Multi-technique characterization of fast pyrolysis oils

• Six bio-oils were produced from three biomasses using two fast pyrolysis units.
• Detailed compositions of bio-oils are described by GC–MS/FID and headspace-GC-FID/MS.
• Biomass type and pyrolysis conditions have both impact on bio-oils composition.

In this study an analytical multi-technique approach was developed in order to describe as fully as possible the composition of several fast pyrolysis oils. Six bio-oils were produced at CIRAD (centre de Coopération Internationale en Recherche Agronomique pour le Développement) and TI (Thünen Institute of Wood Research) using the same three lignocellulosic biomass materials (i.e. hardwood, softwood and wheat straw). Different and complementary analytical tools were used to characterize these samples. Whole bio-oils were first directly analyzed by gas chromatographic (GC) hyphenated techniques with flame ionization detector (FID) and mass spectrometry (MS) (Headspace-GC-FID/MS, GC-FID/MS) and by a high resolution mass spectrometry technique (Fourier transform ion cyclotron resonance mass spectrometry FT-ICR/MS) without any pre-separation step. The GC analyses provide a detailed molecular description (more than 90 compounds) of the composition of the six bio-oils. To achieve a better understanding of the chemical composition of this set of bio-oils, the samples were fractionated into aqueous fractions and water-insoluble fractions (also called pyrolytic lignins). Detailed analysis of sugars was performed by GC-FID/MS after a solid-phase extraction (SPE) and a subsequent derivatization performed on the aqueous fractions. Moreover, FT-ICR/MS analyses show that species having molecular weights up to 900 Da are present in the aqueous phases. The originality of this work is based on the development of complementary analytical tools (i.e., chromatographic and spectrometric techniques) to describe the composition from volatiles (monomeric) to non-volatiles (oligomeric) species of several bio-oils that were produced and stored under controlled conditions.