Synthesis And Catalytic Performance Of Organo-functionalized Mesoporous Silicas With Hydrothermal Stability

Mesoporous silicas with controllable architecture, exceptionally highsurface area and uniform pore size have received considerable attention incatalytic discipline. In comparison with traditional zeolites, suchmaterials, however, have two main shortcomings: weak acidic propertyand low hydrothermal stability. Indeed, the unmodified mesoporoussilicas show low activity and poor hydrothermal stability when beingsubjected to catalytic applications, which limits the range of applications.In this dissertation, zeolite Y seeds originated from inexpensivesodium silicate were used for assembly with varied organotrialkoxysilaneto prepare a series of organo-functionlized mesoporous silicas of MSUwith high hydrothermal stability via a co-condensation method. Theobtained organo-functionalized mesoporous silicas were characterized byXRD, TEM, N₂ adsorption-desorption, FT-IR, solid²⁹Si MAS-NMR, andTG-DSC technique. It was found that the organo-functionlizedmesoporous silicas derived from zeolite Y seeds and organo-trialkoxysilanes possessed high BET surface area, narrow pore sizedistribution, and large pore volume. More importantly, suchorganic-inorganic hybrid materials can retain both the structural integrityand the organic groups on the pore surface of the mesostructure even afterthe treatment in water at 100℃for 150 h.After that, the conversion of-SH groups on the pore surface of themercapto-functionalized mesoporous silicas to-SO₃H gave rise to aseries of solid acidic catalysts. In comparison with traditional solid acidiccatalyst of HY, the sulfonic-functionalized mesoporous silicas showedsuperior catalytic performance in the reaction of acetalization betweenbenzaldehyde and alcohols. Typically, yield of acetal was as high as 90%.Furthermore, such mesostructured solid acidic catalysts can beconveniently recovered for recycled use without significant loss ofcatalytic activity. What is more important is that the catalytic performanceof the mesostructured solid acidic catalysts is not sensitive to the bulk ofalcohol.