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Various organics with quite different oxygen-containing functional groups mixing together in bio-oil lead to the high instability of bio-oils. A liquid–liquid extraction method was developed to separate the bio-oil into different chemical groups by their polarities to stabilize bio-oils and improve the quality. The separated bio-oil had similar oxygen-containing functional groups in different phases. Biomass pyrolysis using Douglas fir pellet and characterization of the bio-oil chemical compounds were conducted, followed by bio-oil liquid–liquid extractions with several solvents (e.g., hexane, petroleum ether, and chloroform). In comparison to the raw bio-oil, the solvent phase had high concentrations (85%) of phenols and guaiacols, while no sugar and very low acid and alcohol contents were detected, which were left in the water phases.

Microwave torrefaction of Douglas fir pellets was investigated and the effects of process conditions on the yields of products were determined. The reaction temperature and time significantly influenced the yields of torrefied biomass, bio-oil, and noncondensable gases. Three linear models were developed to predict the product yield, as a function of reaction temperature and time. Gas chromatography/mass spectroscopy (GC/MS) analysis for bio-oils showed that the bio-oils were mainly composed of furans, phenolics, sugars, ketones/aldehydes, and organic acids. The amounts of each compound varied with the reaction conditions. Over the reaction temperature of 275 °C, noncondensable gases were mainly composed of CO2 and CO and its yields and compositions were significantly influenced by the temperature. Higher heating values (HHVs) of torrefied biomass were 20.90–25.07 MJ/kg, which is an ∼6%–31% increase, compared to the HHV of raw biomass. The energy yields of torrefied biomass, 67.03%–90.06%, implied that mo...

The focus of this study was examination of the hydrothermal pretreatment method applied to the lignocellulosic substrate for bioethanol production, represented by prairie cord grass, and comparison between different conditions, based on the yield of glucose after enzymatic hydrolysis. The treatment did not involve any chemicals usage. Hydrothermal pretreatment was conducted in the Parr high-pressure reactor, in the presence of water. After the pretreatment, material was analyzed via high-performance liquid chromatography (HPLC) for products and scanning electron microscopy (SEM) for biomass structure changes. Enzymatic hydrolysis was performed to examine the amount of glucose that was released from pretreated materials. Results were compared based on the conversion rates of glucose and other sugars, as well as the generation of byproducts. Final results suggested that the most efficient pretreatment conditions involved high temperatures (210 °C) and relatively short reaction times (10 min), after which the lignocellulose structure seems to be the most available for enzymes actions. The pretreatment conversion rate in this case reached a level of 97%.

This study investigated microwave pyrolysis of corn stover with particle sizes from 0.5 to 4 mm and determined the effects of reaction temperature and time of pyrolytic conditions on the yields of bio-oil, syngas, and biochar. Mineral and GC/MS analysis were used to study the pyrolysis of corn stover. A prediction model was satisfactorily developed to describe the biofuel conversion yield as a function of reaction temperature and time. Corn stover with different particle sizes was found to be similarly pyrolyzed by microwave heating. The research results indicate that thermochemical conversion reactions can take place rapidly in large-sized corn stover by using microwave pyrolysis. Mineral analysis indicates that most minerals stayed with the biochar. GC/MS analysis indicates that the bio-oil contained a series of important and useful chemical compounds: phenols, aliphatic hydrocarbons, aromatic hydrocarbons, and furan derivatives. These chemical compounds evolved were related to the pyrolysis conditions.