A grass soda technical lignin (PB1000) underwent a process combining solvent fractionation and treatment with an ionic liquid (IL), and a comprehensive investigation of the structural modifications was performed by using high‐performance size‐exclusion chromatography, 31P NMR spectroscopy, thioacidolysis, and GC–MS. Three fractions with distinct reactivity were recovered from successive ethyl acetate (EA), butanone, and methanol extractions. In parallel, a fraction deprived of EA extractives was obtained. The samples were treated with methyl imidazolium bromide ([HMIM]Br) by using either conventional heating or microwave irradiation. The treatment allowed us to solubilize 28 % of the EA‐insoluble fraction and yielded additional free phenols in all the fractions, as a consequence of depolymerization and demethylation. The gain of the combined process in terms of antioxidant properties was demonstrated through 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH.) radical‐scavenging tests. Integrating further IL safety‐related data and environmental considerations, this study paves the way for the sustainable production of phenolic oligomers competing with commercial antioxidants.
The influence of material properties on the reactivities of activated carbon materials have been studied on a laboratory scale. Carbon samples having diversified origin and properties were characterized using a thermogravimetry (TG) coupled with a differential scanning calorimetry (DSC). Reactivity parameters like the Point of Initial Oxidation (PIO) representing the beginning of the oxidation reactions and the Spontaneous Ignition Temperature (SIT) where the bed combustion takes place in a self sustaining manner were experimentally determined. The intrinsic properties of the activated carbons influencing oxidation and ignition were examined qualitatively followed by quantitative statistical correlations. Results from both qualitative and statistical correlations showed that increase in the oxygen content in the form of surface oxygenated groups increased the reactivity of activated carbons. It was by far the single most influential property discriminated from the analysis. The porosity characteristics like the specific surface area and pore volume did show some vague trends but could not be validated like that of the oxygen content. The effects of these individual properties on the oxidation and ignition reactivity are discussed.T. Jayabalan ( ) · P. Pré · V. Héquet
The aim of this work is to understand the influence of textural, chemical, and structural properties on the reactivity of activated carbons toward air. Multiscale organization of activated carbons was studied using high-resolution transmission electron microscopy (HRTEM) and their quantitative structural data, like individual fringe length, interlayer spacing, and proportion of nonstacked layers, were extracted using a specific image analysis procedure. Intrinsic properties like the specific surface area S
BET, pore volume, micropore width, and elementary composition were also measured. The reactivity of the carbon samples in air was quantified from the measurement of oxidation and ignition temperatures determined by thermogravimetry analysis coupled with a differential scanning calorimetry. The characteristics of the graphitic structures and the properties of the activated carbon materials were found to be dependent on the activation mode and the nature of the material. The results suggest that oxygen present in the form of surface oxygenated groups, the mineral content, and the dimensions of the basic structural units influence the reactivity of activated carbons. Highly stable carbons were found to contain less oxygen to carbon ratio, lower mineral content, and larger and better stacked polyaromatic layers.
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