Impact of Impurities on Carbon Molecular Sieve Membranes for Applications in Olefins Units

The separation of olefins from paraffins is important in the petrochemical industry.The current dominant technology, cryogenic distillation, is highly energy intensive. In 2013 we reported on the use of carbon molecular sieve (CMS) membranes in a hybrid membrane-distillation process to improve energy use with resulting lower energy or increased production.

The CMS membranes are produced by pyrolyzing polyimides like 6FDA:BPDA-DAM and show improved production (flux) and exceptional separation (selectivity) when compared to the precursor polymer and polymeric membranes in general.

The impact of impurities on the CMS membrane must be understood in order to use it in actual production plant applications. This paper will discuss common impurities found in the ethylene plant’s purification train, specifically, the potential impact of these impurities on the membrane. These impurities include hydrogen sulfide, water, carbon dioxide, acetylenics, and carbon monoxide.