Characterization of bio-oils from the alkanolyses of sweet sorghum stalk by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

• Numerous acidic and basic species in BOm and BOe from SSS alkanolyses were detected.
• The most abundant acidic class species in BOm and BOe are O4 and O3, respectively.
• Lignin-derived compounds are characteristic acidic species in the BOs.
• The main basic compounds in the BOs are N2On (n = 1–6) class species.

Bio-oils (BOs) obtained from sweet sorghum stalk (SSS) methanolysis (BOm) and ethanolysis (BOe) at 300 °C for 30 min were analyzed with an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FT-ICR MS). In negative-ion mode, the predominant compounds in BOm and BOe are On (n = 1–10) class species with double bond equivalent (DBE) values of 1–14 and carbon atom numbers (CANs) of 5–35. The most abundant class species in BOm and BOe are O4 and O3, respectively. According to the distribution of On class species and the van Krevelen diagram, lignin-derived compounds are the main acidic species in the BOs. In addition, N1On (n = 0–10) class species with DBE values of 1–14 and CANs of 7–35 were also identified. In positive-ion mode, most of detected compounds in BOm and BOe are N2On (n = 1–6) class species with DBE values of 1–19 and CANs of 10–40, in which N2O2–N2O4 class species with DBE = 8–12 and CAN = 19–28 are the most abundant. These results facilitate understanding thermochemical behavior of SSS.

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