Rice University chemists have figured out how to quickly and cheaply strip carbon dioxide from natural gas at the wellhead, an advance aimed at saving gas companies millions of dollars and, to some degree, curtailing global warming.
The key: Asphalt.
Rice chemistry professor James Tour and his lab have been working on the process for six years. Tour says the industry is keenly interested — oil and gas companies anticipate the U.S. government will soon begin taxing them for releasing carbon dioxide, a byproduct of natural gas processing and a key greenhouse gas charged with exacerbating global warming.
“They are going to have to stop blowing this stuff into the air,” Tour said. “It hasn’t hit yet, but they see it coming.”
Companies can’t sell raw natural gas, which contains 2 to 10 percent carbon dioxide and other impurities, Tour said. But the cleanup is energy-intensive and expensive. Generally, companies have to mine the gas, transport it via pipeline to processing plants, and then push it through fluids called amines in tall towers.
But amines only soak up about 15 percent of their own weight in carbon dioxide, Tour said.
And, to release the gas trapped in the amines, processors have to heat the assembly to over 250 degrees.
Moreover, most don’t collect the escaping carbon, Tour said. They could sell it — there are industrial uses for CO2, including new efforts to stimulate oil and gas recovery in existing wells — but it costs more to capture and transport than it’s worth to sell.
So Tour and his team began working on alternatives. Two years ago, they published research on the use of a porous carbon powder that trapped 82 percent of its weight in carbon dioxide.
Last year, they found an asphalt derivative that worked even better, collecting 114 percent of its weight in the greenhouse gas.
This year, Tour’s lab has again improved its product. In research published this month in the journal Advanced Energy Materials, Tour showed that a new form of the asphalt can trap 154 percent of its weight in carbon dioxide.
Better yet, the new material works at room temperature, and at pressures common inside gas wellheads. It also automatically releases the gas when pressure dips. Tour said companies could add a pipe and some valves at the end of a well and easily clean the natural gas and capture the carbon dioxide at the same time.
They could then transport it for sale, use it to stimulate more oil and gas recovery in existing wells, or reinject it underground.
“If you can do this at the wellhead,” Tour said, “then you can just pump it right back down underground, where it’s been for millions of years.”
The new form of asphalt, a common type called Gilsonite, is much less expensive than the old one, Tour said.
Rice postdoctoral researcher Almaz Jalilov was lead author of the study.
The Houston oil and gas exploration company Apache funded the research and has license to the intellectual property, Tour said.