Abstract: Brønsted acid in Y zeolite plays a key role in the processes of catalyst,and the structure reflects the strength of B acid.The stable structures of Brønsted acid sites of HY,[AlO]+/HY,and [Al(OH)]2+/HY were simulated by periotic models.The relationship between the structures of Brønsted acid sites and its environments was identified by combination of dynamic simulation with DFT calculation.By analyzing the structure and electronic permanent,together with the statistical results of molecular dynamics,it can be found that the strength of Brønsted acid can connected with the number of H atoms in the 12 membered ring that the small number.The weaker the binding ability of H atoms to O atoms in B acid center is,and the more electrons H atoms lose,the stronger the B acid acidity is.The addition of extra⁃framework aluminum can enhance the acidity of B acid,and [Al(OH)]2+ has more obvious effect on B acid properties.These results can lead the synthetic and modification of B acid site in a theoretical support.

Key words: Strength of Brønsted acid, Extra?framework aluminum, Density functional theory, Molecular dynamics

摘要： Y分子筛中B酸的酸性在催化过程中起着主要作用，其结构的变化反应了B酸的强弱。采用周期性模型模拟了HY、[AlO]+/HY及 [Al(OH)]2+/HY中B酸位置的稳定结构，从第一性原理和分子动力学两方面研究了B酸中心的结构变化与周围微环境的关系。通过几何结构、电子结构和分子力学统计结果发现，非骨架铝物种的加入增加了B酸的强度，且与H原子在12元环上的分布数量有关系，H原子越少，其酸性越强。B酸中心H原子与O原子结合能力越弱，并且H原子失去电子越多，B酸酸性越强。非骨架铝的加入能增强B酸的酸性，且[Al(OH)]2+非骨架铝物种对B酸性质的影响明显。研究可为分子筛B酸调变提供理论支持。

关键词: B酸强度, 非骨架铝, 密度泛函理论, 分子动力学