Thermodynamic and Raman spectroscopic studies on [formula omitted] and [formula omitted] tetra- n-butyl ammonium [formula omitted] mixtures containing gas hydrates

Abstract

Phase equilibrium curves of H 2 + tetrahydrofuran and H 2 + tetra- n-butyl ammonium bromide mixed gas hydrates were measured in a pressure range from 0.1 to 13.6 MPa. Each three-phase equilibrium curve converges at the maximum temperature point of pure tetrahydrofuran and tetra- n-butyl ammonium bromide hydrates, respectively. The difference of maximum temperatures is about 8 K, that is, the equilibrium curve of H 2 + tetra- n-butyl ammonium bromide mixed gas hydrate shifts to the high-temperature side from that of H 2 + tetrahydrofuran mixed gas hydrate. It is directly confirmed by use of Raman spectroscopy that H 2 is enclathrated in the hydrate cages by adding a small amount of tetrahydrofuran or tetra- n-butyl ammonium bromide. In both mixed hydrates, H 2 is enclathrated in only the small cage while tetrahydrofuran or tetra- n-butyl ammonium bromide occupies the large cages of each mixed hydrate.