Fast pyrolysis of hot-water-extracted and delignified silver birch (Betula pendula) sawdust by Py-GC/MS

Abstract

The thermochemical behavior of birch (Betula pendula) sawdust both untreated and after various chemical treatments (hot-water extraction, delignification, and hot-water extraction followed by delignification) was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). In each case, major GC-amenable condensable products were classified into several compound groups, and the formation of these monomer-related fragments from feedstock samples with varying mass portions of the structural constituents (cellulose, hemicelluloses, and lignin) were determined at 500 o C and 700 o C at hold times 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 new biorefinery possibilities to produce bio-oils, for example, enriched either with aliphatic or aromatic constituents.

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

“…About 0.5 mg of samples was pyrolyzed in a quartz tube (3.0 cm × 1.0 mm inner diameter, between quartz wool) under an inert atmosphere in the heated interface at a heating rate of 20 °C/ms using a CDS Pyroprobe 1000 resistively heated coil filament pyrolyzer coupled to an HP 5890 II gas chromatograph (Py-GC, Hewlett Packard Company, Wilmington, NC, USA). The pyrolysis temperatures were 500 °C and 700 °C and in each case, the temperature was kept constant for both 5 s and 20 s. The GC conditions were the same as those applied earlier to a similar purpose (Ghalibaf et al 2017). Detection was carried out with an HP 5970 mass spectrometric detector under electron ionization (70 eV) with 2.92 scan/s in the 30-550 m/z interval.…”

“…For the identification of chromatogram peaks, the proper interpretation of the mass spectra (based on the National Institute of Standards and Technology (NIST) mass spectral library) was used. Quantitative analysis was conducted according to an earlier study (Ghalibaf et al 2017), so that pure compounds (the total number was 37) were used as external standards to relatively quantify all the 75 identified peaks from pyrolysis products (Py-GC/MS) by comparing the products to a set of standard samples of known concentration (Table S1 in Supplementary Material). Table 1.…”

“…4 Effects of temperature and residue time on yields of prominent pyrolysis products 2017), these chemical compositions also have some influence on the distribution of pyrolysis products. For example, typically, three times higher amounts of the xylan-derived 3-hydroxy-2-penteno-1,5-lactone are formed from hardwood than softwood; the percentage amount of xylose in birch sawdust (i.e., in B ref ) is 21.3 (Ghalibaf et al 2017) and 5.9 in S ref (Table 1). Furthermore, anhydrosugars (e.g., levoglucosan) detected only in the pyrolysis of hexoses (i.e., d-glucose, d-mannose, and d-galactose) are formed 1.2 times more from S ref than from B ref at 500 °C for 5 s (the hexose portions are 53.3% and 45.9%, respectively).…”

“…It has been established that during pyrolysis, each constituent shows a unique thermochemical behavior (Alén et al 1996(Alén et al , 2002; Anca-Couce 2016; Bai and Kim 2016;Kan et al 2016;Kawamoto 2017;Lappi 2012;Lédé 2012;Patwardhan 2010;Piskorz et al 1986;de Wild 2015;Yang et al 2007;Zhou et al 2017). In previous experiments, for developing novel biorefinery concepts, the fast pyrolysis of hotwater-extracted and pulped hardwood sawdust was studied (Ghalibaf et al 2017). However, the lignin and hemicelluloses present in softwoods differ chemically from those in hardwoods (Alén 2011a).…”

“…The main idea behind this study was to evaluate the suitability of this rapid analytical method for detecting chemical changes that were taking place in the feedstocks during the different chemical treatments performed (i.e., through their pyrolysis product profile) and, on the other hand, with respect to biorefinery aspects to assess the relative suitability of these alternative feedstocks for pyrolytic valorization. In this phase, as was also the case for the corresponding hardwood samples (Ghalibaf et al 2017), only the straightforward formation of condensable products was investigated.…”