Preparation Of The Nitrogen Doped TiO₂Materials With Silica-alumina Carrier And Its Photocatalytic Performance Analysis

Titanium dioxide is an important material which has excellentphotocatalytic property and finds wide application in catalysts field. Buttitanium dioxide is a wide bandgap semiconductor and it can only be stimulatedby ultraviolet rays. To further expand its applications in such fields, it isnecessary to prepare TiO₂materials that can be stimulated by visible light andthat can be easily recycle. Doping and the supported method are two main waysto improve the photocatalysis and recycling performance of the TiO₂. In the lastfew years supported titanium materials has been widely studied.In this work we prepared TiO₂-SiAl using sol-gel method firstly, findingthat the preparation of the material is non-crystal. Then we processed theprecursor by hydrothermal method. The results show that the crystallization ofthe material increased and the samples exhibits high photocatalytic activity.Moreover, we prepared Silicon aluminum titanium glue using water glass. Thisglue has a light photocatalytic ability and the hygroscopicity is strong.Inorganic compounds containing SiO2, Al2O3and TiO₂were used as initialreactants to form silicate framework and to carry TiO₂. With urea as nitrogensource, the nitrogen-doped TiO₂porous materials with silica-alumina carrier（N/TiO₂-SiAl） were fabricated first by hydrothermal method to form productprecursor and then by follow-up sintering procedure. The phase configurationand morphology of the samples were characterized via XRD, FESEM, FTIR,and UV-Vis diffuse reflectance. The photocatalytic activity to visible-light of theproducts was investigated using methyl-orange as the photodegradingcompound. The results show that this material is featured of greater specificarea and well-crystalline anatase octahedrite TiO₂uniformly distributed in theamorphous silica-alumina framework which can restrain the change fromanatase to rutile. N-doping could make the light absorption of the TiO₂ obviously extended into visible-light region, and increase the visible-lightresponsive photocatalytic activity. The results of photocatalytic degradation ofmethyl orange show that the samples exhibits high photocatalytic activity undersolar irradiation and methyl orange degraded more than90%within120min.After four times repeat degradation, the degradation rate of methyl orange isstill in80%.A sort of TiO₂materials supported on mesoporous silica-alumina wasprepared through hydrothermal method. The structure and properties of thesematerials were studied by modern measuring apparatus. The results showed thatthe samples have a very high surface area over1200m2/g and a regularmesoporous structure surrounded by macroporous solids of the silica-aluminamatrix. The mesoporous structure is composed of small units of anatase titanialocated at the surface of pore walls. With the increase of Ti﹕Si mole ratio, TiO₂nanoparticles are getting dense and the mesopores are becoming disordered andwormhole-like at the same time. The electron injection from activated dyemolecules to the conduction band of TiO₂can be improved with a suitableamount of Ti addition. The adsorption and cooperativity of TiO₂with thesilica-alumina matrix can enhance the photocatalytic activity under theirradiation of visible light. The results also showed that the growth anddensification of TiO₂nanoparticles associated with a shrinkage of themesoporous structure was observed with the increase of sintering temperature.The structure remains mesoporous up to850°C and the presence of dense TiO₂nanoparticles at the surface of the pore walls can strengthen the whole structure.An acidic environment can inhibit the growth of impurity crystals and promotethe anantase crystallization. All obtained materials presented higherphotocatalytic activities in the irradiation of simulation solar light. Theintroduction of nitrogen into the TiO₂structure, the adsorption of mesoporousstructure and the cooperativity of TiO₂with the silica-alumina matrix are themain reasons for enhancing the photocatalytic activity under irradiation ofsimulation solar light.