Population balance modeling and simulation of liquid–liquid–liquid phase transfer catalyzed synthesis of mandelic acid from benzaldehyde

Mandelic acid has cosmetic, pharmaceutical, and antibacterial activities and is used in urinary antiseptic medicines. An attractive process for the production of mandelic acid is through reaction between benzaldehyde, sodium hydroxide, and chloroform in the presence of polyethylene glycol 4000 as a phase transfer catalyst. The liquid–liquid phase transfer catalyzed (L–L PTC) reaction can be intensified by converting it into three‐liquid phases (L–L–L PTC). We address the modeling of a well‐stirred reactor for the foregoing process, in which organic droplets surrounded by a thin film of catalyst‐rich phase are suspended in the aqueous phase. A population balance model is formulated for the L–L–L PTC reaction and solved by Monte Carlo simulation using interval of quiescence technique. Transport processes and intrinsic reaction kinetics are extracted from the experiments. This population balance model serves to assess and interpret the relative roles of various processes in L–L–L PTC reaction, such as diffusive transport, reaction, and interaction between dispersed phase droplets. The model is expected to be an effective tool for reactor design and scale up. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Alternative methacrylate‐tethering methods for resin‐modified glass‐ionomer cements

We have explored two novel methacrylate‐tethering methods for resin‐modified glass‐ionomer cements using 2‐hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GM) as a tethering agent. Both were compared with the published method using 2‐isocyanatoethyl methacrylate (IEM). The tethering reactions were monitored using FTIR spectroscopy. It was found that IEM and HEMA tethering reactions were relatively fast compared with the GM‐tethering, even though all three tethering reactions can be completed within 6 h. The cements composed of the IEM‐tethered polymer showed the highest CS, DTS, and modulus, followed by the cements composed of the HEMA‐ and GM‐tethered polymers, which was attributed to different chemical bonds introduced. It appears that both alternative tethering methods are quite equivalent to IEM‐tethering based on the strength and reaction efficiency. The results suggest that HEMA and GM can be used as promising methacrylate‐tethering alternatives for resin‐modified glass‐ionomer applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Measuring enthalpy of fast exothermal reaction with micro‐reactor‐based capillary calorimeter

This work presents a new micro‐reactor‐based capillary calorimeter for the enthalpy measurement of fast exothermal reactions. The new calorimeter was operated in the continuous way and the reaction enthalpy can be easily measured with the online temperatures from detached sensor chips. A standard reaction system and an industrial reaction system were selected to test this new calorimeter with homogeneous and heterogeneous reaction processes. The measurement was taken place at nearly adiabatic situations and the reaction enthalpy was calculated from the rising of temperature. High accuracy and good repeatability were obtained from this new calorimeter with relative experimental errors less than 3.5% and 2.4%, respectively. The temperature response was quick in this new calorimeter too, which was benefit to the low cost of reactive component. The fast and accurate measurement was contributed to the nice mixing performance and strict plug flowing in the calorimeter. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

A novel method for the measurement of wetting efficiency in a trickle‐bed reactor under reaction conditions is introduced. The method exploits reaction rate differences of two first‐order liquid‐limited reactions occurring in parallel, to infer wetting efficiencies without any other knowledge of the reaction kinetics or external mass transfer characteristics. Using the hydrogenation of linear‐ and isooctenes, wetting efficiency is measured in a 50‐mm internal diameter, high‐pressure trickle‐bed reactor. Liquid–solid mass transfer coefficients are also estimated from the experimental conversion data. Measurements were performed for upflow operation and two literature‐defined boundaries of hydrodynamic multiplicity in trickle flow. Hydrodynamic multiplicity in trickle flow gave rise to as much as 10% variation in wetting efficiency, and 10–20% variation in the specific liquid–solid mass transfer coefficient. Conversions for upflow operation were significantly higher in trickle‐flow operation, because of complete wetting and better liquid–solid mass transfer characteristics. © 2010 American Institute of Chemical Engineers AIChE J, 2011.     

Fully resolved numerical simulation of reactive mixing in a T-shaped micromixer using parabolized species equations

This paper introduces and exploits a hybrid numerical approach for fully resolved numerical simulations of reactive mixing in T-shaped microreactors and thereby enables a computational analysis of how chemical reactions interact with convective and diffusive transport. The approach exploits the fast redirection of the flow inside the mixing channel, resulting in a flow field with positive axial flow component everywhere after a short entry zone. This allows handling the axial flow direction as a pseudo-time variable, so that the evolution of the concentration profile can be computed consecutively on successive cross sections, following the main axial flow direction. With this approach the finest length scales, given by the Batchelor length scale, can be resolved for such a reactive mixing process inside a T-microreactor at stationary flow conditions. This allows for a detailed analysis of the mixing state as well as important characteristics of the reactive mixing process like yield and selectivity. The concrete numerical simulations yield local diffusion times inside the reactor, reveal the influence of the strength of the secondary flow on the progress of the chemical reaction and show how local selectivities result from the species transport.     

Finite element solution for gas–solid reactions: Application to the moving boundary problems

Gas–solid reactions are very important in the chemical and metallurgical process industries. Several models described these reactions such as volume reaction model, grain model, and nucleation model. These models give two coupled partial differential equations (CPDEs). In this work an integral transformation and subsequent finite element method is used for solving the coupled partial differential equations of these reactions. In each mesh the Rayleigh–Ritz method is applied. Finally the results of this work are compared with the existing numerical solutions and experimental data successfully.     

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.     

Evaluation of Performance of Periodically Operated Reactors for Single Input Modulations of General Waveforms

The nonlinear frequency response (NFR) method is used for evaluating the time‐average performance of a chemical reactor subjected to single input modulations of general waveforms, by using Fourier series for representing the input and Volterra series for representing the output. Both the input and the output are approximated by finite sums. The obtained results are applied for the case of a square‐wave input modulation. As a case study, the improvement of an isothermal continuous stirred‐tank reactor with simple reaction mechanism with modulation of the inlet reactant concentration is used and the results are tested on a numerical example.     

Mathematical modeling of turbulent heat and mass transfer with chemical conversions

A transient model of heat and mass transfer with nonlinear sources (sinks) caused by first-and second-order chemical reactions is developed. The model uses a matching condition (equal temperature and local flux values) at the reaction zone-coolant interface. A finite-difference numerical solution to the problem is obtained using the alternating direction method. The model is tested by application to fast polymerization processes. The effect of the coolant velocity, reactor radius, and coolant temperature at the reactor inlet on the polymerization efficiency is studied.     

三种反应器微观混合性能的对比

介绍了撞击流、旋转填料床和撞击流-旋转填料床三种反应器的原理;采用化学偶合法,对三种反应器的微观混合性能进行了实验测定与研究,结果表明,撞击流-旋转填料床反应器的微观混合性优于其它两种反应器。     

Mathematical reactor modelling for coupled chemical and electrochemical processes: the ECE system

A procedure for modelling electrochemical reactions and reactors which involve heterogeneous reaction, homogeneous fast chemical reaction and diffusional mass transport is described. The procedure can be applied to any combination of first order reaction processes utilising numerical routines for the solution of initial value differential equations. By the use of collocation it can be extended to higher order processes. The reactor types considered are batch, plug flow and dynamic continuous stirred tanks and reactors with recycle. Operation with either potentiostatic, galvanostatic or constant cell voltage control is described and illustrated using the ECE reaction mechanism, involving successive electrochemical, chemical and electrochemical reaction.     

Synthesis of novel polyimides containing side‐chain azo‐2‐naphthol moieties

An amine‐ester derivative of isoeugenol was prepared in three steps. This amine‐ester was converted to diazonium salt and subsequently was reacted with 2‐naphthol and a novel isoeugenol ester‐azo derivative as a new monomer was obtained in quantitative yield. This monomer was characterized by high‐field ¹H‐NMR, IR, and elemental analysis and then was used for the preparation of model compound and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione was allowed to react with this new monomer. The reaction was very fast and gave only one double adduct by Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer with bistriazolinediones [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] were carried out in N,N‐dimethylacetamide at room temperature. The reactions were exothermic, fast, and gave novel heterocyclic polyimides by repetitive Diels–Alder‐ene polyaddition reactions. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1942–1951, 2003     

Progress in membrane gas–liquid reactors

Gas–liquid reactions are crucially important in chemical synthesis and industries. In recent years, membrane gas–liquid reactors have attracted great attentions due to their high selectivity, productivity and efficiency, and easy process control and scale‐up. Membrane gas–liquid reactors can be divided into three categories: dispersive membrane reactor, non‐dispersive membrane reactor and pore flowthrough reactor. The progress in membrane gas–liquid reactors, including features, applications, advantages and limits, is briefly reviewed. © 2012 Society of Chemical Industry     

Synthesis of novel photoactive heterocyclic polyimides containing naphthalene moieties via cycloaddition reactions

1‐Naphthylacetic acid (1) was reacted with thionyl chloride and 1‐naphthyl‐ acetyl chloride (2) was obtained in a quantitative yield. The reaction of this acid chloride (2) with isoeugenol (3) was performed in chloroform and a novel isoeugenol ester derivative (4) as a monomer was obtained in a high yield. The compound (4) was characterized by ¹H‐NMR, IR, mass, and elemental analyses and then was used for the preparation of a model compound (6) and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione (PhTD) (5) was allowed to react with compound (4). The reaction is very fast and gives only one double adduct (6) via Diels–Alder and ene pathways in an excellent yield. The polymerization reactions of the novel monomer (4) with bistriazolinediones [bis‐(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (7) and 1,6‐bis‐(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (8) were carried out in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic and fast and gave novel heterocyclic polyimides containing a naphthalenic pendant group (9) and (10) via repetitive Diels–Alder‐ene polyaddition reactions. Stereochemical analysis of the model compound and fluorimetric studies of the model compound as well as polymers were done conclusively. Excimer formation of the polymers and its effect on fluorescence emission were investigated and some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 527–536, 2000     

In situ generation of hydrogen peroxide and its use for enzymatic degradation of 2,4,6‐trinitrotoluene

A novel electroenzymatic method hybridizing both electrochemical and enzymatic reactions and using lignin peroxidase (Lip) for treatment of TNT (2,4,6‐trinitrotoluene) waste was studied. In the presence of Phanerochaete chrysosporium lignin peroxidase, TNT was degraded in an electrochemical reactor using hydrogen peroxide, produced by an electrode reaction. The effectiveness of the electroenzymatic method was examined in this study. The efficiency of removal of TNT was greater than that of biochemical methods under optimal conditions. The effects of reaction conditions on TNT degradation and denitrification, TOC removal efficiency, and power consumption were also investigated. A potential (vs Ag/AgCl) of +0.1 V was selected as being optimal for the electroenzymatic reaction. TNT degradation was significantly improved in the combined veratryl alcohol–lignin peroxidase oxidation procedure, showing complementary effects of veratryl alcohol (VA) in the TNT degradation reaction. Denitrification was found to be proportional to the amount of TNT degraded. One intermediate, 2,4‐diamino‐6‐nitrotoluene, derived from the oxidative degradation of TNT, was eluted on an HPLC chromatogram and was detected using mass spectrometry. The electroenzymatic method had a lower power requirement than electrochemical oxidation at ?0.2 and ?0.4 V. The electroenzymatic method may be easily applied to biodegradation systems and provide added benefit for highly recalcitrant chemicals since the system would not be susceptible to the toxicity of the chemical. Also H₂O₂ instability and decomposition in the samples after preparation would not be of concern. © 2001 Society of Chemical Industry     

A Microfluidic Approach to the Rapid Screening of Palladium‐Catalysed Aminocarbonylation Reactions

The evaluation and selection of the most appropriate catalyst for a chemical transformation is an important process in many areas of synthetic chemistry. Conventional catalyst screening involving batch reactor systems can be both time‐consuming and expensive, resulting in a large number of individual chemical reactions. Continuous flow microfluidic reactors are increasingly viewed as a powerful alternative format for reacting and processing larger numbers of small‐scale reactions in a rapid, more controlled and safer fashion. In this study we demonstrate the use of a planar glass microfluidic reactor for performing the three‐component palladium‐catalysed aminocarbonylation reaction of iodobenzene, benzylamine and carbon monoxide to form N‐benzylbenzamide, and screen a series of palladium catalysts over a range of temperatures. N‐Benzylbenzamide product yields for this reaction were found to be highly dependent on the nature of the catalyst and reaction temperature. The majority of catalysts gave good to high yields under typical flow conditions at high temperatures (150 °C), however the palladium(II) chloride‐Xantphos complex [PdCl₂(Xantphos)] proved to be far superior as a catalyst at lower temperatures (75–120 °C). The utilised method was found to be an efficent and reliable way for screening a large number of palladium‐catalysed carbonylation reactions and may prove useful in screening other gas/liquid phase reactions.     

Polynomial ARMA model identification for a continuous styrene polymerization reactor using on‐line measurements of polymer properties

The multiinput–multioutput identification for a continuous styrene polymerization reactor using a polynomial ARMA model is carried out by both simulation and experiment. The pseudorandom multilevel input signals are applied for model identification in which input variables are the jacket inlet temperature and the feed flow rate, whereas the output variables are the monomer conversion and the weight‐average molecular weight. The use of a polynomial ARMA model for identification of the multivariable polymerization reaction system is validated by simulation study. For the experimental corroboration, correlations are developed to convert the on‐line measurements of density and viscosity of the reaction mixture to the monomer conversion and the weight‐average molecular weight. The on‐line values of the conversion and weight‐average molecular weight turn out to be in good agreement with the off‐line measurements. Despite the complex and nonlinear features of the polymerization reaction system, the polynomial ARMA model is found to satisfactorily describe the dynamic behavior of the polymerization reactor. Therefore, one may apply the polynomial ARMA model to the optimization and control of polymerization reactor systems. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1889–1901, 2000     

Modelling and simulation of an oxychlorination reactor in a fluidized bed

Taking 1,2‐dichloroethane from the oxychlorination reaction is a commercially very important process due to the large application of the 1,2‐dichloroethane in the chemical industry of PVC production. This work presents the modeling and simulation of an oxychlorination reactor with a fluidized bed. The pseudo‐homogeneous model with one‐dimensional flow in steady state was applied based on the theory of fluidized bed in two phases. It allows the sensitivity analysis of the operational and project parameters of the reactor. The ordinary differential equations system that represents the mathematical model of the reactor was solved through the application of the numerical method of Newton–Raphson's. The results obtained have proved that the developed model represents the system suitably, in spite of the one‐dimensional model. The effect of different parameters was investigated through the sensitivity analysis, and the results show that the parameters that have the largest influence on the reactor performances are: fluidized bed height, bubble diameter, residence time, cupric chloride weight in the catalyst, and emulsion phase temperature.     

Analysis of a pressure‐driven folding flow microreactor with nearly plug‐flow characteristics

We discuss the possibility of designing a pressure‐driven single‐phase microreactor with characteristics similar to that in an ideal plug‐flow reactor. We consider equations for the moments of the residence time distribution and investigate the behavior of the solution in long spatially‐periodic channels. If the microreactor consists of a large number of folding flow elements, the chaotic advection plays a double role: it mixes the chemical species and suppresses the axial dispersion. It is shown using analytical estimates and numerical modeling that chemical reactions have different sensitivity to the axial dispersion and for some reactions the effect of dispersion can be successfully eliminated. © 2009 American Institute of Chemical Engineers AIChE J, 2010