Methyl ethyl ketone (MEK) peroxidation is carried out in a microchannel reactor under different reaction temperatures, H2O2 and acid concentrations, and feeding rates without using any organic solvent. It is found that at high reaction temperatures the decomposition of the peroxides will be accelerated. Increasing H2O2 concentration will increase the active oxygen content, while increasing H+ concentration will increase the yield. Both the active oxygen content and the yield are not sensitive to feeding rates. Consequently, a microreactor can be used for high throughput production, taking advantage of the fast heat transfer and good temperature control of the microreactor. (c) 2006 Elsevier Ltd. All rights reserved.