Abstract:

Methane in coal mine methane (CMM) serves not merely as a pivotal and sustainable low-carbon energy source, but equally as a disconcerting explosive and greenhouse gas pollutant. Finding a consistent, efficient technique for methane enrichment is of paramount importance in enhancing safety measures within the current coal mining industry and addressing natural gas shortages. Industrial scale application has, however, been impeded by significant impurities present in coal-bed methane, specifically the efficient separation of carbon dioxide and nitrogen contaminants. This paper aimed to encapsulate two major focus areas in the process of coal-bed methane enrichment via vacuum pressure swing adsorption (VPSA): carbon dioxide capture (CO₂/CH₄ separation) and purification of natural gas (CH₄/N₂ separation). Here, effective adsorbents for segregating methane gas mixtures denoted the crux of VPSA technology advancements. Furthermore, it was further focused on analyzing and comparing the differences and similarities of three typical solid adsorbents, namely carbon-based adsorbents, zeolite molecular sieves and metal-organic frameworks, in separating or adsorbing methane in the above two directions. Among them, coupling different functional groups on the adsorbent surface or fine-tuning their pore structure at the nanoscale would be an effective way to continuously improve the adsorption separation efficiency of coalbed methane enrichment. In addition, the challenges and development directions faced by solid porous materials in the future were also discussed, hoping to help researchers understand the technical premise of CMM methane enrichment adsorbents and design novel adsorbents to meet the multiple stringent industrial requirements for methane separation.

Key words: coal mine methane, methane enrichment, solid adsorbents, carbon dioxide capture, natural gas purification

摘要：

煤层气（CMM）中的甲烷不仅是一种重要的绿色可持续的低碳清洁能源，亦是一种令人担忧的爆炸和温室气体污染物。因此寻找一种稳定且高效的甲烷富集技术，对于增加目前煤炭开采业的安全系数及克服常规天然气短缺问题具有重要意义。然而煤层气中存在大量杂质已成为其工业化大规模利用的关键技术障碍，尤其是对二氧化碳和氮气污染物的高效分离。本文综述了在煤层气甲烷富集真空变压吸附工艺（VPSA）过程中的两个主要方向：二氧化碳捕集（CO₂/CH₄分离）和天然气净化（CH₄/N₂分离），其中制备高效分离甲烷气体混合物的固体吸附剂是VPSA技术的核心突破点。进而重点分析和比较了碳基吸附材料、沸石分子筛和金属有机骨架这三种典型的固体吸附剂在上述两个方向上分离或吸附甲烷的差异性与相似性，其中在吸附剂表面耦合不同功能的官能团或在纳米尺度上微调其孔隙结构将是不断提高煤层气甲烷富集吸附分离效率的有效途径。此外还讨论了固体多孔材料未来发展面临的挑战和发展方向，希望在帮助研究人员了解CMM甲烷富集吸附剂的技术前提下，理解并设计出新型吸附剂以期满足工业上多重苛刻的甲烷分离要求。

关键词: 煤层气, 甲烷富集, 固体吸附剂, 二氧化碳捕集, 天然气净化