Lignin In Liquor Research Articles

BEHAVIOR OF EUCALYPTUS GLOBULUS LIGNIN DURING KRAFT PULPING. I. ANALYSIS BY CHEMICAL DEGRADATION METHODS

ABSTRACT Eucalyptus globulus wood was subjected to kraft pulping, reaching different extents of delignification. The residual and dissolved lignins were isolated by soft acidolysis and acidic precipitation, respectively, and submitted to analysis of residual sugars and methoxyl groups, as well as to analysis by nitrobenzene and permanganate oxidation and thioacidolysis. Results from both residual and dissolved lignins analyses indicated that in the initial phase of pulping there is a preferential removal of lignin enriched in guaiacylpropane (G) and p-hydroxyphenylpropane (H) units, which is highly condensed and bonded with polysaccharides, predominantly with xylan. During the bulk and residual phases of pulping, lignin enriched in syringylpropane (S) units is progressively removed, leading to the increase of S/G ratio of black liquor lignin. After a purification step of dissolved lignins, two fractions with distinct levels of carbohydrates and with different structural features were obtained. The overall results were interpreted in terms of the topochemistry of the kraft pulping process.

Application of Solid-State 13C NMR Spectroscopy and Dipolar Dephasing Technique to Determine the Extent of Condensation in Technical Lignins

Solid-state 13C NMR spectroscopy and dipolar dephasing technique was used to determine the extent of condensation in various technical lignins. The accuracy of dipolar dephasing method was first investigated with the aid of some lignin model compounds and two various methods to determine the degree of condensation were compared. On the basis of the model compound experiments both methods based on dipolar dephasing technique can be applied to investigate the extent of condensation in lignin. The lignin results indicate that technical softwood lignins, as well as enzymatically isolated wood lignin, are more condensed than milled wood lignin, which is generally assumed to represent native lignin. Residual lignins isolated after oxygen delignification and peroxide bleaching stages were found more condensed than residual lignin in unbleached pulps. In studies of the spent liquor lignins of flow-through kraft pulping the extent of condensation was found to increase as the cooking proceeded.

Fenton's reagent-mediated degradation of residual Kraft black liquor.

In this work, the effect of Fenton's reagent on the degradation of residual Kraft black liquor was investigated. The effect of Fenton's reagent on the black liquor degradation was dependent on the concentration of H2O2. At low concentrations (5 and 15 mM) of H2O2, Fenton's reagent caused the degradation of phenolic groups (6.8 and 44.8%, respectively), the reduction of reaction medium pH (18.2%), and the polymerization of black liquor lignin. At a high concentration (60 mM) of H2O2, Fenton's reagent induced an extensive degradation of lignin (95-100%) and discoloration of the black liquor. In the presence of traces of iron, the addition of H2O2 alone induced mainly lignin fragmentation. In conclusion, Fenton's reagent and H2O2 alone can degrade residual Kraft black liquor under acidic conditions at room temperature.

Monitoring of Lignin and Hemicelluloses in Spent Cooking Liquor during Kraft Delignification

Summary A direct and rapid method for determining the average molecular weight (MW) and content of lignin and hemicelluloses in spent cooking liquor by high performance size-exclusion chromatography (HPSEC) using a cartridge glass column and 2.5 mM NaOH as an eluent was developed. A Uv290 detector in line with a RI detector was applied to characterise lignin and hemicelluloses, respectively, from liquor during the kraft cooking of grey and black alder wood. During the main delignification stage, the concentration of high-MW wood components in liquor changed through the maximum. The MW values of hemicelluloses in the liquor decreased to DPn = 30 ± 5 and DPw = 55 ± 5. The M̄ n and M̄ w of lignin in spent kraft cooking liquor during the main and final delignification stages did not exceed 3000 and 5000, respectively.

Polyelectrolyte precipitate formation during miscible displacement in porous media

AbstractThe miscible displacement of aqueous lignin solutions (model black liquor) by water from beds formed from glass beads was studied as a function of the presence of cationic polymer in the wash water, bed structure, lignin concentration, and superficial flow rate. The displacement behaviors in homogeneous beds formed from fine beads (121 μm) were compared with results of experiments using a channel bed consisting of a bed formed from fine beads surrounding a channel of coarse beads (638 μm) running the length of the bed in the flow direction. Washing efficiencies, defined as the fraction of lignin removed when one pore volume of eluate was collected, were 84–93% for homogeneous beds washed with water compared with 31–33% for the channel bed; the range in efficiencies reflects the influence of other variables. The presence of cationic polymer in the wash water enhanced the washing efficiency by 1.7 to 2 times with a corresponding 20 to 35% decrease in the permeability of the central channel in the channel bed. The improved washing with polymer was due to selective plugging of the central channel with precipitate formed from complex formation between anionic lignin in the black liquor and the cationic polymer. Breakthrough curves obtained from 12 microconductivity probes located throughout the bed showed that mixing of lignin in the black liquor and the cationic polymer. Breakthrough curves obtained from 12 microconductivity probes located throughout the bed showed that mixing of lignin solution (high conductivity) with wash water (low conductivity) in the displacement front, as expressed by a mixing length, was a maximum in the coarse bead channel and was decreased when the wash water contained cationic polymer.

Determination of Carboxyl and Non-Conjugated Carbonyl Groups in Dissolved and Residual Lignins by IR Spectroscopy

FTIR spectroscopy is a well known method for elucidating the structures of lignin samples. Determination of the ratio between the content of C=O groups and aromatic structures in lignin samples is an important aid to monitoring the degree of delignification during different pulping and bleaching procedures. In the present work a semiquantitative method is described in which calibration mixtures with eight different ratios of tartaric acid to milled wood lignin are prepared in order to account for the different responses of the aromatic band at 1510cm -1 and the C=O band at 1740cm -1 . From the calibration function obtained it is possible to calculate the results in mmoles of C=O/g aromatic lignin. The method is tested on residual lignins and spent liquor lignins from pulps with different degrees of delignification.

Continuous on-line determination of the concentrations of dissolved lignin and hydrogen sulfide ions in kraft cooking liquors

Article Continuous on-line determination of the concentrations of dissolved lignin and hydrogen sulfide ions in kraft cooking liquors was published on December 1, 1996 in the journal Nordic Pulp & Paper Research Journal (volume 11, issue 4).

Lignin Removal During Kraft Pulping. An Investigation by Thioacidolysis

A series of Pinus radiata kraft pulps with yields between 96% and 47% were prepared and examined by thioacidolysis. The levels of uncondensed β-ether units in the residual pulp lignins dropped almost linearly with the decreasing lignin content of the pulp. The drop in the levels of uncondensed β-ether units in the spent liquor lignins was much less rapid than in the fibre lignin. Enol ether units were formed in the dissolved lignin during the bulk phase of cooking, and also to a small extent in the residual fibre lignin (...)

The thermal behaviour of lignins from wasted black pulping liquors

The thermal degradation of lignins separated from black liquor waste from pulping of bagasse and cotton stalks has been investigated. Thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and derivative thermogravimetry (DTG), between 20 and 1000°C, have been used. Activation energies of treated lignins were calculated. Lignins separated from liquors obtained at low pulping temperature have higher activation energies than high-temperature lignins. The use of anthraquinone (AQ) as an additive for accelerating the pulping process raises the activation energy of the lignin in the black liquors waste.

Utilization of complex phenolic compounds by Acinetobacter sp.

Acinetobacter sp. utilized the [ring-14C]dehydropolymer of coniferyl alcohol (DHP) (sp. act. 1.4 × 104 dpm/mg), 14C-labelled teakwood lignin (sp. act. 2.5 × 104 dpm/mg), guaiacolglyceryl ether, 2-methoxy-4-formylphenoxyacetic acid, p-benzyloxyphenol, dehydrodivanillyl alcohol, dehydrodiisoeugenol, veratrylglycerol-β-guaiacyl ether, conidendrin, black liquor lignin and indulin as sole carbon sources. The bacterium produced p-coumaric acid, p-hydroxybenzoic acid, vanillic acid, protocatechuic acid and catechol as intermediates from lignins. Acinetobacter sp. produced catechol 1,2-dioxygenase and protocatechuate 3,4-dioxygenase during the degradation of lignins.

Degradation of Black Liquor Lignin by Microorganisms

On etudie la degradation de la lignine residuelle dans les lessives noires de papeterie a l'aide de diverses souches bacteriennes

クラフトパルプ廃液の電解酸化処理

As an effective treatment of waste liquor from the kraft pulping process, its electrolytic oxidation has been attempted. The waste liquor used in electrolytic experiment was diluted to a concentration of about 1%. The reactivity of lignin in the waste liquor was estimated from the oxidative reaction of the purified thiolignin. To examine the oxidating ability of electrode, platinum, stainless steel and lead-dioxide plates were used as the electrode. The values of COD and absorbances at 280 and 500 nm of the waste liquor after the electrolysis decreased according to the following order of electrodes : lead dioxide stainless steel platinum. From this result, using the lead-dioxide electrode, the controlled-current electrolysis was made at 300 and 600 mA in the range of 10 to 80°C.The effect of electrolytic oxidation on the waste liquor was evaluted by measurements of COD and absorbance of the liquor. The high current density was effective for the treatment of the waste liquor at temperatures above 60°C, whereas the low current density was effective at temperatures below 30°C. The most satisfactory result was obtained at 60°C and 600 mA.

Aqueous size exclusion chomatography of industrial lignins

Aqueous size exclusion chromatography of lignin in effuents from the pulp industry was studied using several mobile phases at pH 8.9–12.0 and an organic semi-rigid high-performance gel (TSK PW type). The calibration and resolution calculations were based on the elution of sodium polystyrenesulphonates. The plate counts nad plate heights of the columns were also determined. The best results were obtained by using as eluent a low-ionic-strength bicarbonate buffer, pH 10.5, with addition of polyethylene glycol. Molecular weights obtained for spent bleaching liquor lignins and lignosulphonate were compared with results obtained with other chromatographic systems. The distribution curves were symmetrical and narrow. The chromatograms of spent E1-stage bleaching liquor obtained with system described and with a Bio-Gel P-60 column were very similar, but differed markedly from the obtained with a Sephadex LH-60 column.

Studies on the Na Xylensulfonate Cooking and Peracetic Acid Bleaching by Adjustment of pH

This work was undertaken in order to investigate the effect of pH at NaXS (Na Xylensulfonate) cooking and PA (peracetic acid) bleaching.After the NaXS cooking of beech chips, pH of the waste liquor showed about 4. When the waste liquor were used repeatedly at the next cooking, pH drops remarkably. Thus, pH of the cooking liquor become about 3 after 5 recyclings, and pulp are also degraded and lost.In order to avoid to decrease pulp yields and viscosity, the cooking liquor must be adjusted about pH 7 by NaOH. Beech chips that were cooked by NaXS contain much lignin. The elimination of lignin from NaXS pulps by washing is ineffective, because soluble lignin in waste liquor become insoluble solid. But, it removed easily by NaOH extraction, and K-value of NaXS pulp reduced.In PA bleaching of NaXS pulp, pulp are degraded at about pH 2 and viscosity goes down. At about pH 4, however, the degradation of pulp is slightly. It has been found from above results that pH of the cooking liquor and the bleach liquor is one of important factors to control pulp quality.

Preparation of Vanillin from Sulphite Waste Liquor. Part. 1

Oxidation process of sulphite waste Liquor to produce vanillin has been investigated about four samples, which were produced from Pinus densiflora Sieb. et Zucc. through various degree of cooking. The oxidation was carried out at a temperature range of 80 to 170°C and under the normal as well as a high pressure.Sulphite waste liquor, in which the concentration of cuastic soda was controlled to be 8 g per 75 cc, was brought into an autoclave, into which oxygen was introduced under a pressure of 10 atm., and heated at a temperature of 170°C. for three hours under rotation. The yield of vanillin thus obtained was 19.4 per cent with respect to the amounts of lignin in the waste liquor used. The later was about 5g per 75cc of it.Next, the whole process was divided into two steps, one is heating process and the other oxidation process, and the waste liquor is subjected to this two processes one after another, Thus waste liquor in the autoclave, into which oxygen was introduced under a pressure of 10 atm., was caused to be oxidized at a temperature of 90 to 95°C under catalytic action of nickel gauze and then heated at a temperature of 170°C after oxygen was removed. The yield of vanillin obtained by this method was 12.65 per cent. On the other hand, the yield of vanillin was 9.3 per cent when waste liquor was firstly heated at a temperature of 150°C for half an hour and then, as the second step, oxidized at a temperature of 100°C in the presence of cupper wire as a catalyst by introducing oxygen under the normal pressure. The same result was also attained when the first heating process was carried out at a temperature of 170°C for five minutes and was followed by the same treatment as above. However, the yield was about 7 per cent when the first heating process at a temperature of 150°C was followed by the oxidation process by cupric oxide at a temperature of 90°C under a normal pressure. In oder to keep effective contact of oxygen with the reaction solution, a new design of apparatus for oxidation process by oxygen was deviced, which might be very interesnitgf rom the industrial point of view. Nickel and cupper proved to be superior catalysts for oxidation by oxygen.The yield of vanillin obtained from sulphite waste liquor which had been produced through lower degree of cooking was larger than that of vanillin from waste liquor produced through higher degree of cooking. This suggests the facts that the degree of cooking of pulp has influence on the yield of vanillin prepared from waste liquor of it.When Tomlinson-Hibbert's method was applied to the sulphite waste liquor employed in this investigation, the yield of vanillin was only 1.5 per cent.