We have found that the use of sulfuric acid in the peptization process of sol-gel method produced SO42--incorporated TiO2 which is mechanically strong by firing at low temperature such as 200 degreesC. The synthesized TiO2 has larger specific surface area and retards the phase transition from anatase to rutile compared with that prepared from the peptization with nitric acid. The S-content of the TiO2 fired at 200 degreesC was 1.52 wt.%; the value has a maximum of 2.74 wt.% at 400 degreesC. The XPS measurements indicate that S exists mainly as SO42-. The TiO2 fired at 400 degreesC showed the highest photocatalytic activity for ethylene degradation. Especially, we would like to emphasize the TiO2 sintered at 200 degreesC because they are extremely hard in spite of such a low sintering temperature. This photocatalyst may provide a great opportunity for extensive applications as self-supporting membranes.