N2-selective adsorbents and membranes for natural gas purification

Conventional natural gas confronts the growing supply shortage due to the fewer formation reserves. As a powerful replenishment, the nitrogen-rich unconventional natural gas, mainly including shale gas and coalbed methane, has attracted much attention in recent years and stimulated the efficient separation processes for N2-CH4 system. Benefiting from the boom in materials science, a large number of advanced adsorbents and membranes have been used for N2-CH4 separation. In this paper, the recent advances in the design and fabrication of N2-selective adsorbents and membranes for N2 removal from unconventional natural gas are reviewed. The physicochemical characteristics of N2-selective adsorption and membrane materials are briefly introduced, and the internal commonalities between different materials are analyzed to identify the underlying reasons for the specific performance. Additionally, the challenges and directions for the future development of N2/CH4 separation materials are discussed.