Hydrothermal liquefaction oil and hydrotreated product from pine feedstock characterized by heteronuclear two-dimensional NMR spectroscopy and FT-ICR mass spectrometry

• Combination of ultrahigh resolution FT-ICR MS and 2D NMR for description of pine-derived HTL oil and upgraded product.
• Comparison of HTL oil and pyrolysis oil from same pine feedstock.
• Identification of hydrotreatment resistant components.

Hydrothermal liquefaction (HTL) oil and hydrotreated product from pine tree farm waste (forest product residual, FPR) have been analyzed by direct infusion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) in both positive- and negative-ionization modes and high-resolution two-dimensional heteronuclear 1H–13C NMR spectroscopy. FT-ICR MS resolves thousands of compounds in complex oils and provides unparalleled compositional details for individual molecules for identification of compound class (heteroatom content), type (number of rings plus double bonds to carbon or double bond equivalents (DBE) and carbon number (degree of alkylation). Heteronuclear 1H–13C NMR spectroscopy provides one-bond and multiple-bond correlations between pairs of 1H and 13C chemical shifts that are characteristic of different organic functional groups. Taken together this information provides a picture of the chemical composition of these oils. Pyrolysis crude oil product from pine wood was characterized for comparison. Generally, pyrolysis oil is comprised of a more diverse distribution of heteroatom classes with higher oxygen number relative to HTL oil as shown by both positive- and negative-ion ESI FT-ICR MS. A total of 300 N1, 594 O1 and 267 O2 compounds were observed as products of hydrotreatment. The relative abundance of N1O1, N1O2, N1O3, N2, N2O1, N2O2 and O3 compounds are reduced to different degrees after hydrotreatment and other higher heteroatom containing species (O4–O10, N1O4, N1O5 and N2O3) are completely removed by hydrotreatment.