DFT法研究分子筛催化trans-2-丁烯的双键异构

利用一个3T簇模型模拟分子筛催化剂的酸性位, 采用密度泛函理论(DFT)的 B3LYP/6-31G(d, p)方法, 研究了分子筛催化1-丁烯双键异构为trans-2-丁烯的反应机理. 对反应各驻点进行了全优化, 经过零点能校正后, 得到了反应的活化能. 研究表明, 反应分三步进行：物理吸附→化学反应→物理脱附. 分子筛的酸性位OH基团首先吸附1-丁烯的双键形成了π配位复合物, 然后按协同反应机理发生双键异构反应, 生成吸附态的trans-2-丁烯, 最后脱附成产物. 计算得到的表观活化能为57.1 kJ?mol^-1, 与实验结果接近.

DFT Study on Double-bond Isomerization of trans-2-butene Catalyzed by Zeolites

Using density functional theory(DFT), the double-bond isomerization of 1-butene to trans-2-butene over zeolites is investigated with a 3T cluster model simulating zeolite. At the B3LYP/6-31G(d, p) level, the complete geometry optimization and the activation energy calculation are performed with a EZP correction. It is found that the process include three steps, physical adsorption→chemical reaction→physical desorption. Firstly, the OH group of the acidic site of zeolite adsorbs the double-bond of 1-butene and forms a π-complex. Secondly, the double-bond isomerization reaction shows a concerted mechanism and yields the adsorbed trans-2-butene. Lastly, trans-2-butene is produced by desorption and the zeolite active site is restored. The calculated apparent activation energy is 57.1 kJ?mol^-1, which is in agreement with the experimental data.