Research Progress on Adsorption and Separation of Methane over Nitrogen by Metal-organic Frameworks
Coalbed methane is a flammable gas mainly composed of methane(CH4)and nitrogen(N2),which is mainly distributed on the surface of coal particles or adsorbed in the pores of coal particles.At present,about 70%of the coalbed methane mined in China belongs to low-quality coalbed methane,of which the methane concentration is less than 30%.Because it is difficult to purify and utilize,this part of low-quality coalbed methane is often directly discharged into the atmosphere,which not only wastes valuable methane resources,but also exacerbates the greenhouse effect and causes serious harm to the ecological environment.The efficient capture and absorption of methane in low-quality coalbed methane is of great significance for energy utilization and sustainable environmental development.Several techniques for separating methane and nitrogen from coalbed methane were introduced,and the differences between low-temperature distillation,membrane separation,solvent adsorption and adsorption separation were compared and analyzed.The research progress on separating methane and nitrogen from three typical adsorbents,namely carbon-based adsorbent materials,zeolite molecular sieves and metal-organic framework materials(MOFs),was discussed,and the current challenges and future development trends of adsorption and separation materials was expounded.