Structure H clathrate hydrate equilibria of methane and adamantane

Abstract

The first phase equilibrium data are presented for Structure H hydrates. The data represent the initial formation of these hydrates from methane, with adamantane— a previously determined Structure H former. Temperature and pressure conditions are consistent with hydrocarbon production/transportation/processing facilities. Structure H hydrates are shown to contain molecules indigenous to petroleum. which may not be present in natural gas.

The Deepwater Subsea Tieback Option for Future Oil and Gas Production in Australia

“…These oil and condensate systems were traditionally regarded as non-hydrate forming systems. Secondly, phase equilibrium measurements of temperature and pressure conditions under which sH hydrates form a stable phase are consistent with those in hydrocarbon production, processing, and transportation facilities [4].…”

SHhydrate equilibria of (methane + water + 2-methylbutane + magnesium chloride), (methane + water + 2,2-dimethylbutane + magnesium chloride), and (methane + water + methylcyclohexane + magnesium chloride)

“…In particular, the S H hydrate formation is becoming increasingly important in petrochemical processes due to the fact that some liquid components in petroleum are transformed into white, crystalline, solid S H hydrates by combining with moisture and light hydrocarbons existing in the plant and pipelines. Lederhos et al (4) reported the first S H hydrate phase equilibrium data of (methane + water + adamantane). Mehta and Sloan (5,6) also provided S H hydrate phase equilibrium data involving a variety of liquid hydrocarbons with methane as the guest components.…”

Icosahedron cage occupancy of structure-H hydrate helped by Xe -1,1-, cis -1,2-, trans-1,2-, and cis-1,4-dimethylcyclohexanes

“…There are three types of cages in the s-H hydrate, pentagonal dodecahedron (5 12 , S-cage), dodecahedron (4 3 5 6 6 3 , S -cage) and icosahedron (5 12 6 8 , U-cage). The large guest molecules, such as adamantane (Lederhos et al, 1992), methylcyclohexane (Metha and Sloan, 1993;Mooijer-van den Heuvel et al, 2000;Sun et al, 2002) or other large guest species (Ripmeester and Ratcliffe, 1990;Metha and Sloan, 1994;Makino et al, 2004), can be entrapped in the U-cage while help gas occupies selectively both S-and S -cages. The structure of s-H hydrate becomes stable with the cooperative interaction between help gas and large guest species which is unable to generate s-H hydrate by itself.…”