【摘要】 研究了富氧条件下SO2对CoH-ZSM-5上CH4选择还原NO(CH4-SCR)的影响,应用SO2-TPSR,NO+(O2)-TPD等方法研究了产生中毒的原因并定量研究了被毒化的活性位.反应在773 K进行时,加入体积分数78×10-6SO2,NO的转化率由72%逐渐降低并稳定在58%,提高反应温度至823 K,NO稳定转化率上升至62%.同时加入2.5%H2O和78×10-6SO2,反应温度为773 K时NO的转化率进一步下降至51%,但对反应在873 K进行时NO的转化率影响不大.SO2-TPSR曲线在690K,810 K和910 K形成3个SO2脱附中心,即使在970 K,吸附的含硫化合物仍未被完全脱附,表明中毒反应过程中,在CoH-ZSM-5表面形成了稳定的含硫化合物.NO+(O2)-TPD结果显示,被SO2毒化后的催化剂吸附NO和活性中间产物—NOy的容量明显下降,表明部分活性位被含硫化合物覆盖,活性中心减少导致CH4-SCR反应活性降低.SO2抑制了CH4转化,且含硫化合物高温脱附释放出部分活性位,使NO最佳转化率温度提高到823 K.更多还原

【Abstract】 Selective catalytic reduction of NO by methane over CoH-ZSM-5 in the presence of SO₂ was studied.SO₂-TPSR and NO+（O₂）-TPD techniques were applied to quantify the active sites and probe the poison effect.At 773 K,addition of 78 ×10^-6 SO₂,the NO to N₂ conversion ratio decreases from 72% and reaches stable level 58%.Increasing the reaction temperature to 823 K,the NO to N₂ conversion ratio increases to 62%.Co-existence of 2.5% H₂O and 78 ×10^-6 SO₂ at 773 K,the NO to N₂ conversion ratio decreases further to 51%,but almost no effect is observed at 873 K.Three SO₂ desorption centers at around 690 K,810 K and 910 K are formed over the SO₂-TPSR spectrum of the poisoned catalyst.Even at 970 K, the species contained sulfur is not desorbed completely.The amount of adsorbed NO and active intermediate —NO_y species decreases over the poisoned catalyst,indicating that partial active sites are covered by the compound contained sulfur.As a result,the NO conversion ratio decreases.On the other hand,the presence of SO₂ inhibits the conversion of CH₄ and the compounds contained sulfur is desorbed further at higher temperature,which causes the temperature where the optimum NO conversion shifts to 823 K.更多还原