Phase equilibria effect on catalytic olefin polymerization
May 20-25, 2018
There are many reasons why phase equilibria during the catalytic polymerization are important and why many researches are interested in exploring them. In any type of catalytic polymerization (solution, slurry, gas-dispersion) the proportional relation of the monomer concentration at the active catalyst site to the polymerization rate is essential. Phase equilibria between a solvent, polymer, monomer(s) and co-monomer(s) and related transport processes are important not only for the polymerization kinetics itself, but also the polymer structure formation or subsequent product degassing are closely related to them. Nowadays many experimental techniques are available (e.g. DSC with pressure cell, low-field NMR, (co-)sorption balances), thus the thermodynamics of polyolefins is persistently studied and a lot of new quantitative knowledge about polyolefin thermodynamics was accumulated. But still there is a need for new data required by new or existing production processes and new grades of polyolefins.
In this contribution we present data relevant for gas-phase and slurry polymerization, i.e. sorption equilibria of polymer/solvent(g) and polymer/diluent(l) systems respectively. Sorption of gaseous penetrants in polymer particles was measured by gravimetric method and the results go hand in hand with swelling data measured in video-microscopic apparatus. Thus we gradually developed a huge database of experimental results including sorption of commonly used hydrocarbon penetrants (C2-C7) in various polyethylene and polypropylene samples (covering the full spectrum of commercially produced grades) at different temperatures (relevant to polymerization conditions). Moreover, by using a pressure-decay apparatus we are able to determine also kinetic parameter – diffusion coefficient of gases in polyolefin particles.
Sorption of liquid penetrants in polyolefins was measured using new methodology developed in our laboratory and we present results for the system polymer (PE or PP) and liquid hydrocarbon (C6-C8). Solubilities are measured at different temperatures. Next we present swelling equilibria of polyolefin particles in various liquid diluents and preliminary results of co-swelling experiments for the system PE-hexane-ethylene are discussed.
Podivinská M., Jindrová K., Chmelař J., Kosek J.: Swelling of polyethylene particles and its relation to sorption equilibria under gas-phase polymerization conditions, Journal of Applied Polymer Science, 2017, 45035: 1-7.
Chmelař, J., R. Pokorný, P. Schneider, K. Smolná, P. Bělský and J. Kosek (2015). "Free and constrained amorphous phases in polyethylene: Interpretation of 1H NMR and SAXS data over a broad range of crystallinity." Polymer 58: 189-198.
Chmelař J., Smolná K., Haškovcová K., Podivinská M., Maršálek J., Kosek J.: Equilibrium sorption of ethylene in polyethylene: Experimental study and PC-SAFT simulations, Polymer, 2015, 59: 270-277.
Chmelař J., Haškovcová K., Podivinská M., Kosek J.: Equilibrium Sorption of Propane and 1‑Hexene in Polyethylene: Experiments and Perturbed-Chain Statistical Associating Fluid Theory Simulations, Industrial and Engineering Chemistry Research, 2017, 56, 6820−6826.
Lenka Krajáková, Martina Podivinská, and Juraj Kosek, "Phase equilibria effect on catalytic olefin polymerization" in "Polymer Reaction Engineering X (PRE 10)", John Tsavalas, University of New Hampshire, USA Fouad Teymour, Illinois Institute of Technology, USA Jeffrey Stubbs, HP Inc., USA Jose R. Leiza, University of the Basque Country, Spain Eds, ECI Symposium Series, (2018). http://dc.engconfintl.org/prex/26