This paper discusses the development of an anthraquinone auto-oxidation (AO) process for the production of hydrogen peroxide with the focus on its key step-liquid-phase hydrogenation of active anthraquinones over Pd/Al2O3 catalyst. The main issues considered in the process development were the selection of a trickle bed as the hydrogenation reactor, the degradation of active anthraquinones and regeneration of their degradation byproducts, the development of a new spherical Pd/Al2O3 hydrogenation catalyst, its deactivation and regeneration, and the examination of its activity, selectivity, life, etc. The establishment of start-up and normal operational procedures ensured minimum degradation of active anthraquinones and maximum stable operation. The experimental results from bench and pilot tests paved the way toward industrial production of hydrogen peroxide. (c) 2007 Elsevier B.V. All rights reserved.