摘要
以La_2O_3为基础,碱土金属作为第二组分的二元氧化物催化剂均具有较高的生成C_2活性,特别是La-Ba-O系催化剂具有优良的甲烷氧化偶联活性和稳定性,当La/Ba原子比为2.5时,C_2收率可达20.3％。第三组分的添加有助于提高C_2选择性,特别是添加碱金属,可以抑制完全氧化反应,并提高乙烯/乙烷比。在La:Ba:Na=2.5:1:0.1的催化剂上进行了500/小时的寿命实验,在整个反应期间,催化剂的活性和选择性相当稳定。X-射线物相分析表明,新鲜催化剂除有少量的碳酸钡外,主要是氧化镧和氧化钡的混合物。500小时后的物相基本上是氧化镧和碳酸钡。使用前后催化剂的比表面积及表面La和Ba的分布均无改变。较高的CH_4/O_3比对提高C_2选择性有利,当CH_4:O_2=4:1时,C_2选择性和收率分别为65.1％和19.1％。
Oxidative coupling of methane was examined over various rare earth -alkaline earth mixed oxide catalysts, in which La-Ba-Na-O system catalyst gave a higher C2-yield more than 20% and showed good stability in a period of 500 hours test. With a higher CH4/O2 molar ratio of 4:1,C2 selectivity of 65% and C2-yield of 19% vere obtained respectively. The synergistic effect of the binary oxide catalyst system was discussed.
关键词
氧化镧
氧化钡
甲烷
氧化偶联
Lanthanum oxide,barium oxide,metal oxide catalyst,methane,oxidative coupling
