Natural gas as an efficient and clean fossil fuel plays an important role in the transformation of energy structure in China. Some conventional and unconventional natural gases contain excessive nitrogen

which could not meet the pipeline specification [nitrogen content < 4%(vol)] and decrease the heat value of natural gas. Therefore

nitrogen removal from natural gas is essential to achieve the efficient utilization of fossil fuel. Compared with traditional separation technologies such as cryogenic distillation and adsorption

the membrane-based gas separation technology possesses distinct advantages of operational flexibility

low investment and low energy consumption

exhibiting great potential in energy and environmental fields. The gas transport mechanisms suitable for CH4-N2 separation are introduced. Moreover

the developments of membrane materials and corresponding membranes for CH4-N2 separation are reviewed from CH4-selective and N2-selective membranes. Furthermore

the feasibility analysis of a two-stage membrane process with CH4-selective or N2-selective membrane is compared in different cases (nitrogen removal from conventional natural gas

shale gas and coalbed gas). Finally

prospects on membrane technology for CH4-N2 separation are presented.