摘要/Abstract

炼厂干气中回收乙烯是扩宽C₂H₄来源的有效途径，但C₂H₄和C₂H₆物理性质和分子尺寸非常接近，分离困难.金属有机骨架材料（MOFs）近年来在低碳烃分离领域展现出广阔的前景.本工作采用氨吸附改性调节UTSA-280的结构，通过一维直孔道大小的调节实现C₂H₄/C₂H₆的高效分离.改性后的UTSA-280具有独特的超微孔结构能提升C₂H₄的吸附，而完全不吸附稍大的C₂H₆，实现理想的C₂H₄/C₂H₆吸附选择性（>1000）.结果表明，改性后的UTSA-280的C₂H₄吸附量可提高至2.83 mmol/g，与未改性的材料相比增加29%，并且能阻挡C₂H₆的吸附，最终达到>1200的C₂H₄/C₂H₆选择性.蒙特卡罗分子模拟（GCMC）计算C₂H₄/C₂H₆混合气体（1：1）的吸附得出，改性后UTSA-280孔内的C₂H₄吸附相比于C₂H₆具有更多的吸附分布.通过C₂H₄/C₂H₆混合气体穿透实验测试，改性后的UTSA-280材料能展现出48 min以上的分离时间，相比于未改性的材料，分离性能提升近1倍.
关键词: 金属有机骨架材料, 氨改性, C₂H₄/C₂H₆分离, 选择性
Recovering C₂H₄ from refinery gas is an effective way to broaden the source of ethylene. However, it's a challenging task to separate C₂H₄ and C₂H₆ due to their very close physical properties and molecular size. Metal-organic frameworks (MOFs) are shown broad prospects in the field of light hydrocarbon separation in recent years. In this work, NH₃ is used to modify the structure of UTSA-280, the efficient separation of C₂H₄/C₂H₆ can be achieved through the adjustment of one-dimensional channels. UTSA-280 has undergone stepwise adsorption of ammonia gas at 298 K and 100 kPa. After partial ammonia removal, we obtained the modified UTSA-280 that ammonia adsorption modification with a mass loading of 5.6% for UTSA-280-M1 and 2.8% for UTSA-280-M2. The NH₃ modified UTSA-280 shows a unique ultramicroporous structure that can enhance the adsorption of C₂H₄ and does not adsorb the slightly larger C₂H₆, achieving the ideal C₂H₄/C₂H₆ adsorption selectivity (more than 1000). Ammonia molecules play the role of perfectly adjusting the size of one-dimensional channels and realize the ideal screening effect of C₂H₄/C₂H₆. The C₂H₄ adsorption capacity of NH₃ modified UTSA-280-M2 can be improved to 2.83 mmol/g at 298 K and 100 kPa (an increase of 29% compared with initial material). And its ultramicroporous structure can fully block the adsorption of C₂H₆, which finally achieves a C₂H₄/C₂H₆ selectivity over 1200. Grand Canonical Monte Carlo (GCMC) simulation of C₂H₄/C₂H₆ mixed gases (equal volume) adsorption results showed that the modified UTSA-280 had more C₂H₄ adsorption distribution in the mixed components than C₂H₆. Through the C₂H₄/C₂H₆ mixed gases breakthrough test at 298 K, NH₃ modified UTSA-280-M2 shows a separation time of more than 48 min, which is more than the initial 25 min. Compared with the unmodified material, the separation performance is nearly doubled. Scalable synthesis, stable structure, and the advantages of controllable performance after ammonia modification have prompted this material to have great prospects in the industrialization of C₂H₄/C₂H₆ separation.
Key words: metal-organic frameworks, NH₃ modification, C₂H₄/C₂H₆ separation, selectivity


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