Preparation of Nb2O5 nanorods and their catalytic property

Abstract

Aim: Nb2O5 nanorods are paid increasing attention due to their unique shape-dependent physical, chemical and catalytic properties. However almost all reported methods to synthesize Nb2O5 nanorods involve complicated processes. We aim to develop a simple route to prepare nanorod-like Nb2O5 and use them as catalysts for methanol dehydration. Materials and Methods: In this work, Nb2O5 nanorods were prepared by calcination of the precursors obtained using a solvothermal method with ammonium niobate oxylate hydrates as a starting material, oleic acid as a structure-directing agent and trioctylamine as a solvent. The crystal structures and morphologies of the as-obtained Nb2O5 nanorods were characterized using XRD and TEM. NH3-TPD was used to evaluate the amount and strength of acid sites for Nb2O5. Results: The reaction times had an influence on structures and morphologies of Nb2O5 nanomaterials. Irregular Nb2O5 nanoparticles with lower crystallinity were obtained when the solvothermal reaction time was 0.5h. Nb2O5 nanorods with well crystallinity were synthesized in high yield at 180 oC for 10h. The rod length ranged from 500 to 2000 nm while the width was 5-30 nm. In addition, the acid amount of Nb2O5 nanorods was higher than that of nanoparticles. When they were used as catalysts for the dehydration reaction of methanol, the conversion of methanol reached 30% at 300℃ with Nb2O5 nanorods as catalysts, while conversion of methanol was 10% for the reaction catalyzed by Nb2O5 nanoparticles. Conclusion: The rod-like Nb2O5 showed higher catalytic activity than the nanoparticles. The more acid content and higher crystallinity of Nb2O5 nanorods were all responsible for their higher activity.