介孔氧化铝负载Ni-Co氧化物催化剂上丙烷氧化脱氢制丙烯

摘要

以非离子型三嵌段共聚物作为模板剂,异丙醇铝为氧化铝的前驱物,采用一锅法合成了一系列介孔氧化铝负载镍氧化物、钴氧化物以及镍-钴双金属氧化物催化剂,并以介孔氧化铝为载体,采用浸渍法制备了负载Ni-Co氧化物催化剂.采用N2吸附-脱附、高分辨透射电镜(HRTEM)、X射线粉末衍射(XRD)、H2程序升温还原(H2-TPR)以及激光拉曼光谱(LRS)等技术对催化剂的结构与性质进行表征,并考察了催化剂的丙烷氧化脱氢反应性能.结果表明:一锅法制备的各催化剂均有大的比表面积和规整的孔道结构,且负载的金属氧化物高度分散;而浸渍法制备的催化剂,其载体的介孔结构被破坏并有Co3O4晶相生成.在考察的催化剂中,一锅法合成的介孔氧化铝负载Ni-Co氧化物催化剂表现出最佳的丙烷氧化脱氢性能.在450℃、C3H8∶O2∶N2的摩尔比为1∶1∶4和空速(GHSV)为10000 mL·g-1·h-1条件下,该催化剂上丙烯产率为10.3％,远高于浸渍法制备的催化剂上所获得的丙烯产率(2.4％).关联催化剂表征和反应结果,讨论了催化剂结构与性能之间的关系.%A series of mesoporous alumina supported nickel oxide,cobalt oxide,and bimetallic nickelcobalt oxide catalysts were synthesized by a one-pot method,using nonionic triblock copolymer as a template and aluminum isopropoxide as the source of aluminum.For comparison,an additional supported Ni-Co oxide catalyst was prepared by impregnation,using mesoporous alumina as the support.The catalysts were tested for the oxidative dehydrogenation of propane,and their structure and properties were characterized by N2 adsorption-desorption,high-resolution transmission electron microscopy (HRTEM),powderX-ray diffraction (XRD),temperature-programmed H2 reduction (H2-TPR),and laser Raman spectroscopy (LRS).All samples synthesized by the one-pot method had large surface area,highly ordered mesoporous structure,and highly dispersed supported oxide species.However,in the sample prepared by impregnation,the mesostructure of the carrier was destroyed with the formation of Co3O4 phase.Among the catalysts studied,the mesoporous alumina supported Ni-Co oxide catalyst from one-pot synthesis showed the best catalytic performance for propane oxidation to propylene.On this catalyst a 10.3％ propylene yield was obtained at 450 ℃,C3H8∶O2∶N2 molar ratio of 1∶1∶4,and gas hourly space velocity (GHSV) of 10000 mL· h-1.g-1.This result was much higher than the yield of 2.4％ obtained from the catalyst prepared by impregnation.Combining the results of characterization and catalytic reaction,the relationship between structure and performance of the catalysts was discussed.The large difference observed in catalytic performance between catalysts prepared by one-pot and impregnation methods was attributed to their different structures,including textural structure,and dispersion of the supported metal oxide species.