Journal of Molecular Catalysis A: Chemical 415 (2016) 56–64 Contents lists available at ScienceDirect Journal of Molecular Catalysis A: Chemical jou rnal h om epa ge: www.elsevier.com/locate/molcata Editor’s choice paper A comparison between photocatalytic and catalytic oxidation of 2-Propanol over Au/TiO 2 –CeO 2 catalysts Roberto Fiorenza a , Marianna Bellardita b , Leonardo Palmisano b , Salvatore Scirè a,∗ a Dip. Scienze Chimiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy b DEIM, Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy a r t i c l e i n f o Article history: Received 8 January 2016 Received in revised form 20 January 2016 Accepted 21 January 2016 Available online 29 January 2016 Keywords: Selective oxidation Catalytic combustion Photocatalysis Titanium dioxide Cerium oxide Gold a b s t r a c t Photocatalytic and catalytic oxidation of 2-propanol, representative of volatile organic compounds (VOC’s), were compared over mixed TiO 2 –CeO 2 -based catalysts. The effect of different amounts of CeO 2 and the presence of gold (1 wt%) on TiO 2 was investigated. In the photocatalytic oxidation CeO 2 had a negative effect on the performance towards the alcohol conversion of both TiO 2 –CeO 2 and Au/TiO 2 –CeO 2 catalysts, being Au/TiO 2 the most active system. On the contrary mixed TiO 2 –CeO 2 and Au/TiO 2 –CeO 2 samples showed a higher catalytic oxidation efficiency for 2-propanol conversion compared to the single oxides. In this case Au/CeO 2 catalyst had the best performance. On the basis of characterization data (XRD, Raman spectroscopy, EDX, BET Surface area determinations, H 2 -TPR, DRIFT and DRS), it was proposed that the interaction of gold with TiO 2 caused an enhancement of the partial photo-oxidation activity to acetone due to an increase of the charge separation between the excited electron and the hole of TiO 2 , whereas the coexistence of gold and both TiO 2 and CeO 2 oxides favoured the total oxidation of the alcohol to CO 2 . The catalytic oxidation of 2-propanol is, instead, mainly directed by the presence of a reducible oxide support as CeO 2 , necessary to enable a strong interaction with gold nanoparticles, providing very active lattice oxygen atoms. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Volatile Organic Compounds (VOC’s) are considered highly dan- gerous pollutants due to both their intrinsic toxicity and indirect production of highly toxic ozone via photochemical reactions. The term VOC’s encompasses many compounds including non- methane hydrocarbons, alcohols, aldehydes and organic acids. Exposure to VOC’s may trigger many serious health problems, such as eye, nose, skin, and throat irritation, coughing, headaches, and cancer, even at very low concentrations [1,2]. Therefore, it is highly desirable to abate efficiently and cost-effectively these compounds. Many practical methods, such as adsorption, thermal combustion, catalytic oxidation and biofiltration have been adopted to remove VOC’s [3–6]. Up to now the catalytic oxidation is one of the most efficient and relatively inexpensive route to reduce VOC’s at low concentrations. Two classes of catalysts, noble metals and transition metal oxides, are the most promising ones in the area of VOC’s combustion [7,8]. Regarding unsupported metal oxide catalysts, CeO 2 alone or com- ∗ Corresponding author. Fax: +39 095 580138. E-mail addresses: sscire@unict.it, salvatorescire.ct@gmail.com (S. Scirè). bined with other elements in mixed or doped oxides (CoOx, MnOx, CuO, ZnO, Fe 2 O 3 , TiO 2 , Al 2 O 3 , ZrO 2 ) is recognized as an efficient catalyst for the total oxidation of several types of VOC molecules [9–11]. It is known that CeO 2 increases the dispersion of active com- ponents because it acts as an oxygen reservoir which stores and releases oxygen via the redox shift between Ce 4+ and Ce 3+ under oxidizing and reducing conditions [12,13]. The VOC’s oxidation performance of CeO 2 can be strongly improved by the presence of gold. Au/CeO 2 is, in fact, among the most active systems for the oxidation of oxygenated VOC’s (alco- hols, aldehydes, ketones and esters) [14] and its performance is dependent on many factors, namely the nature and the proper- ties of the support, loading, size, shape and electronic state of gold nanoparticles, preparation method and pre-treatment conditions of catalysts, nature and concentration of the organic molecule to be combusted [14,15]. The high activity of Au/CeO 2 was ascribed to the high surface oxygen mobility of the gold/CeO 2 system, the lattice oxygen of the oxide being involved in the reaction pathway through a Mars–Van Krevelen (MVK) mechanism [16,17]. In this contest small gold nanoparticles have been reported to enhance the reactivity of CeO 2 lattice oxygen by weakening the surface Ce O bonds adjacent to Au atom [18]. http://dx.doi.org/10.1016/j.molcata.2016.01.025 1381-1169/© 2016 Elsevier B.V. All rights reserved.