Preparation of nanosized silicalite-1 and its application in vapor-phase Beckmann rearrangement of cyclohexanone oxime

Series of silicalite-1 catalysts with particle size varying from 50 to 450 nm were synthesized by hydrothermal method using tetrapropylammonium hydroxide as a template and l-lysine as an additive. The crystal size of silicalite-1 could be easily controlled by regulating the amount of l-lysine. The series of silicalite-1 and their NaOH-modified derivatives were examined as catalysts for vapor-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam in the 330-390 °C range. It was found that the crystal size of silicalite-1 has an effect on catalytic activity, ε-caprolactam selectivity, and catalyst stability. With a decline in crystal size, there was improvement of catalytic activity and catalyst stability. It is deduced that silicalite-1, of a smaller crystal size, is less inclined to pore blocking by coke and hence has better resistance to deactivation.