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A series of CeO 2 catalysts with varying Na content were tested for vapor-phase ketonization of propionic acid at 350 °C. Na+ diffuses into the CeO 2 lattice and excess NaO x accumulates on the surface, which dilutes surface contiguous and partially covers Ce-O acid-base pairs. The intrinsic reaction rate in terms of surface area always decreased with increasing Na, likely originated from the altered acid-base property and the increased distance and steric hindrance between enolate and carboxylate for C-C coupling. On the other hand, the stability was significantly improved, with almost no deactivation being observed for Na 0.1 Ce 0.9 O x. This improvement is resulted from the dilution and/or coverage effects of NaO x , which significantly reduces accumulation of inactive bidentate propionate. This work demonstrates a strategy of dilution and/or coverage of surface acid-base pairs by alkaline metal oxides to reduce bidentate carboxylate and therefore to enhance the stability of metal oxide catalysts toward ketonization of carboxylic acids. [Display omitted] • Na dilutes surface contiguous and partially covers Ce-O acid-base pairs. • Doping Na significantly enhanced the stability of CeO 2 for ketonization reaction. • Na dilution and coverage effects reduced coverage of bidentate propionate. • Reduced coverage of bidentate propionate led to improved stability. [ABSTRACT FROM AUTHOR]