V、Mo修饰SBA-15分子筛结构与催化性质的DFT计算预测

采用密度泛函方法,计算了介空分子筛SBA-15及V和Mo原子修饰后分子筛的几何参数及红外光谱,与实测值比较,确定了分子筛的合理模型。通过分析模型化合物的前线分子轨道,推测了V和Mo原子修饰前后分子筛表面的酸碱中心及氧化还原性质。最后,由计算得到分子筛表面VO4和MoO5基团的Mayer键级推测,当此类催化剂参与酸碱和氧化还原反应时,基团上的三种化学键(MO─Si、M─OSi和MO)中,MO─Si键最容易断裂打开,参加化学反应。

The structure and the properties of the SBA-15-supported vanadium or molybdenum molecular sieves:A DFT prediction

A theoretical study on the model clusters of SBA-15 and SBA-15-supported vanadium or molybdenum molecular sieve was carried out.Two model clusters of SBA-15 and two model clusters of SBA-15 supported vanadium or molybdenum molecular sieve were constructed.Their geometries and IR spectra have been calculated.These calculated values suggested that the model clusters employed were reasonable.The frontier molecular orbitals of these model clusters showed that the VO4 and MoO5 groups on the surface of the molecular sieve were the active centers for the acid-base reaction and oxidation-reduction reaction.The Mayer bond orders of the VO4 and MoO5 groups were calculated and it was found that the MO─Si bond was easier to break than the MO─Si and MO bonds in the process of the chemical reaction.