The present invention discloses fluoropolymer coated membranes and methods
for making and using these membranes. The fluoropolymer coated membranes
described in the current invention are prepared by coating a porous
asymmetric membrane layer with a thin layer of fluoropolymer coating. The
porous asymmetric membrane layer comprises an asymmetric cellulosic
membrane, an asymmetric polymer membrane, or an asymmetric molecular
sieve/polymer mixed matrix membrane with a low selectivity and high
permeance. The fluoropolymer coating improves the selectivity of the
porous asymmetric membrane layer and maintains the membrane performance
with time. The fluoropolymer coated membranes are suitable for a variety
of liquid, gas, and vapor separations such as desalination of water by
reverse osmosis, non-aqueous liquid separation such as deep
desulfurization of gasoline and diesel fuels, ethanol/water separations,
pervaporation dehydration of aqueous/organic mixtures, CO.sub.2/CH.sub.4,
CO.sub.2/N.sub.2, H.sub.2/CH.sub.4, O.sub.2/N.sub.2, olefin/paraffin,
iso/normal paraffins separations, and other light gas mixture
separations.