Chemical Engineering Graduate Seminar

Abstract

Despite decades of academic and industrial research, there still remains large gaps in our fundamental understanding of the complex interactions between the molecular-, micro-, meso- and macroscale phenomena during the polymerization of olefins on supported catalysts as shown in the figure above.  Over the past several years we have been trying to understand these relationships at many different levels.  For the time being we are trusting our chemist colleagues to help elucidate the complexity of the functioning of the active sites of the catalyst, and have focused on issues related to:

1. The transport of active species from the continuous phase to the active sites.  This is going to be governed by the “usual suspects” (i.e. concentration gradients, temperature etc.), but also by the morphology of the growing particles and perhaps more surprisingly by the presence of chemically inactive species present in the reactor to help with heat transfer or as the dispersive medium.  It is clear than an enhanced understanding of the thermodynamics is far more important than we thought. 
2. Polymer Properties are determined by many things, but surprisingly enough to the presences of these same inert compounds.  Recent developments show that it is possible to adjust the concentrations and the nature of inert species to make ultrahigh MW polyethylene in gas phase processes.
3. Polymer particle morphology is clearly a key issue.  We have been exploring the impact of many different factors on polymer particle morphology, which requires specially adapted tools such as stopped flow reactors to capture realistic pictures of what is happening to the particles in the reactor.

This talk will focus on these three points, and we will conclude with some proposals for future important process engineering-related points.

Bio

Timothy McKenna is originally from Canada, where he got his Bachelor’s degree in chemical engineering from McMaster University.  He was fortunate enough to have spent a summer working in the laboratory of Professor Archie Hamielec, which helped him to develop a very strong interest in polymers.  Following his Bachelor’s degree, he completed a PhD, also in Chemical Engineering at the University of Massachusetts at Amherst in 1989.  Upon graduating he moved to France to work for Elf-Aquitaine (now part of Total), where he spent 2 years developing process models of their gas phase UNIPOL process.  As this modelling project led to far more questions than answers about how things work, he opted for a career in academia.  He was fortunate enough to have found a position with the CNRS (Centre National de Recheche Scientifique) in Lyon in 1993, and he has worked there full time since them.  He has been responsible for developing a research programme in polymer reaction engineering for over 30 years, focussing on both emulsion polymerization and on processes for the polymerization of olefins on supported catalysts.  He is currently a Directeur de Recherche Classe Exceptionnelle of the CNRS, and director of the Laboratory for Catalysis, Polymers, Processes and Materials at the University Claude Bernard Lyon 1.