D2 and H2 adsorption capacity and selectivity in CHA zeolites: Effect of Si/Al ratio, cationic composition and temperature
D2 and H2 adsorption capacity and selectivity in CHA zeolites: Effect of Si/Al ratio, cationic composition and temperature
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DOI：
10.1016/j.micromeso.2020.110217
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发表时间：
2020-08-01
影响因子：
5.2
通讯作者：
Behat, Jean-Pierre
中科院分区：
文献类型：
--
作者：
Bezverkhyy, Igor;Pujol, Quentin;Behat, Jean-Pierre
本文研究了CHA分子筛组成对低温下H-2和D-2吸附分离的影响。本工作的第一部分在77.4K下研究了Si/Al比和阳离子组成对H-2和D-2单气体吸附的影响。结果发现，吸附容量增加与Al含量高达Si/Al = 2.1。出乎意料的是，具有最高Al含量（Si/Al = 1.1）的Na-CHA沸石仅吸附可忽略的量，这是因为沸石结构在400 ℃脱水时崩溃。Si/Al = 2.1的含钠菱沸石和含锂菱沸石具有相似的吸附容量。相反，用K+逐步置换Na+导致在77.4K时H-2和D-2吸附量减少，当K+含量高于60 mol. %.在第二部分工作中，用共吸附技术测定了在40- 77.4K、530-650 hPa（对应于高负载）压力范围内Na-、Li-和K-Na菱沸石（Si/Al = 2.1）的D-2/H-2热力学选择性。发现阳离子组合物对D-2/H-2选择性只有很小的影响，该选择性随着温度的降低而呈指数增加。例如在Na3.9Al3.9Si8.1O24菱沸石中，它从77.4 K时的2.6上升到40 K时的13。发现D-2/H-2选择性随温度的变化与一个简单的量子筛分模型相吻合，该模型利用菱沸石腔的孔径大小作为唯一的可调参数。
The work deals with the effect of composition of CHA zeolites on the adsorption and separation of H-2 and D-2 under cryogenic temperatures. In the first part of this work the effect of Si/Al ratio and cationic composition on single gas adsorption of H-2 and D-2 was studied at 77.4 K. It was found that the adsorption capacities increase with Al content up to Si/Al = 2.1. Unexpectedly, Na-CHA zeolite with the highest Al content (Si/Al = 1.1) adsorbs only negligible amount because of the collapse of the zeolite structure upon dehydration at 400 degrees C. The Na- and Li-containing chabazites with Si/Al = 2.1 possess similar adsorption capacities. In contrast, progressive replacement of Na+ with K+ results at 77.4 K in decreasing H-2 and D-2 adsorbed amount which becomes negligible for K+ content higher than similar to 60 mol. %. In the second part of the work the D-2/H-2 thermodynamic selectivity for Na-, Li- and K-Na chabazites (Si/Al = 2.1) was measured using coadsorption technique at 40-77.4 K in the pressure range 530-650 hPa corresponding to high loading. The cationic composition is found to have only minor effect on the D-2/H-2 selectivity which increases exponentially with lowering temperature. For example in Na3.9Al3.9Si8.1O24 chabazite it rises from 2.6 at 77.4 K to 13 at 40 K. It is found that variation of D-2/H-2 selectivity with temperature is in a fair agreement with a simple quantum sieving model making use of the aperture size of the chabazite cavity as a unique adjustable parameter.