Catalytic Ketonization of Palmitic Acid over a Series of Transition Metal Oxides Supported on Zirconia Oxide-based Catalysts

Modification of a ZrO based catalyst with selected transition metals dopants has shown promising improvement in the catalytic activity of palmitic acid ketonization. Small amounts of metal oxide deposition on the surface of the ZrO catalyst enhances the yield of palmitone (16-hentriacontanone) as the major product with pentadecane as the largest side product. This investigation explores the effects of addition of carefully chosen metal oxides (FeO, NiO, MnO, CeO, CuO, CoO, CrO, LaO and ZnO) as dopants on bulk ZrO. The catalysts are prepared a deposition-precipitation method followed by calcination at 550 °C and characterized by XRD, BET-surface area, TPD-CO, TPD-NH, FESEM, TEM and XPS. The screening of synthesized catalysts was carried out with 5% catalyst loading onto 15 g of pristine palmitic acid and the reaction carried out at 340 °C for 3 h. Preliminary studies show catalytic activity improvement with addition of dopants in the order of LaO/ZrO < CoO/ZrO < MnO/ZrO with the highest palmitic acid conversion of 92% and palmitone yield of 27.7% achieved using 5% MnO/ZrO catalyst. Besides, NiO/ZrO exhibits high selectivity exclusively for pentadecane compared to other catalysts with maximum yield of 24.9% and conversion of 64.9% is observed. Therefore, the changes in physicochemical properties of the dopant added ZrO catalysts and their influence in palmitic acid ketonization reaction is discussed in detail.