γ-Al2O3 Modified with Praseodymium: An Application in the Heterogeneous Catalytic Ozonation of Succinic Acid in Aqueous Solution

In an attempt to utilize ozone effectively, a series of praseodymium-modified γ-Al2O3 (Pr/Al2O3) was prepared via incipient wetness impregnation using Pr(NO3)3·6H2O as the precursor. The structure and properties of the catalysts were studied by X-ray diffraction (XRD) and the Brunauer−Emmett−Teller (BET) method. Catalytic activity was evaluated by monitoring the degradation of succinic acid (SA) in the presence of ozone. The praseodymium modification can effectively enhance the ozonation activity of γ-Al2O3 upon SA removal. Increasing the calcination temperature of Pr/Al2O3 is disadvantageous for the catalytic process, whereas increasing the load of praseodymium is helpful. After three successive cycles, the Pr/Al2O3 catalyst remained stable in the catalytic ozonation of SA. Overall, the initial degradation rate of SA, as well as the saturated adsorption capacity of SA, were found to have a linear relation to changes of the surface hydroxyl groups of the catalyst. On this basis, we conclude that the significant enhancement of SA degradation using Pr/Al2O3 as a catalyst should be because praseodymium, in the form of Pr6O11, promoted the formation of surface hydroxyl groups. Hence, the adsorption was increased, and the degradation rate of SA was enhanced.