On the promoting effect of the addition of ceria to platinum based alumina catalysts for VOCs oxidation

• Catalysts prepared: Pt/CeO2–Al2O3 (0, 7, 15, 23 and 51 wt% CeO2).
• Characterizations by SBET, ICP, H2 chemisorption, HRTEM, FESEM, OSC, XRD and TPR.
• Catalytic tests for the complete oxidation of n-butanol and acetic acid.
• Proposition of a reaction pathway to explain the formation of intermediates.
• Impact of ceria on the catalytic activity depending on the nature of the COV.

Pt catalysts supported on CeO2–Al2O3 mixed oxides with different loadings of ceria (0, 7, 15, 23 and 51 wt%) are prepared by sol–gel method and characterized by SBET, inductively coupled plasma (ICP), hydrogen chemisorption, high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), oxygen storage capacity (OSC), X-ray diffraction (XRD) and temperature programmed reduction (TPR). These catalysts are then tested for the complete oxidation of n-butanol and acetic acid. It has been shown that the addition of ceria to alumina influences the physico-chemical properties of the materials and their catalytic activities. A decrease of the surface area is observed when adding ceria to alumina. Moreover XRD patterns show that the addition of low concentrations of ceria (7 and 15 wt%) leads to a loss of the alumina structure while the material with a higher ceria loading shows typical crystallized CeO2 patterns. The reducibility of the materials is enhanced with the increasing ceria loading, which is in accordance with the OSC measurements. Addition of ceria results in the improvement of catalytic performance for n-butanol and acetic acid oxidations even if it also leads to a formation of numerous intermediate products that have mainly been attributed to the actives sites of ceria. A reaction pathway is proposed to explain the formation of these intermediates. The nature of the VOC is found to influence the effect of the addition of ceria on the catalytic activity. In fact, this effect is more pronounced for acetic acid oxidation than n-butanol transformation.

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