Promotional effect of Ti doping on the ketonization of acetic acid over a CeO2 catalyst

Abstract

A series of Ce_1−xTi_xO_2−δ mixed oxide catalysts were synthesized using a homogeneous precipitation method and characterized, and then these catalysts were applied to convert acetic acid to acetone using a gas-phase ketonization reaction. Ti-doped Ce_1−xTi_xO_2−δ catalysts (x = 0.1–0.5) exhibited much better ketonization performance than their parent catalysts of CeO₂ and TiO₂, and such Ti-doping-induced catalysis improvement is attributed to the formation of a Ce–O–Ti structure depending on the Ti content. Among the different Ce_1−xTi_xO_2−δ catalysts, the Ce_0.7Ti_0.3O_2−δ catalyst calcinated at 500 °C showed the best catalysis activity and high stability. A combination of techniques (i.e. TEM, FTIR, H₂-TPR, NH₃/CO₂-TPD and XPS) further revealed that the formation of the Ce–O–Ti structure modified the surface acid–base properties and thus enhanced the redox properties. Moreover, the introduction of Ti into CeO₂ also increased the number of oxygen vacancies on the catalysts’ surface that favored the ketonization of acid molecules. This work provides valuable insights into the design of highly efficient CeO₂-based catalysts for acid removal in the upgrading process of bio-oil.