Studies of CO_2 Hydrate Formation and Dissolution

Abstract

Sequestering waste CO_2 in the deep ocean as a gas, liquid, or hydrate has been variously proposed (1−3). We describe experiments producing CO_2 hydrate that may eventually assist in developing methodology for large-scale creation of this ice-like substance. We produced a simple and inexpensive system for conducting high-pressure experimentation. We established the minimum ratio of CO_2 to water (both deionized water and seawater) needed to produce stable traces of hydrate. We suggested an explanation for the differences observed in forming hydrate from the two media. We demonstrated that hydrate decomposed when exposed to an intermittent flow of water. We proposed a model of pathways involved in forming CO_2 hydrate. Previous reports on hydrate formation have emphasized pressure−temperature relationships and effects thereon. Our experimentation focused on the amount of CO_2 in all phases inside the pressure chamber (designated as Υ-CO_2). The minimum Υ-CO_2 needed for producing hydrate varied with pressure. Hydrate became unstable and decomposed in intermittently flowing water. Our approach has yielded new information regarding requirements for hydrate formation and the potential for dissolution in the deep ocean.

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