Abstract
采用密度泛函理论，研究了Ti-YNU-1/H2O2体系中T3和T6位活性中心上1-己烯和环己烯环氧化反应的催化性能和反应机理。所有计算都在B3LYP/6-31G(d,p)理论水平下进行。结果表明，Ti-YNU-1分子筛中T3位的活性中心是Ti3-η2 (OOH)，T6位活性中心为Ti6-η2(OOH)-H2O 和 Ti6-η2(OOH)-CH3CN。催化活性为Ti6-η2(OOH)-H2O > Ti6-η2(OOH)-CH3CN > Ti3-η2(OOH)。在各活性中心上1-己烯环氧化反应的活化能垒高于环己烯环氧化反应，随着Ti-YNU-1分子筛中Ti含量的增加，更多的Ti插入到10元环正弦孔道中的T3位，形成更多的Ti3-η2(OOH)活性中心位点，由于孔道对环己烯的扩散限制，导致1-己烯转化率增加程度高于环己烯。 The catalytic performances and reaction mechanism of 1-hexene and cyclohexene epoxidations over active centers at the T3 and T6 sites in Ti-YNU-1/H2O2 system have been investigated by us-ing density functional theory. All calculations were performed at the theoretical level of B3LYP/6- 31G(d,p). The results indicated that the active center at T3 is Ti3-η2(OOH), and the active centers at T6 are Ti6-η2(OOH)-H2O and Ti6-η2(OOH)-CH3CN. The catalytic activity has the trend of Ti6-η2(OOH)-H2O > Ti6-η2(OOH)-CH3CN > Ti3-η2(OOH). The activation barriers of 1-hexene epoxidation over different active centers are higher than that of cyclohexene epoxidation. With the increasing of Ti content in Ti-YNU-1, more Ti species are inserted into the T3 site in the 10-membered ring channels, which accretes the numbers of Ti3-η2(OOH). Due to the distribution restrict for cyclohexene, the conversion of 1-hexene epoxidation is much higher than that of cyclohexene epoxidation.
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