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以在水热条件下使用四乙基氢氧化铵为模板剂制备的纳米片状SAPO-34分子筛为催化剂,研究了其在不同温度及质量空速的条件下甲醇制烯烃(MTO)反应.结果发现,催化温度及空速不但会影响催化剂寿命,也会显著地改变乙烯及丙烯的选择性.当升高温度或增大空速时,催化剂的寿命会明显降低.另一方面,升高温度会使乙烯和丙烯选择性之比明显升高,而提高空速更加有利于丙烯的生成.密度泛函理论计算给出,生成丙烯的活化能垒低于生成乙烯的活化能垒.同时,通过吉布斯自由能随温度的变化,可以看出温度的升高更加有利于乙烯的生成.
The reaction of methanol-to-olefins (MTO) at different temperatures and mass-space velocities was carried out using nanosheet SAPO-34 zeolite prepared by using tetraethylammonium hydroxide as a template under hydrothermal conditions. It has been found that the catalytic temperature and the space velocity will not only affect the life of the catalyst but also significantly change the selectivity of ethylene and propylene.When the temperature is increased or the space velocity is increased, the life of the catalyst will be significantly reduced.On the other hand, The selectivity ratio of ethylene to propylene was significantly increased, while the increase of airspeed was more conducive to the formation of propylene. The density functional theory calculation shows that the activation energy barrier to generate propylene is lower than the activation energy barrier to generate ethylene. At the same time, Booth free energy with temperature changes, we can see that the increase of temperature is more conducive to the formation of ethylene.