Crystal growth of ionic semiclathrate hydrate formed in CO2 gas + tetrabutylammonium bromide aqueous solution system

Shunsuke Koyanagi, Ryo Ohmura

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


This article reports the visual observations of the formation and growth of ionic semiclathrate hydrate crystals in the system of aqueous solution of tetrabutylammnonium bromide (TBAB) and CO2 gas. The experimental thermodynamic conditions are (i) the temperature from 286 to 290 K for w TBAB = 0.40 and (ii) 282 to 288 K at wTBAB = 0.10, under the common pressure of 2.3 or 3.4 MPa, where wTBAB denotes the mass fraction of TBAB in the aqueous solution. The lower limit of the temperature was set to avoid the formation of simple TBAB hydrate containing no CO2. The hydrate crystals first formed in the bulk of the aqueous liquid as well as at the gas/liquid interface. The former crystals settled downward and the latter grew to form a hydrate film covering the interface. Both of the hydrate crystals then grew into the aqueous liquid. The morphology of hydrate crystals grown in the aqueous liquid varied distinctly depending on the system subcooling ΔTsub. ΔTsub ≡ Teq - T ex, where Teq is the equilibrium temperature and T ex is the system temperature. When ΔTsub is smaller than ∼2.0 K, hydrate crystals with wedge morphology were observed. At the range of ∼3.1 K > ΔTsub > ∼2.0 K, the wedge crystals were replaced by columnar shaped crystals. At ΔTsub > ∼3.5 K, the hydrate crystals with needle and sword-like morphology were observed. The size of the individual hydrate crystals decreased with increasing ΔTsub.

Original languageEnglish
Pages (from-to)2087-2093
Number of pages7
JournalCrystal Growth and Design
Issue number5
Publication statusPublished - 2013 May 1

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics


Dive into the research topics of 'Crystal growth of ionic semiclathrate hydrate formed in CO<sub>2</sub> gas + tetrabutylammonium bromide aqueous solution system'. Together they form a unique fingerprint.

Cite this