Pt/Ba/Ce/γ-Al_2O_3催化剂H_2-NSR性能影响因素的试验分析

将改进的溶胶-凝胶法与等体积浸渍法相结合制备了Pt/Ba/Ce/γ-Al2O3钙钛矿催化剂,研究了其表面性能;采用NOx存储还原循环试验的方法,以氢气为还原剂,研究了还原剂体积分数、还原时间和空速等反应条件,以及以CO2与HC为代表的发动机排气成分对催化剂存储还原特性的影响.结果表明:所制备的Pt/Ba/Ce/γ-Al2O3催化剂具有良好的催化活性及较大的比表面积;在所研究的范围内,不同还原剂体积分数下存在NOx转化率最高的最佳还原时间,而且随着还原剂体积分数增加,最佳还原时间逐渐缩短;还原剂体积分数的增加将会加速NOx的脱附,若还原剂体积分数过高,则会造成部分NOx溢出过快,还原时间不足而引起转化率降低;在7.0×104 h-1的大空速条件下,NOx转化率仍可以保持在86.9%,Pt/Ba/Ce/γ-Al2O3催化剂的空速特性良好;CO2在一定程度上抑制了NOx的存储,影响催化剂的活性,但催化剂容易再生;采用C3H6模拟排气中的HC,其体积分数较低时对H2还原NOx具有抑制作用,当C3H6的体积分数较高时可以促进NOx的还原转化.

Experimental Study of H2-NSR Performance of Pt/Ba/Ce/γ-Al2O3 Catalyst

Abstract： The perovskite catalyst Pt/Ba/Ce/γ Al2O3 was prepared by the improved Sol Gel method combined with incipient impregnation, and the surface properties were tested. Using the NOx storage reduction circulation test, the impact of the reaction conditions, including reductant concentration, reduction time and space velocity, and components of IC engine exhaust gas represented by CO2 and HC on the performance of NOx storage reduction (NSR) with H2 as reductant were studied. The experimental results indicate that the specific surface area and catalytic activity of Pt/Ba/Ce/γ Al2O3 catalyst are favorable; within the scope of the study, with different reductant concentration there is an optimum reduction time when the NOx conversion rate is the highest, and the optimum reduction time decreases when the reductant concentration increases; the increase of reductant concentration accelerates the NOx desorption; if the reductant concentration is too high, some amount of NOx will spill, and the NOx conversion rate will drop; when the space velocity characteristic is perfect, the NOx conversion rate could still maintain 86.9% under high space velocity of 7.0×104 h-1; to some extent CO2 inhibit the NOx storage activity, but the catalyst can be regenerated; using C3H6 to simulate the exhaust HC, C3H6 has a negative effect on the NOx reduction process when the C3H6 concentration is low, however the C3H6 of high concentration could accelerate this process.