Characterization of the Water-Soluble Fraction of Woody Biomass Pyrolysis Oils

Abstract

This paper reports a study of the chemical composition of the water-soluble (WS) fraction obtained by cold water precipitation of two commercial wood pyrolysis oils (BTG and Amaron). The fraction studied accounts for between 50.3 and 51.3 wt % of the oils. With the most common analytical techniques used today for the characterization of this fraction (KF titration, GC−MS, hydrolyzable sugars, and total carbohydrates), it is possible to quantify only between 45 and 50 wt % of the fraction. Our results confirm that most of the total carbohydrates (hydrolyzable sugars and nonhydrolyzable) are soluble in water. The ion chromatography hydrolysis method showed that between 11.6 and 17.3 wt % of these oils were hydrolyzable sugars. A small quantity of phenols detectable by GC−MS (between 2.5 and 3.9 wt %) were identified. It is postulated that the unknown high molecular weight fraction (30−55 wt %) is formed by highly dehydrated sugars rich in carbonyl groups and WS phenols. The overall content of carbonyl, carboxyl, hydroxyl, and phenolic compounds in the WS fraction was quantified by titration, the Folin−Ciocalteu method, 31 P NMR, and 1 H NMR. The WS fraction contains between 5.5 and 6.2 mmol/g carbonyl groups, between 0.4 and 1.0 mmol/g carboxylic acid groups, between 1.2 and 1.8 mmol/g phenolic −OH, and between 6.0 and 7.9 mmol/g of aliphatic alcohol groups. Translation into weight fractions of the WS was done by supposing surrogate structures for the water-soluble phenols, carbonyl groups, and carboxyl groups, and we estimated the content of WS phenols (21−27 wt %), carbonyls (5−14 wt %), and carboxyls (0−4 wt %). Together with the total carbohydrates (23−27 wt %), this approach leads to >90 wt % of the WS material in the bio-oils being quantified. We speculate the larger portion of the difference between the total carbohydrates and hydrolyzable sugars is the missing furanic fraction. Further refinement of the suggested methods and development of separation schemes to obtain and quantify subfractions with homogeneous composition (e.g., carbohydrates, high molecular weight WS phenols, furans, and dehydrated sugars) warrant further investigation.

Catalytic hydroconversion of pyrolytic bio-oil: Understanding and limiting macromolecules formation

“…During the hydroconversion involving D-glucose, furfural and guaiacol, we observed reactions between guaiacol and macromolecules precursors which effectively avoid the macromolecules formation [32]. This study confirms the role of guaiacol reactivity while converted with BO macromolecules precursors including carbohydrates type components [18,38]. This phenomena was mainly observed before 1 h and below 250°C as regard to the fast reaction kinetics involved on the macromolecules production ( Fig.…”

Pyrolysis of cashew nutshells: Characterization of products and energy balance

“…Since no ultimate analysis was performed for the AP fraction, the amount of each element in this phase was estimated considering its water content (86.0 %) and assuming that acetic acid is the only organic compound it contains. Acetic acid has been extensively mentioned in the literature as a major component of the aqueous fraction of pyrolysis liquids [39,40]. Using this approach, reasonable balance closures were found for the three elements (ranging between 89.8 and 109.0%).…”

Investigation of the Antibacterial Activity and Subacute Toxicity of a Quercus crassifolia Polyphenolic Bark Extract for its Potential Use in Functional Foods

“…QCBe was analyzed by GC‐MS using an Agilent Technologies 7890A set up (Agilent 19091S‐433 HP‐5MS column: 325 °C: 30 m × 250 µm × 0.25 µm, Mass Selective Detector MSD or MS) with electron ionization source and linear quadrupole mass analyzer (Agilent 5975C) NIST 2.0 f Mass Spectral Search Program) as previously described (García‐Pérez et al., ; Stankovikj, McDonald, Helms, Olarte, & Garcia‐Perez, ). Briefly, the purified extract was first filtered (Miller® GP Filter Unit 0.45 µm) and then injected in the inlet (250 °C, total flow He 24 mL/min, septum purge flow 3 mL/min; Split ratio 30:1, 30 mL/min).…”