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A one step synthesis ofcaprolactam out of cyclohexanone by combinded ammoximation and Beckmann rearrangement over Nb-MCM-41 catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
45537 46416 2015 7 PDF Available
Title
A one step synthesis ofcaprolactam out of cyclohexanone by combinded ammoximation and Beckmann rearrangement over Nb-MCM-41 catalysts
Abstract

•Caprolactam was synthesized via one-step liquid phase ammoximation and Beckmann rearrangement over Nb-MCM-41 catalysts.•The influence of temperature, NH3/cyclohexanone ratios and Si/Nb ratios were investigated.•66% caprolactam selectivity and 7.3% cyclohexanone conversion were achieved under best reaction conditions.•Nb-MCM-41 catalysts having different Si/Nb ratios showed that high Nb content samples yield higher caprolactam.•The high activity of these high Nb content Nb-MCM-41 materials is due to weak to medium acid strength.

Caprolactam was synthesized directly in one step out of cyclohexanone via combined liquid phase ammoximation and Beckmann rearrangement using H2O2 and NH3 in presence of Nb-MCM-41 catalysts and ethanol as solvent. Thereby the Beckmann rearrangement of the oxime to caprolactam occurs simultaneously with the ammoximation of cyclohexanone. Nb-incorporated MCM-41 molecular sieves (Si/Nb- 16, 32, 64 and 128) have been synthesized hydrothermally using tetradecyltrimethylammoniumbromide as template in absence of auxiliary organics. Synthesized Nb-MCM-41 samples were characterized using various physical-chemical techniques such as X-ray diffraction, N2-physisorption, Atomic Absorption Spectroscopy (ICP-AAS), Thermal Gravimetric Analysis (TGA-DTA), Raman spectroscopy and H2-Temperature Programmed Reduction (TPR). All spectroscopic characterization techniques revealed that two types of Nb species are present in the samples. One is tetrahedral coordinated framework Nb species and the other type extra framework Nb2O5 species. All these Nb-MCM-41 catalysts were employed to catalyze the ammoximation reaction of cyclohexanone with H2O2 and NH3 and the simultaneously occurring Beckmann rearrangement reaction. The influence of essential reaction parameters such as temperature, NH3/cyclohexanone ratios and Si/Nb ratios were investigated. A caprolactam selectivity of 66% was obtained at a cyclohexanone conversion of 7.3% at NH3/cyclohexanone molar ratio = 1.5, H2O2: cyclohexanone molar ratio = 1.32 over Nb-MCM-41 (Si/Nb-32) at 80 °C.

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Keywords
Ammoximation; Beckmann rearrangement; Cyclohexanone; Nb-MCM-41; Cyclohexanoneoxime; ɛ-Caprolactam
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A one step synthesis ofcaprolactam out of cyclohexanone by combinded ammoximation and Beckmann rearrangement over Nb-MCM-41 catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 165, April 2015, Pages 87–93
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us