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U-M investigation aids in formulating a technique for producing cement precursors from carbon dioxide

Researchers at the University of Michigan have assisted in innovating a technique to transform carbon dioxide, an industrial byproduct that contaminates the air, into a valuable resource: precursors for cement manufacturing.

Chemist Charles McCrory and his team, in collaboration with Jesús Velázquez’s laboratory at the University of California, Davis, and Anastassia Alexandrova’s lab at the University of California, Los Angeles, have devised a technique for seizing carbon dioxide and converting it into metal oxalates, which can subsequently serve as precursors for cement production.

“This study illustrates how we can repurpose carbon dioxide, known widely as a waste material with minimal to no worth, into something that holds value,” remarked McCrory, an associate professor of chemistry and macromolecular science and engineering. “We’re not merely disposing of carbon dioxide; we are capturing it from diverse sources and reallocating it for beneficial uses.”

The investigation was inspired by McCrory’s involvement with the Center for Closing the Carbon Cycle. 4C is an Energy Frontier Research Center sponsored by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, and is directed by Jenny Yang at the University of California, Irvine. One of 4C’s aims is to research techniques for seizing and converting carbon dioxide into valuable fuels and products.

The predominant form of cement is Portland cement, usually produced from limestone and minerals like calcium silicates. According to McCrory, manufacturing this Portland cement incurs a considerable energy expense and carbon footprint. He and his colleagues have been investigating methods to convert carbon dioxide into materials suitable for producing alternative cements.

Metal oxalates, which are simple salts, can serve as an alternative cement precursor. Researchers have established that lead can act as a catalyst—a substance that accelerates a chemical reaction—that facilitates the conversion of carbon dioxide into metal oxalates. However, this approach necessitates substantial quantities of lead catalysts, posing both environmental and health risks.

The 4C team successfully employed polymers to modulate the environment surrounding the lead catalysts, decreasing the required lead for the process to parts per billion—a trace impurity level often found in numerous commercial porous graphite and carbon materials.

McCrory specializes in regulating the microenvironment—the chemical and coordination setting—around catalyst sites. By manipulating the microenvironment, McCrory can enhance the effectiveness of the catalyst. The researchers demonstrated that by adjusting the microenvironment around the lead catalyst during the chemical reaction converting carbon dioxide into oxalate, they can significantly lower the amount of lead necessary for the procedure.

In order to generate the oxalate from carbon dioxide, the researchers utilize a specific set of electrodes. At one electrode, carbon dioxide transforms into oxalate, an ion dissolved in the solution. The second electrode is a metal electrode that is oxidized and discharges metal ions, which bond with the oxalate ion and precipitate out of the solution as a solid metal oxalate.

“Those metal ions are merging with the oxalate to form a solid, and that solid precipitates from the solution,” McCrory explained. “That’s the end product we gather, which can then be integrated into the cement production process.”

Velázquez is a co-lead author of the study and an associate professor of chemistry at UCD. His team originated the idea of utilizing trace amounts of lead to drive the oxalate synthesis reactions and explored the mechanisms governing the chemical reaction of carbon dioxide into oxalate.

“Metal oxalates represent a largely uncharted territory—acting as alternative cementitious materials, synthesis precursors, and even solutions for carbon dioxide storage,” he stated.

Alexandrova, also a co-lead author of the study and a professor of chemistry and materials science at UCLA, conducted calculations to validate the hypothesis that this mechanism would function effectively.

“Catalysts are frequently discovered serendipitously, and successful industrial formulations are often quite complex. These cocktail catalysts are typically identified empirically through experimentation,” Alexandrova noted. “In this investigation, we have an instance of a trace lead impurity serving as a catalyst. I believe there are numerous additional such instances in practical catalysis, suggesting an untapped opportunity for catalyst discovery.”

McCrory asserts that once the carbon dioxide is converted into the solid metal oxalate, it will not be re-released into the atmosphere as carbon dioxide under normal conditions.

“It’s a genuine capture method because you’re producing a solid from it,” he stated. “Furthermore, it’s a valuable capture process since you’re generating a useful product with numerous downstream applications.”

According to McCrory, researchers should be capable of scaling up one element of the process: they are advancing studies on large-scale electrolysis for carbon dioxide. Future steps will include further investigation on how to amplify the portion of the process that generates the solid product.

“We are a considerable distance away, but I am optimistic that it’s a scalable method,” McCrory remarked. “One of our motivations for minimizing the lead catalyst to parts per billion is due to the difficulties associated with scaling up a catalyst reliant on large quantities of lead. This wouldn’t be environmentally responsible, otherwise.”

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