Identification of vicinal silanols and promotion of their formation on MCM-41 via ultrasonic assisted one-step room-temperature synthesis for Beckmann rearrangement

Zichun Wang*, Yijiao Jiang, Yunyao Zhang, Jeffrey Shi, Catherine Stampfl, Michael Hunger, Jun Huang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Siliceous mesoporous MCM-41 materials were synthesized under ultrasonic treatment from 0.5 to 3 h. The obtained U-[Si]MCM-41 catalysts were applied in the Beckmann rearrangement of cyclohexanone oxime (CHO) to ϵ-caprolactam (CPL). The ultrasonic treatment can increase the pore wall thickness, while the density of surface SiOH groups increased slightly. Quantitative 1H MAS NMR studies of the U-[Si]MCM-41 catalysts hint at the presence of isolated and vicinal silanols. After dehydration at 393 K, 1H MAS NMR signals of poly-hydrogen-bonded vicinal silanols occurred, which are strongly reduced after dehydration at 473 K. Correspondingly, a much higher conversion of CHO to CPL was observed for U-[Si]MCM-41 dehydrated at 393 K in comparison with those dehydrated at 473 K. This finding indicates poly-hydrogen-bonded SiOH groups can promote the reaction and improve the catalytic performance of siliceous catalytic materials in the Beckmann rearrangement of CHO in an energy economic way at a suitable activation temperature.

Original languageEnglish
Pages (from-to)5550-5557
Number of pages8
JournalIndustrial and Engineering Chemistry Research
Volume57
Issue number16
DOIs
Publication statusPublished - 25 Apr 2018

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