Rapid characterization of heteroatomic molecules in a bio-oil from pyrolysis of rice husk using atmospheric solids analysis probe mass spectrometry

• Rapid and accurate characterization of bio-oil was carried out using ASAP-TOF-MS.
• Ambient ionization well analyzed bio-oil with viscosity and heterogeneity.
• Compounds that are not revealed by GC/MS were well characterized.
• Difference of DBE distribution for bio-oil was obtained according to solvent polarity.

Bio-oil from pyrolysis of rice husk (RHBO) was investigated using a time-of-flight mass spectrometer equipped with an atmospheric solids analysis probe ion source to afford rapid and accurate characterization of molecular information. RHBO was sequentially extracted with n-hexane, tetrachloromethane, benzene, dichloromethane, trichloromethane and ethyl acetate in order of increasing solvent polarity to acquire extracts E1 to E6. Heteroatomic species, especially oxygen-containing compounds, in the extracts were well characterized and statistically compared. Solvents with low polarity inclined to extract species with relative low molecular mass and low polarity from RHBO. There were amounts of lignin monomers identified in the extracts and most of them contained 1 ∼ 4 oxygen atoms, which was consistent with the acidity of bio-oil due to the existence of phenolic OH inside. Species with molecular mass over 500 Da were detected with around 5% of relative content, which could not be revealed by other analytical methods such as gas chromatography/mass spectrometry.