Influences of ethylenediamine treatment of Silicalite-1 on the catalytic vapor-phase Beckmann rearrangement of cyclohexanone oxime

Silicalite-1 was modified by organic base of ethylenediamine. The characterization results indicated that after alkaline treatment, the crystal structure of S-1 was not destructed or changed; the silanol nests were maintained, but the terminal silanol groups were eliminated. The modified S-1 exhibited better performance in the vapor-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam, especially in terms of the stability. It is inferred that the silanol nests are the most suitable centers for the Beckmann rearrangement reaction, while the terminal and vicinal silanol groups might be responsible for the coke deposition.