Lewis and Brønsted acids in super-acid catalyst SO42−/ZrO2–SiO2

Super-acid catalyst, SO4 2−/ZrO2–SiO2, with high zirconium loading was synthesized and the nature of the surface acid was investigated by FT-IR of pyridine adsorption. With the increasing ZrO2 content, the Lewis and Bronsted acid sites increased and reached the maximum when Zr/Si (molar ratio) = 1.3. The sample with Zr/Si = 1.3 showed the strongest IR adsorption band in the S=O stretching region (1,300–1,400 cm−1). Pyrosulfate and monosulfate species existed on the surface of the catalysts and the acidic strength could be enhanced by induction effect of their S=O groups. And there were two kinds of Bronsted acid sites on the surface of the catalysts.