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Yerrayya A, Natarajan U, Vinu R. Fast pyrolysis of guaiacol to simple phenols: Experiments, theory and kinetic model. Chem Eng Sci 2019. [DOI: 10.1016/j.ces.2019.06.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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2
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Nagel E, Zhang C. Hydrothermal Decomposition of a Lignin Dimer under Neutral and Basic Conditions: A Mechanism Study. Ind Eng Chem Res 2019. [DOI: 10.1021/acs.iecr.9b00400] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eric Nagel
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007, United States
| | - Cheng Zhang
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007, United States
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3
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Kulik HJ. MODELING MECHANOCHEMISTRY FROM FIRST PRINCIPLES. REVIEWS IN COMPUTATIONAL CHEMISTRY 2018. [DOI: 10.1002/9781119518068.ch6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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4
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Zhou X, Wei XY, Ma YM, Zong ZM. Effects of reaction conditions on catalytic hydroconversion of phenethoxybenzene over bifunctional Ni/Hβ. ASIA-PAC J CHEM ENG 2018. [DOI: 10.1002/apj.2228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Xiao Zhou
- Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education; China University of Mining and Technology; Xuzhou China
- Department of Chemical and Environmental Engineering; Xinjiang Institute of Engineering; Urumchi China
| | - Xian-Yong Wei
- Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education; China University of Mining and Technology; Xuzhou China
| | - Yu-Miao Ma
- Department of Chemical and Environmental Engineering; Xinjiang Institute of Engineering; Urumchi China
| | - Zhi-Min Zong
- Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education; China University of Mining and Technology; Xuzhou China
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5
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Zhang T, Li X, Guo L. Initial Reactivity of Linkages and Monomer Rings in Lignin Pyrolysis Revealed by ReaxFF Molecular Dynamics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:11646-11657. [PMID: 28838235 DOI: 10.1021/acs.langmuir.7b02053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The initial conversion pathways of linkages and their linked monomer units in lignin pyrolysis were investigated comprehensively by ReaxFF MD simulations facilitated by the unique VARxMD for reaction analysis. The simulated molecular model contains 15 920 atoms and was constructed on the basis of Adler's softwood lignin model. The simulations uncover the initial conversion ratio of various linkages and their linked aryl monomers. For linkages and their linked monomer aryl rings of α-O-4, β-O-4 and α-O-4 & β-5, the Cα/Cβ ether bond cracking dominates the initial pathway accounting for at least up to 80% of their consumption. For the linkage of β-β & γ-O-α, both the Cα-O ether bond cracking and its linked monomer aryl ring opening are equally important. Ring-opening reactions dominate the initial consumption of other 4-O-5, 5-5, β-1, β-2, and β-5 linkages and their linked monomers. The ether bond cracking of Cα-O and Cβ-O occurs at low temperature, and the aryl ring-opening reactions take place at relatively high temperature. The important intermediates leading to the stable aryl ring opening are the phenoxy radicals, the bridged five-membered and three-membered rings and the bridged six-membered and three-membered rings. In addition, the reactivity of a linkage and its monomer aryl ring may be affected by other linkages. The ether bond cracking of α-O-4 and β-O-4 linkages can activate its neighboring linkage or monomer ring through the formed phenoxy radicals as intermediates. The important intermediates revealed in this article should be of help in deepening the understanding of the controlling mechanism for producing aromatic chemicals from lignin pyrolysis.
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Affiliation(s)
- Tingting Zhang
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences , Beijing 100190, P. R. China
- University of Chinese Academy of Sciences , Beijing 100049, P. R. China
| | - Xiaoxia Li
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences , Beijing 100190, P. R. China
- University of Chinese Academy of Sciences , Beijing 100049, P. R. China
| | - Li Guo
- State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences , Beijing 100190, P. R. China
- University of Chinese Academy of Sciences , Beijing 100049, P. R. China
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6
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Mar BD, Kulik HJ. Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics. J Phys Chem A 2017; 121:532-543. [PMID: 28005362 DOI: 10.1021/acs.jpca.6b11414] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lignocellulosic biomass is an abundant, rich source of aromatic compounds, but direct utilization of raw lignin has been hampered by both the high heterogeneity and variability of linking bonds in this biopolymer. Ab initio steered molecular dynamics (AISMD) has emerged both as a fruitful direct computational screening approach to identify products that occur through mechanical depolymerization (i.e., in sonication or ball-milling) and as a sampling approach. By varying the direction of force and sampling over 750 AISMD trajectories, we identify numerous possible pathways through which lignin depolymerization may occur in pyrolysis or through catalytic depolymerization as well. Here, we present eight unique major depolymerization pathways discovered via AISMD for the recently characterized spirodienone lignin branching linkage that may comprise around 10% weight of all lignin in some softwoods. We extract representative trajectories from AISMD and carry out reaction pathway analysis to identify energetically favorable pathways for lignin depolymerization. Importantly, we identify dynamical effects that could not be observed through more traditional calculations of bond dissociation energies. Such effects include thermodynamically favorable recovery of aromaticity in the dienone ring that leads to near-barrierless subsequent ether cleavage and hydrogen-bonding effects that stabilize newly formed radicals. Some of the most stable spirodienone fragments that reside at most 1 eV above the reactant structure are formed with only 2 eV barriers for C-C bond cleavage, suggesting key targets for catalyst design to drive targeted depolymerization of lignin.
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Affiliation(s)
- Brendan D Mar
- Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Heather J Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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7
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A theoretical research on pyrolysis reactions mechanism of coumarone-contained lignin model compound. COMPUT THEOR CHEM 2016. [DOI: 10.1016/j.comptc.2016.07.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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8
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Elder T, Berstis L, Beckham GT, Crowley MF. Coupling and Reactions of 5-Hydroxyconiferyl Alcohol in Lignin Formation. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:4742-4750. [PMID: 27236926 DOI: 10.1021/acs.jafc.6b02234] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The catechol alcohols, caffeyl and 5-hydroxyconiferyl alcohol, may be incorporated into lignin either naturally or through genetic manipulation. Due to the presence of o-OH groups, these compounds form benzodioxanes, a departure from the interunit connections found in lignins derived from the cinnamyl alcohols. In nature, lignins composed of caffeyl and 5-hydroxyconiferyl alcohol are linear homopolymers and, as such, may have properties that make them amenable for use in value-added products, such as lignin-based carbon fibers. In the current work, results from density functional theory calculations for the reactions of 5-hydroxyconiferyl alcohol, taking stereochemistry into account, are reported. Dehydrogenation and quinone methide formation are found to be thermodynamically favored for 5-hydroxyconiferyl alcohol, over coniferyl alcohol. The comparative energetics of the rearomatization reactions suggest that the formation of the benzodioxane linkage is under kinetic control. Ring-opening reactions of the benzodioxane groups show that the bond dissociation enthalpy of the α-O cleavage reaction is lower than that of the β-O reaction. The catechol lignins represent a novel form of the polymer that may offer new opportunities for bioproducts and genetic targets.
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Affiliation(s)
- Thomas Elder
- Southern Research Station, USDA-Forest Service , 521 Devall Drive, Auburn, Alabama 36849, United States
| | - Laura Berstis
- National Bioenergy Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Gregg T Beckham
- National Bioenergy Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Michael F Crowley
- Biosciences Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
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9
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Wang M, Liu C, Xu X, Li Q. Theoretical study of the pyrolysis of vanillin as a model of secondary lignin pyrolysis. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.03.058] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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10
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Qi YB, Wang XL, Shi T, Liu S, Xu ZH, Li X, Shi X, Xu P, Zhao YL. Multicomponent kinetic analysis and theoretical studies on the phenolic intermediates in the oxidation of eugenol and isoeugenol catalyzed by laccase. Phys Chem Chem Phys 2015; 17:29597-607. [PMID: 26477512 DOI: 10.1039/c5cp03475b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Laccase catalyzes the oxidation of natural phenols and thereby is believed to initialize reactions in lignification and delignification. Numerous phenolic mediators have also been applied in laccase-mediator systems. However, reaction details after the primary O-H rupture of phenols remain obscure. In this work two types of isomeric phenols, EUG (eugenol) and ISO (trans-/cis-isoeugenol), were used as chemical probes to explore the enzymatic reaction pathways, with the combined methods of time-resolved UV-Vis absorption spectra, MCR-ALS, HPLC-MS, and quantum mechanical (QM) calculations. It has been found that the EUG-consuming rate is linear to its concentration, while the ISO not. Besides, an o-methoxy quinone methide intermediate, (E/Z)-4-allylidene-2-methoxycyclohexa-2,5-dienone, was evidenced in the case of EUG with the UV-Vis measurement, mass spectra and TD-DFT calculations; in contrast, an ISO-generating phenoxyl radical, a (E/Z)-2-methoxy-4-(prop-1-en-1-yl) phenoxyl radical, was identified in the case of ISO. Furthermore, QM calculations indicated that the EUG-generating phenoxyl radical (an O-centered radical) can easily transform into an allylic radical (a C-centered radical) by hydrogen atom transfer (HAT) with a calculated activation enthalpy of 5.3 kcal mol(-1) and then be fast oxidized to the observed eugenol quinone methide, rather than an O-radical alkene addition with barriers above 12.8 kcal mol(-1). In contrast, the ISO-generating phenoxyl radical directly undergoes a radical coupling (RC) process, with a barrier of 4.8 kcal mol(-1), while the HAT isomerization between O- and C-centered radicals has a higher reaction barrier of 8.0 kcal mol(-1). The electronic conjugation of the benzyl-type radical and the aromatic allylic radical leads to differentiation of the two pathways. These results imply that competitive reaction pathways exist for the nascent reactive intermediates generated in the laccase-catalyzed oxidation of natural phenols, which is important for understanding the lignin polymerization and may shed some light on the development of efficient laccase-mediator systems.
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Affiliation(s)
- Yan-Bing Qi
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
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11
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Mar BD, Qi HW, Liu F, Kulik HJ. Ab Initio Screening Approach for the Discovery of Lignin Polymer Breaking Pathways. J Phys Chem A 2015; 119:6551-62. [PMID: 26001164 DOI: 10.1021/acs.jpca.5b03503] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The directed depolymerization of lignin biopolymers is of utmost relevance for the valorization or commercialization of biomass fuels. We present a computational and theoretical screening approach to identify potential cleavage pathways and resulting fragments that are formed during depolymerization of lignin oligomers containing two to six monomers. We have developed a chemical discovery technique to identify the chemically relevant putative fragments in eight known polymeric linkage types of lignin. Obtaining these structures is a crucial precursor to the development of any further kinetic modeling. We have developed this approach by adapting steered molecular dynamics calculations under constant force and varying the points of applied force in the molecule to diversify the screening approach. Key observations include relationships between abundance and breaking frequency, the relative diversity of potential pathways for a given linkage, and the observation that readily cleaved bonds can destabilize adjacent bonds, causing subsequent automatic cleavage.
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Affiliation(s)
| | | | - Fang Liu
- §Department of Chemistry, Stanford University, Stanford, California 94305, United States
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12
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Huang J, He C, Liu C, Tong H, Wu L, Wu S. A computational study on thermal decomposition mechanism of β-1 linkage lignin dimer. COMPUT THEOR CHEM 2015. [DOI: 10.1016/j.comptc.2014.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Hayes CJ, Burgess DR, Manion JA. Combustion Pathways of Biofuel Model Compounds. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2015. [DOI: 10.1016/bs.apoc.2015.09.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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14
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Lignin hydrolysis and phosphorylation mechanism during phosphoric acid-acetone pretreatment: a DFT study. Molecules 2014; 19:21335-49. [PMID: 25529020 PMCID: PMC6271813 DOI: 10.3390/molecules191221335] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Revised: 12/07/2014] [Accepted: 12/08/2014] [Indexed: 11/16/2022] Open
Abstract
The study focused on the structural sensitivity of lignin during the phosphoric acid–acetone pretreatment process and the resulting hydrolysis and phosphorylation reaction mechanisms using density functional theory calculations. The chemical stabilities of the seven most common linkages (β-O-4, β-β, 4-O-5, β-1, 5-5, α-O-4, and β-5) of lignin in H3PO4, CH3COCH3, and H2O solutions were detected, which shows that α-O-4 linkage and β-O-4 linkage tend to break during the phosphoric acid–acetone pretreatment process. Then α-O-4 phosphorylation and β-O-4 phosphorylation follow a two-step reaction mechanism in the acid treatment step, respectively. However, since phosphorylation of α-O-4 is more energetically accessible than phosphorylation of β-O-4 in phosphoric acid, the phosphorylation of α-O-4 could be controllably realized under certain operational conditions, which could tune the electron and hole transfer on the right side of β-O-4 in the H2PO4− functionalized lignin. The results provide a fundamental understanding for process-controlled modification of lignin and the potential novel applications in lignin-based imprinted polymers, sensors, and molecular devices.
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15
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Huang J, Liu C, Tong H, Li W, Wu D. A density functional theory study on formation mechanism of CO, CO2 and CH4 in pyrolysis of lignin. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2014.06.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Beste A. ReaxFF study of the oxidation of lignin model compounds for the most common linkages in softwood in view of carbon fiber production. J Phys Chem A 2014; 118:803-14. [PMID: 24428197 DOI: 10.1021/jp410454q] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lignin is an underused but major component of biomass. One possible area of utilization is the production of carbon fiber. A necessary processing step is the stabilization of lignin fiber (typically in an oxygen environment) before high temperature treatment. We investigate oxidative, thermal conversion of lignin using computational methods. Dilignol model compounds for the most common (seven) linkages in softwood are chosen to represent the diverse structure of lignin. We perform molecular dynamics simulation where the potential energy surface is described by a reactive force field (ReaxFF). We calculate overall activation energies for model conversion and reveal initial mechanisms of formaldehyde formation. We record fragmentation patterns and average carbon oxidation numbers at various temperatures. Most importantly, we identify mechanisms for stabilizing reactions that result in cyclic and rigid connections in softwood lignin fibers that are necessary for further processing into carbon fibers.
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Affiliation(s)
- Ariana Beste
- Joint Institute for Computational Sciences, The University of Tennessee , Oak Ridge, Tennessee 37831, United States
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17
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Beste A, Buchanan AC. Computational Investigation of the Pyrolysis Product Selectivity for α-Hydroxy Phenethyl Phenyl Ether and Phenethyl Phenyl Ether: Analysis of Substituent Effects and Reactant Conformer Selection. J Phys Chem A 2013; 117:3235-42. [DOI: 10.1021/jp4015004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ariana Beste
- Joint Institute
for Computational Sciences, The University of Tennessee, Oak Ridge, Tennessee 37831, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee
37831, United States
| | - A. C. Buchanan
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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18
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Beste A, Buchanan AC. Role of Carbon–Carbon Phenyl Migration in the Pyrolysis Mechanism of β-O-4 Lignin Model Compounds: Phenethyl Phenyl Ether and α-Hydroxy Phenethyl Phenyl Ether. J Phys Chem A 2012. [DOI: 10.1021/jp3104694] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ariana Beste
- Joint Institute
for Computational
Sciences, The University of Tennessee,
Oak Ridge, Tennessee 37831, United States
| | - A. C. Buchanan
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
37831, United States
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19
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Kinetic simulation of the thermal degradation of phenethyl phenyl ether, a model compound for the β-O-4 linkage in lignin. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.08.040] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Sangha AK, Parks JM, Standaert RF, Ziebell A, Davis M, Smith JC. Radical Coupling Reactions in Lignin Synthesis: A Density Functional Theory Study. J Phys Chem B 2012; 116:4760-8. [DOI: 10.1021/jp2122449] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Amandeep K. Sangha
- UT/ORNL Center for
Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United
States
| | - Jerry M. Parks
- UT/ORNL Center for
Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United
States
- Bioenergy Science
Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge,
Tennessee 37831, United States
| | - Robert F. Standaert
- Department of Biochemistry
and
Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge,
Tennessee 37831, United States
- Biology and Soft
Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Angela Ziebell
- Bioenergy Science
Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado
80401, United States
| | - Mark Davis
- Bioenergy Science
Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado
80401, United States
| | - Jeremy C. Smith
- UT/ORNL Center for
Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United
States
- Department of Biochemistry
and
Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
- Bioenergy Science
Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge,
Tennessee 37831, United States
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Younker JM, Beste A, Buchanan AC. Computational Study of Bond Dissociation Enthalpies for Substituted β-O-4 Lignin Model Compounds. Chemphyschem 2011; 12:3556-65. [DOI: 10.1002/cphc.201100477] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/18/2011] [Indexed: 11/09/2022]
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22
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Kidder MK, Chaffee AL, Nguyen MHT, Buchanan AC. Pyrolysis of phenethyl phenyl ether tethered in mesoporous silica. Effects of confinement and surface spacer molecules on product selectivity. J Org Chem 2011; 76:6014-23. [PMID: 21696147 DOI: 10.1021/jo200576v] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There has been expanding interest in exploring porous metal oxides as a confining environment for organic molecules resulting in altered chemical and physical properties including chemical transformations. In this paper, we examine the pyrolysis behavior of phenethyl phenyl ether (PPE) confined in mesoporous silica by covalent tethers to the pore walls as a function of tether density and the presence of cotethered surface spacer molecules of varying structure (biphenyl, naphthyl, octyl, and hexadecyl). The PPE pyrolysis product selectivity, which is determined by two competitive free-radical pathways cycling through the two aliphatic radical intermediates (PhCH·CH(2)OPh and PhCH(2)CH·OPh), is shown to be significantly different from that measured in the liquid phase as well as for PPE tethered to the exterior surface of nonporous silica nanoparticles. Tailoring the pore surface with spacer molecules further alters the selectivity such that the PPE reaction channel involving a molecular rearrangement (O-C phenyl shift in PhCH(2)CH·OPh), which accounts for 25% of the products in the liquid phase, can be virtually eliminated under pore confinement conditions. The origin of this change in selectivity is discussed in the context of steric constraints on the rearrangement path inside the pores, surface and pore confinement effects, pore surface curvature, and hydrogen bonding of PPE with residual surface silanols supplemented by nitrogen physisorption data and molecular dynamics simulations.
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Affiliation(s)
- Michelle K Kidder
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6197, USA
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Beste A, Buchanan AC. Kinetic Analysis of the Phenyl-Shift Reaction in β-O-4 Lignin Model Compounds: A Computational Study. J Org Chem 2011; 76:2195-203. [DOI: 10.1021/jo2000385] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ariana Beste
- Joint Institute of Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - A. C. Buchanan
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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24
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Development of Detailed Kinetic Models for the Thermal Conversion of Biomass via First Principle Methods and Rate Estimation Rules. ACTA ACUST UNITED AC 2010. [DOI: 10.1021/bk-2010-1052.ch010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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25
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Beste A. One-dimensional anharmonic oscillator: Quantum versus classical vibrational partition functions. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.05.036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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Beste A, Buchanan AC. Computational Study of Bond Dissociation Enthalpies for Lignin Model Compounds. Substituent Effects in Phenethyl Phenyl Ethers. J Org Chem 2009; 74:2837-41. [DOI: 10.1021/jo9001307] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ariana Beste
- Joint Institute for Computational Sciences, University of Tennessee, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, and Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6197
| | - A. C. Buchanan
- Joint Institute for Computational Sciences, University of Tennessee, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6367, and Chemical Sciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6197
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