脱硫脱硝一体化催化剂SnO_2-TiO_2的程序升温还原及脱附研究

TPR and TPD Research of deSO_x and deNO_x Integration Catalyst SnO_2-TiO_2

对以CO为还原剂同时还原SO2,NO为S和N2的反应,SnO2和TiO2(锐钛矿)没有催化活性,但它们组合成固溶体后,显示出很高的活性,说明它们之间存在协同效应.我们采用CO-TPR和NO-TPD证实SnO2和TiO2之间的协同效应表现为几何效应即TiO2使SnO2良好分散在TiO2的内孔表面和电子效应即TiO2促进SnO2表面晶格氧的还原和削弱NO的吸附能力.CO-TPR研究证明SnO2或SnO2-TiO2中被CO还原的晶格氧数只是总晶格氧数的10-5,说明这部分晶格氧为表面晶格氧,这是在CO存在下SnO2或SnO2-TiO具有催化氧化还原活性的前提.

There is synergism effect between SnO\-2 and TiO\-2 in SnO\-2\|TiO\-2 catalyst for simultaneous reduction of SO\-2 and NO by CO. In this paper the CO\|TPR, NO\|TPD methods were used to study such effect. CO\|TPR results show that there are a low temperature TPR peak (T\-\{rl\}=75 ℃)and three high temperature TPR peaks(T\-\{rh1\}=305 ℃, T\-\{rh2\}=385 ℃, T\-\{rh3\}=480 ℃)for single component SnO\-2 catalyst, in which Trl corresponds to the reduction of adsorbed oxygen on surface of SnO\-2, and T\-\{rh1\} corresponds to the reduction of surface lattice oxygen, and T\-\{rh2\}, T\-\{rh3\} correspond to the reduction of subsurface lattice oxygen. However, differs from SnO\-2, the TPR performance of SnO\-2\|TiO\-2 rather simple, along with the increase of TiO\-2 content in SnO\-2\|TiO\-2(e.g. Sn content: 10~60%), T\-\{rh2\} and T\-\{rh3\} peaks disappear, which represent that subsurface lattice oxygen does not exist in SnO\-2\|TiO\-2( Sn content: 10~60%).Moreover, the expenditure of CO during reduction of SnO\-2\|TiO\-2 increase with the content of TiO\-2(see Tab.1 and fig.2), showing that SnO\-2 is well disperses on the inner pore surface of TiO\-2 which leads to increase the amount of surface lattice oxygen\|one of the active center for redox reaction of SO\-2 and/or NO by CO. Besides the above geometric effect of TiO\-2 to SnO\-2, TiO\-2 also display electronic effect: along with the increase of the content of TiO\-2 in SnO\-2\|TiO\-2, the reduction temperature of SnO\-2 fall ~30 ℃(Fig. 1), and the adsorptivity of NO on SnO\-2\|TiO\-2 weaken(Fig.3).The geometric and electronic effect of TiO\-2 to SnO\-2 result in the increase of deSOx and deNOx activity of SnO\-2\|TiO\-2 with respect to SnO\-2 .By the way, CO\|TPR results show that the number of reducded lattice oxygen only 10\+\{-5\} part of the whole number of lattice oxygen in SnO\-2 or SnO\-2\|TiO\-2, therefore, the reduced lattice oxygen must be the surface lattice oxygen, which are the active center for catalytic redox reaction.