【作者】 姚卫华；

【导师】 王道；

【作者基本信息】 北京工业大学 ， 环境科学， 2003， 硕士

【摘要】 本课题以改性海泡石为原料，经过酸改性和离子交换改性后作载体。采用真空浸渍法制成了用于NOx催化还原的Cu基和Ag基催化剂，同时用稀土元素Ce和Sm等对所制备的催化剂进行了修饰。在稀薄燃烧条件下，考察了其对CO还原NOx的催化活性。对系列催化剂进行了筛选，并进一步运用XRD、TGA、IR、TPR、SEM等方法对所制备的催化剂进行了表征，探讨了各种因素对催化剂活性的影响。实验结果表明：改性海泡石作催化剂的载体具有常规催化剂载体所无法比拟的优越性。以酸改性法制得的载体性能优于离子交换法，通过正交试验优化选择得出了最佳酸改性条件为：盐酸浓度1.2mol/L，固液体积比1:20，改性时间20h，改性温度60℃。Cu/海泡石催化剂的整体性能优于Ag/海泡石催化剂，且Cu/海泡石催化剂在富氧条件下具有良好的耐湿热稳定性和催化活性。活性组分Cu的负载量为5%(wt.)时的催化剂在同类催化剂中对NO的还原有最好的活性，其起燃温度（NO的转化率达到50%）最低，为245℃；活性温度（NO的转换率达到90%）为320℃，也是最低的。加入稀土元素Sm和Ce后，催化剂的活性得到了进一步的提高，且钐铈比为1:4时效果最好。说明这种活性增加不仅与添加物的种类有关，而且与它们之间的比例相关，添加物之间存在着某种协同效应。含Ag量为2%(wt.)的催化剂具有较好的催化活性，在320℃时NO转化率达到最大值80.94%。可见Ag基催化剂的活性低于Cu基催化剂，但其负载量相对来说较低。氧含量对催化剂的活性有一定的影响，O2含量在3.8%(Vol.)以下，催化剂均能表现出很好的NO还原性能。且氧含量为2.2%(Vol.)时，有最好的活性，可见催化剂具有良好的O2适应能力。更多还原

【Abstract】 The natural sepiolite has been treated with hydrochloric acid and modified by ion-exchange method. Then a series of copper and silver catalysts were prepared by vacuum impregnation with the modified sepiolite as support and rare earth elements Cerium and Samarium as supplement catalysts. The catalytic activity for NOx reduction by CO was evaluated under lean burn conditions. Moreover, the means of XRD, TGA, IR, TPR and SEM etc. were used to characterize these catalysts and the factors affecting the activity of catalysts were discussed. It was found that the modified sepiolite was superior to the conventional support over performance. The support treated by acid has better performance than through the ion-exchange method. The best acid treat conditions were gained by orthogonal experiment: concentration of hydrochloric acid is 1.2 mol/L, volume of solid and liquid ratio is 1:20, treating time is 20h and treating temperature is 60℃.The whole performance of Cu/Sep is superior to Ag/Sep, and the former has good anti-water and thermal stable properties and catalytic activity under lean burn conditions. Cu/Sep catalyst (5%wt.) has the best activity over NOx reduction among the series of catalysts, whose light-off temperature (T50%) is the lowest, 245℃; and active temperature(T90%) is 320℃, also the lowest. The addition of rare earth elements Cerium and Samarium further increases the catalytic activity, and that the best activity was achieved when the Sm-Ce ratio is 1:4. It indicated that the increase of activity has relation not only to the elements added but also their ratios. There is some synergetic effect between the added elements.Ag/Sep with silver content 2%(wt.) has better activity, the highest conversion of NOx 80.94% was gained at 320℃. It showed that the activity of Ag/Sep is lower than that of Cu/Sep, well the loading of activity component is a little lower too.Oxygen concentration has much effect on the activity of catalysts. There is better catalytic activity of the catalyst when the oxygen concentration is lower than 3.8%(Vol.), and the best activity was gained when the concentration of oxygen is 2.2%(Vol.), so the catalyst has good adaption to the oxygen.更多还原