Cheap asphalt to trap carbon dioxide created

Washington: Researchers have developed an inexpensive type of asphalt that can capture carbon dioxide from natural gas wells and keep it out of the atmosphere.

The study from the laboratory of James Tour at Rice University found that a compound made cheaply in a few steps from asphalt is even better than a green carbon capture material for wellhead sequestration discovered last year.

The best version made by the Tour lab is a powder that holds 114 per cent of its weight in carbon dioxide.

These new porous carbon materials capture carbon dioxide molecules at room temperature while letting the desired methane natural gas flow through.

The basic compound known as asphalt-porous carbon (A-PC) captures carbon dioxide as it leaves a wellhead under pressure supplied by the rising gas itself.

When the pressure is relieved, A-PC spontaneously releases the carbon dioxide, which can be piped off to storage, pumped back down-hole or repurposed for such uses as enhanced oil recovery.

"This provides an ultra-inexpensive route to a high-value material for the capture of carbon dioxide from natural gas streams," Tour said.

"Not only did we increase its capacity, we lowered the price substantially," said Tour.

He said they tried many grades of asphalt, the black, petroleum-based substance primarily used to build roads, some costing as little as 30 cents per pound.

Tour's goal is to simplify the process of capturing carbon from wellheads at sea, where there's limited room for bulky equipment.

The ability of A-PC to capture and release carbon over many cycles without degrading makes it practical, Tour said.

Lead authors, postdoctoral associate Almaz Jalilov and graduate student Gedeng Ruan, and their Rice colleagues made A-PC by mixing asphalt with potassium hydroxide at high temperature; they turned it into a porous carbon with a lot of surface area: 2,780 square meters per gram.

The material captured 93 per cent of its weight in carbon dioxide. Further experiments showed processing A-PC with ammonia and then hydrogen increased its capacity to 114 per cent.

The research appears in the American Chemical Society journal Applied Materials and Interfaces.