Microreactors provide a novel means for chemical synthesis in a highly controlled way to obtain better yield and selectivity. In the present work hydrogenation of ethylanthraquinone, which is the first step in the commercial production of hydrogen peroxide by Reidl-Pfleiderer process, is carried out in a microreactor packed with supported palladium catalyst. The effects of reaction temperature, hydrogen to liquid reactant flow rate ratio, reactor pressure, ethylanthraquinone concentration and fluid velocity on conversion and reactor space-time yield were studied. The performance data obtained from this microreactor study were compared with the data from conventional reactors reported in the literature. The data show that the reactor space-time yield is much higher in the microreactor than in Conventional reactors. (c) 2007 Elsevier B.V. All rights reserved.