Under the microscope: How energy savings and emission reductions begin at the molecular level

Science & technology

Sometimes you have to think small to make a big breakthrough. Really small. At the molecular level.

Ryan Lively, a professor at Georgia Tech, and Ben McCool, ExxonMobil chemical engineer, have spent years studying the world’s energy challenges through the lens of a microscope. Now they have developed a potentially revolutionary new technology.

This breakthrough has the potential to cut energy costs in the U.S. by nearly $2 billion a year and reduce industry’s global annual carbon dioxide emissions by 45 million tons. That’s equivalent to the annual energy-related carbon dioxide emissions associated with about five million homes in the U.S.

What is it?

Lively, McCool and their respective teams worked to successfully filter hydrocarbons through synthetic carbon membranes at the molecular level: a process called organic solvent reverse osmosis. That’s a mouthful. But the net takeaway is that it’s a manufacturing process that, if proven at large scale, could reduce the amount of energy and emissions associated with the production of raw materials used in plastics and polymers.

The novel approach enables similarly sized molecules to be separated using a molecular-level filter. The molecules you need to produce plastics pass through; the ones you don’t are recycled back into the process. This is a critical step in the production of plastics that currently requires energy-intensive separation processes.

The upshot: Because organic solvent reverse osmosis works at room temperature, it may one day replace existing separation technology—which requires a huge amount of heat—with a much more energy-friendly option. And it has the potential to dramatically reduce the amount of energy required in plastics processing.

Demand for things like auto parts, housing materials, electronics and other products made from plastics and other petrochemicals will continue to grow. There is a premium on improving industrial efficiency while reducing energy consumption and carbon emissions that will help responsibly meet this demand.

Filtering through the possibilities

To achieve this breakthrough, ExxonMobil leveraged its 10-year relationship with Georgia Tech and built on a foundation of proven success: the use of reverse osmosis in another critical area.

“Reverse osmosis using synthetic membranes has been used to desalinate and purify water since the 1960s,” said Lively. “The membrane acts as a filter, microscopically separating molecules of pure water from those attached to salt or contaminants.”

Today, 60 percent of global water desalination occurs using membranes, which has proven to be 10 times more energy efficient than thermal distillation, an alternative method.

“Ryan and I wanted to see if the same process could be used to separate complex hydrocarbon molecules like those used in the production of plastics,” said McCool. “We asked a simple question: Can reverse osmosis be applied to greatly reduce energy use at petrochemical plants?”

The answer wasn’t so simple.

“We experimented with carbon molecular sieve membranes rather than the current state-of-the-art zeolite membranes,” said Lively. “Our work showed that carbon membranes are 10 times more productive at filtration and can operate at room temperature, thereby reducing energy demand.”

The experiment was a success, but challenges remain. “Our next steps are to continue our work in the lab to understand the membrane’s stability and robustness,” said McCool. “If it continues to look promising, we’ll consider moving to testing it on larger demonstration units.”

“But if the development follows at the pace of water-filtration membranes,” added Lively, “we could be looking at a viable alternative to conventional technologies in petrochemical plants in the next few decades.”

Collaborating on progress

Key to that ongoing research is the collaboration between Georgia Tech and ExxonMobil. Lively and McCool personify the collaboration. They met when Lively was a graduate student in 2006 working on ExxonMobil-funded research into mixed-matrix membranes. This was the inception of a broader relationship with the university that has generated numerous patents and volumes of published research over the last 10 years.

The initial study of mixed-matrix membranes evolved into carbon capture research, then into separations and filtration. When Lively returned to Georgia Tech as a professor in 2013, McCool saw an opportunity to work together once again to find more energy efficient separation technology. In less than two years they have made huge strides. But the relationship is bigger than two people.

“Through collaboration with leading universities like Georgia Tech, ExxonMobil gets insights into academic research it can then translate into industrial applications,” said McCool.

“And Georgia Tech benefits from that industrial leadership and experience,” added Lively. “The idea is to leverage our research to find energy solutions.”

Sources

Nature International Science Journal: “Seven Chemical Separations to Change the World”

Georgia Tech News Center: “Researchers List Seven Chemical Separations to Change the World

U.S. Office of Energy Efficiency & Renewable Energy: The BTX Chain: Benzene, Toluene, Xylene

Energy Information Administration: Average power plant operating expenses for major U.S. investor-owned electric utilities, 2004-2014

Energy Information Administration: What is the efficiency of different types of power plants?

Energy Information Administration: How much carbon dioxide is produced per kilowatt hour when generating electricity with fossil fuels?

Energy Information Administration: Average power plant operating expenses for major U.S. investor-owned electric utilities, 2004-2014

Energy Information Administration: What is the efficiency of different types of power plants?

Energy Information Administration: How much carbon dioxide is produced per kilowatt hour when generating electricity with fossil fuels?

U.S. Energy Information Administration: California state profile and energy estimates

Desalination: Technical review and evaluation of the economics of water desalination

AIChE Journal: Water and beyond: Expanding the spectrum of large-scale energy efficient separation process

Tags:   Georgia Techplasticsreverse osmosisUniversity of Texasuniversity partnerships
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