Amorphous-like thermal conductivity and high mechanical stability of cyclopentane clathrate hydrate

• Published in: Physical chemistry chemical physics : PCCP 2024, Vol.26 (22), p.1617-1625
• Main Authors: Andersson, Ove, Saiduzzaman, Md, Brant Carvalho, Paulo H. B, Häussermann, Ulrich
• Format: Article
• Language: English
• Subjects: Amorphization; Atmospheric pressure; Conduction heating; Conduction model; Conductive heat transfer; Gas hydrates; Heat conductivity; Melting points; Miscibility; Stability; Tetrahydrofuran; Thermal conductivity
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d4cp01656d

The thermal conductivity κ of cyclopentane clathrate hydrate (CP CH) of type II was measured at temperatures down to 100 K and at pressures up to 1.3 GPa. The results show that CP CH displays amorphous-like κ characteristic of many crystalline clathrate hydrates, e.g. , tetrahydrofuran (THF) CH. The magnitude of κ is 0.47 W m −1 K −1 near the melting point of 280 K at atmospheric pressure, and it is almost independent of pressure and temperature T : ln  κ = −0.621−40.1/ T at atmospheric pressure (in SI-units). This is slightly less than κ of type II CHs of water-miscible solvents such as THF. Intriguingly, unlike other water-rich type II clathrate hydrates of water-miscible molecules M (M·17 H 2 O), CP CH does not amorphize at pressures up to 1.3 GPa at 130 K and also remains stable up to 0.5 GPa at 240 K. This shows that CP CH is mechanically more stable than the previously studied water-rich type II CHs, and suggests that repulsive forces between CP and the H 2 O cages increase the mechanical stability of crystalline CP CH. Moreover, we show that κ of an ice-CH mixture, which often arises for CHs that form naturally, is described by the average of the parallel and series heat conduction models to within 5% for ice contents up to 22 wt%. The findings provide a better understanding of the thermal and stability properties of clathrate hydrates for their applications such as gas storage compounds. Through the exchange of guest molecules from water-miscible molecules to cyclopentane, the mechanical stability of type II clathrate hydrates increases significantly.