摘要
采用量子力学方法研究了具有不同Brnsted酸强度的Y分子筛酸中心的结构特性,计算了O—H键长(dO—H)、H的Mulliken电荷(qH)、O—H伸缩振动频率(νO—H)、∠Si—O—Al、分子轨道能量等结构参数,并探讨了这些结构参数与分子筛酸强度的对应关系。研究表明,dO—H、qH、νO—H、∠Si—O—Al与分子筛Brnsted酸强度并不呈严格的对应关系,而酸性羟基O—H的反键轨道能量(EO—H*)与酸强度存在良好的对应关系,EO—H*越低,Brnsted酸性越强。因为EO—H*越低,O—H反键轨道越容易被电子填充;反键轨道被电子填充后,体系能量升高,O—H键越容易被破坏,越容易给出H+,从而Brnsted酸性越强。因此,提出可以用EO—H*表征Y分子筛Brnsted酸强度,补充和完善了表征分子筛酸强度的结构参数。
The quantum mechanics method was applied to investigate the structure characteristics of Y zeolite with different Brnsted acid strength.The structural parameters,such as O—H bond distance（dO—H）,H Mulliken charge（qH）,O—H stretching vibration frequency（νO—H）,Si—O—Al angle and molecular orbital energy,were calculated.The relationship between these structural parameters and Brnsted acid strength was discussed.The results showed that there were poor correlations between qH,dO—H,νO—Hor Si—O—Al angle and B-acidity,however,there was a better correlation between anti-bonding orbita energy（EO—H＊）and B-acidity.The lower the EO—H＊,the stronger the B-acidity.An anti-bonding orbit with lower EO—H＊was more easily filled with electron,due to which the energy of the system would rise up to cause the O—H bond broken to give H＋,thus the B-acidity would be stronger.On this basis,EO—H＊was put forward to characterize Brnsted acid strength of Y zeolite,which would be a good complement to the structure parameters for acid site strength of Y zeolite.
作者
袁帅
龙军
赵毅
田辉平
刘宇键
许昀
代振宇
YUAN Shuai LONG Jun ZHAO Yi TIAN Huiping LIU Yujian XU Yun DAI Zhenyu(Research Institute of Petroleum Proccessing, SINOPEC, Beijing 100083, China)
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
2016年第6期1083-1089,共7页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家自然科学基金项目(U1463209)资助
关键词
分子筛
酸强度
结构参数
分子轨道能量
zeolite
acid strength
structural parameters
molecular orbital energy
