Issue 36, 2022

Operando PEPICO unveils the catalytic fast pyrolysis mechanism of the three methoxyphenol isomers

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.

Graphical abstract: Operando PEPICO unveils the catalytic fast pyrolysis mechanism of the three methoxyphenol isomers

Supplementary files

Article information

Article type
Paper
Submitted
16 jun. 2022
Accepted
15 ago. 2022
First published
09 sep. 2022
This article is Open Access
Creative Commons BY-NC license

Phys. Chem. Chem. Phys., 2022,24, 21786-21793

Operando PEPICO unveils the catalytic fast pyrolysis mechanism of the three methoxyphenol isomers

Z. Pan, A. Bodi, J. A. van Bokhoven and P. Hemberger, Phys. Chem. Chem. Phys., 2022, 24, 21786 DOI: 10.1039/D2CP02741K

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