Isomer-dependent catalytic pyrolysis mechanism of the lignin model compounds catechol, resorcinol and hydroquinone

Abstract

Detection of reactive intermediates with synchrotron radiation and photoelectron photoion coincidence methods reveals new mechanistic insights into lignin catalytic pyrolysis. Here we focus on how the isomerism changes the conversion and product formation.

The gas-phase infrared spectra of the 2-methylallyl radical and its high-temperature reaction products

“…52 Further, the CH 2 out-of-plane bending vibration at 910 cm −1 and the ring CC symmetric stretching mode at 1496 cm −1 match the reported wavenumbers well. 52 Note that fulvene has been identified during the pyrolysis of 1 by TPES, 40,53 see Fig. S8 in the ESI †…”

Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion

“…Catalytic pyrolysis of freshly distilled cyclopentadiene is in part initiated by methylation and yields fulvene, benzene, toluene, and indene (Figure 6(b)). 24 revealed contributions of dicyclopentadiene formed in a Diels−Alder dimerization reaction as well as tetrahydronaphthalenes, similar to the product distribution of direct dicyclopentadiene pyrolysis. Besides naphthalene, the m/z 128 ms-TPES also showed contributions of butenylbenzenes pointing toward ring opening in the m/z 132 isomers.…”

On the absolute photoionization cross section and threshold photoelectron spectrum of two reactive ketenes in lignin valorization: fulvenone and 2-carbonyl cyclohexadienone

“…5 We observed fulvenone as the central intermediate in guaiacol and catechol catalytic pyrolysis by imaging photoelectron photoion coincidence (iPEPICO) detection, which combines photoionization mass spectrometry (PIMS) and photoion mass-selected threshold photoelectron spectroscopy (ms-TPES). 7,10 Due to its high reactivity, fulvenone evades detection using standard chemical analysis tools, such as GC/MS and NMR, which is the reason why fulvenone was only observed using photoionization mass spectrometry (PIMS), photoelectron spectroscopy (PES), matrix infrared spectroscopy (IR) and PEPICO detection. 7,[11][12][13] Most recently, Genossar et al recorded the IR spectrum of fulvenone produced by salicylaldehyde pyrolysis.…”

“…7,10 Due to its high reactivity, fulvenone evades detection using standard chemical analysis tools, such as GC/MS and NMR, which is the reason why fulvenone was only observed using photoionization mass spectrometry (PIMS), photoelectron spectroscopy (PES), matrix infrared spectroscopy (IR) and PEPICO detection. 7,[11][12][13] Most recently, Genossar et al recorded the IR spectrum of fulvenone produced by salicylaldehyde pyrolysis. 13 This ketene was also synthesized in situ via pyrolysis of lignin model compounds and characterized by photoelectron spectroscopy.…”