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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57.1kJ·mol-1,与实验结果接近.
A 3T cluster model was used to simulate the acidic sites of the molecular sieve catalyst. The B3LYP / 6-31G (d, p) method of density functional theory (DFT) was used to study the isomerization of 1-butene double bond to trans- Butene reaction mechanism.The reaction sites were fully optimized, after the zero point can be corrected, the activation energy of the reaction was obtained.Research shows that the reaction in three steps: physical adsorption → chemical reaction → physical desorption. Acidic OH groups first adsorbed the double bond of 1-butene to form a π-coordination complex, and then double-bond isomerization occurred according to a synergistic reaction mechanism to produce trans-2-butene in the adsorbed state, finally desorbing into the product The calculated apparent activation energy is 57.1 kJ · mol-1, which is close to the experimental result.