Pyrolysis-mass spectrometry analysis of dehydrogenation lignin polymers with various syringyl/guaiacyl ratios

Abstract

The present paper describes the application of pyrolysis-mass spectrometry (PYMS) to the analyses of lignocellulosic materials. Dehydrogenation lignin polymers (DHPs) with various syringyl/guaiacyl (S/G) ratios, and a standard, milled wood lignin from Aesculus turbinata Blume, were pyrolyzed at 500°C for 4 s and the volatile products were ionized by low-voltage (20 eV) electron impact. The PYMS spectra of the lignins are shown with identification of most mass peaks. Of the observed mass peaks, the intensities of the monomeric peaks corresponding to monomethoxyphenols (m/z 124, 137, 138 and 180) and dimethoxyphenols (m/z 154, 167, 182 and 210) were sensitive to the S/G ratio shifts of the DHPs. Changes in the monomeric mass peak intensities reflected those in the yields of the corresponding products determined by pyrolysis-gas chromatography (PYGC). The S/G pyrolytic ratios, calculated from the summed mass peak intensities of syringyl and guaiacyl monomeric products, showed a linear correlation with syringaldehyde/vanillin (S/V) ratios determined by nitrobenzene oxidation. This finding suggested that the S/V ratios of lignocellulosic materials are predicted from the S/G pyrolytic ratios obtained by PYMS. Similar linear correlations were observed also between the S/G pyrolytic ratios determined by PYGC and the S/V ratios, for the DHPs and for Japanese hardwoods. Unlike the PYGC method, however, the PYMS method does not need time-consuming determinations of the response factor of each product to a flame ionization detector. This advantage may outweigh the inherent problems of PYMS, such as the ambiguous structural assignment of the mass peaks in the quantitative PYMS analyses of lignocellulosic materials. The dimeric mass peaks, which were hardly detected in an analytical system with a gas chromatograph, also contributed to the mass spectra.

Pyrolysis properties and kinetics of mandarin peel

“…It was presumed that as the decomposition of pectin was complete at a low temperature, the generation of other products at higher temperatures hindered the formation of alcohols. The fraction of acids, composed mainly of acetic acid, was highest at 500 o C. In contrast, the yield of phenols, the main products of decomposition of lignin [27], increased with increasing temperature. The yields of ketones and furan derivatives also increased with increasing pyrolysis temperature.…”

“…From our results, the pyrolysis products were in good accordance with the main composition of mandarin peel, i.e., pectin, hemi-cellulose, lignin and cellulose. It was recently reported that acetic acid was mainly formed from hemicellulose [25]; whereas, levoglucosan was from cellulose [26], phenols from lignin [27], and furfural and 1-hydroxy-propanone from holocellulose [28]. Zhou et al [24] studied the formation mechanism of the pyrolysis gases released during the pyrolysis of pectin under conditions that simulated a cigarette smoldering.…”

Analysis of printing and writing papers by using direct analysis in real time mass spectrometry

“…3a; column five of Table 4). The spectra are somewhat visually similar to spectra of aspen wood and lignin obtained by using Py-molecular-beam sampling MS [48]; spectra of beech wood obtained by using temperature-programmed Py-field ionization MS [49]; spectra of cottonwood lignin obtained by using temperature-programmed in-source Py-MS [50]; and spectra of Aesculus turbinata lignin obtained by using in-source Py-MS [51]. However, upon close inspection, there are more differences than similarities between the DART-MS spectra and those obtained by using Py-MS.…”

“…Its molecular ion counterpart with m/z 400 may be seen clearly in in-source Py-MS spectra obtained from wood of Calluna vulgaris and Aesculus turbinata [51,53] and from an organosolv lignin [54]. The structure suggested in Table 4 for this ion is that of an oxidized dimethoxy analog of 3,4-divanillyltetrahydrofuran (shonanin), which is a natural lignan whose syringyl analogs have been found in emissions from the combustion of both hardwoods and softwoods [55].…”

Pyrolysis–GC/MS of sinapyl and coniferyl alcohol

“…Mann et al studied the variation in the S:G ratio of lignin in switchgrass grown in different conditions by comparing pyrolysis product mass intensities of certain sinapyl marker compounds to coniferyl markers [4]. Izumi and Kuroda used Py-MS spectra of lignin model polymers to correlate marker ion mass intensity S:G ratios to the molar S:G ratios in the synthesized polymers [30]. Recently, Asmadi et al [31] pyrolyzed mixtures of syringol and guaiacol in order to understand the reactivities of the aromatic nuclei in hardwood lignins.…”