Using fused silica capillary reactors (FSCRs), we investigated the decomposition of guaiacol during hot compressed water oxidation (HCWO), with H2O2 added in stoichiometric ratios from 100 to 300%. Reactions were performed between 180 and 300 degrees C for durations from 2 to 10 min while the concurrent generation of CO2 during the oxidation process was followed by Raman spectroscopy and the phase behavior of guaiacol in HCW, with or without H2O2, was observed visually under a polarized microscope configured with a heating/cooling stage. We found that complete conversion of guaiacol and 100% yield of CO2 were achieved with a 150% stoichiometric ratio of oxidizer after 10 min at 200 and 300 degrees c, respectively. Based on the global reaction kinetics for the complete conversion of guaiacol to CO2, the reaction is considered to be first order. The activation energy and pre-exponential factor for CO2 formation are 18.62 kJ mol(-1) and 12.81 s(-1) respectively. (C) 2014 Elsevier B.V. All rights reserved.