Membrane processes for N₂-CH₄ separation

An increasing demand for clean energy has led to a search for alternative energies with less environmental impact, of which natural gas is an important option. The large consumption of natural gas requires an effective technology to improve the purity of natural gas, in which inert gases such as nitrogen play a large part. However, current technologies cannot provide economic solutions to remove nitrogen from natural gas, which leads to a decrease in the heat value of the natural gas. Membrane separation by zeolites represents a viable energy-saving method that can potentially offer an effective way to remove nitrogen from natural gas. In particular, SAPO-34 zeolite membranes have been extensively studied for carbon dioxide separation because of their exceptional molecular-sieving effects, higher thermal and chemical resistances. These membranes can also be effective for N₂-CH₄ separation due to their molecular-sieving effects and adsorption properties. In this mini review, we discuss the different technologies employed for nitrogen rejection from natural gas, emphasizing zeolite membranes as an effective and promising technology to economically separate N₂ from CH₄.