Search results for "Lignin"
showing 10 items of 149 documents
NMR Study of Kraft Pulp Mill Waste and Natural Humic Substances
1988
High field proton NMR spectroscopy in DMSO-d6 solution is applied for structural analysis of main high molecular fractions of natural humus and waste lignin from kraft pulp mill. The spectra are similar in great part. Main differences appear in p-disubstituted benzene proton and -CH2 -CO-proton signals which are absent in spectrum of waste lignin obviously due to chlorination. A new observation of 51 Hz 1:1:1 triplet in both spectra is discussed.
Transport of high molecular mass lignin material in the receiving water system of a mechanical pulp mill
1998
High molecular mass material (HMM) of water samples collected from the receiving water system of a mechanical pulp mill was characterized applying cupric oxide oxidation combined with GC and HPLC analysis of the oxidation products. This qualitative method was used to follow the transport of organic HMM discharged by the mill. The interpretation of results was complicated by degradation reactions of HMM in the water system and the assimilation of HMM produced by the mill to natural humic compounds. The analytical data was subjected to the principal component analysis (PCA) to verify the results obtained.
Polarisation and Electoral Realignment: The Case of the Right-Wing Parties in Spain
2020
The article analyses the consequences of elite polarisation at the mass level. We study the electoral re-alignment within the right-wing Spanish electorate in recent years, whereby support for the long-predominant Partido Popular has been eroded dramatically to the benefit of new challengers. Measuring ideological polarisation at the party system level and at the individual level, we show how the polarising strategy implemented by the liberal Ciudadanos - and imitated by PP - to gain support from the right-wing electorate paved the way for a massive transfer of conservative voters to the radical-right Vox. The results provide counter-intuitive evidence about the electoral effects of elite p…
Theoretical Elucidation of β-O-4 Bond Cleavage of Lignin Model Compound Promoted by Sulfonic Acid-Functionalized Ionic Liquid
2019
While the depolymerization of lignin to chemicals catalyzed by ionic liquids has attracted significant attention, the relevant molecular mechanism, especially the cleavage of specific bonds related to efficient depolymerization, still needs to be deeply understood for the complexity of this natural aromatic polymer. This work presents a detailed understanding of the cleavage of the most abundant β-O-4 bond in the model system, guaiacylglycerol β-guaiacyl ether, by a Brønsted acidic IL (1-methyl-3-(propyl-3-sulfonate) imidazolium bisulfate ([C3SO3Hmim][HSO4]) using density functional theory calculation and molecular dynamics simulation. It has been found that [C3SO3Hmim][HSO4] generates zwit…
The effects of land abandonment and long-term afforestation practices on the organic carbon stock and lignin content of Mediterranean humid mountain …
2019
Afforestation is an important strategy that can decrease atmospheric carbon by sequestering carbon in biomass and soil. In Spain, an active afforestation programme was adopted in the 1950s when the soil was severely eroded after widespread abandonment of arable land. The Araguás catchment (Central Spanish Pyrenees) is a good example of this programme because it was afforested with both Pinus sylvestris L. (PS) and Pinus nigra J.F.Arnold (PN). The soil organic carbon (SOC) stock and lignin content (based on the vanillyl, syringyl and cinnamyl contents) of these afforested soils were examined and compared to those of bare soil, secondary succession and meadow soils. Both the SOC stock and lig…
Fast-growing willow (Salix viminalis) as a filler in polyethylene composites
2018
Abstract The study investigated the possibility of using wood flour obtained from fast-growing willow chips (Salix viminalis) as an alternative for standard hard- and softwood flours used in the production of wood polymer composites (WPCs). The composites contained willow flour and polyethylene matrix (OPCs) were prepared, characterized and compared with other WPCs which had been filled with hard- or softwood flours. Moreover, the structural and functional properties were investigated and discussed. Greater hemicellulose contents and lower lignin contents in OPCs resulted in better impact strength values of those materials. Which is interesting, the chemical composition of OPCs was found si…
Electronic paramagnetic resonance power saturation of wooden samples
2009
The deterioration of wood used for artifacts of artistic interest involves the production of different free radicals from the macromolecules of the wooden matrix (cellulose, lignin, and hemicellulose). Among the techniques able to provide information about these free radicals, the contribution of electronic paramagnetic resonance (EPR) can be very valuable. In this paper, the study of EPR signals (with g 2) of both modern and ancient wooden taxa was undertaken in order to analyze some features of the free radicals in natural wood. In particular, we have studied the microwave power saturation behaviors of seasoned wooden samples from ten species, and we have found remarkable differences betw…
Molecular Mass Distribution of Lignin from the Alkaline Pulping of Hardwood, Softwood, and Wheat Straw
2012
Abstract The behavior of lignin during kraft (hardwood, softwood, and wheat straw) and soda-AQ (wheat straw) pulping was studied, mainly in terms of delignification degree and molecular mass distribution (MMD). In the initial delignification phase (at 140°C for 15–60 min), a prominent part of the dissolved softwood kraft lignin (18–25 g/L, MM mostly > 3,000 Da) was found in the liquid phase of chip cavities, rather than in the external bulk black liquor (5–7 g/L, MM mostly < 3,000 Da). The maximum weight average MM values ( w) of the soluble lignin under conventional cooking conditions were detected for the kraft softwood (4,100 Da), and kraft birch (3,400 Da) when the degree of delignifica…
A LASER-INDUCED FLUORESCENCE (LIF) METHOD FOR MONITORING OXYGEN–ALKALI DELIGNIFICATION OF SOFTWOOD KRAFT PULP
2002
ABSTRACT A laser-induced fluorescence (LIF) method for monitoring the oxygen–alkali delignification of pine (Pinus sylvestris) kraft pulp was tested. The fluorescence intensity of the effluent was found to increase systematically during treatment as the lignin content of the pulp decreased. This emission method, compared, for example, to a UV/Vis absorption method, seems to have potential for large-scale applications. Owing both to the complex chemical nature of the effluent from oxygen–alkali delignification and to the complex nature of the fluorescence method, further work on this method is needed before it can be used for industrial purposes.
Thermochemical behavior of Norway spruce ( Picea abies ) at 180-225 °C
2002
Norway spruce (Picea abies) was heated for 2–8 h in the temperature range 180–225 °C, under a steam atmosphere. The chemical analyses of the treated feedstock samples indicated that during heating (total mass loss 1.5–12.5% of the initial DS) carbohydrates (hemicelluloses and cellulose) were clearly more amenable to various degradation reactions than lignin. In addition, major water-soluble products released from the feedstock material during the treatments were classified into several compound groups and changes in the relative mass portion of these groups were monitored by GC during a separate experiment.