Analytical pyrolysis of wood and non-wood materials from integrated biorefinery concepts

Abstract

Wood and non-wood differ with respect to their anatomical, physical, and chemical properties, even among their species, resulting in different behaviors during thermal conversion. Hence, understanding the degradation of these feedstocks by pyrolysis is attractive to establish biorefinery possibilities for renewable resources. Additionally, biomass pretreatment technology plays an important role in many biorefinery processes. Therefore, an approach that integrates such pretreatment with pyrolysis offers an attractive, novel method for improving the end-product spectrum (e.g., enriched either with aliphatic or aromatic constituents). Furthermore, a rapid analytical method for biomass feedstocks characterization was preliminarily developed through their pyrolysis product profiles for detecting chemical changes that were taking place in these feedstocks during different chemical treatments.

In the primary stage of this research, the effect of pyrolysis conditions on the pyrolysis products of differently-treated feedstocks, from hot-water extraction (“autohydrolysis”) and soda-anthraquinone (AQ) delignification was investigated. The further aim was to clarify the difference in the pyrolysis products of wood materials, including hardwood and softwood, with non-wood materials as well as the pretreatment impact on these feedstocks. Hence, the thermochemical behavior of woody silver birch (Betula pendula) and Norway spruce (Picea abies) sawdust, and non-woody okra (Abelmoschus esculentus) and miscanthus (Miscanthus x giganteus) stalks, 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). The formation of the pyrolysis products from feedstock samples with varying mass portions of the structural constituents (cellulose, hemicelluloses, and lignin) were determined at 500 oC and 700 oC at hold times of 5 s and 20 s. In all cases, major GC-amenable condensable products were measured semi-quantitatively and classified into several product groups. Additionally, the formation of pyrolysis products was found to be characteristically dependent on feedstock composition and pyrolysis conditions. In the final stage of research, the main aim was to achieve a better understanding of the studies on lignocellulosic with respect to their main carbohydrate constituents (cellulose and hemicelluloses, including glucomannan and xylan) by the same instrument under the same pyrolysis conditions. Among the product groups, the primary ones, including lactone, furan, and cyclopentenone derivatives, accounted for 72-85 % (from cellulose), 86-90 % (from glucomannan), and 76-81 % (from xylan) of the total amount of pyrolysis products determined.