Effect of autohydrolysis of Eucalyptus globulus wood on lignin structure. Part 2: Influence of autohydrolysis intensity

Holzforschung ◽  
2008 ◽  
Vol 62 (6) ◽  
Author(s):  
Moritz Leschinsky ◽  
Gerhard Zuckerstätter ◽  
Hedda K. Weber ◽  
Rudolf Patt ◽  
Herbert Sixta
Keyword(s):  
Molecular Weight ◽  
Eucalyptus Globulus ◽  
Condensation Reaction ◽  
Insoluble Fraction ◽  
High Reactivity ◽  
Reactor Wall ◽  
Hydroxyl Groups ◽  
Wood Residue ◽  
Fragmentation Reactions ◽  
P Factor

Abstract Three different levels of autohydrolysis intensity, expressed as the prehydrolysis (P)-factor, were applied to Eucalyptus globulus wood at a liquor/wood ratio of 5:1. Lignin fractions were isolated from the wood residue as milled wood lignin (MWL), from the hydrolysate by centrifugation (insoluble fraction) and by ethyl acetate extraction (soluble fraction), and from the reactor wall as precipitate. With increasing autohydrolysis duration, a decrease in the content of aliphatic hydroxyl groups and of β-O-4 structures was detected in all lignin fractions, whereas the content of phenolic hydroxyl groups increased in the same order. MWL isolated from wood residue after autohydrolysis at the highest P-factor contained only half the β-O-4 structures contained in native lignin. Molecular weight distribution measurements revealed that fragmentation reactions dominated over condensation reactions in all lignin samples investigated. However, low-molecular-weight lignin dissolved in autohydrolysate exhibited extremely high reactivity towards acid-catalysed condensation reaction, which inevitably leads to the formation of sticky precipitates during storage at elevated temperature under the acid conditions prevailing.

Effect of autohydrolysis of Eucalyptus globulus wood on lignin structure. Part 1: Comparison of different lignin fractions formed during water prehydrolysis

Holzforschung ◽  
2008 ◽  
Vol 62 (6) ◽  
Author(s):  
Moritz Leschinsky ◽  
Gerhard Zuckerstätter ◽  
Hedda K. Weber ◽  
Rudolf Patt ◽  
Herbert Sixta
Keyword(s):  
Nmr Spectroscopy ◽  
Eucalyptus Globulus ◽  
Lignin Degradation ◽  
Degradation Products ◽  
Chemical Properties ◽  
Size Exclusion ◽  
Strong Increase ◽  
Hydroxyl Groups ◽  
Aryl Ether ◽  
Wood Residue

Abstract The effect of autohydrolysis of Eucalyptus globulus wood was studied with regard to conditions applied in a prehydrolysis-kraft process on the physico-chemical properties of lignin obtained in both the wood residue and hydrolysate. As a reference, milled wood lignin (MWL) was isolated from native wood and compared to three lignin fractions formed during prehydrolysis: 1) lignin from the wood residue isolated as MWL, 2) lignin precipitated from the prehydrolysate during cooling and separated by centrifugation, and 3) lignin degradation products soluble in the prehydrolysate extracted with ethylacetate. All lignin fractions were subjected to Fourier transform infrared (FTIR) spectroscopy, methoxy group determination, elemental analysis, size exclusion chromatography and quantitative nuclear magnetic resonance (NMR) spectroscopy. The results indicate that extensive lignin degradation occurs during prehydrolysis through homolytic cleavage of the aryl-ether bonds resulting in a substantial molecular weight loss of the residual lignin in the treated wood and in the lignin fractions isolated from the prehydrolysate. The aryl-ether cleavage is coupled with a strong increase in phenolic hydroxyl groups and a decrease in aliphatic hydroxyl groups. Indication for condensation reactions were found by NMR spectroscopy.

Fractionation and characterization of lignin-carbohydrate complexes (LCCs) of Eucalyptus globulus in residues left after MWL isolation. Part II: Analyses of xylan-lignin fraction (X-L)

Holzforschung ◽  
2013 ◽  
Vol 67 (6) ◽  
pp. 629-642 ◽  
Author(s):  
Yasuyuki Miyagawa ◽  
Hiroshi Kamitakahara ◽  
Toshiyuki Takano
Keyword(s):  
Eucalyptus Globulus ◽  
Quantum Coherence ◽  
Soluble Fraction ◽  
Insoluble Fraction ◽  
Wood Residue ◽  
Lignin Fraction ◽  
Nuclear Magnetic Resonance Spectra ◽  
Carbohydrate Complex ◽  
Acetic Acid Lignin

Abstract The residual wood meal left after milled wood lignin (MWL) isolation [milled wood residue (MWR)] of 5-year-old Eucalyptus globulus was fractionated to afford a xylan-lignin fraction (X-L) in 2.9% yield (based on MWR) by the method reported previously. X-L was further fractionated with the lignin solvent 1,4-dioxane/water (9:1, v/v) to give a soluble fraction (XL-F1; 24.0%) and an insoluble fraction (XL-F1-residue; 74.6%; both yields based on X-L). XL-F1-residue was further extracted with the good xylan solvent dimethyl sulfoxide and the soluble fraction was termed XL-F2 (43.0%; based on the XL-F1-residue). XL-F1 was mainly composed of lignin with a small amount of xylan and it is similar to purified MWL, whereas XL-F2 was mainly composed of xylan with some amount of lignin and it is similar to a fraction that was prepared by the extraction of crude MWL with acetic acid [lignin-carbohydrate complex (LCC)-AcOH]. The two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectra of XL-F1 and XL-F2 were interpreted that the former has α-ether-type lignin-carbohydrate (LC) linkages and the latter might have LC linkages of the phenyl glycoside type, which are different from those in LCC-AcOH.

Composition of low molecular weight impurities in dimethylmethylpheylsiloxane rubbers with terminal hydroxyl groups

2020 ◽  
Vol 86 (11) ◽  
pp. 20-27
Author(s):  
A. M. Filippov ◽  
N. Yu. Semenkova ◽  
S. M. Gorelov ◽  
T. I. Shulyatieva ◽  
P. A. Storozhenko
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight ◽  
Hydroxyl Groups

scholarly journals High molecular weight SOA formation during limonene ozonolysis: insights from ultrahigh-resolution FT-ICR mass spectrometry characterization

2012 ◽  
Vol 12 (1) ◽  
pp. 2167-2197
Author(s):  
S. Kundu ◽  
R. Fisseha ◽  
A. L. Putman ◽  
T. A. Rahn ◽  
L. R. Mazzoleni
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Homologous Series ◽  
Condensation Reaction ◽  
Reaction Pathways ◽  
Ultrahigh Resolution ◽  
Group Iii ◽  
Group Ii ◽  
Ft Icr

Abstract. The detailed molecular composition of secondary organic aerosols (SOA) from limonene ozonolysis was studied using ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. High molecular weight (MW) compounds (m/z > 300) were found to constitute a significant number fraction of the identified SOA components. Double bond equivalents (DBE = the number of rings plus the number of double bonds) increased with MW. The O:C ratios and relative abundances of compounds decreased with increasing MW. The mass spectra of limonene contain 4 distinct clusters of negative ions: Group I (140 < m/z < 300), Group II (300 < m/z < 500), Group III (500 < m/z < 700) and Group IV (700 < m/z < 850). A number of CH2 and O homologous series of low MW SOA (Group 1) with carbon number 7–15 and oxygen number 3–9 were observed. Their occurrence can be explained with isomerization and elimination reactions of Criegee radicals, reactions between alkyl peroxy radicals, and scission of alkoxy radicals resulting from the Criegee radicals. Additionally, fragmentation analysis and observations of formaldehyde homologous series provide evidence for aerosol growth by the reactive uptake of generated gas-phase carbonyls in limonene ozonolysis. The decreasing O:C ratios between group of compounds indicated the importance of condensation (aldol and esterification) reaction pathways for high MW compound formation. However, the prominent DBE changes of 2 between the groups of compounds and selected fragmentation (MS/MS) analysis of Group II and Group III ions indicated a predominance of non-condensation (hydroperoxide, Criegee and hemi-acetal) reaction pathways. A reaction matrix created with the combination of low MW SOA, hydroperoxides, and Criegee radicals indicated higher frequencies for the hemi-acetal and condensation reaction pathways. Overall, the combined approach confirms the importance of non-condensation reaction pathways over condensation reaction pathways. Among the non-condensation reaction pathways, hemi-acetal reactions appear to be most dominant followed by hydroperoxide and Criegee reactions.

NANOCELLULOSE AND ITS POTENTIAL USE FOR SUSTAINABLE INDUSTRIAL APPLICATIONS

2020 ◽  
Vol 50 (2) ◽  
pp. 59-64
Author(s):  
Carlos Negro ◽  
Ana Balea Martín ◽  
Jose Luis Sanchez-Salvador ◽  
Cristina Campano ◽  
Elena Fuente ◽  
...  
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Industrial Applications ◽  
High Reactivity ◽  
Environmental Benefits ◽  
Hydroxyl Groups ◽  
Paper Briefly ◽  
Potential Availability ◽  
Potential Use ◽  
Market Perspective

Nanocellulose (NC) and its wide applications have attracted high attention due to its desirable properties such as high surface area, extraordinary mechanical properties, high reactivity and easy modification of NC surface due to the presence of primary hydroxyl groups. NC also presents several environmental benefits, including high potential availability because its production is coming from natural sources, renewability and nontoxicity. This paper briefly summarizes some of the activities of the research group “Cellulose, Paper and Water Advanced Treatments” from Complutense University of Madrid that were presented in CAIQ 2019, including the main types of NC, the production processes and their characterization. Additionally, the most promising NC applications are described such as for paper and board, for wastewater treatment, food and cement-based materials. Moreover, a market perspective of NC is also presented.

Fractionation of Rubber

1941 ◽  
Vol 14 (1) ◽  
pp. 1-14 ◽  
Author(s):  
George F. Bloomfield ◽  
Ernest Harold Farmer
Keyword(s):  
Molecular Weight ◽  
Soluble Fraction ◽  
Insoluble Fraction ◽  
The Other ◽  
Major Fraction ◽  
Low Concentrations ◽  
Fractional Dissolution ◽  
Judicious Choice ◽  
Hydrocarbon Molecules ◽  
Soluble Fractions

Abstract Latex rubber which has been purified to the point at which it contains an insignificant amount of nitrogen can be separated by fractional dissolution in a mixture of petroleum and acetone into a series of hydrocarbon fractions of decreasing solubility and increasing molecular magnitude. All these fractions except the highest are soluble in petroleum and in benzene. Crepe rubber, on the other hand, appears invariably to contain a small, most-soluble fraction of oxygenated rubber, and a small similar quite insoluble fraction of material of high molecular weight. Between these extremes the rubber can be divided into fractions of increasing molecular weight, although, up to the present, about 70 per cent of the total rubber has appeared in a single fraction. It may be possible later, by judicious choice of another pair of solvents, to resolve this major fraction into a series of subfractions. Kemp and Peters refer to the effect of polar nonsolvents in reducing the viscosity of rubber solutions and also in assisting to bring gel rubber into solution, phenomena to which the polar molecules conceivably contribute by countering the forces of association between the rubber molecules. The present series of fractionations was conducted throughout in the presence of a polar nonsolvent (acetone), and hence may be considered to approach towards a separation of true rubber molecules as distinct from molecular aggregates. It is found, however, that, whereas the more soluble fractions of acetone-extracted crepe rubber contain small proportions of nitrogen, the least soluble fractions contain substantial proportions. Any effect which the nitrogenous material may have in assisting to link together hydrocarbon molecules to which it is attached, i. e., in contributing to the high-molecular condition of a portion of natural rubber, remains at present uncertain in character. The fractions of rubber, and especially the higher ones, show a strong tendency to become insoluble when they have once been freed from the last traces of solvent. It seems doubtful whether the decreased solubility is due to oxygen as it would require to be effective at exceedingly low concentrations.

STUDIES ON LIGNIN AND RELATED COMPOUNDS: XVI. PHENOL LIGNIN FROM SPRUCE WOOD, FROM FREUDENBERG SPRUCE LIGNIN AND WILLSTÄTTER SPRUCE LIGNIN

1935 ◽  
Vol 13b (2) ◽  
pp. 61-77 ◽  
Author(s):  
Irene Koerber Buckland ◽  
Fritz Brauns ◽  
Harold Hibbert
Keyword(s):  
Condensation Product ◽  
Analytical Data ◽  
Insoluble Fraction ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Condensation Products ◽  
Building Unit ◽  
Spruce Wood ◽  
Analytical Results ◽  
The Difference

The condensation of lignin with phenol by treatment of spruce wood meal with this solvent, using hydrogen chloride as catalyst, yields two chemically different phenol lignins, namely, an ether-insoluble and an ether-dioxane–soluble phenol lignin, in a ratio of approximately 3 to 1. Duplicate preparations gave the same yields of these two fractions, analyses of which gave concordant results, indicating homogeneity and constancy of composition.The analytical results of the ether-insoluble phenol lignin, and of its methylated and acetylated derivatives, can be interpreted on the basis of the Brauns–Hibbert formula for the "native" lignin unit. It is found, in this way, that the ether-insoluble phenol lignin contains three new free phenolic hydroxyl groups capable of methylation with diazomethane, while one phenol group has reacted with one hydroxyl group in the lignin unit with formation of a phenyl-oxygen ether linkage.The analytical results of the ether-dioxane–soluble phenol lignin indicate that a much larger quantity of phenol has condensed with the "native" lignin building unit than in the case of the ether-insoluble fraction. The exact number of phenol molecules reacting to form this condensation product has not been determined experimentally although calculations based on analytical data point to a number as large as 15 or 21.The phenol condensation products were obtained from Freudenberg and Willstätter lignins in nearly quantitative yield and found to differ from the directly extracted phenol lignin in that neither of them could be resolved into two fractions, thus indicating that some change had taken place in the native lignin during the isolation process. The Brauns-Hibbert formula can also be applied to interpret the experimental data in both cases. These lignins appear to contain the same fundamental building unit as the ether-insoluble phenol lignin fraction isolated directly from spruce wood, with the difference that the former probably have one additional hydroxyl group capable of acetylation and diazomethane-methylation.The correlation found to exist in the present investigation between the phenol condensation products from native spruce lignin, isolated Freudenberg lignin and Willstätter lignin is regarded as providing definite experimental evidence indicating the presence of a chemical unit common to various lignins. The phenol condensation products, it is considered, may serve as valuable reference compounds for proving the identity of lignins obtained from different sources and by use of different chemical reagents.

The Chemistry of Phenol-Formaldehyde Resin Vulcanization of EPDM: Part I. Evidence for Methylene Crosslinks

1995 ◽  
Vol 68 (5) ◽  
pp. 717-727 ◽  
Author(s):  
Martin van Duin ◽  
Aniko Souphanthong
Keyword(s):  
Molecular Weight ◽  
Phenol Formaldehyde ◽  
Polymer System ◽  
Phenol Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Low Molecular Weight ◽  
Hydroxyl Groups ◽  
Reaction Products ◽  
Cure Reaction ◽  
Weight Model

Abstract The application of phenol-formaldehyde resins as crosslinking agents is increasing in importance due to the good high temperature properties of the corresponding vulcanizate and the use in thermoplastic vulcanizates. With respect to the chemistry of phenol-formaldehyde cure (reaction mechanism and structure of crosslink) there are still problems that have to be resolved. The reaction products of the phenol-formaldehyde resin curing of EPDM, contain 2-ethylidene norbornene (ENB) as the third monomer, have been studied. Since such an investigation is rather difficult to perform for the polymer system, a low molecular weight model for EPDM was used: 2-ethylidene norbornane (ENBH). Reaction of ENBH and a resole results in scission of the dimethylene ether bridges, i.e. in degradation of the resole into mono-, bis- and terisooctylphenol units. These are consequently converted into products, consisting of two ENBH molecules linked by mono-, bis- and terisooctylphenol units. The solid resole seems to be a technological solution for storing phenol in combination with formaldehyde. These results support the use of 2-hydroxymethylphenol (HMP) as a low molecular weight model for the resole. At low temperatures and/or short reaction times HMP oligomers (= resoles) and HMP oligomers linked to one ENBH molecule are formed, which are converted into ENBH/HMP (1:1) condensation products. The reaction products of ENBH with both the resole and HMP are shown to contain methylene linked structures, as demonstrated by the formation of monisooctylphenol crosslinks and the presence of residual unsaturation and hydroxyl groups, besides chroman linked structures. This is the first experimental evidence that during phenol-formaldehyde resin cure of rubber, formation of methylene bridges occurs.

Effects of Hydroxyl Groups Versus Physical Entanglements on the Electrospinning Behavior of Wheat Protein

2007 ◽  
Vol 1 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Dara L. Woerdeman ◽  
Suresh Shenoy ◽  
Dee Breger
Keyword(s):  
Molecular Weight ◽  
Protein Interactions ◽  
Vinyl Alcohol ◽  
Wheat Gluten ◽  
Fiber Formation ◽  
Poly Vinyl Alcohol ◽  
Hydroxyl Groups ◽  
Scanning Electron Micrographs ◽  
Gluten Protein ◽  
Chain Entanglements

The present work investigates the effects of hydroxyl end groups on the electrospinning behavior of wheat gluten protein. We focus upon the impact of both a low molecular weight additive (a star-branched polyol: ethoxylated trimethylolpropane) and a high molecular weight additive (a synthetic biodegradable polymer: poly(vinyl alcohol) on the ability to form electrospun fibers from wheat gluten. The presence of the star-branched polyol in the system appears to impede the formation of molecular entanglements and intermolecular disulfide bridges required for fiber formation, while the addition of poly(vinyl alcohol) (PVOH) to the system leads to a significant increase in the overall number of physical chain entanglements required for fiber formation. The mechanical testing data support the overriding importance of physical chain entanglements as larger amounts of PVOH are combined with wheat gluten. The tensile strength of the wheat gluten-based electrospun fibrous mats, which, increased by an order of magnitude upon adding 13% (w/w) PVOH to the electrospinning solution, resulted in a rapid increase in the measured toughness at 26% (w/w) PVOH. The corresponding scanning electron micrographs reveal that the addition of PVOH to the gluten system results in the formation of flat, ribbonlike fibers. Dough mixograms were also collected to further elucidate the effect of additional hydroxyl groups on the interactions between the gluten protein chains. Evidence reveals that in the high-concentration, doughy regime, a small fraction of the protein–water interactions are replaced by favorable polyol–protein interactions; however, in the dilute-concentration regime, these favorable polyol–protein interactions appear to develop at the expense of disulfide bond formation, a requirement for obtaining fibers via electrospinning.

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