Ketonization of Valeric Acid to 5‐Nonanone Over Metal Oxides Catalysts

Abstract Valeric acid (VA), readily obtainable in the biorefinery from sugary biomass streams, can be upgraded to 5‐nonanone, a versatile chemical building block with numerous applications. This study investigates the performance of nine metal oxide catalysts (SnO 2 , SiO 2 , Y 2 O 3 , CeO 2 , ZrO 2 , TiO 2 , La 2 O 3 , Cr 2 O 3 , and Al 2 O 3 ) in the gas‐phase ketonization of VA to 5‐nonanone in the 350–450 °C range. The screening reveals a correlation between the metal oxides lattice energy and their catalytic activity for valeric acid ketonization. ZrO 2 , TiO 2 , and La 2 O 3 , characterized by high lattice energy, demonstrate the highest catalytic activity, whereas Y 2 O 3 , SnO 2 , and SiO 2 , showing low lattice energy, are barely active. However, exceptions to this trend were observed: Cr 2 O 3 and Al 2 O 3 displayed poor catalytic performance despite their elevated lattice energy. The comprehensive characterization of the catalysts, encompassing XRD, N 2 ‐physisorption, NH 3 ‐TPD, and CO 2 ‐TPD analyses, has unveiled the crucial role of important parameters including acid–base properties in addition to lattice energy. Only oxides showing amphoteric properties can catalyze the reaction effectively. Interestingly, low‐lattice energy and amphoteric oxides such as SnO 2 (showing poor performance) become significantly active at higher temperature (500 °C). Analysis of by‐products by online GCMS and spent catalyst characterization indicated that in this case the ketonization mechanism changed from the so‐called surface mechanism to the so‐called bulk mechanism.