| Phosphotungstic acid(PTA) immobilized on g-C3N4 as catalyst (PTA/g-C3N4) was prepared via hydrothermal method using phosphotungstic acid and g-C3N4 as raw materials. Also, the structure of the catalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and automatic specific surface area and microporous physical adsorption (BET). Furthermore, the obtained catalyst was applied to the esterification of oleic acid and methanol to prepare biodiesel, and the catalytic performance of the catalyst was studied with the yield of biodiesel as index. The results showed that Keggin structure of PTA active species was still kept after being immobilized on the g-C3N4 surface. Under the conditions of immobilization amount of phosphotungstic acid 40%, reaction time 2 h, reaction temperature 80?℃, molar ratio of methanol to oleic acid 10∶?1 and catalyst dosage 7.5%, the catalyst had the best catalytic performance, and the yield of biodiesel reached 98.4%. |
