含硼分子筛的11B VAS NMR和1H MAS NMR研究

以变角旋转(VAS) NMR方法考察了三配位硼的存在状态,得到其四极作用常数C_q为2.4MHz,电场梯度不对称系数η为0.0.硼引入骨架形成的酸性羟基质子的信号位于2.3ppm,¹H{¹¹B}双共振实验证实其与硼原子的关联很弱.与6.5ppm分子筛吸水峰同时出现的2.7ppm的信号也被认为是吸水的信号,与非骨架铝羟基质子的信号在同一位置,但可通过¹H{²⁷Al}双共振实验加以判别.

11B VAS NMR AND 1H MAS NMR STUDY ON THE BORON-CONTAINING ZEOLITES

The VAS (Variable Angle Spinning) NMR method was applied in the study on the Boron containing ZSM 12 and ZSM 5 zeolites. By the {} {11}B VAS NMR experiment and simulations of the powder patterns, the quadrupolar constant of the tri coordinated boron was determined to be 2.4MHz, and the electrical field gradient coefficient 0.0. The resonance of the Boron Silicon hydroxyl proton is at 2.3ppm, and by the {} 1H{ {11}B} spin echo double resonance it is shown that the 2.3ppm protons are very weakly coupled with the boron atoms. Besides the 6.5ppm adsorbed water peak, a 2.7ppm water adsorption peak was also found, whose position is the same with the extra framework Al hydroxyls. This kind of water adsorption signal can be distinguished by the {} 1H{ {27}Al} spin echo double resonance experiment. ;