Effects of urea in the preparation of supported-molybdenum trioxide via microwave induced technique

Abstract

The effect of urea in the preparation of MoO3 supported on activated carbon (AC) was studied. The experiment was performed by using microwave-induced technique. The bamboo-based activated carbon was used as the supportive material of MoO3. It was prepared via chemical activation using phosphoric acid as an activating agent and carbonized at 400 ?C. Meanwhile, urea was selected as an additive to enhance the formation of MoO3 because of its ability to extract Mo ion from the starting material ammonium heptamolybdate (AHM). The concentrations of urea to AHM were varied to see their effect to the formation of supported-MoO3. Urea was first added to the precursor solution and mixed homogenously before AC was introduced to the reaction media. After that, the mixture was treated under microwave radiation at 800 W for 2 minutes. The AC samples were characterized using BET surface area, Fourier transformed infrared spectroscopy and scanning electron microscope (SEM). Meanwhile, the supported-MoO3 samples were characterized by X-ray diffraction and BET surface area analysis. The BET surface area obtained for AC and C supported-MoO3 was 954.38 m2/g and 79.59 m2/g, respectively. The diffractogram obtained demonstrated the existence of orthorhombic a-MoO3 and C material. After comparison, sample with 1:1 molar ratio of Mo/urea was selected as the optimum ratio to produce the supported-MoO3. Higher concentration of urea led to the formation of amorphous MoO3 and C. As conclusion, with the equal ratio to the Mo precursor solution, urea can be used as an additive in order to enhance the formation of supported-MoO3. The surface area of supported-MoO3 can be enhanced by using activated carbon as supportive material. Finally, the reaction can be well performed using microwave radiation as a greener and faster source of energy.