In the case of development and utilization of bio-oils, a quantitative chemical characterization is necessary to evaluate its actual desired characteristics for downstream production. This paper describes an analytical approach for the determination of families of lightweight chemicals from bio-oils by using GC-MS techniques. And on this basis, new explorations in the field of influence factors, such as feedstocks, pyrolysis temperatures, and low-temperature pretreatment, on the composition and products yields of bio-oil were further investigated. Up to 40% (wt.%) of the bio-oil is successfully quantified by the current method. Chemical functionalities in the bio-oil correlate strongly with the original feedstocks because of their different chemical compositions and structure. Pyrolysis temperature plays a vital role in the yields of value-added compounds, both overall and individually. Higher temperature favored the generation of small aldehydes and acids, accompanied by a reduction of phenols. The optimal temperatures for maximum furans and ketones yields were 520 and 550°C, respectively. The low-temperature pretreatment of biomass has a good enrichment for the lightweight components of the bio-oils. In this case, much higher amounts of compounds, such as furans, ketones, and phenols were produced. Such a determination would contribute greatly to a deeper understanding of the chemical efficiency of the pyrolysis reaction and how the bio-oils could be more properly utilized.

Deep eutectic solvents (DESs) are a potentially high-value lignin extraction methodology. DESs prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBD)—lactic acid (Lac), glycerol, and urea—were evaluated for isolation of willow (Salix matsudana cv. Zhuliu) lignin. DESs types, mole ratio of ChCl to HBD, extraction temperature, and time on the fractionated DES-lignin yield demonstrated that the optimal DES-lignin yield (91.8 wt % based on the initial lignin in willow) with high purity of 94.5% can be reached at a ChCl-to-Lac molar ratio of 1:10, extraction temperature of 120 °C, and time of 12 h. Fourier transform infrared spectroscopy (FT-IR) , 13C-NMR, and 31P-NMR showed that willow lignin extracted by ChCl-Lac was mainly composed of syringyl and guaiacyl units. Serendipitously, a majority of the glucan in willow was preserved after ChCl-Lac treatment.

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Purity, morphology, and structural characterization of synthesized deep eutectic solvent (DES)-lignins (D 6h , D 9h , D 12h , D 18h , D 24h ) extracted from willow (Salix matsudana cv. Zhuliu) after treatment with a 1:10 molar ratio of choline chloride and lactic acid at 120 • C for 6, 9, 12, 18, and 24 h were carried out. The purity of DES-lignin was~95.4%. The proportion of hydrogen (H) in DES-lignin samples increased from 4.22% to 6.90% with lignin extraction time. The DES-lignin samples had low number/weight average molecular weights (1348.1/1806.7 to 920.2/1042.5 g/mol, from D 6h to D 24h ) and low particle sizes (702-400 nm). Atomic force microscopy (AFM) analysis demonstrated that DES-lignin nanoparticles had smooth surfaces and diameters of 200-420 nm. Syringyl (S) units were dominant, and total phenolic hydroxyl content and total hydroxyl content reached their highest values of 2.05 and 3.42 mmol·g −1 in D 12h and D 6h , respectively. β-Aryl ether (β-O-4) linkages were eliminated during DES treatment.

The present research relates a universally practical and feasible approach toward chemically deconstructing the macromolecular architecture of lignin, specifically alkali lignin (AL), for the production of a number of valuable side-stream aromatic nuclei byproducts. The hydrothermolysates obtained at different subcritical conditions were tentatively qualitatively identified by gas chromatography mass spectrometry (GC-MS) and subsequently quantified by gas chromatography (GC). The influence of temperature (220−340 °C), residence time (0−60 min), and ethanol volume-% in a water−ethanol cosolvent (0− 100%) on the conversion of AL and the yield of the side-stream (liquid) products were explored. The results show that the yield and identity of the phenolic and methoxy-benzene compounds were strongly correlated to the conversion temperature and the ethanol volume-%, whereas residence time in the autoclave had only a minor influence. The following individual chemicals (mg liquid side-stream/g lignin) and associated yields were determined from the optimal hydrothermal conditions (30 min, 310 °C, 25% ethanol): phenol (4.25 mg/g), 4-methylguaiacol (2.93 mg/g), 3,5-dimethoxyacetophenone (0.78 mg/g), 1,2,4trimethoxybenzene (2.47 mg/g), and 2,6-dihydroxy-4-methoxyacetophenone (2.47 mg/g). The highest yield of guaiacol (11.87 mg/g) and 2,6-dimethoxyphenol (12.17 mg/g) was obtained at a reaction temperature of 310 °C over 60 min in neat water.

Three nanocomposite catalysts such as Ru/graphene, WO3/graphene, and Ru–W18O49/graphene were synthesized by solvothermolysis to increase the ethylene glycol (EG) yield from the hydrothermal conversion of cellulose. The morphology and composition of the nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller, scanning electron microscopy, and transmission electron microscopy. The results showed a new nanocomposite made up of graphene nanosheets that supported in situ growth of Ru nanoparticles with an average size of ∼7 nm and W18O49 nanowires with an average diameter of ∼5 nm. Compared to Ru/graphene and WO3/graphene nanocomposites, Ru–W18O49/graphene showed nearly unit conversion of cellulose at a yield of 62.5% of EG when the reaction was carried out at 245 °C for 60 min. Moreover, it could be used at least three times with the high yield of EG in the range of 48.7–62.5%; however, with the increase of recycled runs, the tungsten species on the surface of graphene would be slowly dissolved in the aqueous solution and then the selectivity of this catalyst would gradually decrease. Besides, the one-pot solvothermal synthesis enabled reduction of Ru ions, graphene oxide, and growth of W18O49 nanowires to thus provide a simple approach for the preparation of the graphene-based nanocomposite catalysts.