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Gas phase hydrogenation of p-chloronitrobenzene over Pd–Ni/Al2O3

Paper ID Volume ID Publish Year Pages File Format Full-Text
39958 45841 2014 10 PDF Available
Title
Gas phase hydrogenation of p-chloronitrobenzene over Pd–Ni/Al2O3
Abstract

•Selective hydrogenation of p-chloronitrobenzene over Ni/Al2O3 to p-chloroaniline.•Pd/Al2O3 promotes hydrodechlorination/hydrogenation to nitrobenzene and aniline.•Reaction over Pd/Al2O3 + Ni/Al2O3 physical mixtures controlled by Pd/Al2O3.•Pd–Ni/Al2O3 delivers highest activity and 100% selectivity to p-chloroaniline.•Elevated p-chloroaniline yield linked to bimetallic particles in Pd–Ni/Al2O3.

The gas phase (1 atm; T = 393 K) hydrogenation of p-chloronitrobenzene (p-CNB) has been examined over alumina supported mono-(Pd or Ni) and bi-metallic (Pd:Ni = 1:3, 1:1 and 3:1) catalysts prepared by (co-)impregnation. The catalytic action of physical mixtures (Pd/Al2O3 + Ni/Al2O3) was also considered. The catalysts have been characterised by temperature programmed reduction (TPR), H2 chemisorption, powder XRD, HRTEM–EDX and XPS measurements. TPR analysis has provided evidence of a more facile reduction of Pd and Ni in Pd–Ni/Al2O3 relative to Pd/Al2O3 and Ni/Al2O3. TEM–EDX and XPS measurements show Pd surface enrichment in Pd–Ni/Al2O3 with evidence of modification to Pd electronic character. Ni/Al2O3 promoted exclusive -NO2 group reduction to generate p-chloroaniline (p-CAN). Pd/Al2O3 delivered a higher specific p-CNB consumption rate, yielding undesired nitrobenzene and aniline via coupled hydrodechlorination and hydrogenation. The Pd/Al2O3 + Ni/Al2O3 combination generated an overall rate and product distribution equivalent to Pd/Al2O3, i.e. the catalytic response was governed by Pd in the physical mixture. In contrast, reaction over Pd–Ni/Al2O3 resulted in exclusive production of the target p-CAN. This is consistent with lower chlorobenzene hydrodechlorination activity recorded for Pd–Ni/Al2O3 (relative to Pd/Al2O3). Reaction rate was sensitive to composition where Pd:Ni = 1:1 delivered the highest p-CAN yield. We attribute the catalytic response observed for Pd–Ni/Al2O3 to bimetallic particle formation as demonstrated by TPR, XRD and XPS analyses.

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Keywords
Selective hydrogenation; Bimetallic catalyst; p-Chloronitrobenzene; p-Chloroaniline; Co-impregnation; Pd–Ni/Al2O3
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Gas phase hydrogenation of p-chloronitrobenzene over Pd–Ni/Al2O3
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 473, 5 March 2014, Pages 41–50
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