Preparation of millimeter-sized spherical SiO2–Al2O3 with various acid catalysts for the acetalization of glycerol with acetone

Through the sol-gel-oil ammonia column method, millimeter-sized spherical SiO 2 –Al 2 O 3 particles were successfully prepared using aluminum isopropoxide and varying amounts of tetraethyl orthosilicate. The impact of different Al/Si molar ratios on the structure and performance of SiO 2 –Al 2 O 3 materials was thoroughly investigated. The surface of the samples was analyzed for acidic sites (Brønsted and Lewis acids) both qualitatively and quantitatively. The millimeter-sized spherical SiO 2 –Al 2 O 3 materials were used as a catalyst in the Solketal production process, involving acetalization of acetone and glycerol. The glycerin conversion rate reached 88.67% and the Solketal selectivity reached 93.28% when the SiO 2 –Al 2 O 3 spherical particles reached with Al/Si molar ratio of 8. The spherical SiO 2 –Al 2 O 3 exhibits high catalytic activity in the acetalization reaction due to its large specific surface area, thermal stability, and moderate Brønsted and Lewis acidity.