Thermodynamics of Water-Cationic Species-Framework Guest-Host Interactions within Transition Metal Ion-Exchanged Mordenite Relevant to Selective Anaerobic Oxidation of Methane to Methanol

Xianghui Zhang; Cody B Cockreham; Zhiyang Huang; Hui Sun; Chen Yang; Oscar G Marin-Flores; Baodong Wang; Xiaofeng Guo; Su Ha; Hongwu Xu; Di Wu

doi:10.1021/acs.jpclett.0c01331

Thermodynamics of Water-Cationic Species-Framework Guest-Host Interactions within Transition Metal Ion-Exchanged Mordenite Relevant to Selective Anaerobic Oxidation of Methane to Methanol

J Phys Chem Lett. 2020 Jun 18;11(12):4774-4784. doi: 10.1021/acs.jpclett.0c01331. Epub 2020 Jun 4.

Authors

Xianghui Zhang^{1

2}, Cody B Cockreham^{1

2

3}, Zhiyang Huang^{1

2}, Hui Sun^{4

5}, Chen Yang^{1

2}, Oscar G Marin-Flores², Baodong Wang⁶, Xiaofeng Guo^{1

7

8}, Su Ha², Hongwu Xu³, Di Wu^{1

2

7

8}

Affiliations

¹ Alexandra Navrotsky Institute for Experimental Thermodynamics, Washington State University, Pullman, Washington 99163, United States.
² The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States.
³ Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
⁴ Petroleum Processing Research Center, East China University of Science and Technology, Shanghai 200237, China.
⁵ International Joint Research Center of Green Energy Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
⁶ National Institute of Clean-and-Low-Carbon Energy, Beijing 102211, China.
⁷ Department of Chemistry, Washington State University, Pullman, Washington 99163, United States.
⁸ Materials Science and Engineering, Washington State University, Pullman, Washington 99163, United States.

PMID: 32452684
DOI: 10.1021/acs.jpclett.0c01331

Abstract

Low-temperature anaerobic methane conversion to methanol (MTM) using copper ion-exchanged mordenite (Cu-MOR) as the catalyst and water as the sole source of oxygen is promising for sustainable utilization of methane. Integrating in situ calorimetric, spectroscopic, and structural methodologies, we report a systematic study on energetics of water-cationic species-framework guest-host interactions as a function of water loading for several mordenites relevant to low-temperature MTM. Notably, the near-zero coverage hydration enthalpy on Cu-MOR is -133.1 ± 6.0 kJ/mol water, which is related to Cu-MOR regeneration using water as oxidant. The copper oxo sites are thermally stable up to 915 °C and remain chemically intact as an oxygen source after complete hydration and dehydration. This study underscores the importance of manipulating the oxidation state and coordination chemistry of transition metal guest species in zeolites by fine-tuning the partial pressure of water as a strategy for rational design, synthesis, and modification of catalysts.