Formation processes of clathrate hydrates of carbon dioxide and methane

• Main Author: Blackwell, Veronica R.
• Format: Thesis
• Language: English
• Published: 1998
• Subjects: Methane hydrate
• Online Access: https://thesis.library.caltech.edu/302/; https://thesis.library.caltech.edu/302/1/Blackwell_vr_1998.pdf; https://resolver.caltech.edu/CaltechETD:etd-01232008-100246

NOTE: Text or symbols not renderable in plain ASCII are indicated by [.]. Abstract is included in .pdf document. This thesis explores the formation kinetics and mechanisms of clathrate hydrates of carbon dioxide and methane, focusing on the nucleation and early growth of hydrates. Homogenous and heterogeneous systems were studied. The catalysis of hydrate nucleation was accomplished by the addition of certain particles to the hydrate forming solution. Copper (II) oxide, calcium carbonate and some [.] and [.] aluminum oxide particles were found to be effective nucleators while a-iron oxide, magnesium hydroxide, silica and some other [.] and [.] aluminum oxide particles were found ineffective. The induction period for hydrate formation was reduced by as much as 85% with copper oxide particles. The important requisites of a nucleation catalyst included a satisfactory match between the crystal structure faces of ice and catalyst particle. The nature of the surface hydroxyl groups on the particle was also important. Particles nucleated hydrate by encouraging hydrogen bonding between the surface hydroxyl groups on the particles and water molecules near the surface, forming a layer of structured water. These structures then built up into clathrate cages when stabilized by guest molecules. Methane hydrate only formed at the interface between gas and water, because only there were there enough methane molecules to stabilize the structures. Carbon dioxide hydrate formed in the bulk solution because the higher solubility of carbon dioxide in water ensures enough carbon dioxide molecules to stabilize cages and allow them to grow into full hydrate structures.