Determining the role of oxygen vacancies in palmitone selectivity and coke formation over acid metal oxide catalysts for the ketonization of methyl palmitate

Abstract

In the present study, TiO2, CeO2, MnO2, and ZrO2 catalysts were used to investigate the catalytic performance in methyl palmitate ketonization. The reaction was accelerated by weak Lewis acid, while the oxygen vacancies promoted the palmitone selectivity. The use of various characterization techniques revealed that oxygen vacancies played an important role for trapping the hydrogen atom and inhibited its spillover. This caused the suppression of the Lewis acid transformation to new Bronsted acid. Thus, the cracking of palmitone over the new Bronsted acid was diminished, leading to the decrement of selectivity to undesired products. However, when the hydrogen atom was trapped in the oxygen vacancies, the coke deposition was dominant. This phenomenon arose because hydrogen could not suppress the deep dehydrogenation, resulting in the transformation of aliphatic coke to aromatic coke. The role of oxygen vacancies was determined, and it had the positive effect on the palmitone selectivity, whereas it raised the coke formation.