六铝酸盐作涂层的蜂窝陶瓷型La_(0.8)Sr_(0.2)MnO_3催化剂热稳定性

Thermal Stability of Monolithic Honeycomb Ceramic La_(0.8)Sr_(0.2)MnO_3 Catalyst with Hexaaluminate Washcoat

采用共沉淀法分别制备了Sr0.3Ba0.5La0.2MnAl11O19和La0.8Sr0.2MnO3前驱体,并通过浸渍法制备了六铝酸盐作涂层的蜂窝陶瓷型La0.8Sr0.2MnO3催化剂。超声振荡测试结果表明所得催化剂具有较好的粘结强度,30min后脱落率仅为0.3%(wt)。XRD和SEM结果则表明Sr0.3Ba0.5La0.2MnAl11O19和La0.8Sr0.2MnO3具有完善的六铝酸盐和钙钛矿晶型,且经850℃焙烧后La0.8Sr0.2MnO3仍能在六铝酸盐涂层表面高度分散。甲苯催化燃烧活性结果表明所得催化剂具有良好的催化活性,在280℃即可将甲苯完全燃烧。与以γ-Al2O3为涂层的催化剂相比较,以六铝酸盐作涂层的催化剂表现出更好的热稳定性,经850℃高温焙烧3h后,甲苯完全燃烧所需温度只提高了20℃;且在反应气氛下改变温度运行28h后,甲苯转化率未发生任何改变。

Sr0.3Ba0.5La0.2MnAl11O19 hexaaluminate and La0.8Sr0.2MnO3 perovskite were firstly prepared by co-precipitation, and then, by using the hexaaluminate as the washcoat, the honeycomb ceramic La0.8Sr0.2MnO3 catalyst was prepared. It was found that, after 30 min ultrasonic shock, the surface loading cast-off of the catalyst is only 0.3%（wt）. XRD patterns show that both the Sr0.3Ba0.5La0.2MnAl11O19 hexaaluminate and La0.8Sr0.2MnO3 perovskite have perfect crystalline phase, and The SEM image shows that the La0.8Sr0.2MnO3 is well dispersed on the honeycomb ceramic support. The prepared catalyst has very good behavior for toluene catalytic combustion, and the toluene can be fully conversed at 280℃. Furthermore, the hexaaluminate washcoated honeycomb ceramic La0.8Sr0.2MnO3 catalysts exhibit higher thermal stability than that of the γ-Al2O3 washcoated honeycomb ceramic La0.8Sr0.2MnO3 catalysts. After calcinated at 850℃ for 3 h, the T95 （temperature needed for 95% toluene conversion） of the hexaaluminate washcoated catalyst only increases 20℃, while the T95 of the γ-Al2O3 washcoated catalyst increases 80℃.