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

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 H-1-C-13 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 H-1-C-13 NMR spectroscopy provides one-bond and multiple-bond correlations between pairs of H-1 and C-13 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 N-1, 594 O-1 and 267 O-2 compounds were observed as products of hydrotreatment. The relative abundance of N1O1, N1O2, N1O3, N-2, N2O1, N2O2 and O-3 compounds are reduced to different degrees after hydrotreatment and other higher heteroatom containing species (O-4-O-10, N1O4, N1O5 and N2O3) are completely removed by hydrotreatment. (C) 2014 Elsevier Ltd. All rights reserved.