Experimental Microkinetic Approach of De-NOx by NH3 on V2O5/WO3/TiO2 Catalysts. 2. Impact of Superficial Sulfate and/or V<

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• 作者：Fran莽ois Giraud ; Christophe Geantet ; Nolven Guilhaume ; Stephane Loridant ; S茅bastien Gros ; Lynda Porcheron ; Mohamed Kanniche ; Daniel Bianchi
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 24, 2014
• 年：2014
• 卷：118
• 期：29
• 页码：15677-15692
• 全文大小：689K
• ISSN：1932-7455

文摘

The present article is dedicated to the impacts of sulfatation and/or V_xO_y deposition on TiO₂ supports on the individual heats of adsorption of adsorbed NH₃ species. The S and V loadings are similar to those of TiO₂ based commercial catalysts for the selective catalytic reduction of NO_x by NH₃: NH₃鈥揝CR. Two original experimental procedures are used, namely, adsorption equilibrium infrared spectroscopy (AEIR) and temperature-programmed adsorption equilibrium (TPAE). They have been developed in previous works and adapted in Part 1 for the species formed by the adsorption of NH₃ on a sulfate free TiO₂ support (P25 from Degussa). In agreement with the literature, Raman and FTIR spectroscopies show that the impregnation of the sulfate-free and sulfated TiO₂ supports by the vanadium precursor leads to well-dispersed V_xO_y species, which are involved in the adsorption of NH₃ in the temperature T_a range of 300鈥?73 K and for adsorption P_a < 0.5 kPa. Sulfate and V_xO_y groups favor the amount of NH₄⁺ species without modifying their heats of adsorption as compared to the TiO₂ support: they are not detected for temperatures of interest for NH₃鈥揝CR reaction. In these experimental conditions and whatever the solids, two main adsorbed NH₃ species on Lewis sites (denoted NH_3ads-L1 and NH_3ads-L2) are present, characterized by two 未_s IR bands below 1300 cm^鈥? and a common 未_as IR band at 鈮?600 cm^鈥?. By comparison with TiO₂ P25; it is shown that sulfate groups have strong impacts neither on the proportion, x₁ and x₂, of the two adsorbed species nor on their heats of adsorption (E_L1(胃) and E_L2(胃) with 胃 the coverage of the NH_3ads-L1 and NH_3ads-L2 species: x₁ = 0.65, x₂ = 0.35, E_L1(1) = 56 kJ/mol, E_L1(0) = 102 kJ/mol, E_L2(1) = 110 kJ/mol, E_L2(0) = 140 kJ/mol. The deposition of V-containing species on the sulfate-free and sulfated TiO₂ surfaces leads to similar conclusions: in the experimental conditions (T_a and P_a) of the NH₃鈥揝CR, two adsorbed NH₃ species on Lewis sites are detected with comparable proportions and heats of adsorption to those observed on the TiO₂ supports.