A5017144866- Lignin and Wood Chemistry
- Catalysis and Oxidation Reactions
- Zeolite Catalysis and Synthesis
- Catalytic Processes in Materials Science
- Thermochemical Biomass Conversion Processes
- Catalysis for Biomass Conversion
- Catalysis and Hydrodesulfurization Studies
- Advanced Chemical Physics Studies
- Polymer crystallization and properties
- Biochemical and biochemical processes
- Catalysts for Methane Reforming
- Spectroscopy and Laser Applications
- Enzyme-mediated dye degradation
- Industrial Gas Emission Control
- Asymmetric Hydrogenation and Catalysis
- Fermentation and Sensory Analysis
- Microplastics and Plastic Pollution
- Chemical Synthesis and Analysis
- Plant Gene Expression Analysis
- Atmospheric Ozone and Climate
- Subcritical and Supercritical Water Processes
- Photochemistry and Electron Transfer Studies
- Toxic Organic Pollutants Impact
- Petroleum Processing and Analysis
- Biodiesel Production and Applications
Paul Scherrer Institute
2020-2024
ETH Zurich
2020-2024
Bioengineering (Switzerland)
2021
Zhengzhou University
2018-2019
National Institute of Clean and Low-Carbon Energy
2019
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 over H-ZSM-5 catalyst. detailed reaction unveils new pathways leading to most important...
Abstract Understanding hydrocarbon generation in the zeolite-catalysed conversions of methanol and methyl chloride requires advanced spectroscopic approaches to distinguish complex mechanisms governing C–C bond formation, chain growth deposition carbonaceous species. Here operando photoelectron photoion coincidence (PEPICO) spectroscopy enables isomer-selective identification pathways hydrocarbons up C 14 size, providing direct experimental evidence radicals both reactions ketene...
Resistively heated silicon carbide microreactors are widely applied as continuous sources to selectively prepare elusive and reactive intermediates with astrochemical, catalytic, or combustion relevance measure their photoelectron spectrum. These reactors also provide deep mechanistic insights into uni- bimolecular chemistry. However, the sampling conditions effects have not been fully characterized. We use cation velocity map imaging distribution of molecular beam signal quantify scattered,...
Unveiling catalytic mechanisms at a molecular level aids rational catalyst design and selectivity control for process optimization. In this study, we find that the Brønsted acid site density of zeolite efficiently controls guaiacol pyrolysis mechanism. Guaiacol demethylation to catechol initiates reaction, as evidenced by detected methyl radicals. The mechanism branches form either fulvenone (c-C5H4 = C O), reactive ketene intermediate, dehydration, or phenol acid-catalyzed dehydroxylation....
Ketene (CH
Radical-mediated gas-phase reactions play an important role in the conversion of methane under non-oxidative conditions into olefins and aromatics over iron-modified silica catalysts. Herein, we use operando photoelectron photoion coincidence spectroscopy to disentangle elusive C
Abstract Unveiling reaction mechanisms by isomer‐selective detection of reactive intermediates requires advanced spectroscopic knowledge. We study the photoionization fulvenone (c‐C 5 H 4 =C=O), a ketene species relevant in catalytic pyrolysis lignin, which was generated 2‐methoxy acetophenone. The high‐resolution threshold photoelectron spectrum (TPES) with vacuum ultraviolet synchrotron radiation revealed well‐resolved vibrational transitions, assigned to ring deformation modes...
Two reaction paths in the presence of a Sn–Ce catalyst with H<sub>2</sub>O (path 1) and without 2).
Abstract Ketene (CH 2 =C=O) has been postulated as a key intermediate for the first olefin production in zeolite‐catalyzed chemistry of methanol‐to‐olefins (MTO) and syngas‐to‐olefins (STO) processes. The reaction mechanism remains elusive, because short‐lived ethenone ketene its derivatives are difficult to detect, which is further complicated by low expected concentration. We report on experimental detection methylketene 3 −CH=C=O) formed methylation HZSM‐5 via operando synchrotron...
The catalytic pyrolysis of guaiacol-based lignin monomers, vanillin, syringol, and eugenol over commercial HZSM-5 has been investigated using
The absolute photoionization cross section (PICS) of these crucial ketene intermediates supports their quantification in lignin pyrolysis, combustion and organic synthesis.
The development of lignin valorization processes such as catalytic fast pyrolysis (CFP) to produce fine chemicals and fuels leads a more sustainable future. implementation CFP is enabled by understanding the chemistry constituents, which, however, requires thorough mechanistic investigations detecting reactive species. In this contribution, we investigate three methoxyphenol (MP) isomers over H-ZSM-5 utilizing vacuum ultraviolet synchrotron radiation operando photoelectron photoion...
We studied the thermal decomposition of vanillin in a low-pressure pyrolysis microreactor by photoelectron photoion coincidence spectroscopy. The products were identified isomer-selectively mass-selected threshold spectra (ms-TPES) based on Franck–Condon simulations and reference spectra. Methyl loss homolytic C–O bond fission methoxy group is initial unimolecular step. primary intermediate, 2-hydroxy-5-formyl-phenoxy radical (m/z 137), may undergo multiple decarbonylation steps lose...
Abstract Radical‐mediated gas‐phase reactions play an important role in the conversion of methane under non‐oxidative conditions into olefins and aromatics over iron‐modified silica catalysts. Herein, we use operando photoelectron photoion coincidence spectroscopy to disentangle elusive C 2+ radical intermediates participating complex reaction network. Our experiments pinpoint different 2 ‐C 5 species that allow for a stepwise growth hydrocarbon chains. Propargyl radicals (H C−C≡C−H) are...
The thermal decomposition of the three anisaldehyde isomers was studied by photoelectron photoion coincidence spectroscopy. pyrolysis products were identified isomer-selectively their mass-selected threshold spectrum in comparison to reference spectra. C–O bond fission at methoxy group generates methyl and aldehyde phenoxy radicals initial fragmentation step for all isomers. For para meta isomers, these can produce either 1-formyl-2,4-cyclopentadiene-1-yl radical or low-energy removal CO...
Catalytic pyrolysis of pine sawdust with five sodium salts‐supported γ‐Al 2 O 3 was performed in a fixed‐bed reactor at 500°C for liquid products. The products were analyzed its physics and chemical properties, such as product yield, oil phase proportion water content, composition, elemental analysis, calorific value. results indicate that yields decreased the catalysts compared non‐catalytic pyrolysis, whereas separation (oil aqueous phases) observed. content drops sharply to around 10%...
We introduce an effective and flexible high vacuum interface to probe the liquid phase with photoelectron photoion coincidence (liq-PEPICO) spectroscopy at ultraviolet (VUV) beamline of Swiss Light Source. The comprises a high-temperature sheath gas-driven vaporizer, which initially produces aerosols. particles evaporate form molecular beam, is skimmed ionized by VUV radiation. beam characterized using ion velocity map imaging, vaporization parameters liq-PEPICO source have been optimized...
Heterogene Katalyse. In ihrer Zuschrift (e202207777) nutzen Patrick Hemberger et al. PEPICO-Spektroskopie zur Identifizierung von Keten- und Methylketen-Intermediaten in der Methylacetat-Umwandlung über HZSM-5-Zeolith.