Patent ID: 8575414

Claim:
A two stage membrane separation process for treating a natural gas stream comprising sending said natural gas stream to a first-stage membrane to selectively remove hydrocarbons from C 3 to C 35 to control the dew point of natural gas, and a second-stage membrane to selectively remove CO2 from said natural gas, wherein said first-stage membrane comprises a polymer of intrinsic microporosity, wherein the said second-stage membrane comprises a cross-linked polybenzoxazole membrane prepared by fabricating a polyimide membrane from the hydroxyl- and UV crosslinkable functional group-containing polyimide polymer; converting the polyimide membrane to polybenzoxazole membrane by heating between 250° and 600° C. under inert atmosphere; and then converting the polybenzoxazole membrane to said crosslinked polybenzoxazole membrane by UV radiation.