Modeling and Simulation of Olefin Polymerization at Microstructure Level

Document Type: Research Article

Authors

Polymer Engineering Group, Department of Chemical and Petroleum Engineering, Sharif University of Technology, P.O. Box 11155-9465 Tehran, I.R. IRAN

Abstract

A new model based on a combination of the polymeric multigrain and multilayer models has been developed to predict the polymerization rate, particle growth, morphology, effective parameters on broadening of the molecular weight distribution, number and weight average of the molecular weight, isotacticity index and bulk density of polymer. Mathematical correlations and the kinetics used in this model are based on the polymeric multigrain and the multilayer models, respectively. In the modeling, multiplicity of active site using different kinetics parameters as well as deactivation of catalyst during the polymerization have been considered,. Moreover, it considers mass transfer effects on polymerization characteristics. The Effects of physico-chemical aspects of catalyst associated with the polymerization in slurry phase are also considered in this model. In addition, the effects of more important model parameters including time step, number of layers and number of active sites on the produced polymer features are reviewed. The model predictions show that propagation rate constant, multiplicity of active site, concentration of any individual active site type, and the initial size of the catalyst particles have considerable effects on the properties of the final polymer. The results obtained from simulation with this new combined model confirm at least better qualitative prediction of the polymerization characteristics in comparison with simulation results of the multigrain model (MGM) and the two models mentioned above.

Keywords

Main Subjects


[1] Agarwal, U.S., Modelling Olefin Polymerization on Heterogeneous Catalyst: Polymer Resistance at the Microparticle Level, Chemical Engineering Science, 53, 3941 (1998).
[2] Boor, J., “Ziegler-Natta Catalysts and Poly-merization”, Academic Press, New York (1979).
[3] Singh, D. and Merrill, R. P., Molecular Weight Distribution of Polyethylene Produced by Ziegler-Natta Catalysts, Macromolecules, 4(5), 599 (1971).
[4] Schmeal, W.R., Street, J.R., Polymerization in Expanding Catalysts, AIChE J., 17 (5), 1189 (1971).
[5] Floyd, S., Choi, K Y., Taylor, T. W. and Ray, W. H., Polymerization of Olefins through Heterogeneous Catalysis, IV. Modeling of Heat and Mass Transfer Resistance in the Polymer Particle Boundary Layer, Journal of Applied Polymer Science, 31, 2231 (1986a).
[6] Floyd, S., Choi, K. Y., Taylor, T. W. and Ray, W. H., Polymerization of Olefins through Heterogeneous Catalysis, III. Polymer Particle Modeling with an Analysis of Intraparticle Heat and Mass Transfer Effects, Journal of Applied Polymer Science, 32, 2935 (1986b).
[7] Galvan, R. and Tirrell, M., Molecular Weight Distribution Predictions for Heterogeneous Ziegler-Natta Polymerization using a Two-Site Model, Chemical Engineering Science, 41, 2385 (1986).
[8] Sarkar, P., Gupta, S.K., Modelling of Propylene Polymerization in an Isothermal Slurry Reactor, Polymer, 32 (15), 2842 (1991).
[9] Sarkar, P., Gupta, S.K., Simulation of Propylene Polymerization: an Efficient Algorithm, Polymer, 33 (7), 1477 (1992).
[10] Hutchinson, R. A., Chen, C. M. and Ray, W. H., Polymerization of Olefins through Heterogeneous Catalysis, X. Modeling of Particle Growth and Morphology, Journal of Applied Polymer Science, 44, 1389 (1992).
[11] Soares, J.B.P., Hamielec, A.E., General Dynamic Mathematical Modeling of Heterogeneous Ziegler-Natta and Metallocene Catalyzed Copolymerization with Multiple Site Types and Mass and Heat Transfer Resistances, Polym. Reac. Eng., 3(3), 261 (1995).
[12] Kanellopoulos, V., Dompazis, G., Gustafsson, B. and Kiparissides, C., Comprehensive Analysis of Single-Particle Growth in Heterogeneous Olefin Polymerization: The Random-Pore Polymeric Flow Model, Ind. Eng. Chem. Res., 43 (17), 5166 (2004).
[13] Nagel, E. J., Kirillov, V. A. and Ray, W. H., Prediction of Molecular Weight Distributions for High-Density Polyolefins, Industrial & Engineering Chemistry Product Research and Development, 19, 372 (1980).
[14] Floyd, S., Heiskanen, T., Taylor, T. W., Mann, G. E. and Ray, W. H., Polymerization of Olefins through Heterogeneous Catalysis, VI. Effect of Particle Heat and Mass Transfer on Polymerization Behavior and Polymer Properties, Journal of Applied Polymer Science, 33, 1021 (1987).
[15] De Carvalho, A.B., Gloor, P.E., Hamielec, A.E., A Kinetic Mathematical Model for Heterogeneous Ziegler-Natta Copolymerization, Polymer, 30, 280 (1989).
[16] McAuley, K.B., MacGregor, J.F., Hamielec, A.E., A Kinetic Model for Industrial Gas-Phase Ethylene Polymerization, AIChE J., 36 (6), 837 (1990).
[17] Li, J., Tekie, Z., Mizan, T. I. and Morsi, B. I., Gas-Liquid Mass Transfer in a Slurry Reactor Operating Under Olefininc Polymerization Process Conditions, Chemical Engineering Science, 51(4), p. 549 (1996).
[18] Dashti,  A.,  Modeling  of  Particle  Growth  and Morphology of Slurry Phase Polypropylene Polymerization Using Heterogeneous Ziegler Natta Catalysts, M.Sc. Thesis, Sharif University of Technology, Tehran, (2003).