CrOx Anchored on the Black-TiO.sub.2 Surface via Organic Carboxylic Acid Ligand and Its Catalysis in Oxidation of NO

CrO.sub.x/black-TiO.sub.2 catalysts were prepared by ligand-assisted (citric acid, oxalic acid and ethylenediaminetetraacetic acid) impregnation method. These catalysts were characterized in detail by means of X-ray diffraction, Raman, BET, X-ray photoelectron spectroscopy, H.sub.2 and O.sub.2(NO) temperature programmed reduction or desorption and in-suit DFTIR spectra. The results indicated that ligands assistance was beneficial for CrO.sub.x interacted with oxygen vacancies and O-Ti-O structures. Among all the catalysts, CrO.sub.x/black-TiO.sub.2/CA (modified by citric acid) revealed excellent catalytic activity and stability for NO oxidation in the temperature range of 200-450 °C. The characterization results exhibited that the interaction existed between CrO.sub.x and oxygen vacancies resulting in more Cr.sup.6+. Moreover, the strong interaction between CrO.sub.x and O-Ti-O was attributed to the modification of carboxylic acid, which increased the content of Cr.sup.3+ and chemical adsorption oxygen. High content of chemical adsorption oxygen promoted the adsorption ability of O.sub.2, and Cr.sup.6+ enhanced the adsorption capacity of NO. Hence, chemical adsorption oxygen and Cr.sup.6+ synergistically promoted the NO oxidation.