Abstract:

The enrichment of low-concentration coalbed methane is of great significance to alleviate the current situation of the shortage of natural gas in China. However, the nitrogen impurities in coalbed methane greatly limit the further application of this resource. Therefore, it is very important to separate the CH₄/N₂ gas mixture in low concentration coalbed methane. Two low-polar ultra-microporous metal-organic framework materials, Sc-CPM-66A and In-CPM-66A, were prepared to study the performance of the materials in enriching CH₄ from CH₄/N₂ mixture. The structure of the materials was characterized by PXRD, 77 K N₂ adsorption, TGA and FTIR spectra. IAST selectivity calculations showed that the CH₄/N₂ selectivity of Sc-CPM-66A and In-CPM-66A reached 6.0. Benefiting from the large number of methyl groups on the surface of the materials, the adsorption heat of the two materials for CH₄ was lower than that of most reported materials. The weak interaction between the materials and methane molecules was conducive to the desorption and regeneration of the adsorbent in industrial applications. The penetration experiment further showed that CPM-66A could achieve the separation of CH₄/N₂ mixtures under dynamic conditions, and the cyclic penetration experiment showed that this type of material had good repeatability.

Key words: natural gas, CH₄/N₂, low-polar, CPM-66A, selectivity, sorbents

摘要：

低浓度煤层气的提质利用对缓解国内天然气不足的现状具有重要意义，然而煤层气中存在的氮气杂质限制了该类资源的进一步应用，进行低浓度煤层气中CH₄/N₂混合物的分离至关重要。制备了两种具有弱极性超微孔的金属有机框架材料Sc-CPM-66A和In-CPM-66A，研究材料从CH₄/N₂混合物中富集CH₄的性能，利用PXRD、77 K N₂吸附、TGA和FTIR光谱对材料的结构进行了表征。IAST 选择性计算表明，In-CPM-66A和Sc-CPM-66A的CH₄/N₂ 选择性达到6.0。受益于材料表面存在的大量的甲基基团，两种材料对CH₄的吸附热低于被报道的大部分材料，材料与甲烷分子之间弱的相互作用有利于吸附剂的脱附再生。穿透实验进一步表明，CPM-66A可以实现动态条件下CH₄/N₂混合物的分离，循环穿透实验显示该类材料具有良好的可重复性。

关键词: 天然气, CH₄/N₂, 弱极性, CPM-66A, 选择性, 吸附剂