CH4 Gas Extraction by CO2: Substitution in Clathrate Hydrate through Bimolecular Iteration

Xiao Hui Yu, Yuan Liu, San Ya Du, Xu Zheng, Jin Long Zhu, Hong Wu Xu, Jian Zhong Zhang, Shi Yu Du, Xiao Cheng Zeng, J. S. Francisco, Chang Qing Jin, Yu Sheng Zhao, Hui Li

Research output: Contribution to journalArticlepeer-review

Abstract

Methane clathrate hydrate (MCH) is a promising energy resource, but controllable extraction of CH 4 from MCH remains a challenge. Gradually replacing CH 4 in MCH with CO 2 is an attractive scheme, as it is cost efficient and mitigates the environmentally harmful effects of CO 2 by sequestration. However, the practicable implementation of this method has not yet been achieved. In this study, using in situ neutron diffraction, we confirm that CH 4 in the 5 1262 cages of bulk structure-I (sI) MCH can be substituted by gaseous CO 2 under high pressure and low temperature with a high substitution ratio (∼44%) while conserving the structure of the hydrate framework. First-principles calculations indicate that CO 2 binds more strongly to the 5 1262 cages than methane does, and that the diffusion barrier for CH 4 is significantly lowered by an intermediate state in which one hydrate cage is doubly occupied by CH 4 and CO 2. Therefore, exchange of CO 2 for CH 4 in MCH is not only energetically favorable but also kinetically feasible. Experimental and theoretical studies of CH 4/CO 2 substitution elucidate a method to harness energy from these combustible ice resources.

Original languageEnglish (US)
Article number048201
JournalChinese Physics Letters
Volume37
Issue number4
DOIs
StatePublished - Apr 2020

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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