Separation of CO2 and Acetylene by Kinetic Sieving

Optimized Separation of Acetylene from Carbon Dioxide and Ethylene in a  Microporous Material | Journal of the American Chemical Society

Separation processes can benefit greatly from the use of porous materials with precisely engineered micropores. However, it is difficult to tailor the pore structure of the adsorbent to achieve exact discriminating for molecules with essentially identical molecular sizes and physical properties. The kinetic sieving of carbon dioxide (CO2) and acetylene (C2H2), which have nearly equal kinetic diameters, is an example of this.

Sulfonic anion-based pillared ultramicroporous materials for the separation of C2H2 from CO2 have been synthesised by Huabin Xing, Xili Cui, and colleagues at Zhejiang University in Hangzhou, China. Cu2+, isonicotinic acid, 1,2-ethanedisulfonic acid (EDS), and a trace amount of water were initially used to create the ZU-610 material. In the final result, the oxygen atoms of water combine with copper to produce clusters of Cu4(3-O)2. Using sulfonate units as anchors, these metal clusters construct one-dimensional chains linked by isonicotinic acid. This substance prefers C2H2 to carbon dioxide.

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After synthesising ZU-610, the team subjected it to post-synthetic heat treatment in order to create a modified material dubbed ZU-610a, which had smaller pores. ZU-610a, with its narrower pores, exhibited CO2-selectivity rather than C2H2-selectivity. High-purity C2H2 (>99.5%) was created directly from binary mixes of the two gases using ZU-610a for kinetic screening (shown schematically). So, adjusting the pore structure can significantly affect the adsorption. This research may lead to novel approaches for creating adsorbent separation systems that can differentiate between molecules with similar structures.

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