Preparation of Bifunctional Carbon-based Solid Acid and Its Catalytic Alcoholysis of Cellobiose

Chitosan was used as a carbon source to prepare iron-loaded nitrogen-containing activated carbon(ACN-Fe) through metal impregnation and high-temperature carbonization. A series of metal-loaded dual-functional carbon-based solid acid(ACN-Fe-SO₃H) catalysts were further prepared by hydrothermal sulfonation. The catalysts were applied to catalyze the alcoholysis of cellobiose. The catalysts were characterized in detail using X-ray diffraction(XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy(FT-IR), N₂ adsorption/desorption, X-ray photoelectron spectroscopy(XPS), inductively coupled plasma optical emission spectrometry(ICP-OES), and acid-base titration. The results showed that the unsaturated trivalent iron ions in the catalyst had Lewis acidity, while the sulfonic acid groups exhibited Brønsted acidity. The catalyst prepared at a carbonization temperature of 800 ℃(800-ACN-Fe-SO₃H) possessed the strongest acidity(acidity of 0. 81 mmol/g) and the best structural characteristics(specific surface area of 85.7 m²/g), showing the best catalytic performance. With a catalyst dosage of 0. 20 g, a reaction temperature of 200 ℃, and a reaction time of 5 h, the cellobiose conversion rate reached 99. 6%, with yields of levulinic acid(LA) and methyl levulinate(ML) of 15.6% and 62.1%, respectively. After 5 cycles, the cellobiose conversion rate remained 93.1%, with a product yield of 51.1%, indicating good catalyst reusability. Additionally, a preliminary exploration of the reaction mechanism of cellobiose alcoholysis was conducted.