Nb对Li／MgO甲烷氧化偶联催化剂的助催化作用

THE PROMOTION EFFECT OF NIOBIA ON Li/MgO METHANE OXIDATIVE COUPLING CATALYST

Ｌｉ／ＭｇＯ甲烷氧化偶联催化剂引入铌的氧化物可降低活性温度，７５０℃以下便达到最高Ｃ２烃产率．饴与锂、镁有多种结合方式，引入方法对活性测试结果有重要影响．铌不与镁紧密结合且分布于锂、镁之间时作用最好．实验结果分析表明，铌的作用是由于Ｎｂ２Ｏ５的Ｎ型半导性提高了催化剂转移电子的能力，且使Ｌｉ／ＭｇＯ催化剂形成多孔缺陷结构，并通过其酸性作用改变Ｌｉ／ＭｇＯ的结合状态，使活性增加．

Doping niobia to Li/MgO methane oxidative coupling catalyst can lower the temperature of the activation by more than 50 degrees.The niobia-containing catalysts can reach the maximum C2 yield at a temperature lower than 750℃,there exist many combinations of niobia with lithium and magnesium oxides,therefore the incorporation method of niobia is a key factor for reaching optimum promotion effect.The experimental results support the conclusion that the N-type semi-conductivity of niobia enhances the redox ability of the catalyst.The acidity and the combination potential of niobia with Li species and MgO distort the crystalline of the catalyst,so that the activity and stability increase with the introduction of niobia.