Limonene oxidation over V2O5/TiO2 catalysts

Vanadia-titania catalysts prepared by different sol–gel procedures were studied as heterogeneous catalysts for the liquid phase oxidation of limonene. The catalysts were characterized by XRD, XPS, ICP and nitrogen adsorption. According to the XRD results the catalyst samples can be divided in two different groups: anatase samples and anatase + rutile samples. XRD signals of vanadia are not found in the diffractograms. The main reaction products are polymers. Limonene oxide, limonene glycol, carveol and carvone are obtained in small amounts. A number of autoxidation products, alcohols, aldehydes and ketones, are also obtained. The effects of titania composition on the reaction orientation are discussed.