(494e) Modeling the Oxygen Initiated High-Pressure Polymerization of Ethylene in Tubular Reactors
AIChE Annual Meeting
2013
2013 AIChE Annual Meeting
Computing and Systems Technology Division
Modeling and Control of Polymer Processes: A Tribute to John P. Congalidis III
Wednesday, November 6, 2013 - 1:46pm to 2:05pm
For the industrial high-pressure polymerization of ethylene in tubular reactors organic peroxides, oxygen or a combination of both are used as initiators. Oxygen acts furthermore as an inhibitor in a very complex way.[1] Previous publications dealing with oxygen initiated ethylene polymerizations trace back to simplified mechanisms or regression methods.[2,3] In the last case, the resulting phenomenologically fitted reaction rate coefficients can only be used in terms of a coupled dataset. They cannot be extracted and applied detachedly from each other. In this connection, our goal was to derive arrhenius parameters, which can be used in combination with independently measured coefficients from laboratory scale experiments (e.g. coefficients given by Busch).[4] Furthermore, we extended the existing mechanism of Brandolin et al. and supplemented an additional reaction step.[3] The resulting approach allows a good agreement of experimental and simulated temperature profiles as well as microstructural homo and co polymer properties.
Within the inhibition reaction a growing macroradical reacts with an oxygen molecule yielding an oxygen terminated chain with a radical functionality.[2] At this point we assume a subsequent inhibition reaction of the oxygen terminated chain and a second growing macroradical. The resulting macroperoxide slowly decomposes at higher temperatures and re initiates the polymerization. This reaction sequence causes smoothly curved temperature profiles with very broad temperature maxima, which are characteristic for the oxygen initiated process.
A hybrid simulation method is used to model the complex polymerization network. The approach combines the advantages of stochastic and deterministic modeling. It offers a deep insight into the polymeric microstructure of individual macromolecules. In this connection, the exact position of incorporated oxygen or co monomer and the unique branching structure is accessible. Furthermore, the topologic information is used to handle the β-scission in a topological correct way and to determine contraction factors as well as seniority priority distributions.
[1] R. C. M. Zabisky, W. M. Chan, P. E. Gloor, A. E. Hamielec, Polymer 1992, 33, 2243.
[2] Y. Tatsukami, T. Takahashi, H. Yoshioka, Makromol. Chem. 1980, 181, 1107.
[3] A. Brandolin, M. H. Lacunza, P. E. Ugrin, N. J. Capiati, Polym. React. Eng. 1996, 4, 193.
[4] M. Busch, Macromol. Theory. Simul. 2001, 10, 262.
Topics
Checkout
This paper has an Extended Abstract file available; you must purchase the conference proceedings to access it.
Do you already own this?
Log In for instructions on accessing this content.
Pricing
Individuals
AIChE Pro Members | $150.00 |
AIChE Graduate Student Members | Free |
AIChE Undergraduate Student Members | Free |
AIChE Explorer Members | $225.00 |
Non-Members | $225.00 |