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

摘要：

作为一种高效的分离方法，膜法分离非常规天然气具有较理想的应用前景。相较CH₄优先渗透膜，N₂优先渗透膜优势在于分离N₂/CH₄混合气后CH₄处于高压侧，利于后续处理。以均苯三甲酰氯为油相单体，间苯二胺为水相单体，采用界面聚合法在聚砜基膜上制备致密超薄聚酰胺分离层，并通过向其中引入孔径可允许N₂分子通过而不允许CH₄分子通过的纳米颗粒ZIF-90，在膜内形成固定的N₂传递通道，成功制备了用于脱氮提纯CH₄的N₂优先渗透混合基质膜。膜渗透选择性能测试结果显示当混合基质膜中纳米颗粒掺杂量为0.30 g·L^-1时，2 bar（1 bar=0.1 MPa）进料压力下，N₂渗透速率达1.16×10^-9 mol·m^-2·s^-1·Pa^-1，N₂/CH₄分离因子达16.6，分离因子比未掺杂ZIF-90的聚酰胺膜提高46.5%，具有一定的处理非常规天然气脱氮提纯甲烷的应用潜力。

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