Exploiting equilibrium-kinetic synergetic effect for separation of ethylene and ethane in a microporous metal-organic framework.
basic_science · Level V
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- Record sourced from PubMed, PMID 32300657.
- Also identified by DOI 10.1126/sciadv.aaz4322 and PMC identifier 7148085.
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Abstract
Physisorption is a promising technology to cut cost for separating ethylene (C<sub>2</sub>H<sub>4</sub>) from ethane (C<sub>2</sub>H<sub>6</sub>), the most energy-intensive separation process in the petrochemical industry. However, traditional thermodynamically selective adsorbents exhibit limited C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub> selectivity due to their similar physiochemical properties, and the performance enhancement is typically at the expense of elevated adsorption heat. Here, we report highly-efficient C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub> adsorption separation in a phosphate-anion pillared metal-organic framework ZnAtzPO<sub>4</sub> exploiting the equilibrium-kinetic synergetic effect. The periodically expanded and contracted aperture decorated with electronegative groups within ZnAtzPO<sub>4</sub> enables effective trapping of C<sub>2</sub>H<sub>4</sub> and impedes the diffusion of C<sub>2</sub>H<sub>6</sub>, offering an extraordinary equilibrium-kinetic combined selectivity of 32.4. The adsorption heat of C<sub>2</sub>H<sub>4</sub> on ZnAtzPO<sub>4</sub> (17.3 to 30.0 kJ mol<sup>-1</sup>) is substantially lower than many thermodynamically selective adsorbents because its separation capability only partially relies on thermodynamics. The separation mechanism was explored by computational simulations, and breakthrough experiments confirmed the excellent C<sub>2</sub>H<sub>4</sub>/C<sub>2</sub>H<sub>6</sub> separation performance of ZnAtzPO<sub>4</sub>.