scholarly journals Heat-Induced Discoloration of Chromophore Structures in Eucalyptus Lignin

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1686 ◽  
Author(s):  
Peng Zhang ◽  
Yanxia Wei ◽  
Yang Liu ◽  
Jianmin Gao ◽  
Yao Chen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Photoelectron Spectroscopy ◽  
Eucalyptus Grandis ◽  
Gel Permeation Chromatography ◽  
Magic Angle Spinning ◽  
Saturated Steam ◽  
Magic Angle ◽  
13C Cpmas Nmr ◽  
Eucalyptus Wood ◽  
Dehydration Reactions

The color changes corresponding to chromophore structures in lignin caused by exposure of Eucalyptus (Eucalyptus grandis and E. urophylla) to heat were investigated. Eucalyptus wood powders were heat treated under saturated steam atmospheres for 10 h at 110 °C, 130 °C and 150 °C. The lignin was isolated before and after heat treatment. The physicochemical properties of the lignin and changes in chromophore structures during heat treatment was evaluated through wet chemical analysis, Fourier transform infrared spectroscopy (FTIR), diffuse reflectance ultraviolet-visible spectroscopy (DRUV-Vis), gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and 13C Cross polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR). Wood color darkened and reddened with the increase in pressure and temperature. Depolymerization and dehydration reactions occurred via demethoxylation with heat treatment in saturated steam at 110 °C or 130 °C. Lignin condensed to form insoluble compounds after heat treatment in saturated steam at 150 °C. G units increased and S units decreased through demethylation during heat treatment, as revealed by FTIR and 13C-NMR analysis.

scholarly journals Heat-Induced Discoloration of Chromophore Structures in Eucalyptus Lignin

2018 ◽  
Author(s):  
Peng Zhang ◽  
Yanxia Wei ◽  
Yang Liu ◽  
Yao Chen ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Treatment ◽  
13C Nmr ◽  
Eucalyptus Grandis ◽  
Saturated Steam ◽  
Color Changes ◽  
13C Nmr Analysis ◽  
Eucalyptus Wood ◽  
Dehydration Reactions ◽  
Before And After ◽  
Insoluble Compounds

The color changes corresponding to chromophore structures in lignin caused by exposure of Eucalyptus（Eucalyptus grandis and E. urophylla）to heat were investigated. Eucalyptus wood samples were heated in saturated steam atmospheres for 10 h at 110℃, 130℃, and 150℃. The lignin was isolated before and after heat treatment. The physicochemical properties of the lignin and changes in chromophore structures during heat treatment was evaluated through wet chemical analysis, FTIR, UV-Vis, GPC, XPSand 13C-NMR. The color of the wood became darker and redder with the increase in pressure and temperature. Depolymerization and dehydration reactions occurred via demethoxylation with heat treatment in saturated steam at 110℃ or 130℃. Lignin condensed to form insoluble compounds after heat treatment in saturated steam at 150℃. G units increased and S units decreased through demethylation during heat treatment, as revealed by FTIR and 13C-NMR analysis.

Preparation and Characterization of High-Surface-Area Aluminum Nitride Thin Films

1996 ◽  
Vol 454 ◽  
Author(s):  
S. A. Monie ◽  
C. G. Pantano
Keyword(s):  
Heat Treatment ◽  
Aluminum Nitride ◽  
Photoelectron Spectroscopy ◽  
High Surface ◽  
Magic Angle Spinning ◽  
Treatment Temperature ◽  
Magic Angle ◽  
Free Standing ◽  
X Ray ◽  
Alumina Sol

ABSTRACTFree-standing aluminum nitride (AlN) films were prepared by ammonia heat-treatment of pseudoboehmite [AIO(OH)] gels derived from an alumina sol. Supported films on sapphire substrates were also made by spin-coating the alumina sol, followed by ammonia nitridation. The conversion of the specimens to AIN as a function of heat-treatment temperature was studied using various characterization techniques.For the free-standing films, X-ray diffraction (XRD) showed that upon ammonia treatment, the specimens were first transformed from pseudoboehmite to η-alumina and finally to A1N above 1000°C. 27Al magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy confirmed the appearance of Al[N]4 coordination at 1000°C, indicative of AlN. Complete conversion to AlN was achieved after 5 hour nitridation at 1200°C. The 1200°C heat-treated films consisted of crystallites of AlN in the size range 0.01 − 0.15 μm, with pores between 0.03 − 0.25 μm in diameter, as observed by TEM/electron diffraction analyses. These films had BET surface areas of approximately 25 m2/g. Nitridation of the supported films to AlN occurred at lower temperatures (∼900°C), as shown by secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS).

THE LOCAL STRUCTURE OF BISMUTH-BORATES CHARACTERIZED BY 11B MAS NMR

2002 ◽  
Vol 16 (12) ◽  
pp. 423-431 ◽  
Author(s):  
M. VASILESCU ◽  
S. SIMON
Keyword(s):  
Heat Treatment ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
Borate Glasses ◽  
Bismuth Borate ◽  
Mean Values ◽  
Quadrupolar Coupling ◽  
Angle Spinning ◽  
Bismuth Borates

Bismuth-borate glasses and vitroceramics belonging to x Bi 2 O 3 · (100 - x) B 2 O 3 system, 0 ≤ x ≤ 93, doped with 0.5 mol% MnO are investigated by 11 B Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). The 11 B MAS NMR results indicate the presence of three- and tetra-coordinated boron in all investigated bismuth borates. While the fraction of the tetra-coordinated boron present a large maximum in the range 20 ≤ x ≤ 60 in the bismuth-borate glasses, this maximum is reduced to the range 20 ≤ x ≤ 37.5 in the samples obtained after heat treatment. Crystalline phases are developed in the samples with high bismuth content, x ≥ 60, by heat treatment at 550°C, in which two types of three-coordinated boron are identified. The mean values of the NMR parameters like chemical shift, asymmetry parameter and quadrupolar coupling constant are less influenced by the bismuth/boron ratio, showing that boron structural units are relatively stable on the entire investigated composition range.

scholarly journals CHARACTERIZATION OF BULK SOIL HUMIN AND ITS ALKALINE-SOLUBLE AND ALKALINE-INSOLUBLE FRACTIONS

2015 ◽  
Vol 39 (1) ◽  
pp. 120-126 ◽  
Author(s):  
Cuilan Li ◽  
Shuqing Gao ◽  
Qiang Gao ◽  
Lichun Wang ◽  
Jinjing Zhang
Keyword(s):  
Ph Value ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
13C Cpmas Nmr ◽  
Traditional Treatment ◽  
Chemical Structures ◽  
Exhaustive Extraction ◽  
Angle Spinning ◽  
Soil Colloids

Humic substances are the major components of soil organic matter. Among the three humic substance components (humic acid, fulvic acid, and humin), humin is the most insoluble in aqueous solution at any pH value and, in turn, the least understood. Humin has poor solubility mainly because it is tightly bonded to inorganic soil colloids. By breaking the linkage between humin and inorganic soil colloids using inorganic or organic solvents, bulk humin can be partially soluble in alkali, enabling a better understanding of the structure and properties of humin. However, the structural relationship between bulk humin and its alkaline-soluble (AS) and alkaline-insoluble (AIS) fractions is still unknown. In this study, we isolated bulk humin from two soils of Northeast China by exhaustive extraction (25 to 28 times) with 0.1 mol L-1 NaOH + 0.1 mol L-1 Na4P2O7, followed by the traditional treatment with 10 % HF-HCl. The isolated bulk humin was then fractionated into AS-humin and AIS-humin by exhaustive extraction (12 to 15 times) with 0.1 mol L-1 NaOH. Elemental analysis and solid-state 13C cross-polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy were used to characterize and compare the chemical structures of bulk humin and its corresponding fractions. The results showed that, regardless of soil types, bulk humin was the most aliphatic and most hydrophobic, AS-humin was the least aliphatic, and AIS-humin was the least alkylated among the three humic components. The results showed that bulk humin and its corresponding AS-humin and AIS-humin fractions are structurally differed from one another, implying that the functions of these humic components in the soil environment differed.

scholarly journals Comprehension of paraquat adsorption on faujasite zeolite X and Y in sodium form

2017 ◽  
Vol 36 (1-2) ◽  
pp. 684-693 ◽  
Author(s):  
Wina Rongchapo ◽  
Chalermpan Keawkumay ◽  
Nattawut Osakoo ◽  
Krittanun Deekamwong ◽  
Narong Chanlek ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Fourier Transform Infrared Spectroscopy ◽  
Photoelectron Spectroscopy ◽  
Fourier Transform Infrared ◽  
Magic Angle Spinning ◽  
Mas Nmr ◽  
Magic Angle ◽  
Zeolite X ◽  
X Ray

The nature of paraquat adsorption is compared between zeolite NaX and NaY which have the same faujasite structure but different Si/Al ratio, namely 1.2 and 2.2, respectively. The adsorption was proposed to occur via ion exchange and expected to increase with Al content. However, NaX had a lower paraquat adsorption capacity than NaY. The bare and paraquat-containing zeolites (PQX and PQY) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption–desorption analysis, magic-angle spinning nuclear magnetic resonance (MAS) NMR, and X-ray photoelectron spectroscopy. The presence of adsorbed paraquat was confirmed by Fourier transform infrared spectroscopy. Paraquat adsorbed in supercages of the zeolites resulting in a decrease of surface area and displacement of sodium cations. Results from 23Na MAS NMR and X-ray photoelectron spectroscopy indicated that interaction of sodium ions in the cavity of NaX was stronger than that in NaY, making it less exchangeable with paraquat.

scholarly journals Characterization of Y2O3 and CeO2 doped SiO2-SrO-Na2O glasses

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Lana M. Placek ◽  
Timothy J. Keenan ◽  
Fathima Laffir ◽  
Aisling Coughlan ◽  
Anthony W. Wren
Keyword(s):  
Photoelectron Spectroscopy ◽  
Network Connectivity ◽  
Peak Shift ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Network Modifier ◽  
Peak Broadening ◽  
Angle Spinning ◽  
Ce Content

AbstractThe structural effects of yttrium (Y) and cerium (Ce) are investigated when substituted for sodium (Na) in a 0.52SiO2–0.24SrO–(0.24−x)Na2O–xMO (where x = 0.08; MO = Y2O3 and CeO2) glass series. Network connectivity (NC) was calculated assuming both Y and Ce can act as a network modifier (NC = 2.2) or as a network former (NC up to 2.9). Thermal analysis showed an increase in glass transition temperature (Tg) with increasing Y and Ce content, Y causing the greater increase from the control (Con) at 493∘C to 8 mol% Y (HY) at 660∘C. Vickers hardness (HV) was not significantly different between glasses. 29Si Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) did not show peak shift with addition of Y, however Ce produced peak broadening and a negative shift in ppm. The addition of 4 mol% Ce in the YCe and LCe glasses shifted the peak from Con at −81.3 ppm to −82.8 ppm and −82.7 ppm respectively; while the HCe glass produced a much broader peak and a shift to −84.8 ppm. High resolution X-ray Photoelectron Spectroscopy for the O 1s spectral line showed the ratio of bridging (BO) to non-bridging oxygens (NBO), BO:NBO,was altered,where Con had a ratio of 0.7, HY decreased to 0.4 and HCe to 0.5.

A comparative structural study of nitrogen-rich fulvic acids from various Antarctic lakes

2017 ◽  
Vol 14 (8) ◽  
pp. 502 ◽  
Author(s):  
Sahar Farzadnia ◽  
Rama D. Nimmagadda ◽  
Christopher McRae
Keyword(s):  
Fulvic Acid ◽  
13C Nmr ◽  
Photoelectron Spectroscopy ◽  
Fulvic Acids ◽  
Magic Angle Spinning ◽  
Gas Chromatography Mass Spectrometry ◽  
Magic Angle ◽  
Similarities And Differences ◽  
Vestfold Hills ◽  
Cp Mas 13C Nmr

Environmental contextFulvic acids are important naturally occurring organic materials, but unravelling their complex structures remains challenging. This paper suggests chemical analyses to facilitate structural studies of fulvic acids, and to investigate the similarities and differences of fulvic acids from various natural sources. AbstractWe comprehensively examined fulvic acids isolated from three lakes in Vestfold Hills, eastern Antarctica and microbial reference fulvic acid from Pony Lake located in western Antarctica. These fulvic acids were compared in terms of their structural similarities and differences by means of elemental analysis, cross polarisation magic-angle spinning (CP-MAS) 13C NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and tetramethylammonium hydroxide (TMAH) thermochemolysis coupled to gas chromatography–mass spectrometry (GC-MS). The results indicate that these Antarctic fulvic acids show notable differences in chemical composition and structure; in particular XPS demonstrates that the distribution of nitrogen-containing compounds in the nitrogen-rich Antarctic fulvic acids differ significantly from each other. The dissimilarities are also highlighted in terms of quantity and quality of their nitrogenous constituents. For instance, Organic Lake Fulvic Acid (OLFA) contains around 10 times lower amide groups (pyrimidine–peptide N) than Pendant Lake Fulvic Acid (PNFA). It also shows 1.5 times less quaternary amine than Mossel Lake Fulvic Acid (MLFA) and PNFA. According to CP-MAS 13C NMR experiments the carbohydrate content in Vestfold Hills fulvic acid is higher than that of Pony Lake Fulvic Acid (PLFA), suggesting that dissolved organic matter (DOM) from Vestfold Hills Lakes is immature. TMAH–GC-MS demonstrated that Antarctic fulvic acids are enriched in heterocyclic non-aromatic nitrogen-containing components such as pyrimidine structures, with the exception of OLFA. Furthermore, tricyclic terpenoids (dehydroabietic acid) were detected in two out of four fulvic acids tabulated using TMAH–GC-MS. Although diterpenes are commonly associated with plants and fungi, their occurrence in Antarctic fulvic acids could be justified due to their diverse origins from cyanobacteria to aerosols.

scholarly journals Aspects of solid state 13C CPMAS NMR spectroscopy in coals from the Balkan peninsula

2003 ◽  
Vol 68 (8-9) ◽  
pp. 599-606 ◽  
Author(s):  
Andreas Georgakopoulos
Keyword(s):  
Bituminous Coal ◽  
Balkan Peninsula ◽  
Magic Angle Spinning ◽  
Paramagnetic Species ◽  
Magic Angle ◽  
Northern Greece ◽  
13C Cpmas Nmr ◽  
Nmr Spectrum ◽  
Serbia And Montenegro ◽  
Angle Spinning

The cross-polarized magic-angle-spinning NMR (CPMAS-NMR) technique was used in this work to assess the carbon distribution in coals of different rank (peat, lignite, xylite, sub-bituminous coal) from important deposits in Greece and Bulgaria. The technique is assumed to be only semiquantitative due to a number of interferences, such as spinning side bands (SSB) in the spectra, paramagnetic species in the samples, and low or remote protonation of aromatic carbons. The Bulgarian sub-bituminous coal shows the greatest amounts of aromatic structures. The lignite sample from the Drama basin Northern Greece, is relatively unaltered and largely unlettered, and shows the greatest amounts of aliphatic groups. The 13C-NMR spectra of Pliocene lignites from endemic areas in Serbia and Montenegro and Bosnia, taken from published papers, show significantly more intense resonance's for methoxyl phenolic, and polysaccharide moieties compared to the Drama lignite NMR spectrum. Xylite reveals high contents of carbohydrates.

scholarly journals INFLUENCE OF COMMERCIAL THERMAL TREATMENT ON Eucalyptus grandis Hill ex Maiden WOOD PROPERTIES

2021 ◽  
Vol 45 ◽  
Author(s):  
Carolina Aparecida Barros Oliveira ◽  
Karina Aparecida de Oliveira ◽  
Julio Cesar Molina ◽  
Vinicius Borges de Moura Aquino ◽  
André Luis Christoforo
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Thermal Treatment ◽  
Eucalyptus Grandis ◽  
Treated Wood ◽  
Wood Properties ◽  
Treatment Temperature ◽  
Saturated Steam ◽  
Physical Chemical ◽  
Different Temperatures

ABSTRACT This study aimed to evaluate the influence of commercial thermal treatment on Eucalyptus grandis considering its physical, chemical, and mechanical properties. The wood samples were heat-treated in an autoclave with saturated steam and pressure application at four different temperatures: 155, 165, 175, and 185 ºC. The physical, chemical, and mechanical properties were altered due to the heat treatment. The extractives content varied between 6.06% and 28.75%; lignin between 28.93% and 37.96%; holocellulose between 65.01% and 38.12%. The mechanical properties reduced significantly with the increase of the heat treatment temperature. Through the set of data obtained, it was possible to generate significant and high precision regression models capable of estimating such properties for heat treatment temperatures not studied experimentally, enabling the determination of the most suitable temperature of heat treatment to achieve a certain property value of the treated wood.

Sign in / Sign up

Export Citation Format

Share Document