Direct and Postsynthetic Functionalization of Mesoporous B-SBA-15-SO₃H Acid Catalyst and Application to Methyl Propionate Esterification

Organic functionality can be added to mesoporous silicates in two ways: either by covalent grafting (postsynthetic) of various functional groups onto the channel walls or by incorporating functionalities directly during the synthesis (one-pot). If the grafted catalytically active groups experience similar environments and are isolated from each other, catalysis process is greatly facilitated. For this purpose, boric acid, as boron source, was added into the initial reaction mixture and then acid functionalization was performed by post and direct method. The obtained acid catalysts were tested in the esterification of propionic acid with methanol and the activity of these new materials was compared to that of SBA-15-SO₃H. Boron addition has facilitated the methyl propionate esterification for both postsynthetic and direct functionalized acid catalyst. Boron incorporated and postsynthetic functionalized mesoporous acid catalyst has highly enhanced the esterification reaction, compared to direct functionalized acid catalyst. The post functionalization method seems to be superior to one-pot functionalization method for preparation of mesoporous acid catalysts.