Large-scale synthesis of sub-micro sized halloysite-composed CZA with enhanced catalysis performances

Abstract Large scale synthesis of catalyst with intriguing performances is a hot issue in the fields of both chemical and material science. In this paper, sub-micro sized ceria-zirconia-alumina (CZA) oxide material and that composited with halloysite (Hal) were synthesized in multi-gram scale through a simple co-precipitation method. X-ray diffraction (XRD), N2 adsorption-desorption isotherms, transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy(XPS), and temperature-programmed H2 reduction (H2-TPR) were used to characterize the crystalline, textural, morphological characters, and reducibility of the products. Three-way catalytic performances of the supported products were tested in stoichiometric air/fuel condition. The samples were all composed of sub-mirco sized particles. Size of CZA was about 200 nm, while the hybrid material introduced with Hal (CZAH) showed a rod-like and sheet-like morphology consisted of agglomerated nanoparticles with size of about 100 nm. The adaption of PEG-4000 has guided the formation of nanoparticles and their self-assembly into nano-rods in the products. The Hal mineral in the composites retained their tubular morphology and penetrated into bulk of the CZA. The CZAH composite showed larger BET surface area, favorable pore structure, and better oxygen storage capacity than the CZA sample thanks to the introduction of Hal nanotubes. The supported Pd-Rh/CZAH showed the ignition temperature at about 210 °C, and converting efficiency reached near 100% for NOx and CO before 230 °C in TWC tests, which also showed the optimized catalytic performances than CZA matrix.