Pore structure effects on the kinetics of methanol oxidation over nanocast mesoporous perovskites  

孔结构对纳米浇注的中孔钙钛矿上甲醇氧化反应动力学的影响（英文）

作　　者：Mahesh M.Nair Freddy Kleitz Serge Kaliaguine 

机构地区：[1]拉瓦尔大学化学Materiaux Avances研究中心(CERMA),加拿大魁北克G1V 0A6, [2]拉瓦尔大学化工系,加拿大魁北克G1V 0A6

出　　处：《Chinese Journal of Catalysis》2016年第1期32-42,共11页催化学报（英文）

基　　金：supported by the the National Science and Engineering Research Council(Canada);the Fonds Québécois de la Recherche sur la Nature et les Technologies(Province of Quebec)

摘　　要：Mesoporous LaMnO3 perovskite catalysts with high surface area were synthesized by using the recently developed hard templating method designated as ＂nanocasting＂.Ordered mesoporous silica designated as SBA-15 was used as the hard template.It was found that the surface area of the nanocast perovskites can be tuned（80–190 m2/g）by varying the aging temperature of the SBA-15 template.Nanocast LaMnO3 catalysts showed high conversion efficiencies for the total oxidation of methanol under steady state conditions,the one with the highest value of surface area being the best catalysts,as expected.Kinetic studies were performed for all of the synthesized catalysts.Rate constants were found to vary in accordance with the specific surface area of the nanocast catalyst which depends on the aging temperature of the parent template.From the rate constants obtained from experimental conversions at various space velocities（19500 to 78200 h〈sup〉–1）,values of activation energy and pre-exponential factor for the three nanocast LaMnO3 catalysts were determined by the linear regression of the Arrhenius plot.It is observed that the activation energy for all the catalysts remain constant irrespective of the variation in specific surface area.Further,a linear relationship was found to exist between the pre-exponential factor and specific surface areas of the catalysts indicating that the rates per unit surface area remains the same for all the catalysts.限制工业有毒气体(如挥发性有机化合物)的排放是当今社会主要的挑战之一.因此,迫切需要开发出消除污染物、且不造成二次污染的环境友好技术.其中热燃烧技术比较有效,但通常该过程会采用贵金属催化剂以实现低温高活性,由于贵金属催化剂的成本较高,不利于工业应用,因此,人们一直致力于研究和开发新型材料以替代贵金属催化剂.研究发现,在许多部分氧化或完全氧化反应(特别是烃类或挥发性有机物的氧化反应)中,钙钛矿类复合金属氧化物(ABO_3)具有与贵金属类似的催化性能.但是该材料的制备需在高温(>700℃)条件下进行,使得其比表面积(<30m^2/g)很低,因而限制了其应用.可见,欲使该材料在工业上得到广泛应用,必须在制备技术上实现很大的突破,即制得高比表面积的钙钛矿类材料.已有人通过在200℃下焙烧成功地制备了比表面积为100m^2/g的钙钛矿氧化物,但继续提高焙烧温度,所制样品的比表面积下降.在过去20年中,中孔氧化硅及随后众多中孔材料的成功制备,使得合成具有极高比表面积的非硅基材料(如碳,金属氧化物,和碳化物等)成为可能.在这些材料的制备方法中,纳米浇铸法因其特别适用于制备具有高比表面积的单金属或单金属氧化物而备受青睐.采用纳米浇铸法已经成功制得一系列材料,并用于很多催化反应中.但文献报道大多只局限于温度、催化剂组成或比表面积对其活性的影响.为了能将这些材料成功用于工业应用,需要对其表面反应机理和相关反应动力学进行深入的研究.最近,本课题组采用纳米浇铸法制备了高比表面积的中孔钙钛矿类氧化物,并考察了它们的催化性能.结果表明,在各种气相反应中,所制纳米浇注的钙钛矿类氧化物具有比相应体相氧化物更高的催化效率.基于此,本文以在不同温度老化的SBA-15为硬模板,采用纳米浇铸法制备高�

关 键 词：Mesoporous perovskites High surface area NANOCASTING Methanol oxidation KINETICS 

分 类 号：O621.251[理学—有机化学] O643.36[理学—化学]