A series of rare earth oxides were investigated as catalysts in the ketonization of acetic acid. High selectivity to acetone over 99% was obtained by reacting acetic acid over rare earth oxides such as La(2)O(3), CeO(2), Pr(6)O(11), and Nd(2)O(3). Especially, Pr(6)O(11) showed the highest yield of 80% at 350 degrees C among the 14 rare earth oxides. The bulk structure of CeO(2) was stable during the ketonization, while the surface acetate species were observed over CeO(2) after ketonization. In contrast, the other active rare earth oxides such as La(2)O(3), Pr(6)O(11), and Nd(2)O(3) were mainly basic oxides due to the formation of bulk oxyacetate such as MO(AcO), where M is La, Pr, and Nd and AcO indicates CH(3)COO group, in the initial period of the reaction. In any case, the catalytic ketonization proceeds over the surface of the oxyacetates and CeO(2). Catalytic cycle of the ketonization is composed of two steps: the decomposition of surface M(2)O(AcO)(4) to produce MO(AcO), acetone, and carbon dioxide and the regeneration of surface M(2)O(AcO)(4) by reacting MO(AcO) and acetic acid to produce water. (C) 2011 Elsevier B.V. All rights reserved.