Sulfonic Acid‐Functionalized KIT‐6 Solid Acid Catalysts for Glycerol Acetylation

Abstract Blending biodiesel fuel (BDF) with petrodiesel effectively reduces CO₂ emissions in the transportation sector. The carbon footprint can be further minimized by converting crude glycerol, a byproduct of the BDF industry, into high‐value products like triacetin, which can serve as a biofuel additive. This study demonstrated the acetylation of glycerol with acetic acid using propylsulfonic acid‐functionalized KIT‐6 mesoporous silica (PA‐KIT‐6) as a solid catalyst to produce triacetin. A series of PA‐KIT‐6 catalysts was synthesized by post‐synthesis (grafting) and direct‐synthesis (co‐condensation) methods with varying sulfonic acid loading, using 3‐mercaptopropyltrimethoxysilane (MPTMS) and hydrogen peroxide as precursor and oxidant. In‐situ diffuse reflectance infrared Fourier transform spectroscopy and X‐ray photoelectron spectra confirm that all catalysts contained Brønsted acid sites, which increased with sulfonic acid loading. The P‐20PA‐KIT‐6 catalyst, with 0.25 mmol g⁻¹ sulfonic acid loading, exhibited the best performance. Glycerol was rapidly consumed, and 52% selectivity for triacetin was achieved using a 1:9 glycerol‐to‐acetic acid molar ratio and 2.83 wt.% catalyst at 115 °C for 8 h. This catalyst was reusable, maintaining its activity and selectivity over four cycles. This study highlights the intrinsic activity of sulfonic acid‐based solid acids with Brønsted acidity in glycerol acetylation, effectively producing triacetin.