In the bulk, catalyzed polymerization of propene in an industrial-scale recycle reactor, propane is an important
contaminant, and for this reason it is necessary to remove it from the reaction medium in order to maintain
high process productivities. In a typical industrial operation, unreacted propene/propane mixtures are purged
from the recycle stream and vented to a flare, causing a significant negative impact on the process economics.
Despite the potential economic advantages that membrane-based propene recovery may represent industrially,
a comprehensive analysis based on a detailed mathematical model of the system is not available yet. The
main purpose of this study is presenting a mathematical model to simulate the separation of propene/propane
mixtures in a polymerization system using membrane modules. The model developed takes into account two
extreme levels of macromixing that may be observed in the permeation module (namely, perfect mixing and
plug flow), the diffusion of the gaseous mixture through the polymeric membrane, and the effect of operational
variables such as temperature, pressure, flow rates, composition, and membrane area on the separation
performance. It is shown that polyimide-based membranes, such as 6FDA−TMPPD (2,2-bis(3,4-decarboxyphenyl)hexafluoropropane dianhydride and 2,3,5,6-tetramethyl-1,4-phenylenediamine), may be used in
permeation modules to deliver up to 5% gains in the effective propene concentration at the reactor feed,
therefore increasing significantly the reactor productivity. An economic analysis shows that an economic
gain of up to U.S.$1.5 million per year per polymerization plant may be attained.