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asphalt-green

Published on September 27th, 2016 | By: Stephanie Liverani

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Road to reduced carbon emissions might be paved in asphalt

Published on September 27th, 2016 | By: Stephanie Liverani

[Image above] Credit: Matt; Flickr CC BY-ND 2.0

 

 

Cars continue to go “green,” with automotive industry heavy hitters like Nissan investing major bucks in vehicles that boast high performance with zero emissions.

 

The materials (like concrete) we use to build the roads under our cars are getting cleaner, too. But current concrete manufacturing practices are carbon-intensive. In fact, today’s standard Portland cement production accounts for nearly 5% of the world’s total carbon emissions, so researchers are looking to nature for solutions to more sustainable concrete production.

 

And with the U.S. Environmental Protection Agency developing new, stringent standards to reduce emissions, we need more energy efficient solutions across the board when it comes to manufacturing. 

 

But the road to reduced carbon emissions might be paved in asphalt—a new form of porous, carbon-absorbing asphalt, to be specific.

 

Researchers at Rice University in Houston, Texas, have developed a “new form of porous asphalt that can soak up 154% of its weight in carbon dioxide,” according to a university press release.

 

The researchers say this new asphalt could offer a more efficient way to clean raw natural gas, “which typically contains between 2% and 10% carbon dioxide and other impurities that must be removed before the gas can be sold,” the release explains.

 

This development is promising because current cleanup methods are complicated and expensive—the process is energy-intensive and typically involves flowing the gas through fluids called amines that can soak up and remove about 15% of their own weight in carbon dioxide, the release explains.

 

“It’s a big energy sink,” says James Tour, Rice University chemist. Last year, Tour’s lab developed a technique to turn asphalt into a tough, spongey substance that can be swapped for amines—organic molecules containing nitrogen that are relatives of the ammonia used industrially to eliminate CO2 and H2S from natural gas and refinery procedure streams—to remove carbon dioxide from natural gas pumped from ocean wellheads.

 

Tour says the team’s new, improved version of the asphalt sorbent requires a two-step process for fabrication that makes it even more scalable for manufacturing than the initial version.

 

“This shows we can take the least expensive form of asphalt and make it into this very high surface area material to capture carbon dioxide,” Tour explains. “Before, we could only use a very expensive form of asphalt that was not readily available.”

 

To create the new porous material, the researchers heated Gilsonite—a common type of asphalt—at ambient pressure to eliminate any unnecessary organic molecules. Then, they heated it again in the presence of potassium hydroxide for about 20 minutes to synthesize oxygen-enhanced porous carbon with a surface area of 4,200 square meters per gram—much higher than that of the previous materials, the release explains.

 

For comparison, the team’s initial asphalt-based porous carbon collected carbon dioxide from gas streams under pressure at the wellhead and released it when the pressure was released. The carbon dioxide was then repurposed underground while the porous carbon was ready for immediate reuse.

 

The team found that the new and improved version of this material can remove carbon dioxide at just 54 bar pressure.

 

As Tour explains in the release: “One bar is roughly equal to atmospheric pressure at sea level, and the 54 bar measure in the latest experiments is characteristic of the pressure levels typically found at natural gas wellheads.”

 

The study, published in Advanced Energy Materials, is “Ultra-high surface area activated porous asphalt for CO2 capture through competitive adsorption at high pressures” (DOI: 10.1002/aenm.201600693).

 


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