Paraffin separation zeolite membranes

The preceding discussions illustrate that membranes have shown great potential as an alternative for olefin/paraffin separation, yet the performance of current membranes is insufficient for commercial deployment of this technology. Advanced material development is highly desired to improve the membrane properties and reduce cost. Another possible approach involves hybrid membranes with zeolites or CMS incorporated in a continuous polymer phase. More discussion in this regard will be covered later in this chapter. 

This cost differential can be tolerated only in applications in which polymeric membranes completely fail in the separation [78]. Demanding separation applications, where zeolite membranes could be justified, due to the high temperatures involved or the added value of the components, and have been tested at laboratory scale, are the following separation of isomers (i.e., butane isomers, xylene isomers), organic vapor separations, carbon dioxide from methane, LNG (liquefied natural gas) removal, olefines/paraffins and H2 from mixtures. In most cases, the separation is based on selective diffusion, selective adsorption, pore-blocking effects, molecular sieving, or combinations thereof. The performance or efficiency of a membrane in a mixture is determined by two parameters the separation selectivity and the permeation flux through the membrane. 

Several studies concerning the separation of propylene from propane base on faujasite (FAU zeolite) membranes or titanosilicate ETS have been published recently. The olefin/paraffin selectivity of all those materials was comparable to glassy polymers and always below 10. 

Shape selectivity was demonstrated by the separation of /i-paraffins from a naphtha distillate using a zeolite-CaA membrane [21]. The remaining fluid is enriched in branched parrafins and has a high octane number. 

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