The process for the oxidative esterification of furfural and HMF on Au/ZrO2 catalyst has been deeply investigated. Many variables, such as reaction time, temperature, pressure, and nature of the oxidant, have been optimised. For both processes, a considerable effect of the reaction temperature has been evidenced in the range here investigated (60-140 degrees C). As regards furfural, oxygen pressure can be lowered from 6 to 1 bar without significant changes in the catalytic performances. Molecular oxygen can be replaced by the more economic air, still at very low relative pressure (0.5 bar). In the case of HMF, oxygen pressure can be lowered from 6 to 1 bar without significant changes in the catalytic performances. Data on the reaction mechanism have been also verified by FTIR spectroscopy measurements taken in opportune experimental conditions in order to mimic reaction conditions. (C) 2014 Elsevier Inc. All rights reserved.