(258g) High Thermal Stability in Anatase Phase of Vanadium Oxide Catalyst Supported on TiO2-B/Anatase Bi-Crystalline TiO2

High thermal stability in anatase phase of vanadium oxide catalyst supported on TiO₂-B/anatase bi-crystalline TiO₂

Licheng Li¹, Tuo Ji², Jiahua Zhu³, Zhuhong Yang², Xiaohua Lu²

1. College of Chemical Engineering, Nanjing Forest University, Nanjing, 210037, China

2. State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, 210009, China

3. Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, OH 44325, USA

The thermal stability of vanadium oxide/titania catalyst is an important factor for application in selective catalytic reduction (SCR) of deNO_x reactions and its further regeneration. However, the catalytic active anatase titania is inevitably transformed to low-active rutile titania under high temperature of above 500 ^oC. Especially doped with vanadium oxide, the phase transformation of titania will be accelerated which results in an lower anatase-to-rutile transformation temperature. The transformed rutile titania would definitely deactivate the catalytic performance of vanadium oxide/titania catalyst ^[1]. Different from the general method of introducing structural additive, an isomerism effect is proposed in this work to inhibit the generation of rutile titania. TiO₂-B/Anatase shell-core bicrystal titania (abbr. TiO₂) reported in our previous work was chosen as catalyst support^[2]. 1.0 wt% of V₂O₅ was loaded by a facile impregnation process. The composition of crystal phase of V/TiO₂ calcined by various temperatures was studied. It is found that the transforming temperature of rutile titania in V/TiO₂ is 200 ^oC higher than that of conventional anatase titania loaded with vanadium oxide (abbr. V/Anatase).

XRD and Raman results show that TiO₂ and Anatase has no phase transformation when the temperature is lower 600 ^oC. At 600~800 ^oC, the anatase phase of V/Anatase starts to transform to rutile phase. As for V/TiO₂, TiO₂-B turns into anatase and no rutile is generated. The anatase-to-rutile phase transformation of V/TiO₂ occurs when the calcination temperature is higher than 800 ^oC. The difference in the phase transformation between V/TiO₂ and V/Anatase can be attributed to the present of TiO₂-B: TiO₂-B is located at the outer surface of TiO₂, which  prevents the direct contact between anatase titania and vanadium oxide. During the thermal treatment process, TiO₂-B transforms to anatase due to the acceleration effect of vanadium oxide. This process replaces the anatase-to-rutile transformation. As a result, TiO₂ shows the better thermal stability than conventional TiO₂ without the protective TiO₂-B.

Reference:

[1] Wachs I E, Weckhuysen B M, Appl Catal A Gen, 1997, 157: 67

[2] Li W, Liu C, Zhou Y, Bai Y, Feng X, Yang Z, Lu L, Lu X, Chan K-Y, J Phys Chem C, 2008, 112: 20539