Sulfated and persulfated TiO2/MCM-41 prepared by grafting method and their acid-catalytic activities for cyclization of pseudoionone

Solid acid catalysts of SO4TiO2/MCM-41 and S2O82/TiO2/MCM-41 were prepared via grafting method and sulfate/persulfate promotion. The catalysts exhibited desirable activity and better selectivity for cyclization reaction of pseudoionone compared to traditional SO42-/TiO2. A combination of XRD, N-2 adsorption-desorption and FTIR spectroscopy indicated that the catalysts possess well-ordered mesostructure, and the grafted TiO2 are in highly dispersed amorphous form rather than crystalline phase. For S2O/TiO2/MCM-41 higher S content and more Bronsted acid sites can be achieved by persulfation, which is favorable for the protons participated cyclization reaction. The similar Si-O-Ti-O-S=O structure of all acid sites on pore surface of the catalysts is attributed to the improvement of selectivity in comparison with SO42-/TiO2.