Cheaper membrane filters natural gas and oil

"You need hydrogen in order to sweeten crudes," says Benjamin A. Wilhite. "We can use our membrane right now as a hydrogen purifier, which is valuable because hydrogen is extremely useful in the refining industry." (Credit: "oil derricks" via Shutterstock)

Engineers have developed a new gas separation membrane that could make extracting impurities from oil and natural gases easier and less expensive.

Jaime C. Grunlan and Benjamin A. Wilhite of Texas A&M University report the findings in Advanced Materials. They have also filed a patent for this technology due to its commercial potential.

“We use a simple polymer-based film to remove the impurities and it has the promise of a less expensive method for producing purer oil,” says Wilhite, associate professor in the department of chemical engineering. “It is all polymer and we are able to get performances comparable to really expensive materials such as mixed matrix membranes and zeolites.”

“The technology is separating gases,” adds Grunlan, associate professor in the mechanical engineering department. “Gas where they mine it is impure and contains different poison gases you don’t want. If you run gas through this membrane what comes out is much purer than what went in on the other side.”

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The membrane that Grunlan and Wilhite have developed is a layer-by-layer polymer coating that is comprised of alternating individual layers of common, low-cost polyelectrolytes.

The coating can be made by dipping or spraying, making it very easy to apply to existing gas separation systems. These films separate molecules based on size, the smaller ones such as hydrogen pass through, while larger ones such as carbon dioxide and nitrogen are slowed down.

“You can have multiple membranes in a row and it would keep getting purer and purer each time it went through the membranes,” says Grunlan. “Except for a sheet of metal, nothing has higher selectivity than our coating. This cheap easy coating is the best thing after a pure sheet of metal. The processing is easier and the materials are cheaper.”

Turning ‘sour’ crude ‘sweet’

The oil and gas industry could stand to be one of the main benefactors of the new technology. Both oil and gas contain impurities that have to be filtered.

For example, crude oil comes out of the ground with sulfur. If the amount of sulfur is greater than 0.5 percent the crude is considered “sour.” Crude with less than 0.5 percent sulfur is considered “sweet,” and is commonly used for processing into gasoline, kerosene, and high-quality diesel.

“Traditionally we have operated just off sweet crudes,” says Wilhite. “As all the sweet stuff is pretty much gone now, we are increasingly having to tap the holes in the ground we didn’t want 50 to 100 years ago.”

In order for the “sour” crude to be refined into gasoline, the sulfur has to be removed, which is currently done through hydro treating, an expensive process that in turn leads to higher-priced gasoline.

“You need hydrogen in order to sweeten crudes,” Wilhite says. “We can use our membrane right now as a hydrogen purifier, which is valuable because hydrogen is extremely useful in the refining industry.”

Source: Texas A&M University