Influence of nitric acid-assisted hydrothermal conditions on the characteristics of TiO2 catalysts and their activity in the oxidative steam reforming of methanol

Titania (TiO2) nanoparticles (NPs) with different morphologies (spherical, rod-shaped, and mixed) were prepared by hydrothermal treatment of different nitric acid (HNO3)/titanium (IV) isopropoxide (TTIP) molar ratios (0.25, 0.5, 1.0, and 1.7) at different hydrothermal temperatures (90, 150, 200, and 250 degrees C), hydrothermal times (6, 12, and 24 h), and calcination temperatures (500, 625, and 750 degrees C). The crystalline structure, morphology, and surface texture of the obtained TiO2 NPs were characterized by X-ray diffraction, nitrogen adsorption-desorption isotherm, field emission-scanning electron microscopy, and high resolution -transmission electron microscopy analyses. Under a larger HNO3: TTIP molar ratio, higher hydrothermal temperature, and higher hydrothermal time, the spherical mixed anatase-rutile phase TiO2 NPs were converted to a nanorod (NR)-shaped rutile phase (TiO2-R). The TiO2-R NRs gave the highest methanol conversion level (65%) and hydrogen yield (45%) in the oxidative steam reforming of methanol at 400 degrees C. (c) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.