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Pan Z, Bodi A, van Bokhoven JA, Hemberger P. Operando PEPICO unveils the catalytic fast pyrolysis mechanism of the three methoxyphenol isomers. Phys Chem Chem Phys 2022; 24:21786-21793. [PMID: 36082786 PMCID: PMC9491049 DOI: 10.1039/d2cp02741k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The development of lignin valorization processes such as catalytic fast pyrolysis (CFP) to produce fine chemicals and fuels leads to a more sustainable future. The implementation of CFP is enabled by understanding the chemistry of lignin constituents, which, however, requires thorough mechanistic investigations by detecting reactive species. In this contribution, we investigate the CFP of the three methoxyphenol (MP) isomers over H-ZSM-5 utilizing vacuum ultraviolet synchrotron radiation and operando photoelectron photoion coincidence (PEPICO) spectroscopy. All isomers demethylate at first to yield benzenediols, from which dehydroxylation reactions proceed to produce phenol and benzene. Additional pathways to form benzene proceed over cyclopentadiene, methylcyclopentadiene, and fulvene intermediates. The detection of trace amounts of methanol in the product stream suggests a demethoxylation reaction to yield phenol. Guaiacol (2- or ortho-MP) exhibits slightly higher reactivity compared to 3-MP and 4-MP, due to the formation of the fulvenone ketene, which opens additional routes to benzene and phenol. When compared to benzenediol catalytic pyrolysis, the additional methyl group in MP leads to high conversion at lower reactor temperatures, which is mostly owed to the lower H3C–O vs. H–O bond energy and the possibility to demethoxylate to produce phenol. Demethylation, demethoxylation and fulvenone ketene formation determine the reactivity of methoxyphenols over H-ZSM-5 to yield phenols, benzene and toluene. Intermediates are isomer-selectively detected utilizing threshold photoelectron spectroscopy.![]()
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Affiliation(s)
- Zeyou Pan
- Paul Scherrer Institute, 5232 Villigen, Switzerland. .,Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
| | - Andras Bodi
- Paul Scherrer Institute, 5232 Villigen, Switzerland.
| | - Jeroen A van Bokhoven
- Paul Scherrer Institute, 5232 Villigen, Switzerland. .,Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland
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2
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Wu X, Zhou X, Bjelić S, Hemberger P, Bodi A. Valence Photoionization and Energetics of Vanillin, a Sustainable Feedstock Candidate. J Phys Chem A 2021; 125:3327-3340. [PMID: 33872037 DOI: 10.1021/acs.jpca.1c00876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We studied the valence photoionization of vanillin by photoelectron photoion coincidence spectroscopy in the 8.20-19.80 eV photon energy range. Vertical ionization energies by EOM-IP-CCSD calculations reproduce the photoelectron spectral features. Composite method calculations and Franck-Condon simulation of the weak, ground-state band yield the adiabatic ionization energy of the most stable vanillin conformer as 8.306(20) eV. The lowest energy dissociative photoionization channels correspond to hydrogen atom, carbon monoxide, and methyl losses, which form the dominant C8H7O3+ (m/z 151) and the less intense C7H8O2+ (m/z 124) and C7H5O3+ (m/z 137) fragment ions in parallel dissociation channels at modeled 0 K appearance energies of 10.13(1), 10.40(3), and 10.58(10) eV, respectively. On the basis of the breakdown diagram, we explore the energetics of sequential methyl and carbon monoxide loss channels, which dominate the fragmentation mechanism at higher photon energies. The 0 K appearance energy for sequential CO loss from the m/z 151 fragment to C7H7O2+ (m/z 123) is 12.99(10) eV, and for sequential CH3 loss from the m/z 123 fragment to C6H4O2+ (m/z 108), it is 15.40(20) eV based on the model. Finally, we review the thermochemistry of the bi- and trifunctionalized benzene derivatives guaiacol, hydroxybenzaldehyde, anisaldehyde, and vanillin. On the basis of isodesmic functional group exchange reactions, we propose new enthalpies of formations, among them ΔfH°298K(vanillin, g) = -383.5 ± 2.9 kJ mol-1. These mechanistic insights and ab initio thermochemistry results will support analytical works to study lignin conversion involving vanillin.
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Affiliation(s)
- Xiangkun Wu
- Paul Scherrer Institute, 5232 Villigen, Switzerland.,Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Xiaoguo Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China
| | - Saša Bjelić
- Paul Scherrer Institute, 5232 Villigen, Switzerland
| | | | - Andras Bodi
- Paul Scherrer Institute, 5232 Villigen, Switzerland
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Steglich M, Wu X, Bodi A, Hemberger P. Double-Imaging Photoelectron Photoion Coincidence Spectroscopy Reveals the Unimolecular Thermal Decomposition Mechanism of Dimethyl Carbonate. J Phys Chem A 2021; 125:2895-2904. [PMID: 33797917 DOI: 10.1021/acs.jpca.1c00724] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We studied the thermal decomposition of dimethyl carbonate (DMC, C3H6O3) in a flash vacuum pyrolysis reactor in the 1100-1700 K range. The reaction products and intermediates were probed by vacuum ultraviolet synchrotron radiation in a photoelectron photoion coincidence (PEPICO) spectrometer to record isomer-specific photoion mass-selected threshold photoelectron (ms-TPE) spectra. Reaction pathways were explored using quantum chemical calculations, which confirmed the experimental observation that the intramolecular migration of a methyl group, yielding dimethyl ether (DME, C2H6O) and carbon dioxide, dominates the initial unimolecular decomposition chemistry. The role of a second potentially important channel, namely, C-O bond fission to yield methyl radicals, could not be determined experimentally due to the short lifetime of the ·C2H3O3 radical and overlapping sequential decomposition products. However, potential energy surface and microcanonical rate constant calculations predict 2 to 3 orders of magnitude lower rates for this channel than for decarboxylation to yield DME. Consequently, DMC pyrolysis shows bewilderingly similar products and product abundances as DME pyrolysis. This coincides with DMC combustion modeling studies, which found that DME is a key intermediate in the mechanism. Furthermore, we have detected traces of methyl formate and formaldehyde, produced after the hydrogen shift to the central carbon atom in DMC. Ethylene and acetylene could be established as bimolecular reaction products because their abundance depended strongly on the DMC concentration. It is intriguing to compare the decomposition of DMC with that of the structurally similar methylal (dimethoxymethane, DMM). While methanol and formaldehyde are produced in similar quantities in DMM, thanks to low-energy hydrogen-transfer reactions, the methanol channel is almost fully suppressed in DMC due to the absence of hydrogens at the central carbon atom and the thermodynamically favored decarboxylation. These new mechanistic insights may help the development of predictive combustion models for fuel additives and biofuels.
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Affiliation(s)
| | - Xiangkun Wu
- Paul Scherrer Institute, Villigen 5232, Switzerland
| | - Andras Bodi
- Paul Scherrer Institute, Villigen 5232, Switzerland
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Pan Z, Puente-Urbina A, Bodi A, van Bokhoven JA, Hemberger P. Isomer-dependent catalytic pyrolysis mechanism of the lignin model compounds catechol, resorcinol and hydroquinone. Chem Sci 2021; 12:3161-3169. [PMID: 34164083 PMCID: PMC8179379 DOI: 10.1039/d1sc00654a] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 02/05/2021] [Indexed: 12/26/2022] Open
Abstract
The catalytic pyrolysis mechanism of the initial lignin depolymerization products will help us develop biomass valorization strategies. How does isomerism influence reactivity, product formation, selectivities, and side reactions? By using imaging photoelectron photoion coincidence (iPEPICO) spectroscopy with synchrotron radiation, we reveal initial, short-lived reactive intermediates driving benzenediol catalytic pyrolysis over H-ZSM-5 catalyst. The detailed reaction mechanism unveils new pathways leading to the most important products and intermediates. Thanks to the two vicinal hydroxyl groups, catechol (o-benzenediol) is readily dehydrated to form fulvenone, a reactive ketene intermediate, and exhibits the highest reactivity. Fulvenone is hydrogenated on the catalyst surface to phenol or is decarbonylated to produce cyclopentadiene. Hydroquinone (p-benzenediol) mostly dehydrogenates to produce p-benzoquinone. Resorcinol, m-benzenediol, is the most stable isomer, because dehydration and dehydrogenation both involve biradicals owing to the meta position of the hydroxyl groups and are unfavorable. The three isomers may also interconvert in a minor reaction channel, which yields small amounts of cyclopentadiene and phenol via dehydroxylation and decarbonylation. We propose a generalized reaction mechanism for benzenediols in lignin catalytic pyrolysis and provide detailed mechanistic insights on how isomerism influences conversion and product formation. The mechanism accounts for processes ranging from decomposition reactions to molecular growth by initial polycyclic aromatic hydrocarbon (PAH) formation steps to yield, e.g., naphthalene. The latter involves a Diels-Alder dimerization of cyclopentadiene, isomerization, and dehydrogenation.
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Affiliation(s)
- Zeyou Pan
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute 5232 Villigen Switzerland
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich 8093 Zurich Switzerland
| | - Allen Puente-Urbina
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich 8093 Zurich Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute 5232 Villigen Switzerland
| | - Jeroen A van Bokhoven
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich 8093 Zurich Switzerland
- Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute 5232 Villigen Switzerland
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute 5232 Villigen Switzerland
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Grimm S, Baik SJ, Hemberger P, Bodi A, Kempf AM, Kasper T, Atakan B. Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation. Phys Chem Chem Phys 2021; 23:15059-15075. [PMID: 34231583 DOI: 10.1039/d1cp00720c] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Although aluminium acetylacetonate, Al(C5H7O2)3, is a common precursor for chemical vapor deposition (CVD) of aluminium oxide, its gas-phase decomposition is not well-known. Here, we studied its thermal decomposition in a microreactor by double imaging photoelectron photoion coincidence spectroscopy (i2PEPICO) between 325 and 1273 K. The reactor flow field was characterized by CFD. Quantum chemical calculations were used for the assignment of certain species. The dissociative ionization of the room temperature precursor molecule starts at a photon energy of 8.5 eV by the rupture of the bond to an acetylacetonate ligand leading to the formation of the Al(C5H7O2)2+ ion. In pyrolysis experiments, up to 49 species were detected and identified in the gas-phase, including reactive intermediates and isomeric/isobaric hydrocarbons, oxygenated species as well as aluminium containing molecules. We detected aluminium bis(diketo)acetylacetonate-H, Al(C5H7O2)C5H6O2, at m/z 224 together with acetylacetone (C5H8O2) as the major initial products formed at temperatures above 600 K. A second decomposition channel affords Al(OH)2(C5H7O2) along with the formation of a substituted pentalene ring species (C10H12O2) as assigned by Franck-Condon simulations and quantum chemical calculations. Acetylallene (C5H6O), acetone (C3H6O) and ketene (C2H2O) were major secondary decomposition products, formed upon decomposition of the primary products. Three gas-phase aromatic hydrocarbons were also detected and partially assigned for the first time: m/z 210, m/z 186 (C14H18 or C12H10O2) and m/z 146 (C11H14 or C9H6O2) and their formation mechanism is discussed. Finally, Arrhenius parameters are presented on the gas-phase decomposition kinetics of Al(C5H7O2)3, aided by numerical simulation of the flow field.
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Affiliation(s)
- Sebastian Grimm
- University of Duisburg-Essen, Institute of Combustion and Gas Dynamics, Chair of Thermodynamics, Duisburg 47057, Germany. and Center for NanoIntegration Duisburg-Essen (CENIDE), Duisburg 47057, Germany
| | - Seung-Jin Baik
- Center for NanoIntegration Duisburg-Essen (CENIDE), Duisburg 47057, Germany and University of Duisburg-Essen, Institute of Combustion and Gas Dynamics, Chair of Fluid Dynamics, Duisburg 47057, Germany
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland
| | - Andreas M Kempf
- Center for NanoIntegration Duisburg-Essen (CENIDE), Duisburg 47057, Germany and University of Duisburg-Essen, Institute of Combustion and Gas Dynamics, Chair of Fluid Dynamics, Duisburg 47057, Germany
| | - Tina Kasper
- Center for NanoIntegration Duisburg-Essen (CENIDE), Duisburg 47057, Germany and University of Duisburg-Essen, Institute of Combustion and Gas Dynamics, Chair of Mass Spectrometry of Reactive Fluids, Duisburg 47057, Germany
| | - Burak Atakan
- University of Duisburg-Essen, Institute of Combustion and Gas Dynamics, Chair of Thermodynamics, Duisburg 47057, Germany. and Center for NanoIntegration Duisburg-Essen (CENIDE), Duisburg 47057, Germany
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Hemberger P, Pan Z, Bodi A, Bokhoven JA, Ormond TK, Ellison GB, Genossar N, Baraban JH. The Threshold Photoelectron Spectrum of Fulvenone: A Reactive Ketene Derivative in Lignin Valorization. Chemphyschem 2020; 21:2217-2222. [DOI: 10.1002/cphc.202000477] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/29/2020] [Indexed: 11/07/2022]
Affiliation(s)
- Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
| | - Zeyou Pan
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
- Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences ETH Zurich Zurich Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
| | - Jeroen A. Bokhoven
- Institute for Chemical and Bioengineering Department of Chemistry and Applied Biosciences ETH Zurich Zurich Switzerland
- Laboratory for Catalysis and Sustainable Chemistry Paul Scherrer Institute CH-5232 Villigen PSI Switzerland
| | - Thomas K. Ormond
- Department of Chemistry and Biochemistry University of Colorado Boulder Colorado 80309-0215 United States
| | - G. Barney Ellison
- Department of Chemistry and Biochemistry University of Colorado Boulder Colorado 80309-0215 United States
| | - Nadav Genossar
- Department of Chemistry Ben Gurion University of the Negev Beer Sheva 84105 Israel
- Israel Atomic Energy Commission Tel Aviv 61070 Israel
| | - Joshua H. Baraban
- Department of Chemistry Ben Gurion University of the Negev Beer Sheva 84105 Israel
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Chen X, Zhu L, Cui C, Zhu Y, Zhou Z, Qi F. In Situ Atmospheric Pressure Photoionization Mass Spectrometric Monitoring of Initial Pyrolysis Products of Biomass in Real Time. Anal Chem 2020; 92:603-606. [PMID: 31846300 DOI: 10.1021/acs.analchem.9b05200] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Knowledge on the initial and intermediate pyrolysis products of biomass is essential for the mechanistic investigation of biomass pyrolysis and further optimization of upgrading processes. The conventional method can only detect the final products, which do not resemble the initial or intermediate pyrolysis products. Here, we introduce a direct orifice sampling combined with atmospheric pressure photoionization mass spectrometry (APPI-MS) for in situ online analysis of the evolved volatile initial products from the pyrolysis of biomass. Pyrolysis experiments of both dimeric model compound (guaiacylglycerol-β-guaiacyl ether, GGGE) and poplar wood were carried out to validate the generality of the method. Generally, secondary reactions can be reduced by shortening the distance between the sample and sampling orifice. Large molecular-weight initial products up to trimers were detected during the pyrolysis of poplar wood, and no initial products larger than trimers were detected. It is inferred that in situ APPI immediately after sample extraction ensures efficient and effective product detection. Furthermore, the present work offers a promising feasible method for online tracing of reaction intermediates not only in pyrolysis but also in various reactive processes (e.g., catalytic reaction, oxidation) under operando conditions.
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Affiliation(s)
- Xiamin Chen
- Key Laboratory for Power Machinery and Engineering of Ministry of Education (MOE), School of Mechanical Engineering , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , P.R. China
| | - Linyu Zhu
- Key Laboratory for Power Machinery and Engineering of Ministry of Education (MOE), School of Mechanical Engineering , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , P.R. China
| | - Cunhao Cui
- Key Laboratory for Power Machinery and Engineering of Ministry of Education (MOE), School of Mechanical Engineering , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , P.R. China
| | - Yanan Zhu
- Key Laboratory for Power Machinery and Engineering of Ministry of Education (MOE), School of Mechanical Engineering , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , P.R. China
| | - Zhongyue Zhou
- Key Laboratory for Power Machinery and Engineering of Ministry of Education (MOE), School of Mechanical Engineering , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , P.R. China
| | - Fei Qi
- Key Laboratory for Power Machinery and Engineering of Ministry of Education (MOE), School of Mechanical Engineering , Shanghai Jiao Tong University , 800 Dongchuan Road , Shanghai 200240 , P.R. China
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Hemberger P, van Bokhoven JA, Pérez-Ramírez J, Bodi A. New analytical tools for advanced mechanistic studies in catalysis: photoionization and photoelectron photoion coincidence spectroscopy. Catal Sci Technol 2020. [DOI: 10.1039/c9cy02587a] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
How can we detect reactive and elusive intermediates in catalysis to unveil reaction mechanisms? In this mini review, we discuss novel photoionization tools to support this quest.
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Affiliation(s)
- Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry
- Paul Scherrer Institute
- CH-5232 Villigen PSI
- Switzerland
| | - Jeroen A. van Bokhoven
- Laboratory for Catalysis and Sustainable Chemistry
- Paul Scherrer Institute
- CH-5232 Villigen PSI
- Switzerland
- Institute for Chemical and Bioengineering
| | - Javier Pérez-Ramírez
- Institute for Chemical and Bioengineering
- Department of Chemistry and Applied Biosciences
- ETH Zurich
- Zurich
- Switzerland
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry
- Paul Scherrer Institute
- CH-5232 Villigen PSI
- Switzerland
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