A glass-fabricated microreactor was applied to the direct synthesis of hydrogen peroxide from hydrogen and oxygen. The direct synthesis reaction is a three-phase reaction, with gas (hydrogen and oxygen), liquid (reaction solution) and solid (catalyst) being involved. We designed an advanced microreactor in which an ideal gas-liquid distribution could be accomplished throughout the catalyst packed bed. We also set up a reaction system that enables the reaction operation at more than 2 MPa over 1 week. With these efforts, more than 3 wt% of hydrogen peroxide was successfully produced using the microreactor technology. (C) 2010 Elsevier B.V. All rights reserved.