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

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 Br?nsted acid sites on the surface of P-SBA-15. The acidity of the generated Br?nsted 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.