Fast pyrolysis of hot-water-extracted and delignified Norway spruce (Picea abies) sawdust by Py–GC/MS

Abstract

The thermochemical behavior of Norway spruce (Picea abies) sawdust as such and after various chemical treatments (hot-water extraction, delignification, and hotwater extraction followed by delignification) was investigated by analytical pyrolysis-gas chromatography-mass spectrometry. In each case, the yields of major GC-amenable condensable products were semi-quantitatively measured, and the individual compounds were classified into several compound groups. The formation of these groups from feedstock samples with varying mass portions of their structural constituents (carbohydrates and lignin) was determined at 500 °C and 700 °C with a residence time of 5 s and 20 s. The formation of pyrolysis products was shown to be characteristically dependent on feedstock composition as well as on pyrolysis conditions. This kind of approach was of practical importance with respect to efforts not only to develop rapid characterization tools for lignocellulosics, but also to uncover new biorefinery possibilities to produce bio-oils, for example, enriched either with aliphatic or aromatic constituents.

Pyrolytic behavior of lignocellulosic-based polysaccharides

“…Most of these pyrolysis products have been detected earlier in related studies after pyrolysis of polysaccharidescontaining samples or polysaccharides, although in different proportions [4-6, 14-17, 23, 29, 51, 56-60]. In our previous pyrolysis studies with birch wood [4] and spruce wood [5] as well as okra and miscanthus [6], there were several pyrolysis products, such as guaiacol, syringyl, naphthalene, and fatty acid derivatives, that originated from lignin and extractives. However, in this back up study, guaiacol and syringyl derivatives were detected only for xylan, indicating that the xylan preparation used contained some minor guaiacyl-syringyl-type lignin impurities.…”

“…It could be noted that, for example, 3-hydroxy-2-penteno-1,5-lactone (lactone) was primarily formed from xylan (also partly from cellulose), 5H-furan-2-one (lactone) from glucomannan (also partly from cellulose), 3-methylcyclopentane-1,2dione (cyclopentenone) from glucomannan, furfural (furan) from cellulose and xylan, and 5-HMF (furan) from cellulose. Based on the our previous studies [4][5][6], of these major pyrolysis products, especially 3-hydroxy-2-penteno-1,5-lactone was produced by a factor of three from hardwood [4] than from softwood [5] indicating the presence of a higher portion of xylan in hardwood. However, its yield from hardwood was still less than that from xylan, probably due to an effect of its integration with cellulose and lignin.…”

“…The integrated chromatographic system GC/MS applied resolved most of the low-molar-mass compounds released from the model substances during pyrolysis; altogether, 42 from cellulose, 47 from glucomannan, and 41 from xylan were identified in conformity with pure compounds and MS library. For simplicity, the dominant GC-amenable pyrolysis products were classified into illustrative compound groups by the same system as that used earlier for similar purposes [4,5]. It could be roughly concluded that the groups of anhydrosugar (A), cyclopentenone (C), furan (F), indene (I), lactone (L), and pyrone (Y) derivatives originated from carbohydrates, and those of guaiacol (G) and phenol (P) derivatives originated from lignin.…”

“…In our earlier papers, we used pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) for revealing the thermochemical behavior of silver birch [4] and Norway spruce [5] sawdust, as well as non-wood materials, such as okra and miscanthus [6]. In all cases, the effects of pyrolysis conditions on the product distribution were studied.…”

“…In our earlier studies, we investigated the thermochemical behavior of differently treated wood and non-wood materials [4][5][6]. In this comparable study with model substances, firstly, the aim was to further clarify the formation of compound groups under the same pyrolysis conditions as those applied in our previous experiments.…”