Strong Acid Sites Created on Small–Sized Anatase

The acid properties of anatase having different crystalline sizes were estimated by measuring the temperature-programmed desorption (TPD) of ammonia as well as the infrared spectrum of adsorbed pyridine at elevated temperature. The size-controlled anatase was prepared by hydrolysis of the titanium tetraisopropoxide dissolved in propyl alcohol using various amounts of distilled water. The acid properties of the anatase were confirmed to be strongly affected by the crystalline size. Especially, the strength of acid sites was found to remarkably increase with a decrease in the crystalline size. The specific activity and the activation energy for 1-butene isomerization on the anatase also depended on the crystalline size. The generation of strong acid sites on the surface is discussed in terms of the crystalline size.