Surface and acidic properties of mixed titanium and zirconium sulfated oxides

Mixed titanium and zirconium oxides with different sulfate ion contents were prepared from the oxysulfate and sulfate salts, respectively, using ammonium hydroxide as a precipitating agent. These oxides were subjected to heat treatment at different temperatures, then characterized by nitrogen adsorption studies and infrared spectroscopy. Their surface acidity was determined volumetrically by the adsorption of sodium hydroxide from solution, and was found to depend on both the amount of sulfate ions present as well as their state of ligation within the oxide matrix. Surface acidity varied with heat treatment, reaching maximum values within the temperature range of 380–600 °C, corresponding with the appearance of the chelated sulfato groups. This is corroborated by infrared spectroscopy results. A corresponding decreasing trend in surface area suggests that the increase in sulfate ligation results in pore blocking.