The Role of Acidity in Terephthalic Acid Synthesis from Renewable Carbon Source

In this study, manganese-cobalt (MnCo) mixed oxide catalysts were prepared by two different routes: co-precipitation and citrate method. The structures and properties of the mixed oxide catalysts were investigated by several techniques: nitrogen adsorption-desorption isotherms, X-ray diffraction, X-ray photoelectron spectroscopy, SEM, FTIR and UV-Vis spectroscopies, temperature-programmed reduction with H2 (H2-TPR) and temperature-programmed desorption of NH3 (NH3-TPD). Their catalytic performance was investigated in the liquid-phase selective oxidation of naturally occurred p-cymene to terephthalic acid, as an alternative to p-xylene, a fossil derivative fuel component. Within this study, we demonstrate that the materials prepared by the co-precipitation method present strong acid sites that boost the oxidation rate and allow oxidation of p-cymene up to terephthalic acid. The co-existence of a significant number of strong acid and centers in higher oxidation state (Co3+) are required for these materials to be selective.