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Temperature‐ and Pressure‐induced Structural Transition of Binary Clathrate Hydrates
Author(s) -
Ahn YunHo,
Baek Seungjun,
Min Juwon,
Cha Minjun,
Lee Jae W.
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800943
Subject(s) - hydrate , chemistry , clathrate hydrate , raman spectroscopy , phase boundary , phase transition , phase (matter) , crystal structure , molecule , crystallography , thermodynamics , powder diffraction , analytical chemistry (journal) , organic chemistry , physics , optics
We discover new structure II (sII) hydrate forming agents of two C 4 H 8 O molecules (2‐methyl‐2‐propen‐1‐ol and 2‐butanone) and report the abnormal structural transition of binary C 4 H 8 O+CH 4 hydrates between structure I (sI) and sII with varying temperature and pressure conditions. In both (2‐methyl‐2‐propen‐1‐ol+CH 4 ) and (2‐butanone+CH 4 ) systems, the phase boundary of the two different hydrate phases (sI and sII) exists at the slope change of the phase‐equilibrium curve in the semi‐logarithmic plots. We confirm the crystal structures of two hydrates synthesized at low (278 K and 6 MPa) and high (286 K and 15 MPa) temperature and pressure conditions by using high‐resolution powder diffraction and Raman spectroscopy. 2‐Methyl‐2‐propen‐1‐ol and 2‐butanone can occupy the large cages of sII hydrate at low temperature and pressure conditions; however, they are excluded from the hydrate phase at high temperature and pressure conditions, resulting in the formation of pure sI CH 4 hydrate.