Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol

Qi, Long; Chamas, Ali; Jones, Zachary R.; Walter, Eric D.; Hoyt, David W.; Washton, Nancy M.; Scott, Susannah L.

doi:10.1021/jacs.9b09071

Title: Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al₂O₃ in 2-Propanol

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Abstract

The reductive cleavage of aryl ether linkages is a key step in the disassembly of lignin to its monolignol components, where selectivity is determined by the kinetics of multiple parallel and consecutive liquid-phase reactions. Triphasic hydrogenolysis of ¹³C-labeled benzyl phenyl ether (BPE, a model compound with the same C-O bond energy as the major β-O-4 linkage in lignin), catalyzed by Ni/γ-Al₂O₃, was observed directly at elevated temperatures (150 - 175 °C) and pressures (79-89 bar) using operando magic-angle spinning NMR spectroscopy. Liquid-vapor partitioning in the NMR rotor was quantified using the ¹³C NMR resonances for the 2-propanol solvent, whose chemical shifts report on the internal reactor temperature. At 170 °C, BPE is converted to toluene and phenol with k₁ = 0.17 s^-1 g_cat^-1 and an apparent activation barrier of (80 ± 8) kJ mol^-1. Subsequent phenol hydrogenation occurs much more slowly (k₂ = 0.0052 s^-1 g_cat^-1 at 170-175 °C), such that cyclohexanol formation is significant only at higher temperatures. Toluene is stable under these reaction conditions, but its methyl group undergoes facile H/D exchange (k₃ = 0.046 s^-1 g_cat^-1 at 175 °C). While the source of the reducing equivalents for both hydrogenolysis and hydrogenation is exclusively H₂/D_2(g) rather than themore »« less

Authors:

^[1];

^[2]; Jones, Zachary R. ^[2];

^[3];

^[2]

Univ. of California, Santa Barbara, CA (United States); Iowa State Univ., Ames, IA (United States)
Univ. of California, Santa Barbara, CA (United States)
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Publication Date:: Fri Oct 04 00:00:00 EDT 2019

Research Org.:: Ames Lab., Ames, IA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)

Sponsoring Org.:: National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:: 1608537

Alternate Identifier(s):: OSTI ID: 1709115

Report Number(s):: PNNL-SA-148402; IS-J-10,099
Journal ID: ISSN 0002-7863

Grant/Contract Number:: AC05-76RL01830; CBET-1512228; CBET-1604095; AC02-07CH11358; DMR-1121053

Resource Type:: Accepted Manuscript

Journal Name:: Journal of the American Chemical Society

Additional Journal Information:: Journal Volume: 141; Journal Issue: 43; Journal ID: ISSN 0002-7863

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; interfacial reactions; reaction network; C-O bond hydrogenolysis; solvent effect; arene hydrogenation; C-H activation; induction period; operando NMR spectroscopy

Citation Formats


                    Qi, Long, Chamas, Ali, Jones, Zachary R., Walter, Eric D., Hoyt, David W., Washton, Nancy M., and Scott, Susannah L. Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol.  United States: N. p., 2019. 
Web.  doi:10.1021/jacs.9b09071.

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                    Qi, Long, Chamas, Ali, Jones, Zachary R., Walter, Eric D., Hoyt, David W., Washton, Nancy M., & Scott, Susannah L. Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol.  United States.  https://doi.org/10.1021/jacs.9b09071

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                    Qi, Long, Chamas, Ali, Jones, Zachary R., Walter, Eric D., Hoyt, David W., Washton, Nancy M., and Scott, Susannah L. Fri .  
"Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol".  United States.  https://doi.org/10.1021/jacs.9b09071.  https://www.osti.gov/servlets/purl/1608537.

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@article{osti_1608537,

  title        = {Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol},

  author       = {Qi, Long and Chamas, Ali and Jones, Zachary R. and Walter, Eric D. and Hoyt, David W. and Washton, Nancy M. and Scott, Susannah L.},

  abstractNote = {The reductive cleavage of aryl ether linkages is a key step in the disassembly of lignin to its monolignol components, where selectivity is determined by the kinetics of multiple parallel and consecutive liquid-phase reactions. Triphasic hydrogenolysis of 13C-labeled benzyl phenyl ether (BPE, a model compound with the same C-O bond energy as the major β-O-4 linkage in lignin), catalyzed by Ni/γ-Al2O3, was observed directly at elevated temperatures (150 - 175 °C) and pressures (79-89 bar) using operando magic-angle spinning NMR spectroscopy. Liquid-vapor partitioning in the NMR rotor was quantified using the 13C NMR resonances for the 2-propanol solvent, whose chemical shifts report on the internal reactor temperature. At 170 °C, BPE is converted to toluene and phenol with k1 = 0.17 s-1 gcat-1 and an apparent activation barrier of (80 ± 8) kJ mol-1. Subsequent phenol hydrogenation occurs much more slowly (k2 = 0.0052 s-1 gcat-1 at 170-175 °C), such that cyclohexanol formation is significant only at higher temperatures. Toluene is stable under these reaction conditions, but its methyl group undergoes facile H/D exchange (k3 = 0.046 s-1 gcat-1 at 175 °C). While the source of the reducing equivalents for both hydrogenolysis and hydrogenation is exclusively H2/D2(g) rather than the alcohol solvent at these temperatures, the initial isotopic composition of adsorbed H/D on the catalyst surface is principally determined by the solvent isotopic composition (2-PrOH/D). All reactions are preceded by a pronounced induction period associated with catalyst activation. In air, Ni nanoparticles are passivated by a surface oxide monolayer, whose removal under H2 proceeds with an apparent activation barrier of (72 ± 13) kJ mol-1. Finally ,the operando NMR spectra provide molecularly-specific, time-resolved information about the multiple simultaneous and sequential processes as they occur at the solid-liquid interface.},

  doi          = {10.1021/jacs.9b09071},

  journal      = {Journal of the American Chemical Society},

  number       = 43,

  volume       = 141,

  place        = {United States},

  year         = {Fri Oct 04 00:00:00 EDT 2019},

  month        = {Fri Oct 04 00:00:00 EDT 2019}

}

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Title: Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al2O3 in 2-Propanol

Abstract

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Title: Unraveling the Dynamic Network in the Reactions of an Alkyl Aryl Ether Catalyzed by Ni/γ-Al₂O₃ in 2-Propanol