By Michael Padilla
The longstanding mystery of soot formation, which combustion scientists have been trying to explain for decades, appears to be finally solved, thanks to research led by Sandia National Laboratories.
Soot is ubiquitous and has large detrimental effects on human health, agriculture, energy-consumption efficiency, climate and air quality. Responsible for significantly increased rates of cardiovascular and pulmonary diseases and associated deaths, soot also contributes to millions of deaths worldwide annually, largely from indoor cooking and heating in developing nations. It leads to tens of thousands of deaths in the U.S. every year, predominantly from human caused, or anthropogenic, emissions to the atmosphere. In the atmosphere, emissions of soot are known as black carbon.
“By understanding soot formation, we have a better chance of being able to reduce its dangerous emissions from engines, forest fires and cook stoves and control its production and characteristics during industrial processes,” said Sandia researcher Hope Michelsen, adding that everyone knows what soot is, but nobody has been able to explain how gaseous fuel molecules become soot particles.
She said soot formation turns out to be very different from the typical process of gas molecules condensing into a particle, instead, requiring fast chemical reactions rather than condensation.
The solution also can apply to other high-temperature conditions, such as interstellar space, where large quantities of carbon-dust particles are formed, she said.
This groundbreaking work was published in a Science magazine paper, “Resonance-stabilized hydrocarbon-chain reactions may explain soot inception and growth.” Authors include Sandia researchers Michelsen, Olof Johansson, and Paul Schrader; Kevin Wilson from Lawrence Berkeley National Laboratory; and Martin Head-Gordon from the University of California, Berkeley and Lawrence Berkeley National Lab.
The work was funded by the Department of Energy’s Office of Science.