A low-energy, low-cost methane to methanol process

Researchers have developed a new method to directly convert methane to methanol using molecular oxygen.

Liquid methanol is believed to have considerable potential as an alternative fuel, and is used as a feedstock in a variety of other chemicals. However, converting methane, the primary component of natural gas, to methanol is currently a complicated, indirect process which requires high temperature and high pressure.

A team led by Graham J. Hutchings at the Cardiff Catalysis Institute and Christopher J. Kiely at Lehigh University have used colloidal gold palladium (Au-Pd) nanoparticles to directly oxidise methane to methanol with high selectivity in aqueous solution at low temperature.

"Our work has shown that if a stable supply of methyl radicals can be established--for example, by incorporating a very small amount of hydrogen peroxide into the reaction mixture--then the selective oxidation of methane to methanol using molecular oxygen is entirely feasible," said Kiely, the Harold B. Chambers Senior Professor Materials Science and Chemical Engineering at Lehigh.

In a statement from Lehigh University, Kiely explained that the researchers were surprised to discover that for the reaction to work, the Au-Pd nanoparticles had to exist as free-floating colloids in a very weak hydrogen peroxide solution into which they injected pressurised methane and oxygen gas.

“Usually when we use Au-Pd nanoparticles as catalysts they are nearly always dispersed on high surface area oxide supports such as titania," said Kiely. "In this case however, the presence of the ceramic support turned out to be highly detrimental."

Currently, methane is converted to methanol by the production of synthesis gas (CO + H2) at high temperatures and pressures, a process which is both expensive and energy intensive.

"The new simplified approach we have demonstrated brings us a step closer to making the direct conversion of methane to methanol a practically viable proposition," said Kiely.

The team’s research has been published in the journal Science.