In situ functionalized sulfonic copolymer toward recyclable heterogeneous catalyst for efficient Beckmann rearrangement of cyclohexanone oxime

• In situ sulfonated polymer is applied in Beckmann rearrangement for the first time.
• The catalyst possesses plenty of mesopores and high sulfur content.
• High yield is achieved within short reaction time of 1 h.
• The catalyst shows well recyclability and substrate compatibility.

Exploring environmentally friendly, efficient and recyclable heterogeneous catalysts for low-temperature liquid-phase organic reactions are important for the development of green and sustainable processes. In this work, we applied an in situ sulfonated polymeric solid acid H-PDVB-SO3H for catalyzing liquid-phase Beckmann rearrangements for the first time, with post-sulfonated sample and other various counterparts as control catalysts. H-PDVB-SO3H was prepared by copolymerization of divinylbenzene with sodium p-styrene sulfonate under solvothermal condition, followed by ion-exchanging to convert the polymer into proton form. It possessed a large surface area, plenty of mesopores and high sulfur content, and exhibited the high yield to ε-caprolactam (75%) with quite steady reusability in the heterogeneous Beckmann rearrangement of cyclohexanone oxime. The catalyst also showed good substrate compatibility with such a high reaction rate that the reaction time was as short as 1 h. No any co-catalysts or metals were used in the catalytic system, making the catalyst an environmentally friendly and efficient candidate for Beckmann rearrangements.

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