Sulfonic acid functionalized mesoporous SBA-15 for selective synthesis of 4-phenyl-1,3-dioxane

Abstract

Mesoporous SBA-15 silica has been functionalized with propylsulfonic acid groups post-synthetically using 3-mercaptopropyltrimethoxysilane as sulfur source. The materials before and after functionalization have been characterized by BET surface area and pore size distribution by BJH method, powder X-ray diffraction and temperature programmed desorption (TPD) of NH3. The resultant mesoporous material (solid acid catalyst) exhibited hexagonal mesoscopic ordering, which possess 1.3 meq H+ g−1 SiO2 exchange capacity, 96 Å mesopore size diameter, and 660 m2 g−1surface area. Sulfonic acid groups anchored to SBA-15 silica pore surfaces are thermally stable up to 653 K, hydrothermally robust in boiling water and resistant to leaching in organic and aqueous solvents under mild conditions. XRD results indicate that there is no change in the structure after anchoring SBA-15 with SO3H group. SBA-15-SO3H catalyst has been found to be highly active and selective for the Prins condensation of styrene with formaldehyde. Both the conversion of styrene and the selectivity to 4-phenyl-1,3-dioxane are nearly 100%. Presence of more number of acid sites in SBA-15-SO3H catalyst helps in achieving high yields. Furthermore, the conversion and the selectivity to 4-phenyl-1,3-dioxane are found to be consistent in four repeated cycles.