Arginine-Assisted Hydrothermal Synthesis of Urchin-like Nb2O5 Nanostructures Composed of Nanowires and Their Application in Cyclohexanone Ammoximation

Urchin-like Nb2O5 nanostructures have been successfully synthesized by a novel and simple L-arginine-assisted hydro thermal method. They are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption-desorption isotherms, thermogravimetric and differential thermal analysis (TG-DTA), and Fourier transform infrared spectroscopy (FT-IR). The results show that the urchin-like nanostructures are composed of nanowires with diameter less than 15 nm and possess a high specific surface area of 249.9 m(2).g(-1). Urchin-like Nb2O5 nanostructures have been used for the first time as a novel catalyst instead of conventional titanosilicate in the liquid-phase ammoximation of cyclohexanone. The as-prepared urchin-like Nb2O5 nanostructures exhibit high catalytic activity in cyclohexanone ammoximation. Under the optimal reaction conditions, the conversion of cyclohexanone and selectivity of oxime are as high as 98.0% and 88.9%, respectively. Finally, a possible formation mechanism of urchin-like Nb2O5 nanostructures is proposed.