Sulfated and Persulfated TiO2/MCM-41 Prepared by Grafting Method and their Acid-catalytic Activities for Cyclization of Pseudoionone.

Solid acid catalysts of SO/TiO₂/MCM-41 and S₂O/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 SO/TiO₂. A combination of XRD, N₂ 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 Brønsted 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 SO/TiO₂. [ABSTRACT FROM AUTHOR]