Preparation and characterization of manganese oxides supported on functionalized halloysite nanotubes with enhanced catalytic oxidation for toluene

In this study, halloysite (Hal) nanotubes treated with an acid and intercalation, were designed as a functionalized nanotubular structure to load and improve the dispersion of the Mn oxide doping of CeO for the toluene oxidation. The prepared catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average pore size and specific surface areas of Hal nanotubes treated with an acid and intercalation (AI-Hal) offered significant improvement. The XRD and TEM indicated that different types of MnO2 were successfully loaded on the external surface of AI-Hal nanotubes. The XPS data confirmed that the Mn-III and Mn-IV dominated on the surface of MnO2 due to the reversible redox reaction between Mn-III and Mn-IV. The evaluation of catalytic activities showed that the gamma-MnO2/AI-Hal presented good TOC performance of toluene. The doped CeO particles with diameters of approximately 10 nm were adsorbed on the external surfaces and lumen of Hal nanotubes and displayed a homogeneous dispersion state, which significantly improved the catalytic performance of the gamma-MnO2/AI-Hal catalyst system with the T-90 of 265 degrees C. The study indicated that catalytic activity of AI-Hal nanotube-supported manganese oxides was dependent on the valence state, oxygen vacancy and dispersion of active sites, and Hal nanotubes are acceptable reactants for the synthesis of supported catalysts with suitable MnOx.