Stable Facilitated Transport Membrane For Olefin/Paraffin Separation

Currently, the separation of olefins (ethylene, propylene) from paraffins (ethane, propane) on a commercial scale is accomplished almost exclusively by cryogenic distillation in petrochemical industries and is considered highly energy intensive.  Consequently, there is an enormous economic incentive to explore alternative separation technologies with lower energy consumption and an opportunity to achieve related reductions in environmental impact from air pollutant and greenhouse gas (GHG) emissions.

Several attempts have been made in the past to develop alternative separation technologies for this application, including significant work on facilitated transport membranes. One of the main unresolved challenges was membrane instability over time. Imtex Membranes Corporation has developed a membrane that has shown performance stability over thousands of hours of operation on both coupons and spiral wound test units. Imtex membranes are based on Chitosan, a polysaccharide material, and silver nitrate as a facilitation agent.

LyondellBasell and Imtex Membrane Corporation have set up a collaborative effort to evaluate the performance of Imtex membrane in the olefin/paraffin separation, namely C2 and C3 splitter applications.    

The performance results were very encouraging for C2 and C3 splitters as greater than 99.5% purity and 90% recovery were achieved in both cases. Based on the membrane performance results, we believe that the technology presents potential opportunities in upgrading refinery grade propylene to polymer grade propylene as the membrane was evaluated under operating conditions comparable to those of commercial plants.

There is also a promising potential for butene/butane separations where distillation separations require large numbers of trays and extremely high reflux ratios, or are difficult to achieve at all. Applying Imtex membranes in C4 separation can have a very positive impact on the economics of olefin metathesis, an increasingly important source of propylene.