Cost-effective bifunctional lignin-derived carbon supported tin oxide with efficient production of 5-hydroxymethylfurfural from glucose

5-Hydroxymethylfurfural (5-HMF) is one of the important bio-based platform compounds, and the catalytic conversion of glucose to 5-HMF is a highly desirable approach that is receiving increasing attention. Herein, we reported the synthesis of lignin-derived carbon supported tin oxides (SnO_x/LC) catalyst via a two-step hydrothermal-pyrolytic method using wheat straw alkali lignin as a cost-effective carbon source with high carbon content. The key preparation conditions of the catalyst and its catalytic conditions for the conversion of glucose to 5-HMF were investigated, respectively. Results show that under the preparation conditions of tin tetrachloride dosage of 3.0 mmol and pyrolysis temperature of 500 °C, the optimized catalyst (3.0-SnO_x/LC-500) with a high yield of 63.4% exhibits good catalytic performance of 5-HMF yield of 50.1% and reaction selectivity of 86.0% under the optimum conditions of reaction temperature and time of 190 °C and 3 h, initial glucose concentration of 10 %(mass), 3.0-SnO_x/LC-500 dosage of 100 mg in a biphasic solvent system of volume ratio of water to tetrahydrofuran of 1:4. In addition, 3.0-SnO_x/LC-500 exerts an excellent reusability in a five-cycle experiment. Furthermore, SnO_x/LC was characterized in detail using X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), ammonia temperature-programmed-desorption (NH₃-TPD), pyridine adsorption infrared spectroscopy (Py-FTIR), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). Results indicate that Brønsted acid sites and Lewis acid sites coexist on 3.0-SnO_x/LC-500, and more Sn⁴⁺, as well as a proper ratio of weak acidity to medium acidity, are conductive to its catalytic performance in glucose-to-5-HMF reaction.