ZSM-22分子筛催化性能及失活行为探究

Study of the Catalytic Performance and Deactivation of ZSM-22 Zeolite

通过水热合成法制备了ZSM-22分子筛并详细考察了其甲醇制烯烃(MTO)催化性能以及失活行为。结果表明:过低的反应温度不利于甲醇活化;升高温度可以明显提高甲醇转化率,同时也加强了烯烃循环的贡献,从而提高丙烯、丁烯的选择性,而乙烯选择性变化不大;过高的温度会导致甲醇大量裂化成甲烷。甲醇转化率与失活后催化剂的失重量存在明显的折线型关系,说明不同反应时间ZSM-22的失活机理不同。反应初期主要发生孔道内积炭,导致孔道快速堵塞,催化剂迅速失活,而随反应时间延长,积炭主要在外表面生成,催化剂失活速率减缓。

ZSM-22 zeolite was prepared by hydrothermal synthesis and its catalytic performance and deactivation behavior in methanol to olefin（MTO）were explored.The results suggest that low temperature is unfavorable to the activation of methanol,whereas the methanol conversion can be significantly increased with the increase of reaction temperature.Meanwhile,the elevation of reaction temperature can enhance the contribution of alkene cycle,leading to the improvement of the selectivity of propene and butene,while it has less influence on the formation of ethene.However,methanol largely cracks into methane at excessively high temperature.It can be found that there is an obviously fold line relationship between methanol conversion and the amount of coke,illustrating that ZSM-22 has different deactivation behavior with the time on steam.The results verify that the deactivation of ZSM-22 is mainly resulted from the pore blocking at initial period,while the coke species dominantly generate on the external surface of zeolite with the increase of reaction time.