Abstract:

Focusing on the important need for the recovery and separation of low-concentration CH₄ from low-grade coalbed methane, it mainly explores the development of granular carbon adsorbents with excellent CH₄/N₂ separation performance using biomass as a carbon source. Granular rice grains were chosen as carbon source to prepare granular rice-based carbon materials (GRCM) by carbonization and then CO₂ activation. The resulting granular carbon material exhibited a relatively narrow micropore distribution, and its BET specific surface area reached 938.529 m²/g. FT-IR analysis results show that the surface of rice-based granular carbon contains oxygen-containing functional groups such as hydroxyl and carbonyl groups. The CH₄ adsorption capacity and CH₄/N₂ adsorption selectivity of the sample GRCM-900 are as high as 1.32 mmol/g and 5.68 (298 K and 100 kPa), respectively, comparable to most of the reported powdered carbon materials and MOF. Molecular simulation revealed the different contributions of surface hydroxyl/carboxyl/aldehyde groups of GRCM to the adsorption selectivity of CH₄/N₂, and the mechanism of methane and nitrogen adsorption in the slit pores of GRCM. Fixed-bed experiments confirmed that the application of GRCM carbon materials can effectively separate CH₄/N₂ mixtures at normal temperature, and the prepared granular GRCM have potential application prospects in recovering CH₄ from low-concentration CH₄ coal mine gas.

Key words: granular porous carbon, coalbed methane, adsorption isotherm, selectivity, methane, nitrogen

摘要：

主要围绕从低品位煤层气中回收分离低浓度的CH₄这一重要需求，探索以生物质为碳源研制具有优良CH₄/N₂分离性能的颗粒炭吸附剂。选择大米碎粒作为碳源，通过碳化制备颗粒状炭前体，然后应用CO₂进行活化，制备出大米基颗粒炭材料（GRCM），研究其吸附分离CH₄/N₂的性能。所制得的颗粒炭材料具有较窄微孔分布，其中样品GRCM-900的BET比表面积为938.529 m²/g。FT-IR分析结果显示大米基颗粒炭表面含有羟基及羰基等含氧官能团。其CH₄吸附容量和CH₄/N₂吸附选择性分别高达1.32 mmol / g和5.68（在298 K和100 kPa条件下），优于大多数已报道的粉末状炭材料和MOF材料。分子模拟揭示了甲烷和氮气在GRCM炭材料狭缝孔道中的吸附构型和差异。固定床实验证实，应用GRCM炭材料可以在常温条件下有效地分离CH₄/N₂混合物，所制得的颗粒GRCM在从低品位煤层气中回收CH₄方面有很好的应用前景。

关键词: 多孔颗粒炭, 煤层气, 吸附等温线, 选择性, 甲烷, 氮气