Re/HZSM-5体系上的甲烷无氧芳构化反应

Methane Aromatization on Re/HZSM-5 System under Non-oxygen Condition

与Mo/HZSM 5相比 ,Re/HZSM 5也是较好的甲烷无氧芳构化催化剂 ,其初活性较高 ,但随着反应的进行 ,催化剂失活的速率较快 .通过NH3 TPD ,H2 TPR和MASNMR等手段 ,对催化剂的酸性和分子筛骨架铝的变化以及铼物种的还原性能进行了研究 .结果表明 ,催化剂酸性的在反应中起着重要的作用 ,但不同铼担载量的催化剂酸性的变化比较复杂 ,不同于Mo/HZSM 5体系 .总的来看 ,并不是酸性越强或酸量越多 ,催化剂的催化性能就越好 ;催化剂的酸性和酸量都有一个最佳值 .担载铼物种后 ,铼物种可与分子筛的骨架铝发生强烈的相互作用 ,最终导致骨架脱铝 .Re/HZSM 5催化剂具有较高的低温活性 ,在较低温度下可被还原性气氛还原 。

Re/HZSM-5 is also a better catalyst for methane aromatization compared with Mo/HZSM-5 catalyst. The best Re loading is 10%. The original performance of Re/HZSM-5 is much better than Mo/HZSM-5, but its lifetime is much shorter than the latter. The acidity of the catalyst, the change of framework aluminum after impregnation of Re species and the reduction capacity of Re/HZSM-5 were investigated by using NH3-TPD, MAS NMR and H-2-TPR. The results indicated that the acidity of the catalyst also plays a key role in the reaction, and the catalytic performance of the catalyst is probably proportional to its acidity. But it is not that the stronger the acidity is and the more the amount of acid sites and the better the performance of the catalyst. After impregnation of Re, the metal species interacts with framework aluminum intensively and causes the dealumination of the catalyst. Re/HZSM-5 tends to be reduced by H-2 at lower temperature compared with Mo/HZSM-5, and the active species after reduction is singleness.