Hot-water and dilute sulfuric acid pretreatments were performed prior to chemical pulping for silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips to determine if varying pretreatment conditions on the original wood material were detectable via attenuated total reflectance (ATR) infrared spectroscopy. Pretreatment conditions varied with respect to temperature (130°C and 150°C) and treatment time (from 30min to 120min). The effects of the pretreatments on the composition of wood chips were determined by ATR infrared spectroscopy. The spectral data were compared to those determined by common wood chemistry analyses to evaluate the suitability of ATR spectroscopy method for rapid detection of changes in the wood chemical composition caused by different pretreatment conditions. In addition to determining wood species-dependent differences in the wood chemical composition, analytical results indicated that most essential lignin- and carbohydrates-related phenomena taking place during hot-water and acidic pretreatments could be described by applying this simple spectral method requiring only a small sample amount and sample preparation. Such information included, for example, the cleavage of essential lignin bonds (i.e., mainly β-O-4 linkages in guaiacyl and syringyl lignin) and formation of newly condensed lignin structures under different pretreatment conditions. Carbohydrate analyses indicated significant removal of hemicelluloses (especially hardwood xylan) and hemicelluloses-derived acetyl groups during the pretreatments, but they also confirmed the highly resistant nature of cellulose towards mild pretreatments.

"The pyrolytical conversion of birch (Betula pendula/pubescens) lignin fractions separated from hot-water pretreatment/sulfur-free delignification black liquors was investigated by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Based on pyrolytical data, the main condensable compounds were organized into respective component groups, and the relative mass portions of the pyrolysis products (mainly monomer-related fragmented products) formed during pyrolysis of various feedstocks were determined. It could be concluded that relatively pure aromatic fractions, mainly of guaiacol and syringol origin, without carbohydrate impurities, could be produced by this integrated biorefinery approach, in which all biomass fractions can be utilized for manufacturing biobased chemicals and chemical precursors. It could be determined that the formation of the individual pyrolytical components was characteristically dependent on the utilized production conditions (i.e., alkali charge, temperature, pretreatment), creating the possibility for adjustment of the process parameters for pronounced production of desired product fractions. Hence, it could be concluded that this sulfur-free concept facilitated the environmentally friendly production of aromatics, without the need for removing sulfur or carbohydrates-derived impurities from the liquid feedstocks. The practical importance of the approach presented in this manuscript lies in the development of rapid and reliable characterization tools for various lignocellulosics-originated feedstocks possessing potential for thermochemical conversion and for creating novel biorefinery concept alternatives for producing aromatics and chemical precursors from currently underutilized feedstock, lignin."