甲烷在钼/含磷五元环沸石催化剂上的无氧芳构化

The Dehydrogenation and Aromatization of Methane over Mo/ Phosphoric Rare Earth Containing Penta Sil Type High Silica Zeolite Catalyst in the Absence of Oxygen

报道甲烷在无氧条件下，在一种不同于Ｍｏ／ＨＺＳＭ－５催化剂的钼／含磷五元环沸石催化剂上催化转化制高级烃类（苯等）的新反应．实验表明，在钼／含磷五元环沸石催化剂上（简称Ｍｏ／ＨＺＲＰ－１），当Ｍｏ浸渍的重量分数为２０％时，甲烷具有最佳反应活性，其转化率为９．２３％，芳烃选择性为９２．７４％．用ＢＥＴ、ＸＲＤ、ＮＨ３－ＴＰＤ和ＴＰＲ等对Ｍｏ／ＨＺＲＰ－１催化剂的物理和化学性质进行了表征．ＢＥＴ结果表明，随着Ｍｏ含量增加，催化剂的比表面积由原来的３６９ｍ２／ｇ下降为２２１ｍ２／ｇ．这表明随着Ｍｏ担载量的增加，Ｍｏ开始分布在分子筛的孔道中而导致分子筛孔道的堵塞，其结果引起Ｎ２吸附的减少．ＸＲＤ结果显示，当Ｍｏ含量为１５％时，开始出现ＭｏＯ３微晶的特征峰，对应于分子筛的特征峰强度略有下降．表明Ｍｏ与分子筛骨架之间发生了相互作用．ＮＨ３－ＴＰＤ实验表明，随着Ｍｏ含量增加，对应于ＨＺＲＰ－１分子筛的强酸中心数目减少．ＴＰＲ结果表明，当Ｍｏ担载量增加时，ＭｏＯ３的还原峰由２个变成１个，高温峰还原温度下降，表明Ｍｏ物种的可还原性增强．

Methane can be activated and converted into aromatics over Mo/phosphoric rare earth containing penta sil type high silica zeolite catalysts at 973 K in the absence of oxygen. The notation for the catalyst is xMo/HZRP 1 where x denotes the percentage of Mo loading and HZRP 1 denotes the phosphoric rare earth containing penta sil type high silica zeolite. Unlike Mo/HZSM 5 catalysts, Mo/HZRP 1 catalysts with high Mo loading give much better catalytic performance. The maximum conversion of methane is 9.23% with a selectivity of 92.74% on 20 Mo/HZRP 1 catalyst. BET experiment shows that Mo/HZRP 1 catalyst has bigger BET surface area than the Mo/HZSM 5 catalyst for the same Mo loading. XRD patterns show an obvious diffraction peak of small MoO 3 crystallite. NH 3 TPD demonstrates that the amount of strong acid sites decreases as Mo loading increases. The small MoO 3 crystallite, proper acid strength and pore structure of the zeolite are favorable for the methane conversion activity.