The understanding of lignin softening and pyrolysis is important for developing lignocellulosic biorefinery in order to produce carbon fibers, polymers additives, green aromatics, or biofuels. Protobind lignin (produced by soda pulping of a wheat straw) was characterized by thermogravimetry, calorimetry (for glass transition temperature and heat of pyrolysis reactions), in situ 1H NMR (for the analysis of the mobility of protons upon lignin thermal conversion), and solution-state 13C and 31P NMR (determination of functional groups in lignin). In situ rheology reveals the real-time viscoelastic behavior of lignin as a function of temperature. Upon heating, lignin undergoes softening, through glass transition overlapped with depolymerization, and is followed by the solidification of the softened material by cross-linking reactions. The lignin residues were quenched within the rheometer at the midpoint temperatures of softening and solidification regions and were further analyzed by elemental analysis, GPC-UV of acetylated THF soluble fractions, FTIR, solid 13C NMR, and laser desorption ionization (LDI) combined with very high-resolution mass spectrometry (HRMS). We present the first report on lignin biochars analysis by LDI-HRMS. NMR and FTIR analyses provide the evolution of functional moieties in lignin residues. 13C NMR, GPC-UV, and LDI FTICRMS analyses depict the depolymerization mechanism combined with cross-linking and demethoxylation reactions. An overall physical and chemical mechanism for the thermal conversion of alkali lignin is proposed based on these complementary analyses.

The objective of this work was to compare direct infusion in a Q-TOF mass spectrometer through three different atmospheric pressure sources, electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI) coupled to a high resolution Q-TOF mass spectrometer. A complex mixture of PAH and oxy-PAHs, obtained after the air oxidation of fluoranthene on mineral substrates, was used to compare the different ionization abilities of these sources. Here, we propose analytical methods for the use of all sources. Final goal was to provide background to the choice of the most appropriate source in order to analyze complex organic mixtures as those encountered in polluted soils, water, sediments, as well as in petroleum.

Complementary analytical methods have been usedto study the effect of potassium on the primary pyrolysis mechanisms of cellulose and miscanthus. Thermogravimetry, calorimetry, high temperature 1 H NMR (in-situ and real time analysis of the fluid phase formed during pyrolysis) and water extraction of quenched char followed by SEC/MS-ELSD (size exclusion chromatography coupled with mass spectrometry and evaporative light scattering detector have been combined). Pyrolysis was conducted under fixed bed conditions to impose similar mass transfer conditions as TGA/DSC and 1 H NMR to produce charfor SEC/MS. Potassium impregnated in cellulose suppresses the formation of anhydro-sugars measuredby SEC/MS, reduces the formation of mobile protons as observed by in-situ 1 H NMR and gives rise to a mainly exothermic signal (by calorimetry). Interestingly, the evolution of mobile protons formed from Kimpregnated cellulose follows with a very similar pattern the evolution of the mass loss rate with the mobile protons are formed before mass loss commences during pure cellulose pyrolysis. This methodology has been also applied to miscanthus, demineralised miscanthus, potassium re-impregnated miscanthus after demineralization, raw oak and douglas fir. We discuss the mechanism of primary pyrolysis of biomass and notably highlight the importance of the intermediate liquid phase.