This summer I've been in Singapore, doing chemical engineering research, and I've been enjoying it a lot!
I'm working on clathrate hydrate research at the National University of Singapore. Clathrate or gas hydrates are crystalline solids formed from water and a gas. The water forms cages that enclose the gas molecules. Different guest gas molecules result in different hydrate structure, the most common of which are structure I (sI), structure II (sII), and structure H (sH) hydrates. For example, carbon dioxide generally forms structure I hydrates, which have six small dodecahedral cages and two large tetradodecahedral cages. Hydrate formation tends to occur at low temperatures and high pressures, the kinds of conditions that you would find in permafrost or subsea regions.
Why do we care about hydrates? The biggest reason is related to the oil and gas industry. The majority of the earth's methane is in the form of methane hydrates, and we'd like to extract it. We also need to be able to prevent the formation of natural gas hydrates in pipes.
The other main application, the one to which my work is more related, is gas separation and storage, particularly of carbon dioxide. Carbon dioxide emissions make up around 60% of greenhouse gas emissions, but if we could capture and sequester carbon dioxide, then it wouldn't be released into the atmosphere. One solution is hydrate based gas separation. Industrial applications generally involve a mixture of gases including carbon dioxide. If we're clever about the temperatures and pressures we use, we can form hydrates in a way that is very selective for carbon dioxide. For example, fuel gas is 60 percent carbon dioxide and 40 percent hydrogen, but we can form hydrates from fuel gas in which 80 or 90 percent of the guest gas molecules are carbon dioxide. If we do a couple of cycles of forming and dissociating the hydrates, we end up with a gas that is almost entirely carbon dioxide. The hydrogen can then be combusted.
The carbon dioxide can also be stored in hydrate form in the earth; if it's injected into parts of the earth's crust with the right conditions, then the carbon dioxide will form hydrates and not be released to the atmosphere. In fact, researchers have been doing experiments on methane/carbon dioxide hydrate exchange, working on how we could replace the methane in methane hydrates with carbon dioxide so that we can use the methane gas and store the carbon dioxide in hydrate form.
There are basically three general areas that you can study when thinking about gas hydrates: thermodynamics, kinetics, and morphology. They're all pretty closely linked, and I've had the opportunity to do at least a little bit of work on each while I've been in the lab.
