29/03/2024
H2O2 is used commercially for disinfection and bleaching; the global market for the chemical is expected to reach 3.8 million tons this year, according to a 2008 report by Global Industry Analysts. The current method to produce H2O2 is an indirect process that involves sequential hydrogenation and oxidation of an anthraquinone. Direct methods tend not just to hydrogenate O2 into H2O2 but also to convert H2O2 into water.
Hutchings and colleagues, however, have now found that pretreating an activated carbon support with either nitric or acetic acid, then drying the support before adding gold and palladium, results in a reusable catalyst that produces H2O2 with minimal conversion to H2O.
Drawing from a combination of hydrogenation experiments and scanning transmission electron microscopy of prepared catalysts, the researchers propose that acid pretreatment of the catalyst support leads to smaller and better dispersed Au-Pd nanoparticles. The improved nanoparticle dispersion somehow shuts down sites that would convert H2O2 into water, they suggest.
More work needs to be done to evaluate the effect of acid pretreatment for H2O2 synthesis under conditions that more closely mimic a manufacturing setting, Hutchings says.
Nevertheless, "these are intriguing results showing that hydrogen peroxide can be made with high selectivity via a direct process," says D. Wayne Goodman, a chemistry professor at Texas A&M University. "This disclosure will no doubt promote an active search to identify the underlying cause or causes for this spectacular yet poorly understood effect."
Direct Conversion Au-Pd nanoparticles, typically smaller than 10 nm in diameter, on an acid-treated activated carbon support can hydrogenate O2into H2O2 while producing little H2O. Carbon support is gray, Au is yellow, Pd is blue, O is red, and H is white.
