Scientists at the Brookhaven National Laboratory (BNL; Upton, N.Y.; www.bnl.gov) and collaborating institutions have engineered a highly selective catalyst that can convert methane into methanol in a one-step reaction. The system could help make better use of “stranded” natural gas reserves in remote areas by converting methane gas into a transportable liquid.
The researchers developed a palladium-based catalyst (photo) for the reaction based on years of basic research on the three-phase reaction of methane gas, hydrogen peroxide as an oxidant and solid-powder catalysts. Using the catalyst, the direct process for methane-to-methanol conversion runs at lower temperatures than traditional multistep conversions and produces methanol without additional byproducts, the BNL team says.
In addition, this new work “translates the laboratory-scale catalyst synthesis into a more practical process for making kilogram-scale amounts of catalytic powder,” explains BNL chemist Sanjaya Senanayake, co-author of a recent paper describing the work in the Journal of the American Chemical Society.
A key aspect of the catalyst seems to be a layer of carbon between the palladium and cerium oxide. The BNL synthesis method yields Pd-iC-CeO 2, where iC refers to interfacial carbon. BNL chemical engineer and study lead author Juan Jimenez says “Carbon is often overlooked as a catalyst, but in this study, we did a host of experiments and theoretical work that revealed that a fine layer of carbon between palladium and cerium oxide really drove the chemistry.”
Modulating the activity of highly active metal-oxide interfaces by the incorporation of carbon interlayers balances the activation of the oxidant in tandem with the CH 4 to achieve ideal product selectivity, the researchers say. This results in a methanol selectivity of 100% at 75°C, they add.
BNL is exploring collaborations with entrepreneurial partners to bring the technology to market.