Acidity enhanced [Al]MCM-41 via ultrasonic irradiation for the Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam

Zichun Wang, Huajuan Ling, Jeffrey Shi, Catherine Stampfl, Aibing Yu, Michael Hunger, Jun Huang

Research output: Contribution to journalArticleResearchpeer-review

9 Citations (Scopus)

Abstract

Using solid acid catalysts to replace liquid acids in the liquid-phase Beckmann rearrangement of cyclohexanone oxime (CHO) into ɛ-caprolactam (CPL) is crucial for the environmentally friendly production of synthetic fibers, such as Nylon-6. In this work, we prepared aluminum-containing MCM-41 catalysts under ultrasonic irradiation with various Si/Al ratios for this purpose. Quantitative 1H MAS NMR investigations show that ultrasonic irradiation significantly promotes the formation of active Brønsted acid sites (BAS) on the [Al]MCM-41 catalysts up to 8 times higher than those prepared at the same conditions without ultrasonic irradiation, and up to 12 times higher BAS density than those reported in the literatures. The catalytic performance of [Al]MCM-41 catalysts can be strongly improved with increasing the BAS density, particularly to the ratio of BAS/(weakly acidic SiOH groups). Moreover, [Al]MCM-41 catalysts dehydrated at 393 K obtained two time higher CHO conversion and CPL yield than that dehydrated at 473 K. Hydrogen-bonded water molecules retained at low dehydration temperature may block surface SiOH groups and promote the reaction process. With higher BAS density resulting from ultrasonic irradiation, [Al]MCM-41 catalyst (Si/Al = 10) in this work obtained the highest CPL yield among all [Al]MCM-41 materials reported for liquid-phase Beckmann rearrangement up to now. Finally, the reusability of [Al]MCM-41 catalyst was tested and no significant activity loss can be observed after five reaction cycles.

Original languageEnglish
Pages (from-to)71-79
Number of pages9
JournalJournal of Catalysis
Volume358
DOIs
Publication statusPublished - 1 Feb 2018

Keywords

  • Acid sites
  • Beckmann rearrangement
  • MCM-41
  • Room-temperature synthesis by ultrasonic irradiation
  • Solid-state NMR

Cite this

Wang, Zichun ; Ling, Huajuan ; Shi, Jeffrey ; Stampfl, Catherine ; Yu, Aibing ; Hunger, Michael ; Huang, Jun. / Acidity enhanced [Al]MCM-41 via ultrasonic irradiation for the Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam. In: Journal of Catalysis. 2018 ; Vol. 358. pp. 71-79.
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abstract = "Using solid acid catalysts to replace liquid acids in the liquid-phase Beckmann rearrangement of cyclohexanone oxime (CHO) into ɛ-caprolactam (CPL) is crucial for the environmentally friendly production of synthetic fibers, such as Nylon-6. In this work, we prepared aluminum-containing MCM-41 catalysts under ultrasonic irradiation with various Si/Al ratios for this purpose. Quantitative 1H MAS NMR investigations show that ultrasonic irradiation significantly promotes the formation of active Br{\o}nsted acid sites (BAS) on the [Al]MCM-41 catalysts up to 8 times higher than those prepared at the same conditions without ultrasonic irradiation, and up to 12 times higher BAS density than those reported in the literatures. The catalytic performance of [Al]MCM-41 catalysts can be strongly improved with increasing the BAS density, particularly to the ratio of BAS/(weakly acidic SiOH groups). Moreover, [Al]MCM-41 catalysts dehydrated at 393 K obtained two time higher CHO conversion and CPL yield than that dehydrated at 473 K. Hydrogen-bonded water molecules retained at low dehydration temperature may block surface SiOH groups and promote the reaction process. With higher BAS density resulting from ultrasonic irradiation, [Al]MCM-41 catalyst (Si/Al = 10) in this work obtained the highest CPL yield among all [Al]MCM-41 materials reported for liquid-phase Beckmann rearrangement up to now. Finally, the reusability of [Al]MCM-41 catalyst was tested and no significant activity loss can be observed after five reaction cycles.",
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Acidity enhanced [Al]MCM-41 via ultrasonic irradiation for the Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam. / Wang, Zichun; Ling, Huajuan; Shi, Jeffrey; Stampfl, Catherine; Yu, Aibing; Hunger, Michael; Huang, Jun.

In: Journal of Catalysis, Vol. 358, 01.02.2018, p. 71-79.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Acidity enhanced [Al]MCM-41 via ultrasonic irradiation for the Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam

AU - Wang, Zichun

AU - Ling, Huajuan

AU - Shi, Jeffrey

AU - Stampfl, Catherine

AU - Yu, Aibing

AU - Hunger, Michael

AU - Huang, Jun

PY - 2018/2/1

Y1 - 2018/2/1

N2 - Using solid acid catalysts to replace liquid acids in the liquid-phase Beckmann rearrangement of cyclohexanone oxime (CHO) into ɛ-caprolactam (CPL) is crucial for the environmentally friendly production of synthetic fibers, such as Nylon-6. In this work, we prepared aluminum-containing MCM-41 catalysts under ultrasonic irradiation with various Si/Al ratios for this purpose. Quantitative 1H MAS NMR investigations show that ultrasonic irradiation significantly promotes the formation of active Brønsted acid sites (BAS) on the [Al]MCM-41 catalysts up to 8 times higher than those prepared at the same conditions without ultrasonic irradiation, and up to 12 times higher BAS density than those reported in the literatures. The catalytic performance of [Al]MCM-41 catalysts can be strongly improved with increasing the BAS density, particularly to the ratio of BAS/(weakly acidic SiOH groups). Moreover, [Al]MCM-41 catalysts dehydrated at 393 K obtained two time higher CHO conversion and CPL yield than that dehydrated at 473 K. Hydrogen-bonded water molecules retained at low dehydration temperature may block surface SiOH groups and promote the reaction process. With higher BAS density resulting from ultrasonic irradiation, [Al]MCM-41 catalyst (Si/Al = 10) in this work obtained the highest CPL yield among all [Al]MCM-41 materials reported for liquid-phase Beckmann rearrangement up to now. Finally, the reusability of [Al]MCM-41 catalyst was tested and no significant activity loss can be observed after five reaction cycles.

AB - Using solid acid catalysts to replace liquid acids in the liquid-phase Beckmann rearrangement of cyclohexanone oxime (CHO) into ɛ-caprolactam (CPL) is crucial for the environmentally friendly production of synthetic fibers, such as Nylon-6. In this work, we prepared aluminum-containing MCM-41 catalysts under ultrasonic irradiation with various Si/Al ratios for this purpose. Quantitative 1H MAS NMR investigations show that ultrasonic irradiation significantly promotes the formation of active Brønsted acid sites (BAS) on the [Al]MCM-41 catalysts up to 8 times higher than those prepared at the same conditions without ultrasonic irradiation, and up to 12 times higher BAS density than those reported in the literatures. The catalytic performance of [Al]MCM-41 catalysts can be strongly improved with increasing the BAS density, particularly to the ratio of BAS/(weakly acidic SiOH groups). Moreover, [Al]MCM-41 catalysts dehydrated at 393 K obtained two time higher CHO conversion and CPL yield than that dehydrated at 473 K. Hydrogen-bonded water molecules retained at low dehydration temperature may block surface SiOH groups and promote the reaction process. With higher BAS density resulting from ultrasonic irradiation, [Al]MCM-41 catalyst (Si/Al = 10) in this work obtained the highest CPL yield among all [Al]MCM-41 materials reported for liquid-phase Beckmann rearrangement up to now. Finally, the reusability of [Al]MCM-41 catalyst was tested and no significant activity loss can be observed after five reaction cycles.

KW - Acid sites

KW - Beckmann rearrangement

KW - MCM-41

KW - Room-temperature synthesis by ultrasonic irradiation

KW - Solid-state NMR

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DO - 10.1016/j.jcat.2017.11.013

M3 - Article

VL - 358

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EP - 79

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

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