Simple and green route for preparation of tin phosphate catalysts by solid-state grinding for dehydration of glucose to 5-hydroxymethylfurfural (HMF)

Abstract

This work demonstrated a simple and green method for the synthesis of tin phosphate (SnP) catalysts for glucose to HMF transformation. In this process, SnP catalysts with various P/Sn mole ratios were prepared by solid-state grinding of a mixture of SnCl₄·5H₂O and NaH₂PO₄·2H₂O at room temperature, followed by drying with or without calcination. Physicochemical properties of the obtained SnP catalysts were investigated using N₂-physisorption, XRD, FT-IR, Py-IR, NH₃-TPD, and XPS techniques. The characterization studies showed that varying P/Sn ratio affected the textural and surface acid properties of the SnP catalysts. The activity of these catalysts was evaluated for dehydration of glucose for HMF production in water using recyclable low boiling point organic solvent THF as HMF extracting solvent. The experimental results revealed that the catalytic activity of SnP catalysts depended on the P/Sn ratio. Under the optimized reaction conditions, 98% glucose conversion, and 61% HMF yield were achieved over as-synthesized SnP-1 catalyst with P/Sn mole ratio of 1.0. The high catalytic activity of the SnP-1 catalyst can be attributed to its high acidity and the presence of water tolerant Brønsted and Lewis acid sites. Furthermore, the catalytic activity of SnP-1 catalyst is retained even after four cycles indicating its good catalytic stability.