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Vapour phase hydrogenation of phenol over Pd/C catalysts: A relationship between dispersion, metal area and hydrogenation activity

Paper ID Volume ID Publish Year Pages File Format Full-Text
52869 46890 2007 7 PDF Available
Title
Vapour phase hydrogenation of phenol over Pd/C catalysts: A relationship between dispersion, metal area and hydrogenation activity
Abstract

A series of palladium supported on activated carbon catalysts, with Pd varying from 0.5 to 6.0 wt%, were prepared via wet impregnation method using PdCl2 · xH2O as a precursor salt. The dried samples were further reduced at 573 K in hydrogen and characterized by CO adsorption at room temperature in order to determine the dispersion, metal area and particle size. The catalysts were tested for vapour phase phenol hydrogenation in a fixed-bed all glass micro-reactor at a reaction temperature of 453 K under normal atmospheric pressure. The decrease in metal surface area as well as dispersion with corresponding increase in turn-over frequency (TOF) against palladium loadings suggest the unusual inverse relationship that exist between Pd dispersion and phenol hydrogenation activity over Pd/carbon catalysts. The stability of TOF at larger crystallite size indicates that phenol hydrogenation is less sensitive reaction especially beyond 3 wt% of Pd content. It is evident from the results that structural properties of the catalysts strongly influence the availability of Pd atoms on the surface for CO chemisorption and hence for phenol hydrogenation. A comparison between selectivity and product yield of the reaction against overall phenol conversion indicates that changes in reaction selectivity for cyclohexanone or cyclohexanol is independent of phenol conversion level and either of the product is not formed at the cost of another. The stability of the catalysts with reaction time suggests that coke formation on the surface of the catalyst is less significant and the formation of cyclohexanone remains almost total even at higher reaction temperatures.

Keywords
Activated carbon; Palladium dispersion; Phenol activity
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Vapour phase hydrogenation of phenol over Pd/C catalysts: A relationship between dispersion, metal area and hydrogenation activity
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Communications - Volume 8, Issue 3, March 2007, Pages 471–477
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