Synthesis, characterization and catalytic application of mesoporous molecular sieves SBA-15 functionalized with phosphoric acid

Abstract

The phosphoric acid groups has been successfully grafted on the surface of mesoporous molecular sieve SBA-15 to form a solid acid catalyst P-SBA-15 by post-synthesis method. The samples were characterized by means of XRD, FT-IR, SEM, TEM, 31P MAS NMR, NH3-TPD, N2 adsorption/desorption and the esterification reaction. The XRD and N2 adsorption/desorption results indicate that P-SBA-15 catalyst keeps the 2D hexagonal mesoporous structure and opens channels with the lower surface area of 554.35 m2/g compared with that of SBA-15. The SEM and TEM results show that the figuration of P-SBA-15 behaves “rod-like” and phosphoric acid groups is scattered differently on the surface of P-SBA-15. The FT-IR and 31P MAS NMR results display that phosphorus species graft onto the surface of SBA-15, which provide the Bronsted acid sites on the surface of P-SBA-15. The acidity of the generated Bronsted acid sites on P-SBA-15 significantly is verified by NH3-TPD. The esterification reaction results shows that catalytic activity of P-SBA-15 is enhanced significantly compared with that of SBA-15, and its stability is good.