关键词: 变角旋转(VAS) NMR, 硼硅羟基, 双共振

Abstract: The VAS (Variable Angle Spinning) NMR method was applied in the study on the Boron containing ZSM-12 and ZSM-5 zeolites. By the ¹¹B 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{¹¹B} 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{²⁷Al} spin echo double resonance experiment.

Key words: VAS NMR, Boron-Silicon Hydroxyl, Double resonance