Methane can be converted directly to methanol at low temperature through the actions of a solid platinum-based catalyst that exhibits high catalytic activity even after repeated recycling, according to scientists in Germany (Angew. Chem. Int. Ed. 2009, 48, 6909). The study may advance efforts to commercialize technology for converting methane to high-value and easily transported products.
Large reserves of natural gas that sit untapped in remote locations could be exploited commercially if cost-effective methods were available for converting methane, the principal component of natural gas, to easily transported liquids, such as methanol. A number of commercial processes that transform methane to liquid hydrocarbons already exist, but most are based on multistep conversions that proceed via synthesis gas (CO and hydrogen) and high temperatures (>600 °C). Various researchers have also described catalysts that directly convert methane to methanol, but most of those systems suffer from overoxidation, resulting in a large fraction of unwanted by-products.
Now, Regina Palkovits and Ferdi Schüth of Max Planck Institute for Coal Research, in Mülheim, and coworkers report that a triazine-based polymer complex, which they formed from dicyanopyridine trimers and a platinum salt, selectively transforms methane and oleum (fuming sulfuric acid) to methanol in high yield at roughly 200 °C.
The new catalyst shares similarities, such as N–Pt linkages, with a solution-phase methane-to-methanol catalyst developed more than a decade ago by researchers at Catalytica, in Mountain View, Calif. But unlike the older system, which has not been commercialized, the new catalyst is a solid and therefore easily separated from liquid products and recycled. The Mülheim team reports that the new material retains its high catalytic activity even after a half-dozen runs.
"This is an elegant method for immobilizing platinum in a well-defined manner," says Krijn P. de Jong, a professor of chemistry and catalysis at Utrecht University, in the Netherlands. The development is "noteworthy," he says, but he points out that using fuming sulfuric acid as an oxidant poses significant challenges regarding compatible materials and cost.