The influence of the preparation method on the structural, acidic and redox properties of V2O5-TiO2/SO42− catalysts
The influence of the preparation method on the structural, acidic and redox properties of V2O5-TiO2/SO42− catalysts
复制标题
DOI：
10.1016/j.apcata.2008.12.037
复制
发表时间：
2009-03
影响因子：
5.5
通讯作者：
Hang Zhao;S. Bennici;Jianyi Shen;A. Auroux
中科院分区：
文献类型：
--
作者：
Hang Zhao;S. Bennici;Jianyi Shen;A. Auroux
研究了硫酸盐在钒钛催化剂中的引入及制备方法对硫酸盐样品性能的影响。采用共沉淀法、溶胶-凝胶法和机械研磨法制备了一系列V2 O 5-TiO 2/SO 42 −（VTiS）催化剂，并在不同温度下焙烧。采用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、热重分析（TGA）和X射线光电子能谱（XPS）等方法对产物的结构进行了表征。共沉淀法是迄今为止最好的制备方法，在最大化的表面积和介孔性。程序升温还原（TPR）表明，只有氧化钒物种可还原。XRD和FT-IR结果表明，V2 O 5在TiO 2表面均匀分散。XPS分析表明，机械研磨法制备的样品表面钒氧化物主要由化学计量比的V2 O 4和V2 O 5以及V2 O3物种组成。同时，钛在所有VTiS样品中以其完全氧化态存在，并且含硫物质呈现+6的氧化态。采用异丙醇（IPA）在空气中的转化反应来表征表面的酸碱性和氧化还原性。与TiO 2相比，VTiS催化剂的IPA转化活性更高，这可能是由于V2 O 5的加入导致了氧化还原位点的产生。此外，添加SO 42 −后，表面酸性增强，氧化还原性能减弱。
The introduction of sulfates into vanadia-titania catalysts and the influence of the preparation method on the properties of the sulfated samples have been studied. Series of V2O5-TiO2/SO42−(VTiS) catalysts were prepared by co-precipitation, sol–gel and mechanical grinding methods and calcined at different temperatures. Their structural properties were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Co-precipitation was by far the best preparation method in terms of maximizing the surface area and the mesoporosity. Temperature-programmed reduction (TPR) revealed that only the vanadia species were reducible. The results from XRD and FT-IR showed that V2O5was well dispersed on the surface of TiO2. XPS showed that the surface vanadium oxide was composed of stoichiometric V2O4and V2O5, as well as V2O3species especially for the samples prepared by mechanical grinding. Meanwhile, titanium was present in its fully oxidized state in all the VTiS samples, and the sulfur-containing species presented an oxidation state of +6. The reaction of isopropanol (IPA) conversion in air was used to characterize the surface acid/base and redox properties. The higher activity for the IPA conversion over the VTiS catalysts as compared to TiO2was possibly due to the generation of redox sites upon the addition of V2O5. Moreover, the surface acidic properties were enhanced and the redox properties weakened upon addition of SO42−species.