Synthesis of high concentration titanium-incorporated nanoporous silicates (Ti-NPS) and their photocatalytic performance for toluene oxidation

This study investigates the high concentration Ti-incorporated nanoporous silicate (Ti-NPS) as a photocatalyst for aromatic compound removal (toluene). Various Ti-NPS (Si:Ti molar ratios = 1:0 (0%), 3:1 (25%), 1:1 (50%), and 0:1 (100%)) materials were successfully synthesized without any structure damage. In XRD pattern, the main peak of 20 = 25.0 in TiO2 anatase structure did not show until 25% titanium incorporation, even after calcination at 550degreesC for 6 h. This result means that the titanium ions were stably substituted into the silicon site of nanoporous silicate framework. Their surface areas decreased with Ti-incorporated amount, and the particle sizes ranged from 500 to 1000 nm. The hexagonal straight pore size was 2.5 nm in pure NPS. This increased up to 4.0 nm in 25% Ti-NPS, and then decreased to 1.0 nm in 50% Ti-NPS. According to incorporated titanium amount, the Ti-NPS photocatalysts absorbed much water and toluene molecules than those of pure NPS and anatase TiO2. In addition, the activation energy for dehydrogenation was larger. The photocatalytic decomposition for toluene was enhanced in 50% Ti-NPS. In particular, the initial performance for toluene removal, which was attributed to the adsorption ability of nanopores, was higher compared with non-porous titania photocatalyst. (C) 2004 Elsevier B.V. All rights reserved.