The production of H2O2 via direct synthesis has been studied in depth over the last decades, due to the possibilities given by the discovery of active catalysts based on nanotechnology and selective active metals. However, the process is also complicated because of the coexistence of three phases, where mass transfer between gas and liquid (solvent) limits the concentration of O-2 and H-2 in contact with the solid catalyst sites, and subsequently the final H2O2 productivity. High pressures are normally used to enhance mass transfer by increasing the solubility. In this work, we explore the influence of low pressures, in order to optimise the reaction reducing mechanical requirements. Pressures from 0.1 to 0.9 MPa in a semi-continuous reactor have been tested, obtaining H2O2 concentrations up to 1.33 wt.% and a selectivity from 44.9% to 69.0%. A nano-Pd/C commercial catalyst and methanol as solvent have been used. (C) 2010 Elsevier B.V. All rights reserved.