TCF BLEACHED PULPS FROM MISCANTHUS SINENSIS BY THE IMPREGNATION RAPID STEAM PULPING (IRSP) PROCESS

ABSTRACT

The production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated in this work. The impregnation rapid steam pulping process (IRSP) involves impregnating of the lignocellulosic material with the pulping liquor, withdrawing the excess liquor and rapidly steaming the impregnated material at 180–200°C for a short time. In this paper the process variables and their effect on the kappa number, yield and viscosity of the unbleached pulps are discussed. Bleaching by an ozone-based TCF sequence was tested, and the papermaking properties of the bleached pulp were determined. A kappa number of 19 was obtained by impregnating at an alkali charge of 30 + 0.1% anthraquinone carboxylic acid (AQCA) and pulping at 180°C for only 15 min. Kappa was reduced to 16 by extending pulping time to 26 min. The alkali consumption during impregnation and pulping was 10.2 g NaOH/100 g of dry Miscanthus. Screened pulp yield, viscosity and brightness for this pulp were 54.6%, 913 mL/g and 37.3%, respectively. After bleaching, the pulp had an ISO brightness of 87.4% and a viscosity of 700 mL/g. Refining in a PFI mill provided optimal strength properties of the bleached pulp at 4500 revolutions (71°SR): breaking length 7.2 km, tensile index 72 N m/g, and burst index 4.3 kN/g. Tear index was 7.9 mN m²/g at this degree of refining.     

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     

Alkaline sulfite/anthraquinone pulping of pine wood chips biotreated with Ceriporiopsis subvermispora

Pine wood chips were treated for 30 days with Cemporiopsis subvermispora in 20 dm³ bioreactors. A typical selective biodelignification was observed. The biotreated wood chips and undecayed controls were subjected to modified alkaline sulfite/anthraquinone (ASA) cooking at 170 °C or 175 °C applying varying cooking times ranging from 30 to 270 min. In all cases, the residual lignin content of the pulps prepared from biologically pretreated wood chips was lower than that of the control pulp. With increasing cooking time, however, the differences in kappa number became smaller. Wood chips cooked for a short time required mechanical refining for fiber liberation. A disk‐refining step resulted in pulps with low reject content (0.4%) and high screened yield (56–60%). In this case, the use of biotreated wood chips provided pulps with significantly lower kappa numbers than for the control pulp (71 and 83, respectively). The pulp from biologically pretreated wood fibrillated rapidly, reaching 20° SR in only 38 min beating time in a Jokro mill, while the control pulp required 56 min to reach the same beating degree. Although easier to beat, the biopretreated pulps showed tensile and burst indices similar to those of the control samples. However, their tear indices were always lower. Easier delignification after wood biotreatment was not observed for the reactions performed at long cooking times. Oxygen delignification of biotreated and conventional ASA pulps with low kappa numbers reduced kappa number and improved brightness considerably with the biotreated pulps being favored by a better preservation of viscosity. Copyright © 2004 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     

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.     

Reducing wood drying time by application of ultrasound pretreatment

Industrial wood is typically dried artificially after felling. The drying process is often very lengthy and consumes a large amount of energy, however, and inappropriate drying schedule can cause defects in the wood. Pretreatments such as ultrasound show the potential to reduce wood drying time without impacting quality. This study investigated the influence of ultrasound pretreatment on vacuum drying behavior, hydroxyl content, and microstructural properties of fast-growing wood samples. Pretreatments were performed at ultrasound intensity of 10 W cm^?2 and frequencies of 28 and 40 kHz, respectively, for 30, 60, and 90 min, respectively, then pretreated samples were dried at 40°C temperature under absolute pressure of 0.08 MPa. Results showed that ultrasound pretreatment did shorten the wood vacuum drying time, increase effective water diffusivity, open water channels, decompose wood extractives, and decrease hydroxyl content. In effect, ultrasound pretreatment can be applied to successful reduce wood drying time.     

Formic acid/acetone‐organosolv pulping of white‐rotted Pinus radiata softwood

Organosolv pulping of fungally pretreated samples of Pinus radiata was evaluated. A screening study using five white‐rot fungi indicated that Ceriporiopsis subvermisopora and Punctularia artropurpurascens were the most selective ones for lignin degradation. These fungi were further cultured in bioreactors containing 2.5 kg of wood chips. Fungally‐pretreated samples were delignified by formic acid/acetone (7:3) at 150 °C. Pulping kinetics and strength properties of the resulting unbleached pulps were evaluated. Delignification rates and xylan solubilization rates were higher for the decayed samples than for the undecayed control, except for the sample biotreated with P artropurpurascens for 30 days. C subvermispora proved appropriate for treating the wood samples before organosolv pulping, since pretreatment with this fungus resulted in faster wood delignification and pulps with lower residual lignin. Increases in tensile index ranging from 3% to 22% were observed for most pulps prepared from biotreated samples, independently both of the fungal species used in the pretreatment and of the extent of the wood biodegradation expressed as wood weight loss. However, tear and burst indexes and brightness were lower than or similar to those of pulps prepared from the undecayed control. © 2000 Society of Chemical Industry     

Ethanol‐based pulping from Cynara cardunculus L

A non‐conventional pulping process based on the delignification of cardoon (Cynara cardunculus L) in ethanol–water mixtures has been studied to evaluate its pulping potential and to establish the optimum pulping conditions for this lignocellulosic material. The variables analyzed were the concentration of ethanol in the cooking liquor, the pulping time and temperature. Variable optimization was performed by a central composite design. High viscosity, low kappa number and acceptable screened yield were used as pulp quality criteria to optimize cooking conditions. Pulps having low kappa numbers and viscosities greater than 900 cm³/g^?1 were obtained. The total pulp yield was low compared with wood pulping due to the high contents of extractives and ash in cardoon. The amount of rejects in the pulp is of importance, especially for pulps with a high kappa number. The most suitable pulping conditions were 188 °C, 135 min and 50% (w/w) ethanol concentration. In these conditions the kappa number of the pulp was around 26, the pulp viscosity greater than 1100 cm³ g^?1 and a screened pulp yield of about 31% was obtained. Copyright © 2005 Society of Chemical Industry     

Pulping Yield and Delignification Kinetics of Heartwood and Sapwood of Maritime Pine

Abstract

In maritime pine (Pinus pinaster Ait.), heartwood represents a substantial part of the tree stem at final harvest age (80 years) corresponding to 42% at the base of the stem wood diameter and decreasing upward. The rate of heartwood formation was estimated at 0.35 rings/year, beginning at 18 years of age. Differences in the chemical composition between heartwood and sapwood were mainly in the extractives, 19.7% and 5.8%, respectively. The lignin content was 23.1% and 24.5% in the heartwood and sapwood, respectively. Pulping yield of the heartwood was lower than that of the sapwood (40.0% vs. 49.7%) and was negatively correlated with the extractives content. Extraction of heartwood prior to pulping increased the pulp yield and the delignification (lower residual lignin in pulps). Pulping kinetics showed lower yields for heartwood at all pulping stages, the difference occurring especially in the initial reaction phase. However, delignification rate constants were similar for heartwood and sapwood (3.1×10^?2 min^?1 and 2.7×10^?2 min^?1 for the main delignification phase for sapwood and heartwood, respectively), with a lower activation energy for sapwood (68.3 vs. 90.0 kJ · mol^?1). The presence of heartwood decreases the raw‐material quality for pulping and this should be taken into account when harvesting trees for pulping processes.     

Dissolving pulp from TCF bleached Acetosolv beech pulp

Beech wood samples subjected to pulping in HCl‐catalysed acetic acid media (Acetosolv process) under selected conditions were bleached using several Totally Chlorine Free (TCF) sequences including peracetic acid (Paa), alkaline (E), oxygen (O), chelating (Q) and peroxide (P) treatments. PaaEQPP sequences starting from acetic acid media led to pulps with poor brightness, which was improved when the same sequence was carried out starting from aqueous media. An EOQPP sequence led to a pulp with acceptable properties, which were improved by a optimised EOQPaaP sequence, in which a fully bleached pulp was obtained at a SCAN viscosity of 604 cm³ g^?1. EOQPaaP‐bleached pulp was explored for carboxymethyl cellulose (CMC) manufacture employing heterogeneous conditions in isopropanol media, and a CMC with a degree of substitution of 1.16 was obtained. Copyright © 2004 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     

Behavior of Eucalyptus Wood Xylans across Kraft Cooking

Abstract

The 4-O-methylglucuronoxylans isolated from wood, pulp, and black liquor from six eucalyptus wood species were characterized. The ¹H nuclear magnetic resonance (NMR) studies revealed that all eucalyptus wood xylans contain O-2-substituted 4-O-methylglucuronic acid (MeGlcA) groups with hexose residues (9–26%). Their molecular weight (Mw) and polydispersity varied in the range of 26,083–28,405 g.mol^?1 and 1.13–1.17, respectively. The xylan retention during pulping increased with increasing degree of MeGlcA substitution in the xylose ring. An average of 54% xylans was retained in the pulp and the remaining 46% were degraded and/or dissolved in the black liquor (39% degraded and 7% dissolved). The average Mw of the xylans retained in the pulp and dissolved in the black liquor is influenced by pulp kappa number and averaged 20,134 and 14,778 g.mol^?1, respectively, at kappa 17. The average substitution degree of uronic acids, including MeGlcA and hexenuronic acids (HexA) in the xylans isolated from pulps (kappa 17) and black liquors were 1.05 and 1.13/10 xyloses, respectively. Of the total uronic acids present in the six original woods, an average of 36% w/w was retained in the pulps.     

Effect of Totally Chlorine Free and Elemental Chlorine Free Sequences on Whole Stem Kenaf (Hibiscus cannabinus) Pulp Characteristics

Totally chlorine free (TCF) and elemental chlorine free (ECF) single and multistage sequences were used to bleach whole stem kenaf pulp. The results indicated that in contrast to unbleached kraft wood pulps, kraft kenaf pulps can be easily bleached to a brightness of 91.4% using a four-stage TCF [Q₁(PO)Q₂P] bleaching sequence. The ECF bleaching pulps had slightly higher selectivity and yield than those of the TCF bleached pulps. The strength properties of the TCF [Q₁(PO)Q₂P] and ECF (D₁ED₂EP) bleached pulps were comparable, with the exception of tear index and tensile index, which were slightly higher and lower for TCF pulps, respectively.     

Water vapor sorption and diffusivity in bark

Physical properties of importance in drying processes have been compiled for bark, including spruce, pine, and birch in Sweden. Water vapor sorption isotherms were determined for the bark of these trees. At 95% relative humidity and 25°C, outer birch bark reached a moisture ratio (kg water/kg dry mass) of 5%, whereas inner birch bark, spruce bark, and pine bark reached moisture ratios of 21, 28, and 25%, respectively. The transverse water vapor diffusivity in samples of spruce bark, pine bark, inner birch bark, and outer birch bark were determined to be 1.1–1.7 · 10^?6, 2.2–9.2 · 10^?7, 1.5–2.6 · 10^?6, and 4.3–13 · 10^?8 m²/s, respectively. The in-plane diffusivity was of the same magnitude as the transverse diffusivity in inner birch bark, whereas in outer birch bark the in-plane diffusivity was several times higher than the transverse diffusivity. These data can be used to model the drying behavior and can thus aid in the design of efficient bark drying processes.     

Cathodically pretreated poly(1-aminoanthraquinone)-modified electrode for determination of ascorbic acid, dopamine, and uric acid

This paper describes a rapid and reliable method for dopamine (DA), ascorbic acid (AA), and uric acid (UA) determination in human urine using a cathodically pretreated poly(1-aminoanthraquinone) (PAAQ)-modified electrode. By applying a simple cathodic pretreatment to the PAAQ electrode well-defined voltammetric peaks for AA, DA, and UA were obtained. The pretreated PAAQ showed good selectivity, sensitivity, and repeatability for measuring AA, DA, and UA with detection limits of 2.50 × 10^?5, 3.05 × 10^?6, and 1.15 × 10^?5 M, respectively. The practical applicability of the modified electrode is illustrated by selective measurements of AA and UA in human urine without any preliminary treatment. Recovery values between 94.8 and 102 % for AA and between 77.8 and 100 % for UA were obtained with a relative standard deviation of 2.74 and 2.98 %, respectively.     

Bio‐Chemimechanical Pulps from Eucalyptus grandis: Strength Properties,Bleaching, and Brightness Stability

Abstract

Eucalyptus grandis wood chips were treated with the white‐rot fungus Ceriporiopsis subvermispora in a 100‐L bioreactor for 15 days. The treatment was characteristic of a selective biodelignification (7.6±0.2% and 0.3±0.2% of lignin and glucan losses, respectively) with concomitant extractive removal (17.7±0.2%). Biotreated samples and non‐inoculated controls were pre‐cooked in alkaline sulfite and post‐refined in a Jokro mill. The biotreated pulps fibrillated more rapidly and contained lower amounts of rejects than the control. To achieve a freeness of 400 mL, the control pulp required 125 min of beating, whereas the biopulp required only 95 min, a reduction of 24%. Unbleached biopulps had better strength properties than control pulps because higher tensile indexes were obtained for the entire range of tear indexes. Bleaching with 8% hydrogen peroxide increased the brightness of these pulps by 17 points. At low peroxide loads, the brightness increase for biopulps was lower than for the control pulps. Still, the bleachability of sboth pulps was similar for peroxide loads higher than 2%. After a two‐stage H₂O₂‐bleaching sequence, final brightnesses for the control and biopulps were 59.7±0.8% and 60.5±0.4%, respectively. Brightness stability of the bleached control and bio‐CMP pulps to photo and thermal aging were very similar.     

Evaluation of enzymatic hydrolysis of wheat straw pretreated by atmospheric glycerol autocatalysis

BACKGROUND: Because ethanol organosolv pulping requires high pressure and is highly volatile, an atmospheric autocatalytic glycerol organosolv pretreatment process has been investigated. Enzymatic hydrolysis of wheat straw pretreated using this method was evaluated to explore a novel, economically competitive and environmentally friendly pretreatment technology for bioconversion of lignocellulosic biomass. The method also provides economical utilization of industrial glycerol, helping to cope with the challenge of the excess production of glycerol and to further defray the cost of biodiesel production. RESULTS: With preliminary optimization of the parameters in the pretreatment process, pretreatment performed at 240 °C for 4 h with the glycerol addition of 15 g g^?1 dry feedstock and wash at 80 °C led to high recovery of cellulose (95%) and good removal of lignin (>70%), which formed, respectively, 80% and 10% of the pulp. The enzymatic hydrolysis of the pretreated wheat straw yielded 90% of theoretically achievable sugar after 24 h and 92% after 48 h. CONCLUSION: Atmospheric autocatalytic glycerol organosolv pretreatment removed significant amounts of hemicellulose and lignin without affecting good cellulose recovery. The proposed novel strategy increased the susceptible of wheat straw to enzyme attack and led to enzymatic hydrolysis that was comparable with that achieved using ethanol organosolv pretreatment. Copyright © 2007 Society of Chemical Industry     

Alkaline sulfite/anthraquinone pretreatment followed by disk refining of Pinus radiata and Pinus caribaea wood chips for biochemical ethanol production

BACKGROUND: Alkaline sulfite/anthraquinone (ASA) cooking of Pinus radiata and Pinus caribaea wood chips followed by disk refining was used as a pretreatment for the production of low lignified and high fibrillated pulps. The pulps produced with different delignification degrees and refined at different energy inputs (250, 750 and 1600 Wh) were saccharified with cellulases and fermented to ethanol with Saccharomyces cerevisiae using separated hydrolysis and fermentation (SHF) or semi‐simultaneous saccharification and fermentation (SSSF) processes. RESULTS: Delignification of ASA pulps was between 25% and 50%, with low glucans losses. Pulp yield was from 70 to 78% for pulps of P. radiata and 60% for the pulp of P. caribaea. Pulps obtained after refining were evaluated in assays of enzymatic hydrolysis. Glucans‐to‐glucose conversion varied from 20 to 70%, depending on the degree of delignification and fibrillation of the pulps. The best ASA pulp of P. radiata was used in SHF and SSSF experiments of ethanol production. Such experiments produced maximum ethanol concentration of 20 g L^?1, which represented roughly 90% of glucose conversion and an estimated amount of 260 L ethanol ton^?1 wood. P. caribaea pulp also presented good performance in the enzymatic hydrolysis and fermentation but, due to the low amount of cellulose present, only 140 L ethanol would be obtained from each ton of wood. CONCLUSION: ASA cooking followed by disk refining was shown to be an efficient pretreatment process, which generated a low lignified and high‐fibrillated substrate that allowed the production of ethanol from the softwoods with high conversion yields. Copyright © 2012 Society of Chemical Industry     

Alkali pretreatment of softwood spruce and hardwood birch by NaOH/thiourea,NaOH/urea,NaOH/urea/thiourea,and NaOH/PEG to improve ethanol and biogas production

Alkali‐dissolution pretreatment of softwood spruce and hardwood birch to improve ethanol and biogas production was investigated. The pretreatments were carried out at different temperatures between ? 15 and 80 °C with NaOH/thiourea (7/5.5 wt%), NaOH/urea (7/12 wt%), NaOH/urea/thiourea (7/8/6.5 wt%), and NaOH/PEG (7/1 wt%) aqueous solutions. The pretreated materials were then subjected to enzymatic hydrolysis for 72 h. The pretreatments by NaOH/thiourea at ? 15 °C improved the hydrolysis yields of spruce from 11.7% to 57% of theoretical yield, and for birch from 23.1% to 83% of theoretical yield. The enzymatic hydrolysis and fermentation of these pretreated materials by NaOH/thiourea with baker's yeast resulted in 54.0% of theoretical yield compared with 10.9% for untreated spruce and 80.9% of theoretical yield compared with 12.9% for untreated birch. Furthermore, anaerobic digestion of pretreated materials resulted in 0.36 L g^?1 VS methane compared with 0.23 L g^?1 VS for untreated birch, and 0.21 L g^?1 VS compared with 0.03 L g^?1 VS for untreated spruce. Copyright © 2012 Society of Chemical Industry     

The effect of halide ion concentration on capacitor performance

The effect of halide ion concentration on the capacitor performance was considered during this study. Iodide anion has been selected as the most profitable halide taking into account its electrochemical properties and environmental impact. Several concentrations of NaI were tested (from 0.25 to 5 mol L^?1 aqueous solutions) using as electrodes two commercial activated carbons and one KOH-activated carbon. Detailed electrochemical investigation by galvanostatic charging/discharging, cyclic voltammetry, and impedance spectroscopy confirmed the significant impact of iodide concentration on the supercapacitor behavior. The higher concentration of iodide affected especially the performance of positive electrode; increase of iodide concentration changed the potential range of positive electrode and its capacitance increased from 119 F g^?1 for 0.25 mol L^?1 NaI to 475 F g^?1 for 2 mol L^?1 NaI solution. The electrode capacitance measured in two-electrode system at current density of 2 A g^?1 ranged from 198 F g^?1 for 0.25 mol L^?1 NaI to 272 F g^?1 for 2 mol L^?1 NaI solution (capacitance expressed as average of the positive and negative electrode capacitances). It has been proved that 2 mol L^?1 alkali metal iodide solution is an optimal electrolyte for the capacitor based on KOH-activated carbon. High capacitance values and perfect stability (100 % retention) of such systems have been observed during long-term galvanostatic charging/discharging (15,000 cycles). In addition, satisfactory floating tests at extended voltage range (1.2 V) were performed.