By Andrew Mayfair J.D.
Updated Mar 24, 2022
Methane (CH₄) is the simplest hydrocarbon, consisting of one carbon atom bonded to four hydrogen atoms. Although it exists naturally as a gas at ambient conditions, many industrial processes require methane in liquid form to increase energy density and simplify storage. Liquefaction demands both significant pressure and sub‑zero temperatures; the procedure below outlines a safe, reproducible method using a liquid‑nitrogen cryogenic tank and a high‑pressure vacuum system.
Attach the methane canister to the liquid‑nitrogen tank via a plastic gas transfer tube. Open the canister valve to allow methane to flow into the tank. Once all gas has entered, close the cryogenic tank’s shunt valve and remove the transfer tube.
Allow the methane to remain in the liquid‑nitrogen tank for at least 48 hours. Monitor the tank temperature; it should reach a minimum of –150 °C to ensure the gas is fully liquefied before transfer.
Using a new gas transfer tube, move the cooled methane from the cryogenic tank to a pressure vacuum chamber. Open the shunt valves on both vessels, then close them once the transfer is complete.
Set the pressure vacuum to 46 bar. The applied pressure forces the residual methane to condense, forming liquid at the bottom of the chamber. Maintain the pressure until the desired volume of liquid is achieved.
Releasing liquid methane from the vacuum chamber causes rapid vaporization. Always transfer the liquid to a dedicated container that can withstand 46 bar pressure, and follow all relevant safety protocols and local regulations.
