Partial Oxidation of Methane to Acetic Acid with Oxygen Using AuPd/ZSM-5

The selective oxidation of methane to form methanol and acetic acid has been studied using AuPd nanoparticles supported on the zeolite H-ZSM-5 in water at 240 °C using molecular oxygen as the terminal oxidant in the absence of any added coreductant. The addition of Pd to Au/ZSM-5 significantly increases the selectivity to acetic acid to levels approaching almost complete selectivity within the oxygenated products. However, we observe that the reaction conditions employed lead to the corrosion of the stainless-steel components of the autoclave reactor and also leaching of iron from the ZSM-5 zeolite, and hence the AuPd nanoparticles, on reaction, become coated or partially coated with an oxidic Fe shell. The presence of the oxidized iron coating hinders nanoparticle agglomeration preventing deactivation of the AuPd/ZSM-5 catalyst but does not adversely affect the observed catalysis.