Direct synthesis of hydrogen peroxide on palladium catalyst supported on sulfonic acid-functionalized silica

Recently, H2O2 is drawing growing interest in green chemistry 15 because it acts as direct and environmental benign oxidant in organic synthesis [2] and because its high cost limits the use for the production of bulk organic chemicals. The synthesis of hydrogen peroxide by direct reaction between H2 and O2 is a very attractive alternative to traditional anthraquinone 20 process. Direct synthesis over a Pd-based catalyst was first reported by Henkel and Webel in 1914 [3] and several studies have been published since then . However this process has yet to be put into practice. There are two major drawbacks: (i), the explosive limits of H2/O2 gas mixtures are very wide 25 [4] and are further widened with increasing pressure; and (ii), another major problem is to achieve good selectivity to H2O2 yield. To remain outside the explosive region mixtures of H2 and O2 should contain less than about 4% hydrogen.