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Chemoselective hydrogenation of o-, p- and m-chloronitrobenzene at ambient temperature on Au/Fe2O3 catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
39592 45828 2014 10 PDF Available
Title
Chemoselective hydrogenation of o-, p- and m-chloronitrobenzene at ambient temperature on Au/Fe2O3 catalysts
Abstract

•Deposition–precipitation with urea led the best metal dispersion in Au/Fe2O3 catalysts.•Au nanoparticles size influences the catalyst performance in the nitrobenzene hydrogenation.•Au/Fe2O3 promote only hydrogenation of NO2 group of o-, m- and p-chloronitrobenzenes.•0.5%Au/Fe2O3 showed the highest yield and selectivity in o-chloronitrobenzene hydrogenation.

Gold nanoparticles deposited on an α-Fe2O3 substrate were prepared by different procedures including the deposition–precipitation in presence of urea or NaOH, and by the traditional wet impregnation followed by calcination. Metal loading and catalyst structures were determined by ICP-MS and XRD analyses while the size and electronic nature of Au nanoparticles were assessed using TEM and XPS. The effect of the catalyst preparation methodology was evaluated in the catalytic hydrogenation of nitrobenzene (NB) carried out in a batch reactor at 25 °C and 20 bar of H2 pressure. Among the catalysts studied, 1.0%Au/α-Fe2O3 prepared by deposition–precipitation with urea recorded the best performance (TOF = 4.6 s−1) and a selectivity toward aniline of 92%. The XRD and TEM data pointed out that the active sites are small gold particles (3.8 nm) highly dispersed on the substrate surface. Moreover, the effect of Au loading (0.5, 1.0 and 2.0 wt.%) was investigated in the hydrogenation reaction of o-, m- and p-chloronitrobenzene (o, m- and p-CNB) to o-, m- and p-chloroaniline (o-, m- and p-CAN) (a batch reactor; T = 25 °C; P = 20 bar of H2) over Au/α-Fe2O3 catalysts prepared by deposition–precipitation with urea. Regardless of the CNB isomer, maximum activity was recorded for the catalyst with 0.5 wt.% Au loading (m-CNB conversion of 99.7%). At 6 h reaction time, the yields of o-CAN, m-CAN and p-CAN were 97, 93.7 and 91.7 mol.%, respectively. Catalytic activity decreases in the order: m-CNB > o-CNB > p-CNB, but this sequence does not depend on the Au loading. Other factors such as the electronic properties of Au nanoparticles and steric factors of Cl substitute appear to play a major role in the reaction.

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Keywords
Nitroarenes hydrogenation; Iron oxide; Au nanoparticles; Gold catalysts
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Chemoselective hydrogenation of o-, p- and m-chloronitrobenzene at ambient temperature on Au/Fe2O3 catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 482, 22 July 2014, Pages 127–136
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