超临界流体干燥法制备超细镧锰铝气凝胶研究  

Preparation of Ultrafine Lanthanum/Manganese/Aluminium Aerogel by Supercritical Fluid Drying Technology

作　　者：余高奇[1] 赵惠忠[1] 张光德[2] 汪厚植[1] 张宗锁[3] 杨洁[3] 

机构地区：[1]武汉科技大学湖北省耐火材料与高温陶瓷重点实验室,湖北武汉430081 [2]武汉科技大学机械自动化学院,湖北武汉430081 [3]武汉科技大学化工与资源环境学院,湖北武汉430081

出　　处：《中国稀土学报》2005年第2期138-143,共6页Journal of the Chinese Society of Rare Earths

基　　金：湖北省教育厅重点科研资助项目(2002A01018);湖北省教育厅大学 企业合作研究项目(2003BC5)

摘　　要：以La2O3,Mn(NO3)2和Al(NO3)3·9H2O为主要原料,用"溶胶凝胶"法结合"超临界干燥技术"分别制备260℃超细镧锰和镧锰铝气凝胶;煅烧制备850℃超细镧锰和镧锰铝气凝胶。用XRD,TEM等手段对样品进行表征,重点考察pH值、温度等因素对制备的影响,并用CO与NO的反应来比对镧锰气凝胶和镧锰铝气凝胶的催化活性。结果表明:(1)制得镧锰气凝胶为疏松、具有较好分散性的棕黑色粉末;260℃时,镧锰气凝胶由絮状物包裹着若干球形大颗粒组成,球形颗粒直径小于80nm;而絮状物尺寸范围跨度较大,大的约为500nm×150nm,小的直径约为几个纳米;850℃时,镧锰气凝胶结晶度提高,颗粒感增强,并且颗粒间发生一定程度的烧结,煅烧产物为LaMnO3+λ和Mn3O4,球形颗粒粒径小于20nm;(2)镧锰铝气凝胶外观疏松、分散性好、呈棕色;260℃时,镧锰铝气凝胶结晶度较低;850℃时,镧锰铝气凝胶结晶度提高,主要晶相物质包括:LaMnO3+λ,La2O3、不同价态氧化锰和γAl2O3;(3)铝的引入,改变了气凝胶微结构单元,降低了起燃温度,但同时也降低了NO的最终转化率;(4)超细镧锰气凝胶对CO与NO反应有较好的催化活性。Using pure (La_2O_3), (Mn(NO_3)_2) and (Al(NO_3)_3·9H_2O) as main materials, the ultrafine lanthanum manganese aerogel and lanthanum manganese aluminium aerogel were prepared by sol-gel and supercritical fluid drying technique in the condition of (260 ℃) or calcining at (850 ℃) for (2 h). The results show: (1) The method can get brown-black, well-dispersed, incrystalless condition ultrafine powder at (260 ℃), and the powders is composed of big sphere particles and wadding form particles that distributed surrounding. The diameter of big sphere particle is smaller than (80 nm). The range of the size of wadding form is great. The big wadding form particle is about (500 nm)×(150 nm), and the diameter of small particle is about a little nm. Through calcining at (850 ℃), the crystallinity of lanthanum manganese aerogel is enhanced, pellet feeling is boosted up, and there is certain agglutinating between particles. The calcining product is (LaMnO_(3+λ)) and (Mn_3O_4), and the diameter of them is small than 20 nm. (2) Lanthanum/manganese/aluminum aerogel has loose apperance. It is well-dispersed, brown ultrafine powder, and it is composed of (LaMnO_(3+λ)), (La_2O_3), (γ-Al_2O_3) and varying oxidization number manganese oxide. At 260 ℃, the crystallinity of lanthanum manganese aerogel is low. At 850 ℃, the crystallinity of lanthanum manganese aerogel is enhanced. (3) In lanthanum/manganese/aluminum aerogel, drawed into aluminum, the crystal structure is changed, and the star burning temperature is reduced in the purify process of tail gas. At the same time, the conversion rate of NO in the end is reduced too. (4) The superfine lanthanum manganese aerogel has a better catalytic activity to the reaction between CO and NO. O3,γ Al2O3an oxide.At260

关 键 词：LaMnO3+λ Γ-AL2O3 超临界干燥 气凝胶 稀土 

分 类 号：TQ129[化学工程—无机化工]