Photocatalytic decomposition of nitric oxide on TiO2-modified MCM-41 catalysts

Mesoporous siliceous MCM-41 (SiMCM-41) molecular sieves with silicon partially substituted by Al and Ti were synthesized by direct hydrothermal method. Titania-modified MCM-41 molecular sieves (TiO2/MeMCM-41, where Me = Si, Al or Ti) were then prepared from tetrabutyltitanate and the calcined MeMCM-41. The prepared materials were characterized by ICP-mass, XRD, XANES, nitrogen adsorption isotherm, TEM, SEM, IR, UV-visible, Si-29 and Al-27 MAS-NMR, XPS, and EPR spectroscopy. All the spectroscopic studies resulted that Al and Ti located in the framework, and in the titania-modified samples, a well-defined surface layer of TiO2 appeared on the MCM-41 surface. Infrared spectra of pyridine adsorption showed that AlMCM-41 possesses weak Bronsted and Lewis acidities, which were highly enhanced by the modified surface titania. The EPR spectra of the TiO2/MeMCM-41 after being reduced by evacuating or in hydrogen at 500 degrees C, showed strong signals upon NO adsorption, and exhibited highly catalytic activity for the NO decomposition under UV irradiation.