La2Zr2O7催化剂结构相变对甲烷氧化偶联反应性能的影响  

Effect of phase transformation of La2Zr2O7 catalysts on catalytic performance for the oxidative coupling of methane

作　　者：孟豪 林明桂[1] 牛鹏宇 王俊刚[1] 侯博[1] 李德宝[1,3] MENG Hao;LIN Ming-gui;NIU Peng-yu;WANG Jun-gang;HOU Bo;LI De-bao(State Key Laboratory of Coal Conversion,Institute of Coal Chemistry,Chinese Academy of Sciences,Taiyuan 030001,China;University of Chinese Academy of Sciences,Beijing 100049,China;Dalian National Laboratory for Clean Energy,Dalian 116023,China)

机构地区：[1]中国科学院山西煤炭化学研究所煤转化国家重点实验室,山西太原030001 [2]中国科学院大学,北京100049 [3]中国科学院洁净能源创新研究院,辽宁大连116023

出　　处：《燃料化学学报》2020年第8期949-959,I0005,共12页Journal of Fuel Chemistry and Technology

基　　金：山西省科技计划揭榜招标项目(20191102006);煤转化国家重点实验室自主研究课题(2020BWZ003)资助。

摘　　要：采用共沉淀法并通过改变焙烧温度制备了一系列具有不同晶相结构的La2Zr2O7催化剂,在微型固定床反应器上评价其甲烷氧化偶联反应性能,并利用XRD、Raman、CO2-TPD、XPS等表征手段,探究催化剂的物相结构、表面碱性以及表面氧物种的变化规律。结果表明,随着焙烧温度从700℃逐渐升高到1200℃,La 2Zr2O7催化剂结晶度不断提高,晶相发生明显变化,从无定形结构逐渐向缺陷萤石结构过渡,最终转变成烧绿石结构。焙烧温度提高促使La2Zr2O7晶相转变过程中,催化剂表面的碱性强度减弱,中等碱性位数量以及具有催化活性的表面氧物种O2^2-和O2^-的相对含量不断减少,致使催化剂的CH4转化率和C2+选择性不断降低。其中,无定形LZO-CP-700催化剂表现出最佳的甲烷氧化偶联反应性能。La 2Zr 2O 7 catalyst was prepared using co-precipitation method and then calcined at different temperatures to obtain a series of catalysts with different phase structures.Their catalytic performances for oxidative coupling of methane were evaluated in a fixed bed micro-reactor.Meanwhile,the changes of phase structure,surface base sites and surface oxygen species upon these samples were characterized with XRD,Raman,CO2-TPD,and XPS.With the increase of the calcination temperature from 700 to 1200℃,the crystallinity of La 2Zr2O7 catalysts increased continuously and the crystal phase changed obviously.The structure of the catalysts gradually changed from amorphous to disordered defective fluorite structure,and ultimately to phrochlore structure.Both the number of medium basic sites and the electrophilic oxygen species,such as O2^2- and O2^-,on the catalysts decreased with the phase transition caused by the temperature raising,resulting in the decrease of CH4 conversion and C2+selectivity.The amorphous LZO-CP-700 catalyst showed the best performance in methane oxidation coupling reaction.

关 键 词：La 2Zr 2O 7 结构变化 表面碱性 氧物种 甲烷氧化偶联反应 

分 类 号：O643[理学—物理化学]