Near-Infrared Spectroscopy and Chemometric Analysis for Determining Oxygen Delignification Yield

Abstract

Oxygen delignification studies were carried out using a softwood kraft pulp under varying reaction temperatures (80–140°C) and alkaline charges (1–12%). Near-infrared (NIR) spectroscopy combined with chemometric methods was employed to analyze oxygen delignification pulp yields, which were compared to gravimetric analysis. Principal component analysis (PCA) of the NIR spectra data was performed and a partial least-square (PLS) regression model was developed to predict the pulp yield of oxygen delignified pulps based on the NIR spectra data. PCA analysis indicated that 99.1% of total variances of NIR spectra data in the range of 1100–2266 nm could be expressed by three principle components. A PLS1 model based on the NIR spectra data had good predictive ability and appeared to be an effective tool for pulp yield prediction for the oxygen delignification process.     

Investigation of the Chemistry of Oxygen Delignification of Low Kappa Softwood Kraft Pulp using an Organic/Inorganic Chemical Selectivity System

Abstract

Oxygen delignification (OD) of low kappa softwood kraft pulp was examined in two steps without inter‐stage washing as part of an overall program to evaluate the efficiency of a selectivity enhancement system consisting of phenol and magnesium sulfate. Black liquor carryover in the reaction system did not substantially affect delignification and the selectivity of these OD reactions. The residual lignins from both the original pulp and oxygen‐delignified pulp with and without the phenol/MgSO₄ selectivity enhancement system were prepared and characterized using NMR spectroscopy. The effluent lignins after oxygen delignification were also prepared and characterized. The lignin characterizations provided the basis for the rationalization of the selectivity observed. A significant finding of this study was that the phenol/MgSO₄ system in the oxygen delignification reaction appeared to hinder phenolic guaiacyl unit condensation. It also appeared to enrich the levels of p‐hydroxyphenyls in the residual lignin.     

Characterization of the Residual Kraft Pulp Lignin In Situ by Sulfite Treatments

Abstract

The O₂ delignification of kraft pulps from Norway spruce was shown having a significant impact on the reactivity of the residual pulp lignin as revealed from their responses to sulfite treatments at pH 7.5. A substantial higher ratio of lignin sulfonation to the phenolic hydroxyl group content of residual pulp lignin was observed for the O₂ -delignified kraft pulps (～ 0.8) as compared to a value of ～ 0.3 for the unbleached samples and ～ 1 for the spruce wood lignin. Under the prevailing sulfite treatment conditions, the sulfonation would be largely attributed to the phenolic lignin component and the etherified structures containing an α -carbonyl or -unsaturated group. The contribution from the latter units, evaluated by a borohydride pretreatment of pulps prior to the sulfite treatment, can only account for approximately 15% of the sulfonation observed for the O₂ -delignified sample. Thus, the nature of phenolic structures in the O₂ -delignified pulps was more similar to that of the wood lignin than that of the kraft pulps.     

Soda Pulping of Hardwoods Catalyzed by Anthraquinone and Methyl Substituted Anthraquinones

Abstract

Black liquor gasification (BLG) as well as the recovery of lignin and other organic compounds from pulping black liquor would be aided if an efficient sulfur‐free pulping process could be developed. This has provided new impetus for research on soda pulping with redox catalysts instead of sodium sulfide that is presently used in the kraft process. Soda/anthraquinone (AQ) pulping afforded white birch (Betula papyrifera) and sugar maple (Acer saccharum) pulps with equal if not superior strength to kraft pulps. However, the delignification rate was significantly lower for soda/AQ pulping. When AQ was replaced by 2‐methylanthraquinone (2‐MAQ) a delignification rate only slightly lower than that of kraft pulping was obtained at the same effective alkali (EA). At a kappa number of ～20, a soda/2‐MAQ pulp was produced from sugar maple at a higher yield (1.2% on chips) than for a kraft pulp. 2‐MAQ was synthesized, as a powder, at 75% yield using an AlCl₃–mediated Friedel‐Crafts reaction that is one of the methods used for commercial production of AQ.     

Soda—Oxygen bleaching of kraft bagasse pulp

Soda—oxygen bleaching of commercially available kraft bagasse pulp has been investigated. Alkali charge, temperature and oxygen pressure are important factors in controlling brightness and physical properties of the pulps produced. Pulp yields, lignin and degree of polymerisation of the bleached pulps decreased with increasing alkali charge from 2 to 6%. Strength properties as well as brightness increased by increasing alkali charge at 368 K, whereas optimum strength properties are obtained with 4% alkali at 383 K. In the range of oxygen pressure used, 5–8 kg cm^?2, DP as well as strength properties of the bleached pulps increased with increasing oxygen pressure. Brightness up to 61% was reached by soda-oxygen alone. To obtain higher brightness an afterbleaching step is necessary. The soda—oxygen—hypochlorite and soda—oxygen—chlorite pulps prepared have strength properties comparable with those of conventionally bleached pulps.     

枫香树材硫酸盐浆氧脱木素工艺技术

通过对枫香树材硫酸盐浆氧脱木素用碱量、氧压、温度和时间四因素三水平方差分析工艺技术研究,在用碱量2%～4%、氧压0.3～0.7 MPa、温度90～120℃和时间60～120 min内,得到枫香树材硫酸盐浆氧脱木素较为适宜的工艺条件:用碱量3%,氧压0.7 MPa,温度105℃,时间60 min。其氧脱木素结果为:得率89.8%,卡伯值7.6,黏度559.2 mL/g,白度48.2%ISO。     

氧脱木质素对稻草SFP浆性能的影响

亚硫酸盐―甲醛―蒽醌(SFP-AQ)法是适合于草类原料的一种制浆方法。文章研究了氧脱木质素对稻草SFP浆的卡伯值、白度、粘度及强度性能的影响。结果表明,较高的用碱量有助于残余木质素的脱除,在合适的工艺条件下,稻草SFP浆单段氧脱木质素的脱木质素率可达50%以上。在氧脱木质素用碱量3.5%、氧压0.4 MPa、温度110℃、时间60 min或90 min的条件下,稻草SFP浆的卡伯值较低、白度较高,而同时具有良好的粘度和强度性能。     

枫香树材清洁制浆技术

对速生阔叶木枫香树材的纤维形态、主要化学组成、清洁制浆及绿色漂白工艺进行了一系列探讨。结果显示,枫香木纤维平均长度较长,长宽比均比杨木大,且其综纤维素和戊聚糖含量高而Klason木素含量低,是一种很有发展潜力的制浆造纸原料。采用硫酸盐法制浆,蒸煮后所得细浆得率为49.9%,卡伯值为23.0,白度为23.8%ISO,黏度为734.7 mL/g。利用环境友好型漂白法——氧脱木素技术处理该枫香树材硫酸盐浆,并在此过程中创造性地使用助剂蒽醌。四因素三水平正交试验结果表明:用碱量、氧压、温度和时间对枫香树材硫酸盐浆添加蒽醌氧脱木素后浆料的性能均有很大的影响。其中,温度对得率、卡伯值、白度和黏度等的影响最大,时间对卡伯值、白度和黏度的影响最小。枫香树材硫酸盐浆添加蒽醌氧脱木素的较为适宜的工艺为:用碱量3%,氧压0.7 MPa,温度105℃,保温时间90 min,浆浓20%,MgSO4用量0.5%,蒽醌用量0.1%。在该条件下所得浆料得率90.7%,卡伯值7.0,黏度545.1 mL/g,白度51.0%ISO,脱木素选择性8.42×10-2。与相同条件下常规氧脱相比,卡伯值和白度相近,但得率、黏度和脱木素选择性都有所提高。蒽醌在枫香树材硫酸盐浆氧脱木素过程中可保护碳水化合物,提高脱木素选择性,是一种良好的氧脱木素助剂。     

Kraft pulping of Eucalyptus nitens wood chips biotreated by Ceriporiopsis subvermispora

Eucalyptus nitens and E. globulus are wood species used in kraft pulping in Chile and Australia. Although E. nitens adapts very well to cold regions it requires more severe cooking conditions to produce bleachable kraft pulps. An attempt was made to find out whether a pre‐treatment with Ceriporiopsis subvermispora would improve its performance during kraft pulping and the pulp properties. The biotreatment of the chips carried out for a period of 15 days resulted in 13.3% lignin loss and a limited glucan degradation (2%). The pulping of biotreated samples required lower active alkali charge to reach the target kappa number compared to the control untreated sample and exhibited better pulping selectivity. The pulp yield increased by 3% and 1.5% for the pulps of 22 and 16 kappa numbers, respectively. The biotreated pulp's strength properties were improved and were similar to those of E. globulus reference pulp. Copyright © 2006 Society of Chemical Industry     

Integrating laccase–mediator treatment into an industrial‐type sequence for totally chlorine‐free bleaching of eucalypt kraft pulp

Enzymatic delignification using the high‐redox potential thermostable laccase from the fungus Pycnoporus cinnabarinus and a chemical mediator (1‐hydroxybenzotriazole) was investigated to improve totally chlorine‐free (TCF) bleaching of Eucalyptus globulus kraft pulps. Different points of incorporation of the enzyme treatment into an industrial‐type bleaching sequence (consisting of double oxygen, chelation and peroxide stages) were investigated in pressurized laboratory reactors. The best final pulp properties were obtained using an O? O? L? Q? PoP sequence, where a laccase–mediator stage (L) was incorporated between double oxygen and chelation. The worse results, when the enzymatic and chelation treatments were combined in a unique stage, seemed related to partial inhibition of laccase‐mediator activity by the chelator. The new TCF sequence including the laccase stage permitted to improve eucalypt pulp delignification to values around kappa 5 (hexenuronic acid contribution over 50%) compared to kappa 7 using only TCF chemical reagents. In a similar way, the final brightness obtained, over 91% ISO, was 3–4 points higher than that obtained in the chemical sequences. Although technical and economic issues are to be solved, the results obtained show the feasibility of integrating a laccase–mediator treatment into a TCF sequence for bleaching eucalypt kraft pulp. Copyright © 2006 Society of Chemical Industry     

Preliminary Results on an Approach for the Quantification of Lignin-Carbohydrate Complexes (LCC) in Hardwood Pulps

Abstract

The literature on biomass research contains many references to lignin-carbohydrate complexes (LCC) decreasing the rate of delignification in chemical pulp production, decreasing the yield of cellulosic ethanol via fermentation, and decreasing forage digestibility. However, it is difficult to find correlations between rates of the processes above and initial LCC concentration. One of the main reasons for the lack of such correlations is the absence of methods for accurate quantification of LCC. In this investigation, repeatable and reproducible determinations of bound sugars at monomeric concentrations as low as 0.3 wt% on enzymatic lignin (EL) have been achieved. The bound sugars are hydrolyzed by H₂SO₄, most likely as low molecular weight oligomers. In the same H₂SO₄ treatment, the oligomers are hydrolyzed to monomers which are subsequently quantified by ¹H NMR analyses. A significant enrichment of bound arabinan was previously reported when a crude milled wood lignin (MWL) was compared to the starting wood meal. A similar arabinan enrichment was observed for ELs from kraft and soda-AQ (SAQ) pulps in the present study. Also, well-resolved cross-peaks have been obtained in 2D HSQC NMR analyses of ELs. It has so far been confirmed that the EL from a 30.6 kappa number SAQ pulp from sugar maple contained ～30% more benzyl ethers linked to primary-OH groups in sugar units than the corresponding EL from a 33.7 kappa number kraft pulp.     

Investigation of Laccase/N-Hydroxybenzotriazole Delignification of Kraft Pulp

Abstract

N-hydroxybenzotriazole, a mediator for laccase delignification of kraft pulps, was shown to be unstable under the biobleaching conditions. The treatment of N-hydroxybenzotriazole either with laccase alone or in the presence of kraft pulp yielded benzotriazole. The reductive conversion of N-hydroxybenzotriazole to benzotriazole was found to occur rapidly in the presence of pulp. Furthermore, benzotriazole was found to be inactive as a mediator for laccase catalyzed delignification of kraft pulps. Hence, the overall conversion of N-hydroxybenzotriazole to benzotriazole is detrimental towards the bio-delignification process.     

The Potential of Hydrothermally Pretreated Industrial Barks From E. globulus as a Feedstock for Pulp Production

This study focused on the use of industrial eucalyptus globulus bark as an alternative fiber source for bleached pulp and paper production. Bark has high extractives and ash contents (7.7% and 3.5%, respectively) but a mild hydrothermal pretreatment was tested, decreasing its values to 2.8% and 2.4%, respectively. Untreated and pretreated bark were kraft pulped at 15% and 20% (as Na₂O) active alkali conditions. The pretreatment improved delignification when using low active alkali; kappa number 25.4 vs 17.5, and shives 3.1% vs 0%, respectively, with untreated and pretreated bark. The pretreatment resulted in a lower chemical demand to obtain pulps with similar yield and kappa number. It was possible to produce bleached pulps with good handsheet optical, physical, and mechanical properties with slightly lower values than those of industrial eucalypt wood pulps; e.g., brightness > 85% vs 87%, tear index > 4.2 vs 5.6 mn.m².g^?1, tensile index > 62 vs 69 n.m.g^?1 for bark and wood pulps, respectively.     

Delignification of Pinus taeda wood chips treated with Ceriporiopsis subvermispora for preparing high‐yield kraft pulps

Pinus taeda wood chips were treated with the white‐rot fungus Ceriporiopsis subvermispora in 20‐dm³ bioreactors for periods varying from 15 to 90 days. Decayed samples, non‐inoculated controls and extractive‐free wood samples were submitted to kraft pulping using 25% of sulfidity and different active alkali concentrations in the cooking liquor. Cooking reactions were carried out isothermally at 170 °C. Residual lignin contents of pulps prepared from biotreated wood chips were lower than those observed in pulps from the undecayed control. Delignification kinetic studies showed that the initial delignification phase was accelerated and shortened by the fungal pretreatment. At a cooking time fixed before the end of the bulk delignification phase, the fungal pretreatment provided pulps with significantly lower kappa numbers or pulps with a fixed kappa number were obtained by reducing the amount of active alkali added to the liquor. Pulps of kappa 80 were obtained both from the undecayed control cooked with 20.8% of active alkali and from the 15‐day‐biotreated sample cooked with only 15% of active alkali. The biopulping benefits were neither proportional to the extent of the biodelignification nor to the biological removal of some specific wood component. DFRC‐determination (derivatization followed by reductive cleavage) of the amount of aryl–ether linkages in residual lignins of biotreated samples indicated an extensive depolymerization during the initial stages of biodegradation, which suggested that bio‐depolymerized lignin was easily released during the first stages of cooking, resulting in a faster and shorter initial delignification phase. © 2002 Society of Chemical Industry     

The Use of Ozone or Oxygen in The First Bleaching Stage

An ODED or a ZEDED sequence bleached kraft hardwood and softwood pulps to 87 — 89‰ ISO brightness. The bleached yields were similar for a given pulp, whether oxygen or ozone was used in the first stage. The strength properties of the fully bleached pulps were essentially the same as those of the unbleached pulps. The COD and colour values of the effluents after ozone delignification and subsequent extraction were 25‰ and 60‰ lower, respectively, than those of the effluents after an oxygen treatment.     

Totally chlorine‐free bleaching of Acetosolv pulps: a clean approach to dissolving pulp manufacture

Eucalyptus globulus wood samples were delignified in media containing concentrated acetic acid, water and hydrochloric acid (Acetosolv process) under optimized conditions, and the pulps were subjected to totally chlorine‐free (TCF) bleaching. Alkaline extractions, oxygen delignification, ozone treatment, enzymatic xylan removal and hydrogen peroxide oxidation in alkaline media were investigated as individual steps in selected bleaching sequences. Under the best conditions, fully bleached pulps with favourable characteristics for dissolving pulp manufacture were obtained. © 2001 Society of Chemical Industry     

Kraft pulping of Drimys winteri wood chips biotreated with Ganoderma australe

Drimys winteri, a native hardwood from Chile, presents some interesting characteristics that make it suitable for the pulp and paper industry. In this work, the potential of D winteri for the conventional kraft and biokraft pulp production was evaluated. For biokraft pulping, wood chips were biotreated with the white‐rot fungus Ganoderma australe. During the biotreatment, a selective pattern of biodelignification was observed and the wood chips biotreated for 15, 30 and 45 days were submitted to kraft cooking. At low cooking severity (H‐factor below 1500 h^?1, 15% active alkali and 25% sulfidity), all biopulps presented lower kappa numbers than control pulps and approximately the same screened pulp yield. Biopulps were easily refined in a PFI mill, requiring less PFI revolutions to achieve the same fibrillation degree. The strength properties of the biopulps were similar to those of the control pulps. Copyright © 2005 Society of Chemical Industry     

Base‐catalyzed organosolv pulping of jute

Jute fibers were pulped using a novel caustic soda and ethanol–alkali (EtOH–NaOH) pulping process with the aim of minimizing problems associated with conventional chemical pulping. The effects of reaction conditions on the pulp yield, degree of delignification and selected physical properties were evaluated. The results indicate that adding ethanol to the conventional soda process was effective for improving both delignification and the physical properties of jute pulps. It was found that the delignification proceeded more rapidly and more selectively with ethanol–alkali than with alkali alone, giving higher yields at a given kappa number. Strength properties were markedly improved. The greatest values for burst (5.8 kPa m² g^?1) and tensile strength (68 N m g^?1) were obtained at 175 °C and 2.5 h reaction time. Copyright © 2003 Society of Chemical Industry     

裂解-气质联用分析氧漂过程中木素结构的变化

从针叶木硫酸盐原浆、氧漂浆以及氧漂后的废液中分离出残余木素,在四甲基氢氧化铵（TMAH）存在下,采用裂解气相色谱-质谱联用(Py-GC-MS)的方法研究了氧漂过程中木素分子结构的变化.对裂解产物的分析表明,木素裂解时产生多种甲基化的芳香化合物,以愈创木基型化合物为主;氧漂能够氧化和降解木素分子,产生更多的羧基化合物,氧化程度高的木素分子容易从纸浆中溶出,氧漂优先脱除沉积在纤维表面上的短侧链木素.     

马尾松硫酸盐浆两段氧脱木素影响因素的研究

研究了马尾松硫酸盐浆段间不洗涤的第二段氧脱木素的影响因素。研究结果表明 ,在给定的第一段氧脱木素的条件下 ,第二段氧脱木素采用如下条件 :氧压 0 .4～ 0 .5MPa ;温度 80～ 90℃ ;时间 40～ 60min ;用碱量2 %～ 4%。可以在纸浆粘度不致于降低很大的前提下 ,纸浆的木素总脱出率较高。