Leila Alvila

IR spectroscopy as a quantitative and predictive analysis method of phenol–formaldehyde resol resins

A set of resin samples was characterized by IR and 13C-NMR spectroscopy. The suitability of IR spectroscopy for the quantitative analysis of resins was evaluated by statistical methods using the NMR reference data as calibration. The values of interesting properties, for example, the amount of free phenol and the formaldehyde-to-phenol (F/P) molar ratio, of the resins being similar to the calibration resins were predicted from the IR spectra. Also, the predicted results were compared with the ones observed by 13C-NMR spectroscopy.

Phenolic compounds in silver birch (Betula pendula Roth) wood

Abstract Three new phenolic compounds (4-hydroxy-2-methoxyphenyl-6-O-syringoyl-β-D-glucopyranoside, 2-hydroxy-4-methoxyphenyl-6-O-syringoyl-β-D-glucopyranoside, and 4-hydroxymethyl-2-methoxyphenyl-6-O-syringoyl-β-D-glucopyranoside) and 15 known phenolic compounds (two phenyl glucoside esters, five lignans, three diarylheptanoids and five simple aldehydes or ketones) were isolated from the secondary xylem of mature Betula pendula Roth. The compounds were identified on the basis of their NMR (1D and 2D) and mass spectral data. In total, 23 phenolic extractives present in the sapwood of two winter-dormant B. pendula trees felled at different growing sites (rich in nutrients and scarce in nutrients) were quantified by GC. Their amounts were mostly low, 0.01–0.18 mg g−1 of dry wood. Total amounts of the phenolic extractives isolated were 1.2 mg g−1 of dry wood (5.6% of the total methanol-soluble extractives) in the tree felled at the site rich in nutrients, and 1.9 mg g–1 of dry wood (10% of the total methanol-soluble extractives) in the tree felled at the site scarce in nutrients.

Chemical changes in silver birch (Betula pendula Roth) wood caused by hydrogen peroxide bleaching and monitored by color measurement (CIELab) and UV-Vis, FTIR and UVRR spectroscopy

Abstract Silver birch (Betula pendula Roth) wood was subjected to bleaching with acidic hydrogen peroxide solution. The color change and chemical changes occurring on bleaching were investigated by CIELab color measurements and UV-Vis, FTIR and UVRR spectroscopy. With bleaching, the color of birch wood changed notably towards white, less red and more yellow, revealed by the CIELab color measurements, however, followed by notable yellowing in 343 days. The chemical changes occurring with the bleaching treatment in the xylem of birch, demonstrated by UV-Vis, FTIR and UVRR spectroscopy, indicated degradation of aromatic structures with a simultaneous increase in relative amounts of unconjugated carbonyl structures. The results indicate that the degradation of aromatic structures involved opening of the aromatic ring possibly leading to the formation of muconic acids or other low molecular weight products rich in carbonyl structures. In addition, in birch wood subjected to bleaching treatment with acidic hydrogen peroxide solution, syringyl structures provided favorable sites for the degradation of aromatic structures.

Characterization of Brauns’ lignin from fresh and vacuum-dried birch (Betula pendula) wood

AbstractBrauns’ lignins present in the methanol extracts of fresh birch (Betula pendula) xylem and of sawn birch board subjected to vacuum drying were characterized by 1H and 13C NMR spectroscopy (1D and 2D), IR spectroscopy, gel permeation chromatography (GPC) and colour measurements (CIELab) in order to find out whether Brauns’ lignin could contribute to the colour change of sawn timber that occurred during vacuum drying. The two Brauns’ lignin samples contained about equal amounts of syringylpropane and guaiacylpropane units linked with β-O-4 and β–β side-chain structures. Molecular weight of the Brauns’ lignin of vacuum-dried birch board (acetylated: 5,200xa0gxa0mol−1) was higher than that of the Brauns’ lignin of fresh birch wood (acetylated: 4,400xa0gxa0mol−1). The Brauns’ lignin of vacuum-dried wood was also clearly darker and more prominently yellow and red; nn

NMR imaging of aluminum oxide catalyst spheres

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Discolouration of birch wood: analysis of extractives from discoloured surface of vacuum-dried European white birch (Betula pubescens) board

between the Brauns’ lignin samples was 23.59. The differences in the molecular weights and colours suggest that the Brauns’ lignin underwent a chemical change during vacuum drying of the wood and that this change may have affected the colour of the wood.

Nuclear magnetic resonance imaging – a potential method for analysis of bone material

Abstract The effect of growth site type, felling season, storage time and kiln drying on the contents and distributions of phenolic extractives and low molar mass carbohydrates in secondary xylem of silver birch Betula pendula was studied. The results indicated that the total amount of methanol-soluble extractives did not change markedly under the prevailing conditions of the study. However, the contents of phenolic compounds, (+)-catechin and (+)-catechin-7-O-β-D-xylopyranoside, and low molar mass sugars, D(+)-xylose, D(−)-fructose, D(+)-glucose, sucrose, maltose and raffinose, changed with season, storage time, radial location in the stem or growth site type. The glycosidic bond in (+)-catechin-7-O-β-D-xylopyranoside, sucrose, maltose and raffinose was hydrolysed with kiln drying, resulting in elevated contents of the monosaccharides, D(+)-xylose, D(−)-fructose, D(+)-glucose, in kiln dried boards. Surprisingly, the content of (+)-catechin did not increase simultaneously with the breakdown of (+)-catechin-7-O-β-D-xylopyranoside, indicating that (+)-catechin may polymerise or have another bonding pattern with other wood components due to elevated temperatures during kiln drying. In addition, the relative amount of phenolic compounds, (+)-catechin monomer and its glycoside, (+)-catechin-7-O-β-D-xylopyranoside, in the methanol extracts decreased with partial vacuum drying.

Modification of phenol–formaldehyde resol resins by lignin, starch, and urea

Spatially resolved NMR Imaging techniques have been applied in the study of the three-dimensional structure of aluminum oxide catalyst spheres, since the possible heterogeneities have been found to affect strongly the performance of porous materials as catalysts or catalyst carriers. A special form of activated alumina suitable for Claus catalytic converters was studied. The catalyst spheres were found to exhibit a uniform ball structure with spherically layered structures and voids, ensuring for example optimum flow conditions through the converters.