Fernand Pla

Optimization and non-linear control of a batch emulsion polymerization reactor

The optimal temperature policy which minimizes the terminal time in a batch emulsion polymerization reactor of styrene and α-methylstyrene was determined by means of orthogonal collocation techniques combined with a general non-linear programming method. The constraints concern the final latex properties and the thermal limitations of the pilot plant. An experimental validation has been realized. The optimal temperature profile was tracked using a non-linear geometric control technique which is particularly adapted to polymerization reactor control. An extended Kalman filter was used to estimate the non-measured state variables. Experimental results showed excellent agreement with predictions for this complex system. A good temperature tracking was observed and the product quality was well predicted and controlled.

Studies on chemical oxidative copolymerization of aniline and o-alkoxysulfonated anilines:: I. Synthesis and characterization of novel self-doped polyanilines

Abstract The chemical oxidative copolymerization of aniline (An) with o -alkoxysulfonated anilines, i.e., 1-( o -amino)-propane-3-sulfonic acid (APPrS) and 1-( o -amino)-butane-3-sulfonic acid (APBuS), was a new way to produce water-soluble and self-doped polyaniline derivatives. Poly(An- co -APPrS) and poly(An- co -APBuS) were obtained in H 2 SO 4 acidic medium by chemical oxidation, using ammonium persulfate, of a comonomer mixture containing An and APPrS, or APBuS, in various initial ratios. The copolymers thus obtained with high or low yields, were characterized by elemental microanalysis, FTIR spectroscopy, size exclusion chromatography and conductivity measurements. Due to the electron-donating effects of the alkoxysulfonated groups, the two aniline-derivatives were easily incorporated in the macromolecular chains and strongly enhanced water-solubility of the products. The electrical conductivities of these copolymers, which depend on both self- and external-dopings, were reduced by the incorporation of alkoxysulfonated substituents compared with the one of parent polyaniline.

Nonlinear adaptive control of batch styrene polymerization

Abstract A nonlinear control strategy-input/output linearizing by nonlinear state feedback-is suitable for trajectory tracking in batch processes. But based closely on the system model, the controller is sensitive to model parameter errors, which limit its application. In this paper, a technique of adaptive control of linearizable systems, together with an extended Kalman filter, was applied to a simulated batch styrene polymerization reactor to realize the output (extent of reaction) tracking in the presence of model parameter uncertainties. Simulation results show that this technique can ensure the output tracking performance even in the presence of two model parameter uncertainties, the first one being the gel effect, the other one the heat transfer coefficient.

Multicriteria optimization of an emulsion polymerization process

Abstract This study deals with the development of a multicriteria optimization procedure and its application to emulsion polymerization processes for which several criteria, related to the productivity and to the quality of the final materials (in terms of end use properties), must be optimized simultaneously. An approach by Pareto domain determination and ranking by decision making support is presented.

Multicriteria optimization and decision engineering of an extrusion process aided by a diploid genetic algorithm

In many, if not most, optimization problems, industrialists are often confronted with multiobjective decision problems. For example, in manufacturing processes, it may be necessary to optimize several criteria to take into account all the market constraints. So, the purpose is to choose the best tradeoffs among all the defined and conflicting objectives. In multicriteria optimization, after the decision maker has chosen all his objectives, he has to determine the multicriteria optimal zone by using the concept of domination criterion called Pareto domination. Two points in the research domain are compared. If one is better for all attributes, it is a nondominating solution. All the nondominating points form the Paretos region. In this paper, several multiobjective optimization algorithms are used to obtain this zone. These methods are based on a diploid genetic algorithm and are compared to an industrial application: food granulation. In the optimal zone, the decision maker has to choose the best solution after he has made a ranking with all potential solutions. A partition is made and the decision maker has more information on the process. Finally, a decision support system shell is developed in order to classify all solutions.

Multicriteria dynamic optimization of an emulsion copolymerization reactor

Abstract A multicriteria optimization approach based on an evolutionary algorithm has been developed to determine the optimal control policy for a fed-batch emulsion copolymerization reactor, particularly for styrene and butyl acrylate in the presence of n-C12 mercaptan as chain transfer agent. The process model was elaborated and validated experimentally in order to predict the global monomer conversion, the number and weight average molecular weights, the particle size distribution and the residual monomers mass fraction. The process objectives were to produce core–shell particles (hard core and smooth shell) with specific end-use properties and high productivity. This has been achieved by the maximization of the monomers overall conversion at the end of the process and the minimization of the error between the glass transition temperature and a designed profile subject to a set of operational constraints. The nondominated Pareto solutions obtained were ranked according to a decision making aid method based on a decision maker preferences and experience using multi-attribute utility theory. Finally, the best solution was implemented experimentally.

Selective hydrogenation of butadiene–styrene copolymers using a Ziegler–Natta type catalyst: 1. Kinetic study

Abstract The hydrogenation of styrene–butadiene copolymers of known global composition, monomeric distribution, molecular weight and microstructure is here reported. The saturation was carried out through a sequential polymerization–hydrogenation process which efficiency relies on the use of the polymerization solvent and initiator (cyclohexane and n -butyllithium) as the hydrogenation solvent and catalyst promoter, respectively. The SBRs, dissolved in cyclohexane, were homogeneously hydrogenated using a Ziegler–Natta type catalyst, prepared with nickel acetylacetonate and n -butyllithium. The only species, which was not present in both parts of the global process, is the catalyst for the homogeneous hydrogenation: nickel acetylacetonate. Three types of SBRs were investigated on the basis of their monomeric distribution: diblock (D-SBR), triblock with polystyrene extremes (T-SBR) and random (R-SBR). All the copolymers studied were synthesized by anionic solution polymerization. The precursors and corresponding hydrogenated polymers were analyzed by infrared spectroscopy (FTIR) and nuclear magnetic resonance ( 1 HNMR) to determine the 1,2-vinyl and 1,4- trans double bond content in the butadiene portion of the copolymers. These data were used to calculate the saturation degree, X , considering the amount of double bonds of the precursor copolymers and the corresponding hydrogenated copolymer: X =( C i 0 − C i )/ C i 0 .

Studies on chemical oxidative copolymerization of aniline and o-alkoxysulfonated anilines II. Mechanistic approach and monomer reactivity ratios

Abstract The copolymerization of aniline (An) with o-alkoxysulfonated anilines, i.e. 1-(o-amino)-propane-3-sulfonic acid (APPrS) and 1-(o-amino)-butane-4-sulfonic acid (APBuS), was a new way to produce water-soluble and self-doped polyaniline derivatives. Poly(An-co-APPrS) and poly(An-co-APBuS) were synthesized, in H2SO4 acidic medium, by chemical oxidation using ammonium persulfate. The mechanistic study showed that, during their copolymerization, aniline and alkoxysulfonated-derivatives exhibit two opposite behaviors towards the initial mechanism of dimerization and the following growing process. Because of the steric hindrance of the bulky alkoxysulfonated groups, the dimerization process involved at least one molecule of aniline. On the contrary, in the course of the propagation step, due to the electron-donating effect of the substituent, both alkoxysulfonated anilines exhibited much greater reactivity than aniline and hence were easily incorporated into the growing polymer chains. The comonomer reactivity ratios, computed by using the extended Kelen–Tudos method, were as follows: rAn=0.04±0.01, rAPPrS=27±9 and rAn=0.04±0.01, rAPBuS=12±6. These findings strongly suggest the formation of block copolymers.

Selective hydrogenation of butadiene–styrene copolymers using a Ziegler–Natta type catalyst 2. Thermal properties

Abstract Three types of butadiene–styrene copolymers, diblock, triblock and random, were partially hydrogenated in their elastomeric units in order to determine the influence of hydrogenation extent on their thermal properties. The hydrogenation reactions were carried out using a Ziegler–Natta type catalyst and the extent of hydrogenation was evaluated by FTIR spectroscopic technique. The percentage of crystallinity was determined by differential scanning calorimetry (DSC), considering the low density polyethylene (LDPE) as reference since the saturation of elastomeric units with low content of 1,2-vinyl bonds gives a structure which resembles to LDPE, thus semi-crystalline polymers were obtained. On the other hand, the glass transition temperature ( T g ) for the hydrogenated and non-hydrogenated copolymers as well as their heat of fusion, were also determined by DSC. An equation to evaluate the T g of partially hydrogenated random copolymers is proposed considering both the saturated and unsaturated fractions. The thermo-oxidative behaviour of certain hydrogenated and non-hydrogenated copolymers was evaluated by thermogravimetric analyses (TGA). The results obtained by TGA suggest that a minimum saturation level is necessary in order to improve the thermo-oxidative resistance of the polymers.

Experimental study of the nonlinear geometric control of a batch emulsion polymerization reactor

Abstract The industrial interest in controlling polymerization reactors is great. The present study is an illustration of productivity improvement and good polymer quality control by modern control techniques (optimal control, nonlinear geometric control, nonlinear state estimation). Furthermore, these techniques are applied to a complex polymerization reaction: emulsion polymerization which still remains difficult to control, because of the complex phenomena involved.