Energy & Fuels, Vol.30, No.9, 7419-7427, 2016
Preparation and Catalytic Activity of Thermosensitive Ga2O3 Nanorods
Gallium oxide (beta-Ga2O3) nanorods were prepared by ultrasonic irradiation of molten gallium in warm water to form alpha-GaO (OH). This precursor was then subjected to calcination in air at 600 degrees C for 3 h to form beta-Ga2O3 as confirmed by Xray diffraction (XRD). Field emission scanning electron microscopy (FE-SEM)/high-resolution transmission electron microscopy (HRTEM) micrographs revealed the formation of well-organized nanotubes/nanorods with homogeneous size distribution. The average length of the beta-Ga2O3 nanorods was affected by the temperature of the water during sonication, decreasing from 480 to 72 nm with an increase in the temperature from 25 to 50 degrees C. A sharp decline in the particle size was also observed when the temperature was above 35 degrees C. The catalytic activity of the beta-Ga2O3 nanorods was examined, as a model, during the dehydration reaction of xylose to furfural. Furfural is a versatile biomass-derived platform compound used for the synthesis of several strategic chemicals. This nanoscale catalyst has a large surface area, which enhances its catalytic activity and enables it to completely convert xylose to furfural at 150 degrees C within 12 h without any trace of byproducts, as confirmed by high-performance liquid chromatography (HPLC), C-13 nuclear magnetic resonance (NMR), and H-1 NMR The XRD pattern of the used beta-Ga2O3 nanorods was identical to that of pristine Ga2O3, indicating the possible reusability of this catalyst. beta-Ga2O3 was reused for more reduction cycles, with similar results to the freshly prepared beta-Ga2O3. HPLC analysis demonstrated that the selectivity of furfural is up to 94% compared to the 30% obtained with GaO(OH) as a catalyst.