High carbon content filamentary membrane and method of making the same

A high carbon content membrane and method for making the same are disclosed. The carbon membrane includes an asymmetric hollow filamentary carbon membrane, including a partial carbonization product of an asymmetric hollow filament including an aromatic imide polymer material. The carbon membrane is at least 95 weight percent carbon, and has a dense layer located in the outside surface portion of the hollow filamentary membrane and a porous base layer continued from the dense layer and located in the inside portion of the hollow filamentary membrane. A process for separating CO2 from natural gas is described including: contacting a mixture of CO2 and natural gas with a first side of a carbon membrane in a manner to cause a portion of the mixture to pass through the carbon membrane to a permeate side. The resulting mixture on the permeate side becomes enriched in CO2 over that of the mixture on the first side. The contacting step occurs at a pressure of at least about 200 psia.