The kinetics of C-5 sugars (xylose/xylan) conversion to furfural in an industrial prehydrolysis liquor (PHL) in both acetic acid (HAc)-catalyzed system and sulfuric acid (H2SO4)-catalyzed system, were determined in a temperature range of 150-190 C. The main reactions involved during the process included: 1) C-5 sugars consumption for furfural formation and side reactions; 2) furfural degradation. It was found that these reactions followed first order kinetics. A consecutive reaction model (from xylose to furfural, then to degradation products) fitted into the data obtained in the H2SO4-catalyzed system; while a consecutive/parallel model suited for the HAc-catalyzed system due to side reactions, which also consumed C-5 sugars. The activation energy for C-5 sugar disappearance, and the furfural degradation, was 151 kJ mol(-1) and 115 kJ mol(-1), respectively, in the HAc-catalyzed system. (C) 2014 Elsevier Ltd. All rights reserved.