Tender X-rays show how one of nature’s strongest bonds breaks

Short flashes of an unusual kind of X-ray light at SwissFEL and SLS bring scientists closer to developing better catalysts to transform the greenhouse gas methane into a less harmful chemical. The result, published in the journal Science, reveals for the first time how carbon-hydrogen bonds of alkanes break and how the catalyst works in this reaction.

Methane, one of the most potent greenhouse gases, is being released into the atmosphere at an increasing rate by livestock farming as well as the continuing unfreezing of permafrost. Transforming methane and longer-chain alkanes into less harmful and in fact useful chemicals would remove the associated threats, and in turn make available a huge feedstock for the chemical industry. However, transforming methane necessitates as a first step the breaking of a C-H bond, one of the strongest chemical linkages in nature.

Forty years ago, molecular metal catalysts were discovered that can easily split C-H bonds. The only thing found to be necessary was a short flash of visible light to “switch on” the catalyst and – bafflingly – the strong C-H bonds of alkanes passing nearby were easily broken almost without using any energy. Despite the importance of this so-called C-H activation reaction, it has remained unknown how that catalyst performs this function. Now, experiments at Swiss FEL and SLS have enabled a research team led by scientists at Uppsala University to directly watch the catalyst at work and reveal how it breaks the C-H bonds.

Read more on the PSI website

Image: An X-ray flash illuminates a molecule

Credit: University of Uppsala / Raphael Jay

Ancient fluid in quartz provides key to finding new uranium deposits

Saskatchewan’s Athabasca Basin is home to some of the world’s largest and richest uranium deposits, but it can still be tricky to find them.

Researchers at the University of Regina are studying how the deposits formed more than 1.5 billion years ago to help figure out the best places to look.

“We’re trying to understand the geological factors that control the formation of these deposits so that we know what features we should be looking for to find more uranium resources,” said Dr. Guoxiang Chi, a geologist at the University of Regina.

Chi, his Ph.D. student, Morteza Rabiei, and colleagues used the Canadian Light Source (CLS) at the University of Saskatchewan to analyze samples of quartz from areas known to contain uranium and nearby barren regions, the quartz having formed at the same time as the Athabascan uranium ore. They sliced the quartz into thin sections and studied the tiny droplets of primordial fluid trapped inside. It was from this fluid, circulating through geological fault lines billions of years ago, that today’s uranium ore formed. “By getting information about this paleo-fluid and seeing how it is distributed we can infer where the original uranium came from and what factors control its deposition,” said Chi. Understanding the conditions under which uranium ore is likely to form can help mining companies know where to look.

The results, however, were more complex than expected, he said. Fluid from ore-bearing areas had high levels of uranium, as expected, but so did the fluid from areas with no uranium ore. On the one hand, that is good news as it means that the uranium-rich fluid is more pervasive than first thought, but it also complicates the search for new deposits.

“We were hoping to see a major difference, but found uranium-rich fluid in both places,” he said. “So, if we want to use it as a guide to locate ore, we’ll have to understand the other factors that control deposition.” Chi said those other factors likely involve reducing agents that allow precipitation of the oxidized uranium in the fluid. “Without a reducing agent, you can’t have ore.”

Read more on CLS website