The direct synthesis of hydrogen peroxide out of hydrogen and oxygen has been studied in a wall-coated microchannel. A silica wash-coat layer embedded with Au-Pd colloidal nanoparticles served as an active catalyst for the direct synthesis reaction. The influence of different reaction variables has been evaluated in order to identify optimal process conditions and to maximize the concentration of peroxide produced in the liquid phase. The gas mixture used in this study contained hydrogen and oxygen concentrations that would be considered explosive in conventional reactors. The results presented here show that combining the active Au-Pd catalyst with microchannel technology can lead up to 5 wt% peroxide solutions at hydrogen conversions as high as 80%. (C) 2014 Elsevier B.V. All rights reserved.