Nitrogen Rejection from Methane via a "trapdoor" K-ZSM-25 Zeolite

Jianhua Zhao, Seyed Hesam Mousavi, Gongkui Xiao, Abdol Hadi Mokarizadeh, Thomas Moore, Kaifei Chen, Qinfen Gu, Ranjeet Singh, Ali Zavabeti, Jefferson Zhe Liu, Paul A. Webley, Gang Kevin Li

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Nitrogen (N2) rejection from methane (CH4) is the most challenging step in natural gas processing because of the close similarity of their physical-chemical properties. For decades, efforts to find a functioning material that can selectively discriminate N2 had little outcome. Here, we report a molecular trapdoor zeolite K-ZSM-25 that has the largest unit cell among all zeolites, with the ability to capture N2 in favor of CH4 with a selectivity as high as 34. This zeolite was found to show a temperature-regulated gas adsorption wherein gas molecules' accessibility to the internal pores of the crystal is determined by the effect of the gas-cation interaction on the thermal oscillation of the "door-keeping"cation. N2 and CH4 molecules were differentiated by different admission-trigger temperatures. A mild working temperature range of 240-300 K was determined wherein N2 gas molecules were able to access the internal pores of K-ZSM-25 while CH4 was rejected. As confirmed by experimental, molecular dynamic, and ab initio density functional theory studies, the outstanding N2/CH4 selectivity is achieved within a specific temperature range where the thermal oscillation of door-blocking K+ provides enough space only for the relatively smaller molecule (N2) to diffuse into and through the zeolite supercages. Such temperature-regulated adsorption of the K-ZSM-25 trapdoor zeolite opens up a new approach for rejecting N2 from CH4 in the gas industry without deploying energy-intensive cryogenic distillation around 100 K.

Original languageEnglish
Pages (from-to)15195-15204
Number of pages10
JournalJournal of the American Chemical Society
Issue number37
Early online date13 Sept 2021
Publication statusPublished - 22 Sept 2021


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