Analysis of the elimination process of polymerisation inhibitors from styrene by means of adsorption

This work is focused on the analysis, modelling and scale‐up of a process of styrene purification. The first step in synthetic rubber production is to eliminate 4‐tert‐butylcatechol (TBC) which is added to styrene to prevent homopolymerisation during transport and storage. This process is carried out on an industrial scale by means of adsorption onto activated alumina. Equilibrium experiments at 10 °C correlated to the Langmuir–Freundlich equation: with a weighted standard deviation of 3.38%. Fixed bed column experiments were carried out on a laboratory scale to obtain breakthrough curves. A mathematical model that considers film and pore mass transfer resistances described satisfactorily the experimental results with a value of D_p = 3.96 × 10^?9 m² s^?1 which was obtained from correlation of experimental data to simulated curves. Finally, a pilot plant was built and operated in order to verify the validity of the mathematical model and parameters obtained previously. © 2002 Society of Chemical Industry     

Piloting of anionic polymerization of styrene in tetrahydrofurant

Anionic polymerization of styrene in THF with n‐butyllithium/alpha‐methylstyrene initiator is described as a first step in preparation of a styrenic block copoly‐mer. In order to suppress rapid decay of living alpha‐methylstyrene unimers, which occurred at room temperature, the initiation reaction was carried out at ?20(+5)°C. The kinetic parameters of this decay reaction were determined and used for process optimization. By combining experiments with modelling of styrene propagation reaction all key process parameters were defined for l‐L, 38‐L, and 189‐L reactors. A good match was demonstrated between the model and experimental propagation exotherm for semibatch reaction conditions. Overall, it was demonstrated that technical grade THF and styrene could be used at pilot plant scale to prepare well‐defined polymers up to Mn 22 000 via the “living” polymerization mechanism. The resulting polymers had narrow molecular weight distributions (1.06 < Mw/Mn < 1.30).     

Investigation of a fixed-bed pilot plant reactor by dynamic experimentation. Part 2. Simulation of reactor behaviour

Data collected with forced uncorrelated sinusoidal changes of the process variables are used to simulate the behaviour of a non-isothermal non-adiabatic pilot plant fixed-bed reactor. The test reaction applied is the hydrogenation of toluene to methylcyclohexane on an industrial nickel catalyst. A pseudo-homogeneous two-dimensional model as well as a one-dimensional model are applied to describe the reactor behaviour. The model parameters are estimated by defining an objective function based upon residuals of the discretized differential equations instead of upon deviation from the observed variables. This procedure leads to a drastic reduction of computer expenditure. Measured and simulated temperature and concentration profiles are compared on the basis of a number of plots and fitting quality criteria. The model parameters estimated from data collected during dynamic runs are comparable to those obtained from a series of stationary experiments (2₃ experimental design). However, with the dynamic experiments the data necessary for modelling can be collected much more efficiently.     

Investigation on the morphological and mechanical properties of (polyamide 6)/(poly[styrene‐co‐acrylonitrile])/(poly[styrene‐b‐{ethylene‐co‐butylene}‐b‐styrene]) ternary blends

In this work, ternary polymer blends based on (polyamide 6)/(poly[styrene‐co‐acrylonitrile])/(poly[styrene‐b‐{ethylene‐co‐butylene}‐b‐styrene]) (SEBS) triblock copolymer and a varying concentration of the reactive (maleic anhydride)‐grafted SEBS were prepared by using a melt‐blending process. The effects of the material parameters (composition of ternary blends and SEBS/[{maleic anhydride}‐grafted SEBS] concentration ratio) and blending sequence on the morphological and mechanical properties of ternary blends were studied. Taguchi experimental design methodology was employed to design the experiments and select the material and processing parameters for the optimized mechanical properties. Tensile properties (Young's modulus and yield stress) and impact strength were considered as the response variables. It was demonstrated that there is a meaningful relationship between the composition of blends, processing parameters, observed phase structure, and obtained mechanical properties. The mechanical tests showed that the highest impact strength was achieved as the dispersion of the rubbery phase achieved an optimum size of about 1 μm. J. VINYL ADDIT. TECHNOL., 23:329–337, 2017. © 2015 Society of Plastics Engineers     

Continuous‐Flow Surface Aeration Systems

An aeration process in an activated sludge plant is a continuous‐flow system. In this system, there is a steady input flow (flow from the primary clarifier or settling tank with some part from the secondary clarifier or secondary settling tank) and output flow connection to the secondary clarifier or settling tank. The experimental and numerical results obtained through batch systems can not be relied on and applied for the designing of a continuous aeration tank. In order to scale up laboratory results for field application, it is imperative to know the geometric parameters of a continuous system. Geometric parameters have a greater influence on the mass transfer process of surface aeration systems. The present work establishes the optimal geometric configuration of a continuous‐flow surface aeration system. It is found that the maintenance of these optimal geometric parameters systems result in maximum aeration efficiency. By maintaining the obtained optimal geometric parameters, further experiments are conducted in continuous‐flow surface aerators with three different sizes in order to develop design curves correlating the oxygen transfer coefficient and power number with the rotor speed. The design methodology to implement the presently developed optimal geometric parameters and correlation equations for field application is discussed.     

Parameter Sensitivity Analysis of a Spouted Bed

A three‐layer neural network, based on 192 sets of experimental data obtained by the authors, was built in order to simulate the influence of four main process parameters on the minimum and stationary spouting velocity and on the pressure drop in a spouted bed. The simulations with the neural net are in good agreement with experimental learning data, and the overall average absolute error is 5.43 %. The neural net was used in the framework of a Monte Carlo simulation using CRYSTAL BALL^®. The result of 100,000 trials revealed the percentage contributions of the process parameters to the variance of the selected state variables. Since there is significant uncertainty concerning the design equations of spouted beds, the results of this work should be useful for the design of such devices.     

Experimental study and mathematical model on remediation of Cd spiked kaolinite by electrokinetics

An experimental study on electrokinetic removal of cadmium from kaolinitic clays is presented in this work, which is aimed to investigate the effect of surface reactions on the electrokinetic process. Enhanced electrokinetic tests were performed in which the pH of the compartments was controlled. Cadmium spiked kaolin was adopted in the experimental runs. On the basis of the experimental results, a numerical model was formulated to simulate the cadmium (Cd) transport under an electric field by combining a one-dimensional diffusion-advection model with a geochemical model: the combined model describes the contaminant transport driven by chemical and electrical gradients, as well as the effect of the surface reactions. The geochemical model utilized parameters derived from the literature, and it was validated by experimental data obtained by sorption and titration experiments. Electrokinetic tests were utilized to validate the results of the proposed model. A good prediction of the behaviour of the soil/cadmium ions system under electrical field was obtained: the differences between experimental and model predicted profiles for the species considered were less than 5% in all the examined conditions.     

Computational Fluid Dynamics Study of a Styrene Polymerization Reactor

The computational fluid dynamics (CFD) approach was adopted to simulate benzoyl peroxide (BPO)‐initiated styrene polymerization in a laboratory‐scale continuous stirred‐tank reactor (CSTR). The CFD results revealed the effects of non‐homogeneity and the short‐circuiting of the unreacted styrene and initiator on the reactor performance. The study also investigated the effects of the impeller speed and the residence time on the conversion and the flow behavior of the system. The CFD simulation showed that intense mixing remained confined to a small region near the impeller. With increasing impeller speed, it was found that the perfectly mixed region near the impeller expanded, thus reducing non‐homogeneity. Different contours were generated and exhibited the effect of the mixing parameters on the propagation rate and styrene conversion. The monomer and initiator conversions predicted with the CFD model were compared to those obtained with a CSTR model. The CFD model accounts for the non‐ideality behavior of the polymerization reactor, and hence conversion predictions are more realistic.     

Enhancement of Creep Properties of TATB‐Based Polymer‐Bonded Explosive Using Styrene Copolymer

In order to investigate the effects of binder component on the creep properties of polymer‐bonded explosive (PBX), three‐point bending creep behaviors of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)‐based PBX and its styrene copolymer modified formulation were studied by dynamic mechanical analyzer. The experimental results showed that owing to the addition of reinforcing agent (styrene copolymer) with high glass transition temperature and high mechanical strength, the creep resistance performance of the modified formulation was improved with reduced creep strain and constant creep rate and prolonged creep failure time. A six‐element mechanical model was applied to simulate the creep behaviors of TATB‐based PBX and its modified formulation. The constitutive equation of creep curves under different conditions were obtained by nonlinear fit. The predicted theoretical results coincided quite well with the experimental data.     

Dynamic behaviour and simulation of a liquid-liquid extraction column

Dynamic behaviour of a stirred liquid-liquid extraction column was studied experimentally. Various input variables of the column were varied stepwise and the resulting variations in the system and output variables were measured. In addition to experimental work, a computer model was developed on the basis of the dispersion model to simulate the dynamic behaviour of the extractor. This model forms a component program of the dynamic process simulator DIVA, developed at the TU Stuttgart. The experiments showed that the hydrodynamic parameters exhibit no significant dynamic behaviour of their own. Therefore, changes occurring in these parameters closely follow variations in input and system variables. As a result, steady-state relationships for the calculation of flow parameters could be used in the simulation program. The simulator satisfactorily reproduced the experimental results for a number of disturbances. However, this was not always the case. As shown in the following, the model did not take into account the column level controller which, under certain conditions, exerts a very strong influence on the column's dynamic behaviour. As a result, larger differences occurred between experimental and simulated data. This influence on the extractor's dynamic behaviour can, however, be eliminated by a simple modification of the level controller arrangement.     

Determination of the relative importance of process factors on particle size distribution in suspension polymerization using a Bayesian experimental design technique

The use of a Bayesian experimental design technique to determine the relative importance of factors that control particle size distribution (PSD) in suspension copolymerization of styrene and divinylbenzene is reported. Six factors and two responses are considered in this study. The experimental trials are of the two‐level factorial type designed with a Bayesian method. The experiments were carried out in a 5‐L pilot plant reactor. The matrix of variances of the parameter means (the prior knowledge) was estimated with the use of a preliminary compartment‐mixing (CM) model for PSD in suspension polymerization and our subjective judgement (process understanding). The responses, mean particle size and coefficient of variation, were calculated from distributions obtained with a Coulter particle counter. The results of this study provided the criteria needed to guide the future improvement of our CM‐PSD model in a balanced and effective way. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5577–5586, 2006     

Investigation and prediction on the nonlinear viscoelastic behaviors of nylon1212 toughened with elastomer

Studies on the nonlinear viscoelastic behaviors of nylon1212 toughened with styrene‐[ethylene‐(ethylene‐propylene)]‐styrene block copolymer (SEEPS) were carried out. The linear relaxation curves at relatively low shear strains show good overlap, the relaxation time and modulus corresponding to the characteristic relaxation modes were also acquired through simulating the linear relaxation modulus curves using Maxwell model. The nonlinear relaxation curves of nylon1212 blends at different shear strains have been obtained and their damping functions were evaluated. Meanwhile, it is found that most blends in the experimental windows follow the strain‐time separation principle and Laun double exponential model can predict damping curves well. The successive start‐up of shear behavior was investigated. The results showed that Wagner model, derived from the K‐BKZ (Kearsley‐Bernstein, Kearsley, Zapas) constitutive equation, could simulate the experiment data of nylon 1212 blend with 10 wt % SEEPS well, but there exists some deviation for experiment data of nylon1212 blends with high SEEPS concentrations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Lag phase model for transient growth of pseudomonas putida on phenol

The successful design of large‐scale bioreactors requires the ability to predict both steady‐state and dynamic operating conditions. At the same time, mathematical models should not be too complex in order to reduce experimental work required to determine kinetic parameters. A simple model which predicts the behaviour of batch and transient continuous culture operations is presented and experimentally verified. The model is based on two regions of metabolic activity: the lag phase and the active phase. Pseudomonas putida growing on phenol as a substrate in a well‐mixed bioreactor was tested in three modes of operation: batch, continuous start‐up and continuous step‐change. The model is demonstrated to predict all the qualitative aspects of the dynamic phases of growth and is quantitatively accurate.     

BULK POLYMERIZATION OF STYRENE IN A STATIC MIXER

An experimental investigation of thermal bulk polymerization of styrene in a pilot plant will be reported. The plant is composed of a recycle tubular reactor followed by a tubular reactor. The conversion of the pre-polymerization part is in the range of 0 to 60% and at the outlet of the pilot plant up to 96%. Studies on the residence time distribution show plug-flow behaviour for a variety of different conditions with respect to viscosity and density gradient. The polymers obtained are characterized by gel permeation chromatography and compared to commercial products.     

Modeling and simulation of the sequencing batch reactor at a full‐scale municipal wastewater treatment plant

In this work, we attempted to modify the Activated Sludge Model No.3 and to simulate the performance of a full‐scale sequencing batch reactor (SBR) plant for municipal wastewater treatment. The long‐term dynamic data from the continuous operation of this SBR plant were simulated. The influent wastewater composition was characterized using batch measurements. After incorporating all the relevant processes, the sensitivity of the stoichiometric and kinetic coefficients for the model was thoroughly analyzed prior to the model calibration. The modified model was calibrated and validated with the data from both batch‐ and full‐scale experiments. Model predictions were compared with routine data in terms of chemical oxygen demand, NH₄⁺‐N and mixed liquid volatile suspended solids in the SBR, combined with batch experimental data under different conditions. The model predictions match the experimental results well, demonstrating that the model is appropriate to simulate the performance of a full‐scale wastewater treatment plant even operated under perturbation conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Macroscopic model of concrete subjected to alkali-aggregate reaction

The structural behaviour of concrete affected by alkali-aggregate reaction (AAR) is difficult to model due to the amount of random parameters that govern this chemical process. The aim of this work is to present a macroscopic approach whose main features are the consideration of uncoupling between AAR and stress and the representation of the anisotropic characteristic of chemical swelling. Experimental results concerning reactive concrete samples were simulated to verify whether the model was capable of describing the behaviour of affected structures under certain loading and boundary conditions. Loading-unloading response was also considered to simulate the effect of joints opening, which is a commonly used technique for releasing AAR generated stresses in affected structural elements. The obtained results were compared to test data and showed good agreement.     

Fluid catalytic cracking: Selectivity and product yield patterns

Fluid catalytic cracking, a common secondary process employed in the petroleum industry, is used to convert heavier feedstocks into products such as liquefied Petroleum Gas (LPG), motor gasoline, diesel etc. The present study focuses on developing a three lump fraction kinetic model to estimate the yield of C5 up to 370°C cut (motor gasoline and middle distillates). A Micro Activity Test (MAT) apparatus was used to estimate the parameters in the kinetic model. The study is useful in evolving a procedure to simulate plant performance using experimental data obtained in the MAT apparatus for a particular catalyst and feedstock in terms of the product yield pattern.     

MMA－ST乳液共聚合成核阶段的数学模型

研究了ＭＭＡ－ＳＴ乳液共聚合动力学规律，提出了成核阶段数学模型，进行了计算机模拟，并对模型预计结果与实验数据进行了比较和讨论     

Kinetics and Equilibrium Modeling of Sterol Adsorption on Styrene‐Divinylbenzene Cation‐Exchange Resins

The potential of recovering phytosterols from fatty acid methyl esters by an adsorption‐desorption process is demonstrated using a strong‐acid ion‐exchange styrene‐divinylbenzene resin (SA‐R) as an adsorbent and ethanol as a desorbent. Since the operating cost of the overall process significantly depends on the efficiency of SA‐R in the adsorption step, the behavior of SA‐R in sterol adsorption is investigated in detail using a model solution of stigmasterol in n‐heptane. The results indicate that stigmasterol was associatively and exothermically adsorbed on SA‐R. Based on the experimental results, a simple pseudo‐second‐order model and a modified Langmuir isotherm with their parameters, which well predicted kinetics and adsorption capacity of SA‐R, are proposed.     

Development of new concepts for the control of polymerization processes: Multiobjective optimization and decision engineering. II. Application of a Choquet integral to an emulsion copolymerization process

In polymer industry, engineers seek to obtain polymers with prescribed end‐use properties, high productivities, and low cost. Thus, the optimization of a manufacturing process with all those goals and constraints belongs to a problem domain that aims to achieve the best trade‐off possible. This article concerns the optimization of the batch emulsion polymerization of styrene and α‐methylstyrene. An accurate model was developed to describe the complete patterns of the emulsion polymerization. Key parameters of the model were identified on the basis of batch experimental data. The model was then used to simulate, under several operating conditions, the polymerization rate, the overall conversion of monomers, and the number and weight‐average molecular weights. Amulticriteria optimization approach based on an evolutionary algorithm and the concept of dominance from the Pareto frontier theory was used. Last, a decision aid system based on the Choquet integral was proposed to determine the optimal operating conditions with the preferences of the decision maker taken into account. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011