Scientists have found a way to make their asphalt-based sorbents better at capturing carbon dioxide from gas wells: Adding water.
The lab of chemist James Tour, a chair in chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice University, discovered that treating grains of inexpensive Gilsonite asphalt with water allows the material to adsorb more than two times its weight in the greenhouse gas. The treated asphalt selects carbon dioxide over valuable methane at a ratio of more than 200-to-1.
The material performs well at ambient temperatures and under the pressures typically found at wellheads. When the pressure abates, the material releases the carbon dioxide, which can then be stored, sold for other industrial uses, or pumped back downhole.
Natural gas at the wellhead typically contains between 3 and 7 percent carbon dioxide, but at some locations may contain up to 70 percent. Oil and gas producers traditionally use one of two strategies to sequester carbon dioxide: physically through the use of membranes or solid sorbents like zeolites or porous carbons, or chemically through filtering with liquid amine, a derivative of ammonia.