reaction rate and the presence of enzyme inhibition by substrate and products was examined. A kinetic expression was then proposed to describe the reaction. Kinetic parameters were determined for the optimum operating conditions and the proposed model was verified with the experimental results. Next, this reaction was scaled up to a fed batch stirred tank reactor. Batch reactor and fed batch reactor configurations were compared for better conversions. The effects of aqueous phase hold‐up, substrate concentration and feed flow rate on the conversion of the reaction were also studied. Higher conversions were obtained in a fed batch reactor when compared with the batch reactor. In the fed batch reactor, increased conversions were observed with lower feed flowrates and high aqueous phase hold‐up. © 2001 Society of Chemical Industry     

A preliminary evaluation of a continuous‐flow reactor for liquid–liquid–solid phase‐transfer catalyzed synthesis of n‐butyl phenyl ether

This study evaluates the feasibility of using a continuous‐flow stirred vessel reactor (CFSVR) to synthesize n‐butyl phenyl ether (ROPh) from n‐butyl bromide (RBr) and sodium phenolate (NaOPh) by liquid–liquid–solid phase‐transfer catalysis (triphase catalysis). The factors affecting the preparation of triphase catalysts, the etherification reaction in a batch reactor, and the performance in a CFSVR were investigated. The kinetic study with a batch reactor indicated that when the initial concentration of NaOPh or RBr was high, the conversion of RBr would depend on the initial concentration of both RBr and NaOPh. The reaction can be represented by a pseudo‐first‐order kinetic model when the concentration of NaOPh is in proper excess to that of RBr, and the apparent activation energy is 87.8 kJ mol^?1. When the etherification reaction was carried out in the CFSVR, the catalyst particles did not flow out of the reactor, even at a high agitation speed. The conversion of RBr in the CFSVR was, as predicted, lower than that in the batch reactor, but was higher than the theoretical value because the dispersed phase is not completely mixed. Copyright © 2004 Society of Chemical Industry     

Kinetics of the L‐aminoacylase‐catalyzed resolution of N‐acetyl‐DL‐butyrine

The kinetics of the asymmetric hydrolysis of N‐acetyl‐DL ‐butyrine catalyzed by L ‐aminoacylase to obtain optically pure L ‐butyrine is described. Some of the constants are determined from the initial reaction rates and others from long‐term experiments in batch reactors by the numerical integration of the reactor design equation and minimization of the kinetic parameters. The methodology described can be applied to the kinetic study of other complex biocatalytic systems. Studies on enzyme activation by adding different divalent metal ions and enzymatic deactivation are also included. © 2002 Society of Chemical Industry     

间歇化学反应温度先进控制系统

由于间歇化学反应器中动力学参数的不确定性和时变性,使其成为先进控制算法工业应用的主要对象。本文对以预测函数控制算法（PFC）为核心并结合PID控制的先进控制算法进行了研究,针对间歇化学反应器的温度跟踪控制问题,提出了包括PFC在内的四种控制方案的先进控制策略。并在SUPCON－JX300集散控制系统上开发了间歇反应温度跟踪先进控制软件包,工业现场运行取得了很好的结果。     

A homogeneous chemical reactor analysis and design laboratory: The reaction kinetics of dye and bleach

An experimental module for senior-level reaction engineering/reactor design students is described. The module is used to characterize the kinetics of dye (food coloring) neutralization by household bleach, and the reactor system is configurable for use in either batch reactor or continuous-stirred tank reactor (CSTR) modes. The reactor temperature, volume, reactant feed rates, and reactant concentrations may be adjusted to enable students to obtain a wide range of kinetic data. Dye concentrations in the reactor are monitored by absorbance spectroscopy, and the kinetic rate law is determined directly from the batch reactor performance data. Students use the completed kinetic rate law to compare experimental steady-state CSTR performance data to the mathematical models derived from reactor design equations. Finally, the students use the kinetic behavior of the system to design a hypothetical plug-flow reactor for the same chemical reaction and a set of stated operational goals.     

Leaching kinetics of calcined magnesite in acetic acid solutions

The leaching kinetics of calcined magnesite by using acetic acid solutions was investigated in a batch reactor by using the parameters such as temperature, acid concentration and particle size. The experimental results were successfully correlated by linear regression using Statistica Package Program. Dissolution curves were evaluated in order to test shrinking core models for fluid–solid systems. It was concluded that the leaching of calcined magnesite was controlled by chemical reaction. In addition, the fact that leaching was controlled by the chemical reaction was also supported with the relationship between the reaction rate constant and the particle radius. The apparent activation energy of dissolution process was found as 34.60 kJ mol^?1.     

Esterification of acrylic acid with methanol by reactive chromatography: Experiments and simulations

The esterification of acrylic acid with methanol using Amberlyst 15 as a stationary phase has been investigated using a chromatographic reactor. Several experimental runs at various operating conditions have been conducted on a batch column. A classical reactive chromatography model including lumped kinetics, a linear driving force transport model and a heterogeneous kinetic model for the catalytic reaction has been developed. The additional dispersion of concentration fronts due to density gradient effects has been accounted for in the model. The model parameters have been determined in a fast and reliable way by directly fitting the batch column experiments. In general, a good agreement between experimental and calculated results is obtained. The evaluation of the covariance of the fitted model parameters reveals important insights about the system behavior.Based on the detailed batch column model, a complete model of a simulated-moving-bed reactor has been implemented and its optimal point of operation for the synthesis of methyl acrylate from acrylic acid has been determined. Particularly when considering the low-operating temperature, we can regard this process as a possible competition for current technologies.     

Modeling the Dispersion of Volatile Organic Compounds in Indoor Environment

Indoor air pollution belongs to the factors which puts the health of the corresponding occupants at risk. Effects of ventilation and, hence, various air flow regimes as parameters contributing to reduced air pollution in indoor spaces were further studied. For this purpose, air flow and distribution of the pollutant concentration were three‐dimensionally modeled at various ventilation rates. Results indicate that an increase in input air flow rate into the room in early times directly contributes to enhanced concentration of the pollutant in the indoor space. In general, with increasing the ventilation rate and changing the fluid‐flow regime from laminar to turbulent, the average concentration of the pollutant inside the indoor space decreased significantly.     

Self-adaptive predictive functional control of the temperature in an exothermic batch reactor

In this paper we study a self-adaptive predictive functional control algorithm as an approach to the control of the temperature in an exothermic batch reactor. The batch reactor is located in a pharmaceutical company in Slovenia and is used in the production of medicines. Due to mixed discrete and continuous inputs the reactor is considered as a hybrid system. The model of the reactor used for the simulation experiment is explained in the paper. Next, we assumed an exothermic chemical reaction that is carried out in the reactor core. The dynamics of the chemical reaction that comply with the Arrhenius relation have been well documented in the literature and are also summarized in the paper. In addition, the online recursive least-squares identification of the process parameters and the self-adaptive predictive functional control algorithm are thoroughly explained. We tested the proposed approach on the batch-reactor simulation example that included the exothermic chemical reaction kinetic model. The results suggest that such an implementation meets the control demands, despite the strongly exothermic nature of the chemical reaction. The reference is suitably tracked, which results in a shorter overall batch-time. In addition, there is no overshoot of the controlled variable T, which yields a higher-quality production. Finally, by introducing a suitable discrete switching logic in order to deal with the hybrid nature of the batch reactor, we were able to reduce the switching of the on/off valves to a minimum and therefore relieve the wear-out of the actuators as well as reduce the energy consumption needed for control.     

Catalytic removal of phenol from aqueous solutions in a trickle‐bed reactor

The degradation of high concentrations of phenol (1g/dm^?3) in aqueous media at high temperatures (100–190 °C) and pressures (2.0 MPa) has been studied by catalytic wet air oxidation in a trickle‐bed reactor. The effect of reaction temperature, weight hourly space velocity (WHSV) and hydrogen peroxide concentration on phenol concentration, total organic carbon (TOC) and chemical oxygen demand (COD) conversion by using a commercial copper catalyst has been investigated. At 150 °C, TOC removal increased by 28% with the WHSV of 62.5 h^?1. The addition of hydrogen peroxide as a free radical promoter significantly enhanced the depletion rate of phenol. A kinetic study has been carried out leading to the determination of the kinetic constants for the removal of TOC. Copyright © 2005 Society of Chemical Industry     

Concomitant use of liquid–liquid batch and continuous plug flow reactors for kinetic model discrimination. Application to the Rh/TPPTS catalysed reduction of the C–C double bond in dimethylitaconate

The biphasic catalytic reduction of the C–C double bond of dimethylitaconate with a water soluble rhodium/triphenylphosphinetrisulphonated sodium salt (TPPTS) complex is investigated. Kinetic studies in a well-mixed batch reactor provide kinetics parameters and an activation energy of 71 kJ mol⁻¹ but cannot discriminate between a first order or a complex kinetic model within the range of substrate concentration where the approximation of linear liquid/liquid partition is respected. Catalytic tests in the centrifugal partition chromatograph (CPC) reactor under steady-state operations in chemical regime and plug flow mode allow discriminating the kinetic models, the complex kinetic rate law being preferred.     

Modeling and simulation for acrylamide polymerization of super absorbent polymer

In view of the scale up of a batch reactor for super absorbent polymer (SAP), a dynamic mathematical model of a commercial scale batch reactor was developed with mass balance, energy balance, and complex polymerization kinetics. The kinetic parameters of the polymerization were estimated on the basis of the established mathematical model and reference data. Simulation results were validated with less than 10% marginal error compared with reference data. A case study was executed in terms of dynamic simulation for eight different initial concentrations of initiator and monomer to analyze the influence of initial concentration and predict the operation condition for desired product. The results were compared with various reference data, and good agreement was achieved. From the results, we argue that the methodology and results from this study can be used for the scale up of a polymerization batch reactor from the early stage of design.     

Mass transfer limitations in slurry photocatalytic reactors: Experimental validation

In the present work the existence of mass transfer limitations in slurry, photocatalytic reactors is studied. Experimental validation is made in a flat plate reactor that is part of a recycling system. The reactor is described with a mathematical model previously developed [Ballari et al., 2008a. Chemical Engineering Journal 136, 50], considering a transient, two-dimensional mass balance (TDM). The complete reactor model was developed to show the existence of these effects, which result from the occurrence of concentration gradients in reaction space. They develop when these reactors are operated under some operating conditions whose effects should be always analyzed before assuming the validity of existence of perfect mixing in reaction space. Dichloroacetic acid (DCA) was the adopted model compound. To solve TDM, a kinetic expression for DCA acid was determined before under well mixed conditions [Ballari et al., 2009. Industrial and Engineering Chemistry Research 48(4), 1847]. The studied variables are flow rate, catalyst loading, and irradiation rates. The experimental data agree quite well when they are interpreted in terms of the two-dimensional model (TDM) regardless of the operating mode. The perfect mixing model (PMM), normally employed to describe this and other types of slurry photoreactors, does not have the same level of universal application; i.e. it is restricted to perfect mixing, but in many cases far simpler to use. However, it can be concluded that when the photocatalytic reaction is not fast, employing catalyst loadings below 1 g L^–1, irradiation rates at the reactor wall below 1×10^?6 Einstein cm^?2 s^?1 and good mixing operation (Re>1700) it will be always safe to assume that mass transport limitations in the bulk of the fluid are nonexistent. In a typical batch reactor the above flow conditions are equivalent to very intense mixing. If the catalyst concentration is increased, the mixing conditions should be improved in the same proportion. Within limits, higher solid loadings can be compensated with lower irradiation rates [Ballari et al., 2008a. Chemical Engineering Journal 136, 50]. In addition, with the validated model, additional simulations are shown, operating the reactor under different virtual reactor thicknesses to widen amplitude of the reached conclusions. These findings will be useful in kinetic studies to prevent incursion in certain ranges of experimental conditions that could lead to erroneous interpretation of the obtained kinetic data.     

Kinetics studies of ketazine formation: Effect of temperature and catalyst concentration

Formation of methyl ethyl ketazine is a distinct case of homogeneous catalyzed gas–liquid–liquid reactions. Kinetics studies of methyl ethyl ketazine formation has been carried out in a semi‐batch reactor. The effects of temperature and catalyst concentration on the percentage yield of ketazine have been studied extensively. The yield of ketazine is found to increase with increase in temperature and then levels off. Increase in catalyst concentration favours the formation of ketazine. The conversion of peroxide is found to increase with increase in temperature thus indicating that chemical reaction is rate‐limiting step in the system. The desired temperature for carrying out the reaction is found to be 60°C and the required catalyst to peroxide ratio is 2.5. The activation energy for the reaction is 24.5 kJ/mol.     

Dynamic modelling of heterogeneous catalytic reactions—I. Theoretical considerations

The problem of modelling heterogeneous catalytic reactions by dynamic methods is considered, using a one-dimensional heterogeneous plug-flow model. Assuming constant reactor inlet temperature, uniform initial temperature profile, reactor inlet concentration step changes and absence of part of the reactants, it is shown that the reactor outlet concentration transients may be used to determine individual steps of the reaction scheme and to estimate kinetic parameters. Reaction steps can be determined by comparison of measured transients with classified transients for typical model reactions. Estimation of kinetic parameters is carried out by using the concentration transients and their time derivatives.     

BATCH AND SEMIBATCH REACTORS MODELLING AND VALIDATION BASED ON ON-LINE pH MEASUREMENT

Based on on-line pH measurement, a comparative study between batch and semibalch reactors performance has been carried out in a glass-jacketed reactor of 51 provided with the measuring, data acquiring and controlling system. The reaction system chosen was an acid-base reaction, the concentrations of the species in the reactor were obtained simply by measuring the pH of reaction solution. Based on the conductivity profiles of the solution at different temperatures, the kinetic equation of this acid-base reaction was established. The thermal behaviors of batch reactor were investigated by heating and cooling water in the reactor. The dynamic behavior of batch reaction could be described by a set of differential equations resulting from the mass and energy balance of the reaction mixture, the energy balance of the jacket wall and the circulating fluid inside the jacket. This model has been validated with experimental results, and could be applied to the complex control situations.