Analysis of styrene polymerization in a continuous flow tubular reactor

A mathematical model has been developed to predict the spatial variations in temperature, velocity and composition which occur during thermal polymerization of styrene in a laminar flow tubular reactor. The resulting computer simulation model is capable of analysing the effects of coupled momentum, heat and mass transfer including system parameter variations and different operational conditions on reactor stability and conversion rate. It was found that a tube of radius up to 2 cm can be unconditionally used for continuous flow polymerization. Above this radius, thermal runaway, flow channelling and steep radial gradients in all principal variables may occur.     

The performance of the emulsion polymerization of styrene in a continuous loop tubular reactor

The emulsion polymerization of styrene in a continuous loop tubular reactor (CLTR) has been used to study the process kinetics under eigth levels of sodium lauryl sulfate (SLS) concentration, eight levels of potassium persulfate (KPS) concentration, and three levels of styrene monomer (St) concentration. A critical surfactant concentration for the overshoot phenomenon in the monomer conversion exists between 8.02 and 12.40 g-SLS/1-water. Overshoot was not eliminated by changing concentrations of the initiator and monomer. The overshoot in the number concentration of polymer particles was observed in all the polymerizations studied. The dependences of the rate of polymerization and the number concentration of particles in the steady state on the SLS and KPS concentrations are presented. The growth of the average cumulant diameter of particles shows a transient period followed by a steady state. The dependences of the volumetric growth rate of polymer particles on diameter are of the order of 1 for the lower SLS concentration and 0.5 for the higher SLS concentration, respectively. The steady state cumulant diameter depends on an order of ?0.24 for the SLS concentration.     

The effect of flow regime on the continuous emulsion polymerization of styrene in a tubular reactor

Five isothermal emulsion polymerizations of styrene in a tubular reactor were studied experimentally using an emulsifier concentration in the vicinity of the critical micelle concentration (CMC). The flow regime was characterized by an emulsion Reynolds Number (N_Re)_e calculated using the emulsion properties prior to any appreciable reaction. It was found that the rate of polymerization was a maximum at the laminar-turbulent transition based on (N_Re)_e. This behavior is similar to emulsion polymerizations carried out in batch reactors where a maximum rate of polymerization has been observed when the agitation level (agitator rotation rate) is varied. The controlling mechanisms appear to be similar at high agitation levels but differ when the emulsion is weakly agitated.     

Emulsion polymerization of styrene in a continuous stirred reactor

The emulsion polymerization of styrene has been carried out in a continuous stirred reactor at 50°C. Polymerization rates were initially very high but declined subsequently. These rates did not always attain a steady value, but sometimes oscillated with time. Size analysis of the polymer particles showed that particle nucleation almost stopped soon after start-up. A new generation of particles appeared later in the process. The average number of radicals per particle was usually, but not always, >0.5. The time-average polymerization rate was only weakly dependent on the initiator concentration but varied with the first power of the emulsifier concentration.     

Polymerization of styrene with n-butyllithium in a batch reactor. A mathematical model

Sytrene was polymerized in a 0.8-liter vessel which was operated as an isothermal and a nonisothermal batch reactor. Styrene and n-butyllithium conversions were determined for different reaction times. Rate equations were developed by use of the isothermal data and then used to estimate the conversions for the nonisothermal experiments. The importance of using nonisothermal data in the development of rate equations is illustrated.     

Modeling of a continuous electrochemical tubular reactor for phenol removal

In this study, the treatment of highly polluted synthetic phenolic wastewater in a tubular continuous electrochemical reactor was modeled and solved by the finite difference method. The reaction conditions were previously optimized with batch reactor experiments, and the synthetic wastewater containing 443 mg/L and 3063 mg/L initial phenol concentrations was treated in the runs at 25°C with 120 g/L electrolyte concentration. For the model solution, the column was divided into 10 nodes in z-direction and 9 nodes in r-direction with the intervals j z=3.5 cm, j r=0.5 cm, and j t=10 s and 1.2 min for 443 mg/L and 3063 mg/L phenol feed concentrations, respectively. The results of the model solution correlated with the experimental data fairly well, which could be useful in the design and scale up of tubular continuous electrochemical reactors for phenol removal.     

Polymer property control in a continuous styrene polymerization reactor using model-on-demand predictive controller

The model-on-demand (MoD) framework was extended to the model predictive control (MPC) to design a multiple variable model-on-demand predictive controller (MoD-PC). This control algorithm was applied to the property control of polymer product in a continuous styrene polymerization reactor. For this purpose, a local auto-regressive exogenous input (ARX) model was constructed with a small portion of data located in the region of interest at every sample time. With this model an output prediction equation was formulated to calculate the optimal control input sequence. Jacket inlet temperature and conversion were chosen as the elements of regressor state vector in data searching step. Simulation studies were conducted by applying the MoD-PC to MIMO control problems associated with the continuous styrene polymerization reactor. The control performance of the MoD-PC was then compared with that of a nonlinear MPC based on the polynomial auto-regressive moving average (ARMA) model for disturbance rejection as well as for setpoint-tracking. As a result, the MoD-PC was found to be an effective strategy for the production of polymers with desired properties.     

High performance pressure sensitive adhesives by miniemulsion photopolymerization in a continuous tubular reactor

High solids content PU/(meth)acrylics latexes for application as pressure sensitive adhesives (PSAs) were successfully synthesized by miniemulsion photopolymerization in a continuous tubular reactor at room temperature. It was shown that the process is very flexible and the polymer microstructure can be widely changed by simply controlling the radical initiation using different photoinitiator types and concentrations and varying the incident light irradiance. PSAs presenting a whole spectrum adhesive properties were obtained, some of them having the desired and unusual combination of high work of adhesion and maximum shear adhesion failure temperature (SAFT > 210 °C). The adhesive properties were analyzed in terms of the molecular weight distribution of the whole sample measured by asymmetric flow field flow fractionation.     

Methanolysis of amides under high-temperature and high-pressure conditions with a continuous tubular reactor

The methanolysis of amides, which is widely employed in the synthetic organic chemistry, hardly occurs under mild conditions. To safely and controllably intensify the methanolysis reaction with hightemperature and high-pressure environment, a continuous tubular reaction technology is developed,whose space–time yield is over twice of that of the conventional batch reaction. The methanolysis of acetanilide is selected as the representative reaction, and the influences of temperature, pressure, rea...     

Emulsion copolymerization in a tubular reactor

A study was conducted on the emulsion copolymerization of vinyl acetate and butyl acrylate in a tubular reactor. It was performed at a constant temperature of 60°C and at different fluid velocities and feed compositions. Conversion, particle size distribution, and copolymer composition were measured, respectively, with gravimetric method, laser light scattering, and nuclear magnetic resonance. Maximum conversions were found for each of the monomer compositions; this maximum conversion varied, however, with the recipe used. The amount of butyl acrylate has a direct effect on the number of particles and on the final conversion. In lower levels of butyl acrylate particle size distribution is wide and bimodal. High levels of butyl acrylate leads to narrow and monomodal particle size distribution. Therefore the level of butyl acrylate and the velocity of fluid flowing inside the tube have strong effects on the shape (monomodal‐bimodal) and the width of particle size distributions. This effect may vary at different levels of butyl acrylate and flow rate. The results obtained from copolymer composition show that an alternating block copolymer is made during the reaction. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 833–842, 2000     

超临界连续化制备生物柴油单管扩大试验

在小试基础上,建立了一套百吨级超临界连续化制备生物柴油单管扩大试验装置,主要包括反应系统、产品精制系统和自动控制系统3个部分.以大豆油和甲醇为原料进行了扩大试验.考察了在连续反应条件下超临界甲醇法制备生物柴油中不同反应条件对脂肪酸甲酯收率的影响.试验结果表明,装置运行良好,适宜的工艺条件为:反应温度300℃,反应压力15 MPa,反应停留时间1 200 s,醇油摩尔比为40:1,在该条件下,生物柴油收率可达95%.反应物的混合状况对酯交换反应有重要影响.在相同工艺条件下,扩大试验装置中反应混合物流动的雷诺数是小试的2倍,传质系数增大,甲酯收率显著高于小试结果.     

Mathematical modeling and analysis of an interfacial polycarbonate polymerization in a continuous multizone tubular reactor

A detailed mathematical model is presented to describe the steady state behavior of a continuous multizone tubular reactor for the synthesis of aromatic polycarbonate by interfacial polycondensation mechanism. In this process, bisphenol‐A dissolved in a dispersed aqueous phase reacts with phosgene dissolved in a continuous organic phase and hence, the reaction initiates at the interface of the two phases. A liquid‐liquid mass transfer process is incorporated into a reaction kinetic model to calculate the reaction rates and polymer molecular weight distribution. The kinetic model has also been used in developing a steady state multizone tubular reactor model for continuous production of polycarbonate. The model simulations are compared with proprietary plant data and excellent agreement has been obtained. POLYM. ENG. SCI., 58:438–446, 2018. © 2017 Society of Plastics Engineers     

An experimental study for property control in a continuous styrene polymerization reactor using a polynomial ARMA model

By using a multivariable nonlinear model predictive controller (NLMPC), the control experiments for the monomer conversion and the weight-average molecular weight are conducted in a continuous styrene polymerization reactor. Instead of a complex first-principles model, a polynomial auto-regressive moving average model (ARMA) is used to describe the nonlinear behavior of the polymerization reactor. The pseudorandom multilevel input signals mounted on the jacket inlet temperature and the feed flow rate are applied to the polymerization reaction system to identify a polynomial ARMA model. In the experiments of identification and control, the monomer conversion and the weight-average molecular weight are measured by on-line densitometer and viscometer with appropriate correlations. The on-line measurements are found to be in good agreement with the off-line analysis by the gravimetry and the gel permeation chromatography. Since a polynomial ARMA model is expected to give a higher order objective function of input variables, we employ the extended Kalman filter based NLMPC scheme to reduce the computational requirement in the control experiments. The NLMPC based on the polynomial ARMA model is found to perform satisfactorily for the control of the polymer properties during a grade-transition period as well as under the steady-state operation.     

Calcination of limestone in a tubular reactor

Theoretical expressions were developed for the design of a tubular reactor for the calcination of limestone, pneumatically conveyed by flue gas. The total residence time and the length of the reactor are affected in particular by the particle size, the excess thermal capacity of the gas and the heat transfer coefficient. High throughput can be achieved in relatively small reactors. An experimental investigation verified a theoretical prediction, that a considerable part of the decomposition takes place in the first few centimeters of the reactor length. The rate of heat transfer in this section was high, with Nusselt numbers of 9.9 to 31.7.     

Dynamic simulation and control of auto-refrigerated CSTR and tubular reactor for bulk styrene polymerization

Dynamic simulation and control of a two-stage continuous bulk styrene polymerization process is developed to predict the performance of auto-refrigerated CSTR and tubular reactors. The tubular reactor is subdivided into three temperature-control jacket zones. In this paper temperature control of auto-refrigerated continuous stirred tank reactor and tubular reactor are carried out, simultaneously. Two strategies are proposed for the control of tubular reactor. At the first strategy the controlled variable is jacket temperature and in the second strategy the controlled variable is the reactor temperature at the exit of each section. The set points for polymer grade transition are obtained using optimization of reactors temperatures via genetic algorithm (GA). Simulation results show that both of the control strategies are successful but second strategy has better performance in the control of polymer properties in the presence of disturbance and model mismatch.     

A continuous tubular reactor for core–shell latex particles

High solids content poly(butyl acrylate)/poly(methyl methacrylate) core–shell latex particles were produced using miniemulsion polymerisation in a continuous linear tubular reactor. The resulting products were and shown to be comparable to a batch process. Final solids contents of 41 and 48 wt.% were shown to be possible in a simple tubular reactor. Differential scanning calorimeter analysis indicated that core–shell particles were formed under these conditions. © 2011 Canadian Society for Chemical Engineering     

Numerical simulation of a tubular polymerization reactor

A mathematical model for a tubular emulsion polymerization reactor is developed. The partial differential equations describing the mass balances on initiator, monomer, and number of polymer particles are numerically solved using an implicit–explicit scheme based on the Crank–Nicholson method. The model adequately simulates experimental results reported by Rollin and co-workers and sufficiently explains the unusual behavior of the reactor when operating at relatively low emulsifier concentrations.     

Transient behaviour of a non-ideal tubular reactor

Experimental data are reported for the unsteady state behaviour of a laminar flow reactor with first order homogeneous liquid phase reaction. The data are in agreement with the predictions of the dispersion model, using previously reported reaction-dependent dispersion coefficients which directly gives the bulk mean concentration. The use of proper boundary conditions, ignored in a recent paper on this topic⁽¹⁹⁾, is found to significantly influence the predictions. Unlike the conclusion drawn in⁽¹⁹⁾ it is shown that the Taylor model is unable to correctly predict the reactor length for fast reactions even for high conversions.