碱土Sr对Co/Al_2O_3催化剂甲烷部分氧化反应的影响  

Effects of alkaline-earth strontium on the performance of Co/Al_2O_3 catalyst for methane partial oxidation

作　　者：余长林[1] 周晓春[1] 翁维正[2] 胡久彪[1] 陈喜蓉[1] 魏龙福[1] 

机构地区：[1]江西理工大学冶金与化学工程学院,江西赣州341000 [2]厦门大学化学系固体表面物理化学国家重点实验室,福建厦门361005

出　　处：《燃料化学学报》2012年第10期1222-1229,共8页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(21067004;21263005);厦门大学固体表面物理化学国家重点实验室开放基金(200906);江西省自然科学基金(2010-GZH0048);江西省教育厅科技项目(GJJ12344);江西省青年科学家培养对象资助(20122BCB23015)

摘　　要：以γ-Al2O3为载体,采用共浸渍法制备了Sr-Co/Al2O3系列催化剂,研究了助剂Sr对Co/Al2O3催化剂上甲烷部分氧化(POM)制合成气反应的影响,并利用N2物理吸附、X射线衍射、H2-程序升温还原和热重等技术对催化剂的理化性质进行了表征。结果表明,未添加助剂的Co/Al2O3和800℃焙烧的Sr-Co/Al2O3催化剂在POM反应初期催化活性很低,然而,当添加Sr的质量分数高于2%时,催化剂表现出很好的催化活性和稳定性。焙烧后的新鲜催化剂上主要存在两类Co物种,一类是与载体相互作用较弱、易被H2还原为单质的Co3O4;另一类是与载体相互作用较强、难还原、无催化活性的CoAl2O4尖晶石。在焙烧过程中,Sr易形成Sr4Al14O25,从而削弱Co与Al2O3之间的相互作用,能在一定程度上抑制CoAl2O4物种的形成,提高催化剂的稳定性和活性。未添加Sr的Co/Al2O3在反应时易发生物相改变生成尖晶石,导致催化剂迅速失活;但当焙烧温度达到800℃时,添加有限量的Sr还是无法阻止CoAl2O4的产生。A series of Sr-Co/Al2O3 catalysts were prepared by co-impregnation method using γ-Al2O3 as the support.The effect of strontium promoter on the catalytic performance of Co/Al2O3 catalyst for partial oxidation of methane（POM） to synthesis gas was studied.The catalysts were characterized by some physicochemical characterizations such as N2 physical adsorption,X-ray diffraction（XRD）,H2-temperature programmed reduction（H2-TPR） and thermogravimetry（TG）.The results show that both Co/Al2O3 calcined at 700 ℃ and Sr-Co/Al2O3 calcined at 800 ℃ exhibit low activity and deactivate at the initial stage of POM reaction.The addition of above 2% mass fraction of strontium will greatly enhance the activity and stability of Co/Al2O3.Two types of Co species were identified on the fresh calcined catalysts.One is Co3O4 which weakly interacts with Al2O3（easily reduced by H2） and the other is the spinel CoAl2O4（non-catalytic performance） which strongly interacts with the support.During the course of calcination,strontium can react with Al2O3 to form Sr4Al14O25 which will restrain the generation of the CoAl2O4 species and promote the stability and activity of catalysts.Without strontium promoter,CoAl2O4 is easy to be formed over Co/Al2O3 in the POM reaction.However,the formation of CoAl2O4 cannot be avoided with the addition of limited strontium when the calcination temperature is over 800 ℃.

关 键 词：助剂锶 钴 甲烷部分氧化 尖石晶 氧化铝 

分 类 号：O643[理学—物理化学]