Process for the separation of olefins from paraffins using membranes

A process to treat a gaseous feed stream comprising from 99 to 1 mole % of one or more C1-8 olefins and from 1 to 99 mole % of one or more C1-8 paraffins, said stream comprising less than 500 ppm of C2-4 acetylenes, said process comprising:

• (i) passing said stream through an adsorption bed to reduce the concentration of sulfur compounds in the stream to less than 100 ppm;
• (ii) passing the resulting stream through a humidifier so that the stream takes up at least 85% of the water required to saturate the stream;
• (iii) passing the resulting stream through a demister to remove any liquid droplets entrained in the stream;
• (iv) passing the resulting stream at a pressure from 14 to 1500 psig, and a temperature from 20° C. to 60° C. to the feed side of a composite membrane comprising a support layer permeable or semi-permeable to said olefin and a polysaccharide layer in which has been chelated from 30 to 60 weight % on a dry basis based on the weight of the polysaccharide layer of one or more compounds selected from the group consisting of copper and silver compounds capable of forming complexes with at least one olefin in said stream or a mixture thereof, so that not less than 80 mole % of the olefins in said feed stream pass through said composite membrane;
• and
• (v) recovering a permeate stream comprising not less than 90 mole % of olefin and not more than 10 mole % of paraffin.