稀土氧化物Sm_2O_3对Li／MgO催化剂在甲烷氧化偶联反应中的促进作用

Promotion effect of Sm2O3 on Li/MgO for oxidative coupling of methane

讨论了稀土金属氧化物Ｓｍ２Ｏ３对Ｌｉ／ＭｇＯ催化剂在甲烷氧化偶联反应中的促进作用。Ｌｉ／ＭｇＯ催化剂经Ｓｍ２Ｏ３调变后，在７５０℃条件下反应生成Ｃ２烃的选择性由４８％提高到６９％，Ｃ２烃收率可达１７％以上，由于操作温度比原催化剂低５０～６０℃，增长了稳定运转时间。ＣＯ２－ＴＰＤ实验结果表明，调变后的催化剂碱中心数目增多了。ＸＲＤ谱图显示，加Ｓｍ后催化剂结构中有新的未知相生成。与热化学分析数据关联起来推测，该未知相可能是一种多元复合氧化物相，由Ｓｍ、Ｌｉ、Ｍｇ和氧在高温焙烧时形成的。多元复合氧化物的产生可能导致氧空穴的增加，对反应产生有利影响。

he effect of Sm2O3 promoter on Li/MgOcatalyst for oxidative coupling of methane isdiscussed. The reaction at 750℃ over Li/MgO catalyst promoted by Sm2O3 gives an increase of C2-hydrocarbon selectivity from 48%to 69% with a C2 yield of more than 17%, andthe stable operation can be prolonged as theoperating temperature is 50～60℃ lower thanthat of the original one. The experimental results by CO2-TPD and XRD show an increaseof base sites of the catalyst and a new phaseformed, respectively, after doping Sm2O3 toLi/MgO system. It is suggested, when correlated with the data of thermochemical analysis, that this unknown phase is probably amultioomponent oxide compound formed during high temperature calcination of Sm, Li,and Mg with O2, resulting in more oxygen vacancies and having a favorable effect on the reaction