CeO_(2)对钒基催化剂NH_(3)-SCR反应性能的影响

Effect of CeO_(2) on Performance of Vanadia-based Catalyst for Selective Catalytic Reduction of NO with NH_(3)

氮氧化物(NO_(x))是一种主要的大气污染物,采用氨选择性催化还原(NH_(3)-SCR)是实现NOx排放控制的最有效手段。以V_(2)O_(5)/TiO_(2)为研究对象,通过引入CeO_(2)对其结构及表面性质进行改性,显著提高了V_(2)O_(5)/TiO_(2)催化剂的NH_(3)-SCR反应性能,其中1%(质量分数)V_(2)O_(5)/Ce_(0.1)Ti_(0.9)O_(2)催化剂在180~470℃内NO_(x)的转化率在80%以上,具有较宽的温度操作窗口和良好的抗硫稳定性。表征结果表明:CeO_(2)的引入可抑制TiO_(2)晶体的长大,产生更多的结构畸变,并显著增大催化剂的比表面积。V和Ce物种之间的相互作用促进了催化剂表面V5+物种的形成,增强了催化剂对NO的吸附和氧化能力,并提供较多的弱和中等强度的酸性位,导致其低温SCR反应性能的显著升高;但同时表面强酸中心数量的减少以及NH_(3)非选择性氧化能力的升高,使其高温区SCR的活性明显降低。

Nitrogen oxides(NO_(x)),as a main atmospheric pollutant,has caused fearful harm for human health and environment.The selective catalytic reduction of NO_(x) by ammonia(NH3-SCR)is the most effective technology for the removal of NO_(x).In this paper,the CeO_(2) was used to modify the structure and surface properties of V_(2)O_(5)/TiO_(2) catalyst,which promoted the SCR activity significantly.Among them,1% V_(2)O_(5)/Ce_(0.1)Ti_(0.9)O_(2) catalyst exhibited the best catalytic performance of NH3-SCR reaction and obtained more than 80% NO_(x) conversion in the temperature range of 180~470℃,it also showed the high sulfur resistance.The characterization results showed that the doped CeO_(2) blocked the growth of TiO_(2) crystallite and obviously increased the surface area.The synergy between V and Ce species promoted the formation of surface V5+species,enhanced the adsorption and oxidation of NO and provided more weak/medium acid sites,which improved the SCR activity in the low temperature range.However,the enhanced oxidation ability and reduced the strong surface acid sites decreased the SCR activities of V_(2)O_(5)/CexTi1-xO_(2) in the high temperature range.