Researchers at North Carolina State University (NCSU), Raleigh, N.C., have used computer simulations to develop new molecular models that could be used to design cheaper and more efficient versions of the amine chemicals currently used in scrubbers to reduce carbon dioxide emissions.
In 2014, coal-fired power plants produced more than 14 billion mt of CO2, representing 40% of the total amount generated by human activity worldwide, according to the International Energy Agency (IEA), Paris, France. At the same time, new environmental regulations and public incentives are progressively being put in place to limit the amount of CO2 emissions from industry and to encourage new research for its storage and recycling.
However, as the IEA points out, with the average cost of capturing and storing CO2 ranging between $50 and $100/mt, current scrubbing technology is too expensive to become a sustainable solution.
Part of the problem here is the inefficient amine-based solutions still used in industrial scrubbing applications require very costly absorbent regeneration. Even those that are considered good candidates, such as tertiary amines, can have CO2 properties that differ drastically from one analogue to another despite apparently high structural similarity.
To tackle this issue, NCSU researchers are looking for new amine chemicals with better qualities such as faster absorption rates, higher CO2 capacity and lower heats of reaction. Denis Fourches, assistant professor of chemistry at NCSU, and postdoctoral researcher Melaine Kuenemann, worked to create computer models that could predict an amine’s absorption properties based on its chemical structure.
They collected and curated experimental data from the literature and built a modeling set based on 41 publicly available amine solutions together with all their chemical and absorption properties.
Then they analyzed the chemical and structural characteristics of each amine and grouped them into families of chemicals with similar structural properties. Next, they looked at how well and how quickly these amines could absorb carbon. Using these data, the researchers created a series of models known as quantitative structure-property relationships models that can predict the amines’ CO2 absorption properties solely based on their structural characteristics.
These models utilize machine-learning techniques to predict which chemical structures are likely to have the best overall absorption properties. The researchers found the models to be reliably discriminating between amines with high absorption properties versus those that were less efficient.
“This work is the first attempt to develop computer models for fully evaluating and predicting carbon dioxide absorption properties of amine solutions,” Fourches says. “The next step for us is to utilize these computer models to screen a virtual library of hundreds of thousands of new amines, and identify some new amine candidates predicted to have way better carbon absorption properties.”
He adds, “If you had to test all of these thousands of compounds experimentally, it would take decades of work. With the powerful computers we have access to, this virtual screening can be done in a matter of days and is very inexpensive. This is a game changer for designing and prioritizing new compounds.”
Meanwhile, the U.S. Department of Energy’s Office of Fossil Energy (FE) has selected seven projects to receive $5.9 million in funds to focus on novel ways to use CO2. The seven will directly support FE’s carbon use and reuse R&D portfolio, which in turn will develop and test novel approaches to convert captured CO2 into usable products.
The projects fall into three technical areas: biological-based concepts for beneficial use of CO2; mineralization concepts utilizing CO2 with industrial wastes; and novel physical and chemical processes for beneficial use of the gas.
Five of the projects fall in the third category, with each getting nearly $800,000 in FE funding. Among them, the University of Delaware, Newark, is to develop and test a two-stage electrolyzer process for converting flue-gas-derived CO2 into C2 and C3 alcohols such as ethanol and propanol. The Gas Technology Institute, Des Plaines, Ill., is working on a direct, high-energy electron beam synthesis process to produce chemicals such as acetic acid, methanol and carbon monoxide from CO2. Development of a sorbent-based, thermocatalytic process to convert captured CO2 into syngas is the focus for TDA Research, Wheat Ridge, Colo.
In another development, Emissions Reduction Alberta has announced the Round Two winners of its competition for technology to productively use CO2. For details, see “Carbon Contest Chooses Winners.”
Seán Ottewell is Chemical Processing's Editor at Large. You can email him at email@example.com.