CexZn1–xO2 catalysts for conversion of propanoic acid to 3-pentanone via ketonization

Abstract

Ketonization of carboxylic acids offers a highly effective strategy for upgrading bio-oil by reducing its oxygen content and enhancing fuel properties. In this study, a series of Ce_xZn_1–xO₂ catalysts with varying Ce/Zn ratios were synthesized and evaluated for the ketonization of propanoic acid to produce 3-pentanone, a valuable intermediate with improved thermal stability and hydrophobicity. Among the catalysts tested, Ce_0.7Zn_0.3O₂ catalyst exhibited exceptional performance, achieving >99% conversion of propanoic acid and >99% selectivity toward 3-pentanone at 350 °C, with stable catalytic activity maintained over a period of 3 h. BET surface area analysis revealed that all the catalysts possess mesoporous structures characterized by type-IV isotherms with H3 hysteresis loops. PXRD results indicated the formation of a CeO₂-dominated solid solution, with highly dispersed ZnO phase undetectable by diffraction. However, AAS, Raman analysis and FT-IR studies supports the presence of ZnO in the Ce_xZn_1–xO₂ catalysts. CO₂ and NH₃-TPD measurements demonstrated that Zn incorporation significantly enhanced the acidic and basic surface sites, which are crucial for propanoic acid ketonization activity. These findings highlight the potential of Ce_xZn_1–xO₂ catalysts for efficient bio-oil upgrading and contribute to the advancement of renewable fuel technologies through catalytic conversion of low-molecular-weight carboxylic acids.

Graphical abstract

Ce_xZn_1–xO₂ catalysts with varying Ce/Zn ratios were synthesized and evaluated for the ketonization of propanoic acid to produce 3-pentanone. Among the catalysts tested, Ce_0.7Zn_0.3O₂ catalyst exhibited exceptional performance, achieving >99% propanoic acid and >99% 3-pentanone selectivity at 350 °C, with stable catalytic activity maintained over a period of 3 h.