Modelling the catalyst fragmentation pattern in relation to molecular properties and particle overheating in olefin polymerization

Document Type : Original research


Iran Polymer and Petrochemical Institute, P.O. Box: 14975/112, Tehran, Iran


A two-dimensional single particle finite element model was used to examine the effects of particle fragmental pattern on the average molecular weights, polymerization rate and particle overheating in heterogeneous Ziegler-Natta olefin polymerization. A two-site catalyst kinetic mechanism was employed together with a dynamic two-dimensional molecular species in diffusion-reaction equation. The initial catalyst active sites distribution was assumed to be uniform, while the monomer diffusion coefficient was considered to be different inside the fragments and cracks. In other words, the cracks were distinguished from fragments with higher monomer diffusion coefficient. To model the particle temperature a lumped heat transfer model was used. The fragmentation pattern was considered to remain unchanged during the polymerization. A Galerkin finite element method was used to solve the resulting two-dimensional (2-D) moving boundary value, diffusion-reaction problem. A two-dimensional polymeric flow model (PFM) was implemented on the finite element meshes. The simulation results showed that the fragmentation pattern had effects on the molecular properties, reaction rate and the particle temperature at early stages of polymerization.


Main Subjects

  1. McKenna TF, Soares JBP (2001) Single particle modelling for olefin polymerization on supported catalysts: A review and proposals for future developments. Chem Eng Sci 56: 3931–3949
  2. McKenna TF, Di Martino A, Weickert G, Soares JBP (2010) Particle growth during the polymerisation of olefins on supported catalysts, 1-nascent polymer structures. Macromol React Eng 4: 40–64
  3. Schmeal WR, Street JR (1971) Polymerization in expanding catalyst particles, AIChE J 17: 1188- 1197
  4. Singh D, Merrill RP (1971) Molecular weight distribution of polyethylene produced by Ziegler- Natta catalysts. Macromolecules 4: 599-604
  5. Galvan R, Tirrell M (1986) Molecular weight distribution predictions for heterogeneous Ziegler-Natta polymerization using a two-site model. Chem Eng Sci 41: 2385-2393
  6. Byrne GD (1993) The taming of co-polymerization problem with VODE. Impact Comput Sci Eng 5: 318-344
  7. Hoel EL, Cozewith C, Byrne GD (1994) Effect of diffusion on heterogeneous ethylene propylene copolymerization. AIChE J 40: 1669-1684
  8. Veera UP, Weickert G, Agarwal US (2002) Modeling monomer transport by convection during olefin polymerization. AIChE J 48: 1062- 1070
  9. Kanellopoulos V, Dompazis G, Gustafsson B, Kiparissides C (2004) Comprehensive analysis of single-particle growth in heterogeneous olefin polymerization: The random - pore polymeric flow model. Ind Eng Chem Res 43: 5166-5180
  10.  Nagel EJ, Klrillov VA, Ray WH (1980) Prediction of molecular weight distributions for high-density polyolefins. Ind Eng Chem Prod Res Dev 79: 372-379
  11. Floyd S, Choi KY, Taylor TW, Ray WH(1986) Polymerization of olefins through heterogeneous catalysis. III. Polymer particle modelling with an analysis of intra particle heat and mass transfer effects. J Appl Polym Sci 32: 2935-2960
  12. Floyd S, Choi KY, Taylor TW, Ray WH (1986) Polymerization of olefins through heterogeneous catalysis. IV. Modeling of heat transfer resistance in the polymer particle boundary Layer. J Appl Polym Sci 31: 2231-2265
  13. Floyd S, Heiskanen T, Taylor TW, Mann GE, Ray WH (1987) Polymerization of olefins through heterogeneous catalysis. VI. Effect of particle heat and mass transfer on polymerization behavior and polymer properties. J Appl Polym Sci 33: 1021- 1065
  14. Hutchinson RA, Chen CM, Ray WH (1992) Polymerization of olefins through heterogeneous catalysts X: Modelling of particle growth and morphology. J Appl Polym Sci 44: 1389
  15. Weickert G, Meier GB, Pater JTM, Westerterp KR (1999) The particle as a microreactor: Catalytic propylene polymerization with supported metallocene and Ziegler–Natta catalysis. Chem Eng Sci 54: 3291
  16. Mckenna TF, Dupuy J, Spitz R (1995) Modeling of transfer phenomena on heterogeneous Ziegler catalysts: Differences between theory and experiment in olefin polymerization (an introduction). J Appl Polym Sci 57: 371-384
  17. Mckenna TF, Dupuy J, Spitz R (1997) Modeling of transfer phenomena on heterogeneous Ziegler catalysts. III. Modeling of intraparticle mass transfer resistance. J Appl Polym Sci 63: 315–322
  18. Mckenna TF, Mattioli V (2001) Progress in describing particle growth for polyolefins: A look at particle morphology, Macromol Symp 173: 149-162
  19. Kosek J, Grof Z, Novak A, Stepanek F, Marek M (2001) Dynamics of particle growth and overheating in gas-phase polymerization reactors. Chem Eng Sci 56: 3951–3977
  20. Dompazis G, Kanellopoulos V, Touloupides V, Kiparissides C (2008) Development of a multi-scale, multi-phase, multi-zone dynamic model for the prediction of particle segregation in catalytic olefin polymerization FBRs. Chem Eng Sci 63: 4735-4753
  21. Ferrero MA, Chiovetta MG (1987) Catalyst fragmentation during propylene polymerization: Part I: The effects of grain size and structure. Polym Eng Sci 27: 1436
  22. Ferrero MA, Chiovetta MG (1987) Catalyst fragmentation during propylene polymerization: Part II: Microparticle diffusion and reaction effects. Polym Eng Sci 27: 1448-1460
  23.  Alexiadis A, Andes C, Ferrari D, Korber F, Hauschild K, Bochmann M, Fink G (2004) Mathematical modeling of homopolymerization on supported metallocene catalysts. Macromol Mater Eng 289: 457–466
  24. Bonini F, Fraaije V, Fink G (1995) Propylene polymerization through supported metallocene/ MAO catalysts: kinetic analysis and modelling. J Polym Sci Part A Polym Chem 33: 2393-2402
  25. Kittilsen P, Svendsen H, Mc Kenna TF, Jakobsen HA, Fredriksen SB (2001) The interaction between mass transfer effects and morphology in heterogeneous olefin polymerization. Chem Eng Sci 56: 4015-4024
  26. Kittilsen P, Svendsen H, Mc Kenna TF (2003) Viscoelastic model for particle fragmentation in olefin polymerization. AIChE J 49: 1495-1507
  27. Kittilsen P, Svendsen H (2004) Three-level mass-transfer model for the heterogeneous polymerization of olefins. J Appl Polym Sci 91: 2158–2167
  28. Grof Z, Kosek J, Marek M (2005) Modeling of morphogenesis of growing polyolefin particles. AIChEJ 51: 2048–2067
  29. Grof Z, Kosek J, Marek, M (2005) Principles of the morphogenesis of polyolefin particles. Ind Eng Chem Res 44:2389-2404
  30. Horackova B, Grof Z, Kosek J (2007) Dynamics of fragmentation of catalyst carriers in catalytic polymerization of olefins. Chem Eng Sci 62: 5264-5270
  31. Bobak M, Gregor T, Bachman B, Kosek J (2008) Estimation of morphology characteristics of porous poly (propylene) particles from degassing measurements. Macromol React Eng 2: 176–189
  32. Machado F, Lima EL, Pinto JC, Mc Kenna TF (2001) An experimental study on the early stages of gas-phase olefin polymerizations using supported Ziegler–Natta and metallocene catalysts. Polym Eng Sci 51: doi/10.1002/pen.v51.2/issuetoc302–310
  33. Najafi M, Parvazinia M, Ghoreishy MHR, Kiparissides C (2013) Development of a 2D single particle model to analyze the effect of initial particle shape and break agein olefin polymerization. Macromol React Eng 8: 29-45
  34. Hatzantonis H, Yiannoulakis H, Yiagopoulos A, Kiparissides C (2000) Recent developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors: The effect of bubble size variation on the reactor’s performance. Chem Eng Sci 55: 3237-3259
  35. De Carvalho AB, Gloor PE, Hamielec AE (1989) A kinetic mathematical model for heterogeneous Ziegler-Natta copolymerization. Polymer 30: 280–296
  36. Mc Auley KB, Mac Gregor JF, Hamielec AE (1990) Kinetic model for industrial gas-phase ethylene copolymerization. AIChE J 36: 837-850
  37. Sun J, Eberstein C, Reichert KH (1997) Particle growth modeling of gas phase polymerization of butadiene. J Appl Polym Sci 64: 203-212
  38. Yiagopoulos, A, Yiannoulakis H, Dimos V, Kiparissides C (2001) Heat and mass transfer phenomena during the early growth of a catalyst particle in gas-phase olefin polymerization: the effect of prepolymerization temperature and time. Chem Eng Sci 56: 3979–3995