Evaluation of the Catalytic Activity of Metal Phosphates and Related Oxides in the Ketonization of Propionic Acid

In recent years, the upgrading of lignocellulose bio-oils from fast-pyrolysis by means of ketonization has emerged as a frontier research domain to produce a new generation of biofuels. Propionic acid (PA) ketonization is extensively investigated as a model reaction over metal oxides, but the activity of other materials, such as metal phosphates, is mostly unknown. Therefore, PA ketonization was preliminarily investigated in the gas phase over both phosphates and oxides of Al, Zr, and La. Their catalytic activity was correlated to the physicochemical properties of the materials characterized by means of XRD, XRF, BET N2 porosimetry, and CO2 - and NH3 -TPD. Noteworthy, monoclinic ZrO2 proved to be the most promising candidate for the target reaction, leading to a 3-pentanone productivity as high as 5.6 h−1 in the optimized conditions. This value is higher than most of those reported for the same reaction in both the academic and patent literature.