Acetalization of glycerol with hexanal in the presence of SBA-15 with sulfonic acid groups

Acetalization of glycerol with hexanal was studied over sulfonic acid-functionalized mesoporous silica (SBA-15), at 70 ºC. The product obtained were (2-pentyl-1,3-dioxolan-4-yl)methanol and 2-pentyl-1,3-dioxan-5-ol. Materials with different amounts of sulfonic acid groups were prepared. The support functionalization was achieved by the introduction of 3-(mercaptopropyl)trimethoxysilane onto the surface of these materials by grafting technique. The [SO₃H]-SBA-15 catalysts were characterized by nitrogen adsorption at 77 K, X-ray diffraction, SEM and titrations. All the catalysts were active in the studied reaction being the [SO₃H]₃-SBA-15 the best one. It was observed that the reaction rate increase with the amount of sulfonic acid groups on SBA-15 until a maximum. With high amounts of sulfonic groups, a decrease of activity is observed. Good values of selectivity to (2-pentyl-1,3-dioxolan-4-yl)methanol were obtained with mesoporous silicas anchored sulfonic acid groups. Catalytic stability of the [SO₃H]₃-SBA-15 was evaluated by performing consecutive batch runs with the same catalyst sample. The material showed a good catalytic stabilization.