关键词: 气体, 分离, N₂/CH₄ 分离, 界面聚合, 膜, 混合基质膜

Abstract:

Unconventional natural gas after pretreatment still contains high concentration of N₂, which can not meet the requirements of pipeline transportation. As an efficient separation method, membrane separation of unconventional natural gas has an ideal application prospect, and the membranes used for separation of unconventional natural gas can be divided into CH₄ preferential permeation membrane and N₂ preferential permeation membrane. Compared with the CH₄ preferential permeation membrane, the advantage of N₂ preferential permeation membrane is that the CH₄ product is at the high pressure side after separating N₂/CH₄ mixture, which is conducive to the subsequent treatment. In this work, trimesoyl chloride was used as the oil phase monomer, m-phenylenediamine was used as the water phase monomer, and a dense ultra-thin polyamide separation layer was prepared on polysulfone by interfacial polymerization. By introducing ZIF-90 nanoparticles with pore size that can allow N₂ molecules to pass through but not CH₄ molecules, a fixed N₂ transfer channel was formed in the membrane and the mixed matrix membrane with N₂ preferential permeation was successfully prepared for N₂ removal and CH₄ purification. The permselectivity test results show that the permeation rate of N₂ is 1.16×10^-9 mol·m^-2·s^-1·Pa^-1 and the separation factor of N₂/CH₄ is 16.6 when the content of nanoparticles in the composite membrane is 0.30 g·L^-1 and the feed pressure is 2 bar. The separation factor is 46.5% higher than that of the non doping ZIF-90, which shows the potential of the mixed matrix membrane to remove N₂ and_{purify CH4 for unconventional natural gas.}

Key words: gas, separation, N₂/CH₄ separation, interfacial polymerization, membrane, mixed matrix membrane