乙醇催化脱水制乙烯反应条件及飞温现象

Operational conditions and runaway phenomenon of dehydration of ethanol into ethylene

以HZSM-5分子筛为乙醇脱水催化剂,考察了催化剂的硅铝摩尔比和反应工艺条件对乙醇转化率及生成乙烯选择性的影响,分析了反应初期的飞温现象,用X射线衍射(XRD)、环境扫描电镜(SEM)和热分析(TG-DTA)对其催化剂进行了表征。结果表明:硅铝摩尔比为50∶1的HZSM-5催化乙醇脱水制乙烯反应在温度300℃、液体质量空速7h-1时,乙醇转化率大于99.8%,乙烯选择性达99.1%。HZSM-5催化乙醇脱水反应初期的飞温过程生成的聚合物堵塞和覆盖部分催化剂孔道,导致催化剂活性下降和乙烯选择性显著降低,适当降低进料温度可有效控制飞温现象发生。

The influences of Si/Al ratio and reaction parameters on the ethanol conversion and the ethylene selectivity over HZSM-5 zeolite were discussed. The runaway phenomenon in the initial process was analyzed. The catalyst was characterized by X-ray diffraction, scan electron microscopy, and thermal analysis. The ethanol conversion exceeded 99.8% and the ethylene selectivity reached 99. 1% under the operational conditions of Si/Al ratio 50, reaction temperature 300 ℃, and space velocity 7 h^-1. Resinous materials formed and blocked pores of HZSM-5 zeolite as a result of the runaway phenomenon in the initial process, and incurred decline of the activity. Decreasing the feeding temperature was effective in avoiding the runaway phenomenon.