Lignin oxidation mechanisms under oxygen delignification conditions. Part 2: Advanced methods for the detailed characterization of lignin oxidation mechanisms

Holzforschung ◽  
2011 ◽  
Vol 65 (4) ◽  
Author(s):  
Stella Rovio ◽  
Susanna Kuitunen ◽  
Taina Ohra-aho ◽  
Sami Alakurtti ◽  
Anna Kalliola ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Degradation Products ◽  
Hydroxyl Groups ◽  
Reaction Products ◽  
Oxygen Delignification ◽  
Additional Information ◽  
Lignin Oxidation ◽  
Advanced Analysis ◽  
Lignin Macromolecule ◽  
Oxidation Mechanisms

Abstract Advanced analysis methods have been developed to follow the reactions of lignin during alkaline oxygen delignification conditions more comprehensively than before. This aim was attained by monitoring both the lignin macromolecule and the dissolved reaction products. Softwood (SW) and hardwood (HW) kraft spent liquor lignins were studied as substrates under various reaction conditions. The decrease in the contents of different types of free phenolic hydroxyl groups and the concurrent formation of carboxylic acids was followed by 31P NMR of the phosphitylated products. In addition, the formation of acidic degradation products with low molecular weight was determined by capillary zone electrophoresis (CE). This way, it was possible to distinguish the carboxylic acids bound to the lignin macromolecule from the cleaved reaction products, even if they partly co-precipitated during sample preparation. Peak deconvolution was applied to get information on syringyl type phenolic structures and on C(5) condensed guaiacyl structures in hardwood lignin. Pyrolysis-GC/MS was applied to provide additional information about the distribution of guaiacyl/syringyl/p-hydroxyphenyl (G/S/H) type lignin subunits, as well as changes in the phenylpropane side chain.

Lignin Degradation in Oxygen Delignification Catalysed by [PMo7V5O40]8- Polyanion. Part II. Study on Lignin Monomeric Model Compounds

Holzforschung ◽  
2000 ◽  
Vol 54 (5) ◽  
pp. 511-518 ◽  
Author(s):  
D.V. Evtuguin ◽  
C. Pascoal Neto ◽  
H. Carapuça ◽  
J. Soares
Keyword(s):  
Reaction System ◽  
Veratryl Alcohol ◽  
Vanillyl Alcohol ◽  
Coupling Reactions ◽  
Reaction Products ◽  
Oxygen Delignification ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Oxidation ◽  
Lignin Model

Summary Vanillyl and veratryl alcohols were used as monomeric lignin model compounds in experiments aiming to enhance the understanding of the lignin oxidation mechanisms involved in the oxygen delignification in acidic media catalysed by [PMo7V5O40]8− (HPA-5) heteropolyanion. Based on the model compound experiments, the first step of lignin oxidation is suggested to be a one-electron oxidation by the catalyst. This step is followed by coupling reactions and/or by further oxidation by the catalyst. The ratio of coupling/oxidation reaction products depends on the oxidation conditions and decreases with temperature raise. The higher oxidation rate of vanillyl alcohol as compared to the veratryl alcohol in the reaction system O2/HPA-5 was explained by the redox properties of the catalyst. The insufficiently high redox potential of HPA-5 did not allow the efficient oxidation of veratryl alcohol. The former was oxidised by VO2 + ions dissociated from the HPA-5 under the acidic conditions. The reactivity of different lignin structural units in the reaction system O2/HPA-5 was estimated by electrochemical methods using various lignin model compounds.

Bleaching ability of pre-hydrolyzed pulps in the context of a biorefinery mill

TAPPI Journal ◽  
2013 ◽  
Vol 12 (11) ◽  
pp. 49-53 ◽  
Author(s):  
CHRISTINE CHIRAT ◽  
LUCIE BOIRON ◽  
DOMINIQUE LACHENAL
Keyword(s):  
Carbon Content ◽  
Acid Hydrolysis ◽  
13C Nmr ◽  
Kraft Lignin ◽  
Kappa Number ◽  
Hydroxyl Groups ◽  
Kraft Pulps ◽  
Quaternary Carbon ◽  
Oxygen Delignification

Autohydrolysis and acid hydrolysis treatments were applied on mixed softwood chips. The cooking ability was studied by varying the alkali and duration of the cook. Pulps with kappa numbers varying from 30 to 70 were obtained. The bleaching ability of these pulps was studied and compared to control kraft pulps. The prehydrolyzed pulps were shown to be more efficiently delignified by oxygen than the control kraft pulps starting from the same kappa number. Furthermore, the final bleaching was also easier for these pulps. It was also shown that extensive oxygen delignification applied on high-kappa pre-hydrolyzed pulps could be a way to improve the overall yield, which is a prerequisite for the development of such biorefinery concepts. Lignin was isolated from the control kraft and the two pre-hydrolyzed kraft pulps and analyzed by 13C NMR. Lignins from pre-hydrolyzed kraft pulps had similar free phenolic groups content to the control kraft lignin, but their aliphatic hydroxyl groups and β-O-4 content were lower than for the control lignin. The quaternary carbon content was the same for all the samples.

Characterization of dissolved material during the initial phase of softwood kraft pulping

TAPPI Journal ◽  
2013 ◽  
Vol 12 (1) ◽  
pp. 37-43 ◽  
Author(s):  
HANNU PAKKANEN ◽  
TEEMU PALOHEIMO ◽  
RAIMO ALÉN
Keyword(s):  
Mass Transfer ◽  
Molecular Mass ◽  
Initial Phase ◽  
Degradation Products ◽  
Kraft Pulping ◽  
Reaction Products ◽  
Cooking Temperature ◽  
Molecular Masses ◽  
Aliphatic Carboxylic Acids

The influence of various cooking parameters, such as effective alkali, cooking temperature, and cooking time on the formation of high molecular mass lignin-derived and low molecular mass carbohydrates-derived (aliphatic carboxylic acids) degradation products, mainly during the initial phase of softwood kraft pulping was studied. In addition, the mass transfer of all of these degradation products was clarified based on their concentrations in the cooking liquor inside and outside of the chips. The results indicated that the degradation of the major hemicellulose component, galactoglucomannan, typically was dependent on temperature, and the maximum degradation amount was about 60%. In addition, about 60 min at 284°F (140°C) was needed for leveling off the concentrations of the characteristic reaction products (3,4-dideoxy-pentonic and glucoisosaccharinic acids) between these cooking liquors. Compared with low molecular mass aliphatic acids, the mass transfer of soluble lignin fragments with much higher molecular masses was clearly slower.

scholarly journals Zn(II) and Ag(I) complexes of N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids and products their proton- and iodocyclization

2019 ◽  
Vol 85 (3) ◽  
pp. 3-19
Author(s):  
Polina Borovyk ◽  
Mariia Litvinchuk ◽  
Anton Bentya ◽  
Svitlana Orysyk ◽  
Yurii Zborovskiy ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Metal Ion ◽  
Polymer Chains ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Polymer Complexes ◽  
Vis Spectroscopy ◽  
Polynuclear Coordination Compounds ◽  
Complexation Reactions ◽  
Oxygen Atoms

The possibility of using N-allylcarbothioamide derivatives as well as products of their iodine- and proton-initiated electrophilic heterocyclizations as chelating agents in complexation reactions with Zn(II) and Ag(I) ions is shown. Processing of the obtained experimental data showed that N-allythioamides of pyrimidinyl (cyclohexenyl) carboxylic acids H2L1 – H2L3 and their proton- and iodo-cyclization products HL4, HL5 containing four nucleophilic reaction centers (two oxygen atoms of the carbonyl and hydroxyl groups and N-, S-carbothioamide groups or N-atoms of the dihydrothiazole moiety) are polydentate ligands capable of coordinating with metal ions to form stable six-membered chelate metallocycles. A series of new chelating mono-, bi- and polynuclear complexes Zn(II) and Ag (I) of the composition [Zn2L1,32]n, [Zn2(HL1-3)2(CH3COO)2], [Ag2(HL1,3)2]n, [Zn(HL1-3)2], [Ag(H2L3)2NO3], [Zn(HL4,5)2], K[Ag(HL4,5)2] were synthesized and isolated in solid state. Their molecular structure was established by methods of elemental chemical analysis, NMR 1H, IR and UV-Vis spectroscopy. At a ratio of M:L 1:2, complexes were isolated in which two ligand molecules H2L1 − H2L3 are coordinated to the metal ion by the sulfur atoms of the carbothioamide group and the oxygen of the mono-deprotonated hydroxyl group. It was established that the products of the proton-/iodocyclization HL4, HL5 in the complex formation pass into the thione tautomeric form with coordination through the oxygen atoms of the deprotonated hydroxyl group and nitrogen atoms of the dihydrothiazole heterocycle. At M:L 1:1, binuclear or polynuclear coordination compounds are formed. It was shown that polymerisation in complexes [Zn2L1,32]n and [Ag2(HL1,3)2]n is due to the formation of Zn−(O2SN)−Zn and Ag−O−Ag polymer chains. Investigation of the solubility of the resulting complexes showed that the polymer complexes are weakly soluble or insoluble in DMSO, DMF, while the mononuclear are soluble in methanol, as well as in water.

scholarly journals Synthesis and biotical activity of bacterial cellulose 6-(2-phthalimidoethanesulfonate)

2020 ◽  
Vol 61 (2) ◽  
pp. 29-36
Author(s):  
Zoya P. Belousova ◽  
Keyword(s):  
Bacterial Cellulose ◽  
Side Reaction ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Cellulose Derivatives ◽  
Wound Surface ◽  
Reaction Products ◽  
Absorption Bands ◽  
Hydroxymethyl Group ◽  
Antibacterial And Antifungal

Bacterial cellulose obtained by culturing Gluconacetobacter sucrofermentans in HS environment was converted to sulfonate derivatives using methane-, toluene- and 2-phthalimidoethanesulfonic acids in pyridine. When the ratio of the starting reagents is 1 : 1, the modification of bacterial cellulose according to the primary hydroxyl group of glucopyranose fragments is most likely. The formation of 6-substituted bacterial cellulose derivatives was observed in the reaction mixture. The IR spectra of the reaction products contain absorption bands, which are specific for (O–SO2) group in the region 1377-1338 cm−1 (as), 1178-1154 cm−1 (s), fragments of the corresponding sulfonic acids, as well as free hydroxyl groups of glucopyranose in the region 3495-3382 cm−1. Bacterial cellulose 2-phthalimidoethanesulfonate was dissolved in pyridine. After drying with a desiccant in a desiccator, it turned into a dense transparent film of brown color. The increased molecular film allows to explain the side reaction occurring between the oxo group and fragments of one of the chains of modified cellulose and the non-substituted hydroxymethyl group. The IR spectrum of bacterial cellulose 6-(2-phthalimidoethanesulfonate) contains absorption bands in the region 1711 cm−1, which are specific for (Ar–CO–O) group, and absorption bands in the region 1618 cm−1, which prove the presence of (CO–NH) group. In order to impart antibiotic properties to the bacterial cellulose 6-(2-phthalimido-ethanesulfonate) film, it was physically modified with clotrimazole. The obtained experimental data showed that the films subjected to treatment with a 1% solution of clotrimazole have antibacterial and antifungal effects and prevent the growth of pathogenic microbiota on the wound surface. The exit rates of clotrimazole from the bacterial cellulose 6-(2-phthalimidoethanesulfonate) film and from the pure bacterial cellulose film differed, but only slightly. 2-Phthalimidoethanesulfonate bacterial cellulose films can be used to form composites of effective wound covering, since in addition to the unique properties of bacterial cellulose itself (low allergenicity and adhesion to the wound surface, high hygroscopicity) they will have a regenerating effect.

scholarly journals Strecker degradation products of aspartic and glutamic acids and their amides

2013 ◽  
Vol 19 (No. 2) ◽  
pp. 41-45 ◽  
Author(s):  
J. Rössner ◽  
J. Velíšek ◽  
F. Pudil ◽  
J. Davídek
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Degradation Products ◽  
Dicarboxylic Acids ◽  
Reaction Products ◽  
Degradation Reactions ◽  
Strecker Aldehydes ◽  
Volatile Products ◽  
Acid Acid

Aspartic and glutamic acids, asparagine and glutamine were oxidised with either potassium peroxodisulphate or glyoxal. Nonvolatile products were derivatised and analysed by GC/FID and GC/MS. Volatile reaction products were isolated and analysed by the same methods. It was found that the degradation reactions of amino acids are complex. Amino acids are principally degraded via the corresponding a-keto acids to Strecker aldehydes (aspartic acid to oxalacetic and 3-oxopropionic acids and glutamic acid to a-ketoglutaric and 4-oxobutyric acids), which are unstable and decomposed by decarboxylation to the corresponding aldehydes. Aspartic acid also eliminates ammonia and yields fumaric acid whereas glutamic acid gives rise to an imine, pyroglutamic acid. A recombination of free radicals leads to dicarboxylic acids (succinic acid from aspartic acid, succinic, glutaric and adipic acids from glutamic acid). The major volatile products (besides the aldehydes) are lower carboxylic acids (acetic acid from aspartic acid and propionic acid acid from glutamic acid) that can at least partly arise by radical reactions. In both quality and quantity terms, a higher amount of degradation products arises by oxidation of amino acids by peroxodisulphate.

scholarly journals The Formation of Glycerol Oligomers with Two New Types of End Groups in the Presence of a Homogeneous Alkaline Catalyst

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 144 ◽  
Author(s):  
Dawid Kansy ◽  
Kornelia Bosowska ◽  
Krystyna Czaja ◽  
Anna Poliwoda
Keyword(s):  
Catalyst Concentration ◽  
Reaction Medium ◽  
Hydroxyl Groups ◽  
Ionization Mass ◽  
Carboxylate Group ◽  
Reaction Products ◽  
Direct Infusion ◽  
Alkaline Catalyst ◽  
End Groups ◽  
First Time

The purpose of this work was to synthesize and characterize oligoglycerols with the chains of more than four repeating units. Those oligoglycerols may have some interesting applications, among others, as polyoxyalkylation starters. The glycerol oligomerization process was carried out during 12 h, at 230 °C, under the pressure of 0.4 bar, with the use of sodium carbonate as a homogeneous basic catalyst; various concentrations of the catalyst in the reaction medium were used. The reaction products were analyzed with the use of direct infusion electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (13C NMR) and Fourier transform infrared spectroscopy (FTIR) techniques. Based on the analytical findings, the compositions of the obtained product mixtures and the structures of oligoglycerols present in individual fractions were determined. The effect of catalyst concentration on the composition of the post-reaction mixture was observed. Moreover, in addition to the conventional linear oligomers (α,α-oligoglycerols), two new types of the oligomers were for the first time detected in the post-reaction mixture: one with two hydroxyl groups and the other with a carboxylate group at the α-carbon atom.

scholarly journals Bacterial Conversion of Hydroxylamino Aromatic Compounds by both Lyase and Mutase Enzymes Involves Intramolecular Transfer of Hydroxyl Groups

2003 ◽  
Vol 69 (5) ◽  
pp. 2786-2793 ◽  
Author(s):  
Lloyd J. Nadeau ◽  
Zhongqi He ◽  
Jim C. Spain
Keyword(s):  
Aromatic Compounds ◽  
Ralstonia Eutropha ◽  
Transfer Mechanism ◽  
Bacterial Degradation ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Reaction Products ◽  
Comamonas Acidovorans ◽  
Label Incorporation ◽  
Intramolecular Transfer

ABSTRACT Hydroxylamino aromatic compounds are converted to either the corresponding aminophenols or protocatechuate during the bacterial degradation of nitroaromatic compounds. The origin of the hydroxyl group of the products could be the substrate itself (intramolecular transfer mechanism) or the solvent water (intermolecular transfer mechanism). The conversion of hydroxylaminobenzene to 2-aminophenol catalyzed by a mutase from Pseudomonas pseudoalcaligenes JS45 proceeds by an intramolecular hydroxyl transfer. The conversions of hydroxylaminobenzene to 2- and 4-aminophenol by a mutase from Ralstonia eutropha JMP134 and to 4-hydroxylaminobenzoate to protocatechuate by a lyase from Comamonas acidovorans NBA-10 and Pseudomonas sp. strain 4NT were proposed, but not experimentally proved, to proceed by the intermolecular transfer mechanism. GC-MS analysis of the reaction products formed in H2 18O did not indicate any 18O-label incorporation during the conversion of hydroxylaminobenzene to 2- and 4-aminophenols catalyzed by the mutase from R. eutropha JMP134. During the conversion of 4-hydroxylaminobenzoate catalyzed by the hydroxylaminolyase from Pseudomonas sp. strain 4NT, only one of the two hydroxyl groups in the product, protocatechuate, was 18O labeled. The other hydroxyl group in the product must have come from the substrate. The mutase in strain JS45 converted 4-hydroxylaminobenzoate to 4-amino-3-hydroxybenzoate, and the lyase in Pseudomonas strain 4NT converted hydroxylaminobenzene to aniline and 2-aminophenol but not to catechol. The results indicate that all three types of enzyme-catalyzed rearrangements of hydroxylamino aromatic compounds proceed via intramolecular transfer of hydroxyl groups.

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.

scholarly journals Intracrystalline biomolecules in Recent and fossil brachiopod shells - the biochemistry of shell coloration

1992 ◽  
Vol 6 ◽  
pp. 59-59
Author(s):  
Heather Clegg ◽  
Gordon B. Curry
Keyword(s):  
Gas Chromatography ◽  
Carboxylic Acids ◽  
High Performance ◽  
Mass Spectra ◽  
Organic Molecules ◽  
Degradation Products ◽  
Polyacrylamide Gel Electrophoresis ◽  
Reference Points ◽  
Gas Chromatography Mass Spectrometry ◽  
Magnesium Calcite

The study of fossil biomolecules requires not only well preserved fossil samples, but abundant Recent material so that reference points can be established. Ideally it would also be possible to study the in situ decay of organic molecules in samples of different geological ages, and hence determine how degradation proceeds with time. The shells of brachiopods fulfill both these criteria, containing up to 1% organic components entombed within their shells, which are composed of highly stable, low magnesium calcite, that survives well in the fossil record for hundreds of millions of years.This particular study has concentrated on Plio-Pleistocene brachiopods from New Zealand. These fossils are the ancestors of living species, and hence it is possible to investigate intracrystalline biomolecules in modern day shells, as well as the degradation products of such biomolecules in fossil shells of the same species.Three of the species investigated have bright red shells in life, and during the study it became clear that this coloration was caused by a carotenoprotein which was embedded within, rather than around, the calcite fibres of the brachiopod shell. Carotenoproteins are composite molecules composed of a protein and a prosthetic carotenoid group. The protein has been characterised by hplc (high performance liquid chromatography) and SDS PAGE (sodium dodecylsulphate polyacrylamide gel electrophoresis), and the amino acids at the N-termini have been sequenced, demonstrating that this is a small protein which has a molecular weight of 6.5 kDa and is identical in all 3 species.At least two different types of carotenoids were detected after initial purification, and these were characterised using direct probe mass spectra, and hplc/mass spectra. Using these techniques the two carotenoids have been tentatively identified as canthaxanthin and the mono acetylenic analogue of asthaxanthin.In addition to the carotenoproteins, the calcite crystals of recent brachiopod shells contain lipids (carboxylic acids) and carbohydrates, which were characterised by gas chromatography (GC) and gas chromatography/mass spectrometry analyses (GC/MS).Fossil brachiopod shells could be distinguished from recent shells due to their lack of unsaturated acids and smaller amounts of carboxylic acids present. However there was no trend of decreasing quantities of fatty acid with increasing age.The presence of organic molecules such as carotenoproteins, lipids and carbohydrates within calcite crystals poses two questions. Firstly, are these compounds merely wastes metabolic products and are deposited within the shell during growth or, secondly, do they play an important role in the process of biomineralisation? At present these questions remain largely unanswered, because at present only the function of the carotenoprotein has been determined from the spectrum of biomolecules present within the shell (and the carotenoprotein may have other functions apart from coloration).

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