Acetic acid is typically made from methanol and carbon monoxide, both of which are derived from methane, the major component of natural gas.
The technology used in this three-step process is expensive because it requires the chemicals to be blasted at temperatures up to 900 degrees Celsius.
But USC chemist Roy Periana has cut out two of the steps and made acetic acid directly from methane at 180 degrees Celsius. His research is published in the Aug. 8 edition of the journal Science.
"What our chemistry shows for the first time is that you don't have to take the methane, blast it to pieces and then recombine it," said Periana, a chemistry professor in the College of Letters, Arts & Sciences. "We are making acetic acid in our process, but it's made at 180 degrees and it's made in one step."
The key was the catalyst.
Periana and his team, which included USC graduate students Oleg Mironov, Gaurav Bhalla and C.J. Jones, used palladium, a precious metal.
They introduced the methane into a solution of sulfuric acid containing palladium sulfate, heated the mixture to 180 degrees Celsius and watched as the methane was converted to acetic acid and methanol.
"This is the first time we've obtained acetic acid with methane as the only starting material with any of the catalysts we've tried," Periana said. "This reaction cannot be commercialized as it is, but it shows the first possibility for making the acetic acid molecule in a fundamentally different way than it was made before."
Finding new, cheaper ways to convert natural gas - one of the planet's most abundant resources - to useful products is considered one of the "Holy Grails" of chemistry, Periana said.
The way to lower costs is to find an alternative to the high- temperature chemistry that requires expensive processors and high costs to run the plants.
"I wouldn't say this has solved that problem, but it adds another piece to the solution," Periana said. "We are inventing the next generation of catalysts that will allow us to convert methane at lower temperatures."
There is still much work to be done, he added. While palladium did the job, it had a very short life span. The goal now will be to study and then design a better catalyst that could one day have commercial applications.
Surya Prakash, a fellow USC chemistry professor who was not involved in the study, said he expects the scientific community will be excited with the study's results.
"This is a major breakthrough in methane utilization," he said. "If this chemistry can be made practical and economically feasible, I am sure that the work will have a major impact on acetic acid production."
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Science