title: Gas-phase synthesis and characterization of CH4-loaded hydroquinone clathrates.
abstract: A CH(4)-loaded hydroquinone (HQ) clathrate was synthesized via a gas-phase reaction using the alpha-form of crystalline HQ and CH(4) gas at 12 MPa and room temperature. Solid-state (13)C cross-polarization/magic angle spinning (CP/MAS) NMR and Raman spectroscopic measurements confirm the incorporation of CH(4) molecules into the cages of the HQ clathrate framework. The chemical analysis indicates that about 69% of the cages are filled by CH(4) molecules, that is, 0.69 CH(4) per three HQ molecules. Rietveld refinement using synchrotron X-ray powder diffraction (XRD) data shows that the CH(4)-loaded HQ clathrate adopts the beta-form of HQ clathrate in a hexagonal space group R3 with lattice parameters of a = 16.6191 A and c = 5.5038 A. Time-resolved synchrotron XRD and quadrupole mass spectroscopic measurements show that the CH(4)-loaded HQ clathrate is stable up to 368 K and gradually transforms to the alpha-form by releasing the confined CH(4) gases between 368-378 K. Using solid-state (13)C CP/MAS NMR, the reaction kinetics between the alpha-form HQ and CH(4) gas is qualitatively described in terms of the particle size of the crystalline HQ.
authors.affiliation: Department of Environmental Engineering, Kongju National University, Chungnam 331-717, Korea.
authors.forename: Jong-Won
authors.initials: JW
authors.lastname: Lee
authors.forename: Yongjae
authors.initials: Y
authors.lastname: Lee
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takeya
authors.forename: Taro
authors.initials: T
authors.lastname: Kawamura
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yun-Je
authors.initials: YJ
authors.lastname: Lee
authors.forename: Ji-Ho
authors.initials: JH
authors.lastname: Yoon