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Title: Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols

Abstract

The stability of palladium supported on ceria (Pd/CeO 2) was studied during liquid flow transfer hydrogenation using primary and secondary alcohols as hydrogen donors. For primary alcohols, the ceria support was reduced to cerium hydroxy carbonate within 14 h and was a contributing factor toward catalyst deactivation. For secondary alcohols, cerium hydroxy carbonate was not observed during the same time period and the catalyst was stable upon prolonged reaction. Regeneration through oxidation/reduction does not restore initial activity likely due to irreversible catalyst restructuring. Lastly, a deactivation mechanism involving C–C scission of acyl and carboxylate intermediates is proposed.

Authors:
 [1];  [1]; ORCiD logo [1]
  1. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States). Dept. of Chemistry
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1347899
Report Number(s):
IS-J-9188
Journal ID: ISSN 1932-7447
Grant/Contract Number:
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 120; Journal Issue: 49; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Nelson, Nicholas C., Manzano, J. Sebastián, and Slowing, Igor I. Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols. United States: N. p., 2016. Web. doi:10.1021/acs.jpcc.6b09828.
Nelson, Nicholas C., Manzano, J. Sebastián, & Slowing, Igor I. Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols. United States. doi:10.1021/acs.jpcc.6b09828.
Nelson, Nicholas C., Manzano, J. Sebastián, and Slowing, Igor I. Mon . "Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols". United States. doi:10.1021/acs.jpcc.6b09828. https://www.osti.gov/servlets/purl/1347899.
@article{osti_1347899,
title = {Deactivation of Ceria Supported Palladium through C–C Scission during Transfer Hydrogenation of Phenol with Alcohols},
author = {Nelson, Nicholas C. and Manzano, J. Sebastián and Slowing, Igor I.},
abstractNote = {The stability of palladium supported on ceria (Pd/CeO2) was studied during liquid flow transfer hydrogenation using primary and secondary alcohols as hydrogen donors. For primary alcohols, the ceria support was reduced to cerium hydroxy carbonate within 14 h and was a contributing factor toward catalyst deactivation. For secondary alcohols, cerium hydroxy carbonate was not observed during the same time period and the catalyst was stable upon prolonged reaction. Regeneration through oxidation/reduction does not restore initial activity likely due to irreversible catalyst restructuring. Lastly, a deactivation mechanism involving C–C scission of acyl and carboxylate intermediates is proposed.},
doi = {10.1021/acs.jpcc.6b09828},
journal = {Journal of Physical Chemistry. C},
number = 49,
volume = 120,
place = {United States},
year = {Mon Nov 21 00:00:00 EST 2016},
month = {Mon Nov 21 00:00:00 EST 2016}
}

Journal Article:
Free Publicly Available Full Text
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  • Two series of highly dispersed palladium catalysts supported on alumina have been prepared by adsorption from solution, with palladium contents varying from 0.25 to 2.0 wt %. The first series was calcined at 773 K for 4 h in air, whereas the second series was just heated at 423 K for 1 h in nitrogen, before reduction. Complete dispersion of the metal has been found for the calcined catalysts, and metal dispersion was favored with low palladium contents for the noncalcined catalysts. The kinetic behavior of the catalysts has been analyzed for the liquid-phase hydrogenation of phenol in a stirredmore » tank reactor, ensuring a chemically controlled regime for stirring speed above 750 rpm and catalyst particle below 0.08--0.16 mm in the studied conditions. Despite their higher metallic dispersion, the calcined catalysts presented lower activity than their corresponding noncalcined catalysts. The influence of hydrogen partial pressure on activity showed a reaction order of 2. The apparent activation energy resulted in 56.8 kJ/mol. Selectivity to cyclohexanone was found to be very high for all experiments. Some conclusions on the kinetic reaction rate equations and the apparent activation energies of phenol to cyclohexanone and cyclohexanone to cyclohexanol are given.« less
  • The initial reaction observed between N-heterocyclic carbene IMes (IMes = 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene) and molybdenum and tungsten hydride complexes CpM(CO) 2(PPh 3)H (M = Mo, W) is deprotonation of the metal hydride by IMes, giving [(IMes)H] +[CpM(CO) 2(PPh 3)] . At longer reaction times and higher temperatures, the reaction of IMes with CpM(CO) 2(PR 3)H (M = Mo, W; R = Me, Ph) produces CpM(CO) 2(IMes)H. Hydride transfer from CpW(CO) 2(IMes)H to Ph 3C +B(C 6F 5) 4 - gives CpW(CO) 2(IMes) +B(C 6F 5) 4 - which was crystallographically characterized using x-ray radiation from a synchrotron. The IMes is bondedmore » as a bidentate ligand, through the carbon of the carbene as well as forming a weak bond from the metal to a C =C bond of one mesityl ring. The weakly bound C =C ligand is hemilabile, being readily displaced by H 2, THF, ketones or alcohols. Reaction of CpW(CO) 2(IMes) + with H 2 gives the dihydride complex [CpW(CO) 2(IMes)(H) 2] +. Addition of Et 2CH–OH to CpW(CO) 2(IMes) +B(C 6F 5) 4 - gives the alcohol complex [CpM(CO) 2(IMes)(Et 2CH–OH)] +[B(C 6F 5) 4] which was characterized by crystallography and exhibits no evidence for hydrogen bonding of the bound OH group. Addition of H 2 to the ketone complex [CpW(CO) 2(IMes)(Et 2C =O)] +[B(C 6F 5) 4] produces an equilibrium with the dihydride [CpW(CO) 2(IMes)(H) 2] + (K eq = 1.1 x 103 at 25 °C). The tungsten ketone complex [CpW(CO) 2(IMes)(Et 2C =O)] +[B(C 6F 5) 4] serves as a modest catalyst for hydrogenation of Et 2C =O to Et 2CH–OH in neat ketone solvent. Decomposition of the catalyst produces [H(IMes)] +B(C 6F 5) 4 -, indicating that these catalysts with N-heterocyclic carbenes ligands are vulnerable to decomposition by a reaction that produces a protonated imidazolium cation.« less
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