La_2O_3/γ-Al_2O_3复合产物的浸渍-燃烧法制备及表征

Preparation and characterization of La_2O_3/γ-Al_2O_3 compounds by immersion and combustion method

采用浸渍-燃烧法制备了La2O3/γ-Al2O3复合产物,原料为La(NO3)3.6H2O(A.R)、一水合柠檬酸和工业级的拟薄水铝石.以六水合硝酸镧和一水合柠檬酸分别为镧源和燃烧剂,柠檬酸与六水硝酸镧的摩尔比为5∶6左右.将拟薄水铝石研磨成粉末并溶于柠檬酸和镧的配合物溶液中,搅拌至凝胶状,110℃干燥2h,再放入马弗炉中焙烧2 h得到产物.采用XRD、BET、XPS进行分析和表征,结果表明La3+的加入提高了γ-Al2O3的热稳定性,随着样品焙烧温度升高,比表面积下降,孔容、孔径变大.随着La3+的量的增加,样品的比表面积增大,孔径尺寸分布变宽.通过控制La3+加入的量以及焙烧温度,可调控多孔γ-Al2O3粉体的比表面积、孔容、孔径大小及孔径分布.

La2O3/γ-Al2O3 compounds were synthesized by immersion and combustion method,raw materials were La（NO3）3·6H2O（A.R）,Citric acid monohydrate and commercial boehmite.Citric acid monohydrate as the complexing agent and La（NO3）3·6H2O（A.R） as the lanthanum source,stirred to dissolve and obtained the citric acid-lanthanum nitrate solution,formed the complexes of the citric acid and lanthanum nitrate,and the ratio of the citric acid and the lanthanum nitrate was about 5∶ 6.Grinded the boehmite into power,then took the power dissolved in the complexes of the citric acid and lanthanum nitrate,stirring made full contact.Using magnetic blender mixed to gel,110 ℃ dried 2 h,then took the gel into muffle furnace in 2 h roasting and got products.The final products were characterized by XRD,BET,XPS.It studied the surface areas and the pore size distributions of the compounds in the different treatment temperatures by the comparison study.It resulted that the La3＋ was effective on the thermal stability of the γ-Al2O3 compounds.While the sample roasting temperature increased,specific surface area would decrease,the pore volume and pore size all get bigger.Along with the increase of the quantity of La3＋,the specific surface area of the sample increased and the distribution of pore diameter would be wider.We can control the specific surface area,pore volume,pore size and the distribution of pore diameter of the porous γ-alumina powder through the control of the quantity of La3＋ and the calcination temperature.