The solvent-free liquid phase epoxidation of cyclohexene with tert-butyl hydroperoxide over alumina-supported VPO and VPO bulk catalysts has been widely investigated using in situ Raman spectroscopy. Real-time Raman monitoring provides non-invasive insight during epoxidation of cyclohexene in the presence of heterogeneous catalysts in the absence of any solvent. The progress of the reaction was monitored following the changes in intensity of the characteristic Raman bands, which is more reliable than the use of gas chromatography analyses. The results obtained by real-time Raman monitoring confirms the reaction mechanism and provides a mean to monitor the deactivation of catalysts. The interaction between vanadium oxide species and VPO phases generates the active site. Their interaction renders the catalytic system efficient for production of 1,2-epoxycyclohexane. (C) 2012 Elsevier B.V. All rights reserved.