IIT Madras produces gas hydrates by mimicking interstellar conditions

from left - prof. rajnish kumar, jyotirmoy ghosh and prof. pradeep around the ultrahigh vacuum chamber - jpg-optimized
The methane and carbon dioxide hydrates were produced in the lab at very low pressures and temperature to simulate the conditions seen in deep space, say Pradeep (right), Rajnish Kumar (left) and Jyotirmoy Ghosh.

IIT Madras researchers have produced in the lab methane and carbon dioxide hydrates by simulating the low temperature and pressure conditions seen in deep space. The work raises the possibility of sequestering carbon dioxide as hydrates. IIT Madras is already collaborating with GAIL to recover methane from methane hydrate from the Krishna-Godavari Basin and simultaneously sequester carbon dioxide.

Researchers at Indian Institute of Technology (IIT) Madras have experimentally shown that methane and carbon dioxide can exist as gas hydrates at temperatures and pressures seen in interstellar atmosphere. Gas hydrates are formed when a gas such as methane gets trapped in well-defined cages of water molecules forming crystalline solids. In terrestrial conditions, gas hydrates are formed naturally under the sea bed and glaciers under high pressure, low temperature conditions. Methane hydrate is a potential source of natural gas.

The methane and carbon dioxide hydrates were produced in the lab at very low pressures (ten thousand billionth of atmospheric pressure) and temperature (as low as -263 degree C) to simulate the conditions seen in deep space.

Experimental work

“We have been conducting such experiments for the last five years but have never seen gas hydrates forming,” says Prof. T. Pradeep from the Department of Chemistry at IIT Madras who led the team. That was because the researchers conducted the experiments only for a few hours. “Since ice and methane exist in space for millions of years we decided to carry out the experiments for a longer time. We saw new features of hydrate forming when we continued the experiment for a day. Several experiments were then done under controlled conditions,” he recalls.

Water and methane were originally deposited at -263 degree C (10 K). When the temperature was increased to -243 degree C (30 K), the researchers could observe methane hydrate forming after 25 hours. About 10% of methane present was found in the hydrate form at the end of 25 hours. “By the end of 75 hours, most methane got converted into hydrate,” says Jyotirmoy Ghosh from IIT Madras and the first author of a paper published in the journal Proceedings of the National Academy of Sciences.

Though both ice and methane are in a frozen state (solid), prolonging the experiment at a very low temperature enhanced the mobility of methane molecules and led to their insertion into the cage of water molecules to form methane hydrate.

To validate the findings, the researchers repeated the experiment using carbon dioxide. Other researchers have experimentally produced carbon dioxide hydrate at higher temperature and pressure. Unlike in the case of methane hydrate, the IIT Madras team used an even lower temperature (-263 degree C) to produce carbon dioxide hydrate.

Applications

The carbon dioxide hydrate produced in the lab raises the possibility of sequestering or storing carbon dioxide as hydrates by taking advantage of ice already existing in environmental conditions favourable for hydrate formation. “In these environments, the carbon dioxide will have enough energy to interact with ice. So both molecules will have enough mobility to allow interaction to form carbon dioxide hydrate,” he says.

“Carbon dioxide hydrate is thermodynamically more stable than methane hydrate. So if methane hydrate has remained stable for millions of years under the sea bed, it would be possible to sequester gaseous carbon dioxide as solid hydrate under the sea bed,” Prof. Rajnish Kumar from the Department of Chemical Engineering at IIT Madras and a co-corresponding author of the paper.

IIT Madras in collaboration with GAIL is working to recover methane from methane hydrate from the Krishna-Godavari Basin and sequester carbon dioxide simultaneously, says Prof. Kumar.

Published in The Hindu on January 8, 2019

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