Mathematical modeling the effect of catalyst initial shape and the crack pattern in olefin copolymerization

Document Type : Original research

Authors

1 Iran Polymer and Petrochemical Institute (IPPI), P. O. Box 14975/112, Tehran, Iran

2 Qom University of Technology, P. O. Box 1519-37195, Qom, Iran

Abstract

A two-dimensional (2D) single particle model for the copolymerization of propylene-ethylene with heterogeneous Ziegler-Natta catalyst is developed. The model accounts for the effects of the initial shape of the catalyst and carck/ pore patterns on the copolymer composition, polymerization rate and the average molecular weight properties. The spherical and oblate ellipsoidal shapes of catalyst particle and four different pattern distributions of cracks and pores in a growing particle are studied in this simulation. It is assumed that the diffusion coefficient of monomers in the cracks/pores is 10 times higher than the compact zone of the particle.In other word, the cracks are distinguished from parts with higher monomer diffusion coefficient.The dynamic 2D monomer diffusion-reaction equation is solved together with a two-site catalyst kinetic mechanism using the finite element method. Simulation results indicate that the initial shape of catalyst changes the average copolymer composition only in the early stage of polymerization, but the crack/pore patterns in the growing particle have a strong impact on the copolymer composition in the polymer particles due to the change ofmass transfer limitations.

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References

  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. Dube MA, Soares JBP, Penlidis A, Hamielec, JBP (1997) Mathematical modelling of multipcomponent chain-growth polymerizations in batch, semi-batch, and continuous reactors: A review. Ind Eng Chem Res 36: 966-1015
  3. Mattos Neto AG, Pinto JC (2001) Steady state modeling of slurry and bulk propylene polymerization. Chem Eng Sci 56: 4043–4057
  4. Schmeal WR, Street JR (1971) Polymerization in Expanding Catalyst Particles. AIChE J 17:1188-1197
  5. Singh D, Merrill RP (1971) Molecular weight distribution of polyethylene produced by Ziegler- Natta catalysts. Macromolecules 4: 599-604
  6. 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
  7. 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
  8. Floyd S, Choi KY, Taylor TW, Ray WH (1986) Polymerization of olefins through heterogeneous catalysis. III. Polymer particle modelling with an analysis of intraparticle heat and mass transfer effects. J Appl Polym Sci 32: 2935-2960
  9. 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
  10. 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: 389-1414
  11. Debling JA, Ray WH (1995) Heat and mass transfer effects in multistage polymerization processes: impact polypropylene. Ind Eng Chem Res 34: 3466-3480
  12. Hoel EL, Cosewith C, Byrne GD (1994) Effect of diffusion on heterogeneous ethylene propylene copolymerization. AIChE J 40: 1669-1684
  13. Sarkar P, Gupta SK (1991) Modelling of propylene polymerization in an isothermal slurry reactor. Polymer 32: 2842-2852
  14. Chen Y, Liu X (2005) Modeling mass transport of propylene polymerization on Ziegler-Natta catalyst. Polymer 46: 9434-9442
  15. Soares JBP, Hamielec AE (1995) General dynamic mathematical modeling of heterogeneous Ziegler- Natta and metallocene catalyzed copolymerization with multiple site types and mass and heat transfer resistances. Polym React Eng 3: 61-324
  16. Wang W, Zheng ZW, Luo ZH (2011) Coupled single-particle and Monte Carlo model for propylene polymerization. J Appl Polym Sci 119: 352-362
  17. Najafi M, Parvazinia M, Ghoreishy MH, Kiparissides C (2014) Development of a two dimensional finite element isothermal particle model to analyse the effect of initial particle shape and breakage in Ziegler-Natta olefin polymerization. Macromol React Eng 8: 29-45
  18. Soares JBP (2001) Mathematical modeling of the microstructure of polyolefins made by coordination polymerization: A review. Chem Eng Sci 56: 4131-4153
  19. Ahmadi M, Nekoomanesh M, Arabi H (2010) A simplified comprehensive kinetic scheme for modeling of ethylene/1-butene copolymerization using Ziegler-Natta catalysts. Macromol React Eng 4: 135-144
  20. Soares JBP, McKenna T, Cheng CP (2007) In: Polymer reaction engineering, Asua JM (ed) 1st ed, Blackwell, Ch. 2, 29-117
  21. Dompazis G, Kanellopoulos V, Touloupides V, Kiparissides C (2008) Development of a multiscale, multi-phase, multi-zone dynamic model for the prediction of particle segregation in catalytic olefin polymerization FBRs. Chem Eng Sci 63: 4735-4753
  22. Soares JBP, Hamielec AE (1996) Copolymerization of olefins in a series of continuous stirred-tank slurry-reactors using heterogeneous Ziegler-Natta and metalocene catalysts. I. General dynamic mathematical model, Polym Reac Eng 4: 153-191
  23. Najafi M, Parvazinia M, Ghoreishy MH (2014) Modelling the effects of fragment patterns on molecular properties and particle overheating in olefin polymerization. Polyolefins J 1: 77-91
  24. Najafi M, Parvazinia M (2015) Computational Modeling of Particle Fragmentation in the Heterogeneous Olefin Polymerization. Macromol Theory Simul 24: 28-40
  25. Zubov A, Pechackova L, Seda L, Bobak M, Kosek J (2010) Transport and reaction in reconstructed porous polypropylene particle: Model validation. Chem Eng Sci 65: 2361-2372

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History

  • Receive Date: 14 March 2015
  • Revise Date: 12 May 2015
  • Accept Date: 12 May 2015

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