Adsorptive separation of light olefins from paraffins

Equilibrium and kinetic data for the sorption of light olefins and paraffins are reviewed. The equilibrium selectivities of cation rich zeolites are about 12 (at ordinary temperatures) but, since the desired pure product (the olefin) is the preferentially adsorbed species this has proved insufficient to achieve the required product purity without recourse to complex process cycles. Recent research has therefore focused on the possibility of developing a kinetic separation based on differences in sorption rate. In recent patents [5] and [6] it has been shown that certain 8-ring silica zeolites, notably SiCHA and DD3R, show surprisingly high kinetic selectivities (DC3H6/DC3H8∼104DC3H6/DC3H8∼104), suggesting that a kinetic separation process should be practically feasible and should be capable of yielding a high purity olefin product.