Effect of Si/Zr Ratio on the Catalytic Transformation of Glycerol to Solketal Over Sulfated Zr-MCM-41 Catalysts

Sulfated Zr-MCM-41 (SZM) was found to be a highly efficient and reusable mesoporous catalyst with 97% glycerol conversion and 99% solketal selectivity under ambient conditions. All Zr-MCM-41 catalysts were synthesized using the sol–gel method, with varying Si/Zr ratios ranging from 250 to 40. Subsequently, the catalysts were impregnated with sulfate derived from sulfuric acid. Furthermore, the impact of Zr content and sulfonation on the rate of reaction was also investigated. X-ray diffraction (XRD) and nitrogen sorption investigations provided evidence of the mesoporous characteristics of SZM catalysts, demonstrating a favorable surface area and porosity. SEM-EDAX and TEM investigations provided clear evidence of the preserved spherical morphology and hexagonal structure of the MCM-41 material following Zr incorporation and sulfonation treatments. XPS results indicated the existence of Zr and sulfate ions on the catalyst surface. Ex-Situ pyridine-adsorbed IR (Py-IR) and NH3-TPD analysis results confirmed that the Lewis/Bronsted acidity of catalysts was boosted as the Zr content increased, and this effect was further amplified by sulfonation, which was corroborated by the solid-state 29Si MAS NMR data. The catalyst exhibited sustained activity even after being used up to five times.