Integrated processes for use of pulps and lignins obtained from sugarcane bagasse and straw

Sugarcane bagasse and straw can be converted into pulps, oils, controlled-release formulations, chelating agents, and composites. This article reviews bagasse and straw conversion efforts in Brazil. Laboratory-scale processes were developed aiming at the integral use of these biomass byproducts. Organosolv pulping and oxidation of lignin are the most promising processes for the rational use of sugarcane residues. Fungal pretreatment and spectroscopic characterization are also discussed.     

Bioconversion of rice straw hemicellulose hydrolysate for the production of xylitol

Applied Biochemistry and Biotechnology - Xylitol production by the yeastCandida guilliermondii was evaluated in a rice straw hemicellulose hydrolysate under different conditions of initial pH and...     

DTA study of thermal degradation of bagasse and rice straw hemicelluloses

DTA curves of the title substances were recorded up to 773 K, in static air. Bagasse hemicellulose (B) exhibited three overlapping exothermic effects, at 545, 618 and 700 K, while rice straw hemicellulose (R) displayed two exothermic effects, at 548 and 635 K. The absence of the third effect for R is ascribed to the catalytic effect of silica ash in promoting volatilization of the degradation products without allowing a char residue intermediate. The activation energy associated with each stage was derived by applying the Borchardt-Daniels general method, the Prout-Tompkins law, and integrated peak areas plotted as logg() vs. 1/T. A second-order linearization of the data proved best, with apparent activation energies of 143, 249 and 289 kJ mol^–1 for B, and 131 and 189 kJ mol^–1 for R. The total peak areas for R, when normalized to ash-free mass, were equal to those evaluated for B, indicating that approximately identical energies are evolved in the temperature range studied.

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Zusammenfassung In statischer LuftatmosphÄre wurden die DTA-Kurven der Titelsubstanzen bis 773 K aufgenommen. Bagasse-Hemizellulose (B) zeigte bei 545, 618 und 800 K drei überlappende exotherme Effekte, wÄhrend sich bei Reisstroh-Hemizellulose (R) zwei exotherme Effekte bei 548 und 635 K ergaben. Das Fehlen des dritten Effektes für R wird dem katalytischen Effekt von Kieselerdeasche bei der Förderung des Freisetzen der Abbauprodukte zugeschrieben, ohne koksige Zwischenprodukte zuzulassen. Die zu den einzelnen Stufen gehörenden Aktivierungsenergien wurden durch Anwendung der allgemeinen Borchardt-Daniels-Methode, des Prout-Tompkinsschen Gesetzes und der graphischen Darstellung der integrierten PeakflÄchen in einem logg() vs. 1/T Diagramm erhalten. Eine quadratische Linearisierung der Daten ergab die besten Ergebnisse mit den scheinbaren Aktivierungsenergien von 143, 249 und 289 kJmol^–1 für B und mit 131 und 189 kJmol^–1 für R. Die totalen PeakflÄchen für R zeigen nach Normalisierung auf aschefreie Massen die gleichen Werte, die auch für B erhalten wurden.

     

Production of ethanol from sugar cane bagasse hemicellulose hydrolyzate byPichia stipitis

The ability ofPichia stipitis to fermentd-xylose andd-glucose in the acid-hydrolyzed hemicellulose component of sugar cane bagasse depends on the alkali used to neutralize the hydrolyzate to pH 6.5. With NH₄OH and NaOH no fermentation occurred, whereas neutralization with Ca(OH)₂ gave the best results (Q_pmax=0.25 g/L-h; Y_p/s =0.38 g/g sugar). However, the volumetric productivity was still considerably less than observed in a semisynthetic medium with a sugar composition similar to the hydrolyzate. L-arabinose was not fermented but assimilated. Sequential neutralization methods failed to improve the fermentation. Acetic acid and lignin derivatives present in the hydrolyzate were major components that inhibited the fermentation.     

Thermal behavior of silicophosphate gels obtained from different precursors

Phosphosilicate glasses are of great interest in important fields, such as optical active systems, energy generating systems, humidity sensors, and as materials for biomedical applications. Many studies were accomplished to establish the influence of different reaction parameters on the evolution and final structure of sol–gel prepared phosphosilicate gels. In the present work, we studied the thermal behavior of the silicophosphate gels obtained starting with different phosphorous precursors, the influence of these precursors on the composition and structure of the resultant gels, and their evolution with thermal treatment. By Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and thermodifferential analysis (DTA/TG), and Differential Scanning calorimetry coupled with Mass Spectrometry (DSC-MS), it was established that the type of the precursors essentially influences the composition and structure and consequently the thermal behavior of the obtained gels. In the case of triethylphosphate precursor, all used methods of investigation have shown that the ester is trapped in the silica matrix and it is eliminated during the thermal treatment. Triethylphosphite partially hydrolizes and reacts with the silica network during post-preparation thermal treatment. Only in the case of H₃PO₄, an interaction with TEOS takes place and leads to Si–O–P bond formation. By thermal treatment, the gels with different composition and structure lead to materials with different properties.     

N-halamines from rice straw

The cellulosic part of rice straw was modified to develop N-halamine derivatives for disinfection. The process involved cross-linking of the cellulosic material with amino/amide/imide containing compounds; cyclic and acyclic. The structures of the prepared materials were identified using FTIR and solid state ¹³CNMR. The modified materials were halogenated to form N-halamines and the antimicrobial activity of each evaluated against examples of Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) using a variety of methods; agar plate, blended agar, stirred flask and in columns. One of the N-halamines achieved a 9 log reduction against both E. coli and S. aureus in 4 h. In addition, no S. aureus growth was recorded on agar plates blended with 0.5 g of this same material.     

麦草半纤维素的快速热裂解实验研究

采用管式炉反应器在550℃~850℃进行了半纤维素的高温快速热裂解实验,以了解其热裂解产物分布及热解规律。结果表明,半纤维素热解三相产物中,气体产物产率最大且随着温度的升高而增加,其主要成分为H₂、CO、CO₂、CH₄ 以及小分子烃类。液相产物中主要是酸类、醇类、呋喃、环戊烯酮类化合物,以及苯酚等芳香化合物,其产率随着温度的升高无明显变化。而焦炭产率则随着温度的升高而降低,且其中残留有大量的有机化合物如醇类、酮类及脱水糖等。     

Fast pyrolysis of rice straw,sugarcane bagasse and coconut shell in an induction-heating reactor

With the application of induction heating, a fast pyrolysis was used for producing valuable products from rice straw, sugarcane bagasse and coconut shell in an externally heated fixed-bed reactor. The effect of process parameters such as pyrolysis temperature, heating rate and holding time on the yields of pyrolysis products and their chemical compositions were investigated. The maximum yield of ca. 50% on the pyrolysis liquid product could be obtained at the proper process conditions. The chemical characterization by elemental (CHNO), calorific, Fourier transform infrared (FT-IR) spectroscopy and gas chromatography/mass spectrometry (GC–MS) showed that the pyrolysis liquid products contain large amounts of water (>65 wt.%), and fewer contents of oxygenated hydrocarbons composing of carbonyl groups, resulting in low pH and low heating values. The results were very similar to bio-oils obtained from other biomass materials. The residual solid (char or charcoal) was also characterized in the present study.     

Two-step preparation and thermal characterization of cationic 2-hydroxypropyltrimethylammonium chloride hemicellulose polymers from sugarcane bagasse

Cationic sugarcane bagasse hemicellulose derivatives with a relatively low degree of substitution (0.01-0.54) containing quaternary ammonium groups were prepared by etherification with 3-chloro-2-hydroxypropyltrimethylammonium chloride or preferably with 2,3-epoxypropyltrimethylammonium chloride using sodium hydroxide as a catalyst in aqueous solution. The extent of etherification was measured by yield percentage and degree of substitution (DS). The DS values of the products could be controlled by adjusting the molar ratio of etherifying agent to anhydroxylose units in hemicelluloses and the molar ratio of sodium hydroxide to etherifying reagent. In comparison, the etherified hemicellulose preparations were characterized by both degradative methods such as thermal analysis, and non-degradative techniques such as gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), and ¹³C nuclear magnetic resonance (NMR) spectroscopy. It was found that a significant degradation of the hemicellulose polymers occurred during etherification under the alkaline conditions used. The thermal stability of the etherified hemicelluloses was lower than that of the unmodified hemicellulose polymers.     

Pretreatment of sugarcane bagasse hemicellulose hydrolysate for xylitol production byCandida guilliermondii

Applied Biochemistry and Biotechnology - In order to remove or reduce the concentrations of toxic substances present in the sugarcane bagasse hemicellulose hydrolysate for xyloseto-xylitol...     

Lime pretreatment of crop residues bagasse and wheat straw

Lime (calcium hydroxide) was used as a pretreatment agent to enhance the enzymatic digestibility of two common crop residues: bagasse and wheat straw. A systematic study of pretreatment conditions suggested that for short pretreatment times (1–3 h), high temperatures (85-135°C) were required to achieve high sugar yields, whereas for long pretreatment times (e.g., 24 h), low temperatures (50–65°C) were effective. The recommended lime loading is 0.1 g Ca(OH)₂/g dry biomass. Water loading had little effect on the digestibility. Under the recommended conditions, the 3-d reducing sugar yield of the pretreated bagasse increased from 153 to 659 mg Eq glucose/g dry biomass, and that of the pretreated wheat straw increased from 65 to 650 mg Eq glucose/g dry biomass. A material balance study on bagasse showed that the biomass yield after lime pretreatment is 93.6%. No glucan or xylan was removed from bagasse by the pretreatment, whereas 14% of lignin became solubilized. A lime recovery study showed that 86% of added calcium was removed from the pretreated bagasse by ten washings and could be recovered by carbonating the wash water with CO₂ at pH 9.5.     

Pretreatment of sugar cane bagasse hemicellulose hydrolyzate for ethanol production by yeast

The cellulase system ofBacillus circulans F-2 effectively hydrolyzed carboxymethyl cellulose (CMC), xylan, avicel, cellobiose, filter paper, cotton, andp-nitrophenyl-Β-D-cellobioside, and the crude enzyme produced mainly glucose from digestion of avicel. Two major and one minor peaks of enzyme activities were eluted on DEAE ion-exchange chromatography, and designated cellulase complex I(C-I) and complex II(C-II) for the two major peaks, and cellulase-III for a minor peak. C-I and C-II were further purified on gel filtration column of a TSK-Gel SW G3000 ×L. The molecular masses of C-I and C-II were estimated to be about 669 and 443 kDa, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the C-I and C-II complexes showed that the C-I complex was present as a multiple protein complex, consisting of at least five CMCases and two xylanases, and that the C-II complex was consisted of at least three CMCase and four xylan ases. C-I showed high activities of cellohydrolase, CMCase, xylanase, and Β-glucosidase, whereas C-II showed high activities of CMCase, xylanase, avicelase, and Β-glucosidase. The outstanding property of the C-II was its high hydrolytic activity toward filter paper, a highly resistant substrate against enzymatic degradation. However, cellulaseIII showed only strong avicelase activity. These results indicated that the cellulase system of the strain exists as multiple complex forms.     

Thermal and mechanical behavior of polyethylene film obtained by orientational crystallization

The thermal and mechanical behaviour was measured in the U. S.for a polyethylene that had been prepared and highly drawn in the U. S. S. R. The melting point and percent crystallinity were evaluated in this studies as a function of heating rate and recrystallization. The Young's modulus and tensile stress to break in the orientation direction were 4.1 and 0.15 GPa, respectively.The tensile strain to break was about 8%.

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Zusammenfassung Das thermische und mechanische Verhalten eines in der UdssR hergestellten und stark gezogenen Polyäthylens wurde in den U. S. A. gemessen. Schmelzpunkt und Prozentsatz der Kristallinität wurden als Funktion der Aufheizgeschwindigkeit und Rekristallisation in den Untersuchungen ausgewertet. Der Young-sche Modulus und die Zugspannung zum Reissen in der Orientierungsrichtung betrugen 4.1, bzw. 0.15 GPa. Die Dehnung bis zum Bruch betrug etwa 8 %.

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Résumé On a effectué, aux Etats Unis, l'étude du comportement thermique et mécanique d'un polyéthylène préparé et fortement étiré en URSS. Le point de fusion et le pourcentage de cristallinité ont été évalués en fonction de la vitesse de chauffage et de la recristallisation. Lesvaleurs respectives du module d'Young et de la limite de rupture dans la direction d'orientation s'élèvent respectivement à 4.1 et 0.15 GPa. L'allongement à la rupture est d'environ 8%.

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, . . . 4.1 0.15 . 8%.

     

Production of xylitol byCandida mogii from rice straw hydrolysate

The influence of aeration level, initial pH, initial cell concentration, and fermentation time on the xylitol production from rice straw hemicellulose hydrolysate byCandida mogii was studied. A multifactorial experimental design was adopted to evaluate this influence. A statistical analysis of the results showed that the aeration level and the initial pH had significant effects on yield factor, volumetric productivity, and xylose consumption. For the latter, fermentation time was also a significant variable. Based on the response surface methodology, models for the range investigated were proposed. The maximum values for the yield factor (Y_p/s) and volumetric productivity (Q_p) were, respectively, 0.71 g/g and 0.46 g(Lh).     

烟煤-稻草混合焦样共气化过程协同行为机理研究

基于热重分析仪考察了神府烟煤焦、稻草焦和神府烟煤-稻草混合焦样气化反应活性及共气化过程协同行为。并借助电感耦合等离子体发射光谱仪和扫描电子显微镜-能谱仪联用装置探讨了共气化过程活性矿物组分的迁移转化特性,以关联解释共气化协同行为演变。结果表明,与煤焦单独气化相比,稻草焦掺混有利于提高煤焦整体气化反应活性。混合焦样共气化过程协同行为随碳转化率的提高呈先逐渐减弱的抑制作用,达到某一碳转化率(记为转折碳转化率)后呈不断增强的协同促进作用,且转折碳转化率随气化温度升高而提高。神府烟煤-稻草混合焦样共气化过程协同行为演变主要归因于共气化过程活性K和Ca转化特性的共同影响。神府烟煤-稻草混合焦样共气化整体协同行为呈协同促进作用,并随气化温度的升高而减弱。     

Thermal analysis and static strength of polyurethanes obtained from glycolysates

In this work thermal stability and tensile strength of polyurethanes obtained from glycolysates was investigated. The glycolysates were produced via glycolysis of waste polyurethane foam (PUR) in the reaction with 1,3-propylene glycol (PG). Polyurethanes were synthesized from the obtained intermediates by the prepolymer method using diisocyanate (MDI) and glycolysis product of molecular mass ranging from 700 to 1000, while 1,4-butylene glycol (BDO) was used as a chain elongation agent. The influence of NCO group concentration in prepolymer on tensile strength and elongation at break of polyurethanes was investigated using Zwick universal tensile tester. Thermal decomposition of the obtained glycolysates and polyurethanes was followed by TG coupled with FTIR spectroscopy. The main products of thermal decomposition have been identified.     

Bleachability and characterization by fourier transform infrared principal component analysis of acetosolv pulps obtained from sugarcane bagasse

Sugarcane bagasse Acetosolv pulps were bleached by xylanase and the pulps classified by using Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA). Pulp was treated with xylanase for 4–8 h with stirring at 30°C. Some samples were further extracted with NaOH for 1 h at 65°C. FTIR spectra were recorded directly from the dried pulp samples by using the diffuse reflectance technique. Reduction in kappa number of 69% was obtained after sequence xylanase (4 h)-alkaline extraction. During bleaching the viscosity decreased only 12%. FTIR-PCA showed that the first three principal components (PCs) explained more than 90% of the total variance of the pulp spectra. PC2×PC1 plot showed that the points related to pulps from sequence xylanase (4 h)-alkaline extraction are different from the other. This group isenlarged by plotting PC3×PC1 or PC3×PC2 containing all pulps submitted to alkaline extraction. PC2 and PC3 are the principal factor for differentiation of the pulps. These PCs suffer influence of the ester bands (1740 and 1244 cm⁻¹). On the other hand, the pulps bleached only with xylanase could not be differentiated from the nonbleached pulps.     

Enzymatic hydrolysis of ammonia-treated rice straw

Rice straw pretreated with liquid anhydrous ammonia was hydrolyzed with cellulase, cellobiase, and hemicellulase. Ammonia-processing conditions were 1.5 g of NH₃/g of dry matter, 85°C, and several sample moisture contents. There were four ammonia addition time (min)-processing time (min) combinations. Sugars produced were analyzed as reducing sugars (dinitrosalicylic acid method) and by high-performance liquid chromatography. Monomeric sugars increased from 11% in the nontreated rice straw to 61% of theoretical in treated rice straw (79.2% conversion as reducing sugars). Production of monosaccharides was greater at higher moisture content and was processing time dependent. Glucose was the monosaccharide produced in greater amounts, 56.0%, followed by xylose, arabinose, and fructose, with 35.8, 6.6, and 1.4%, respectively.     

Surface characterization of untreated and solvent-extracted rice straw

Surface characteristics of untreated and solvent extracted rice straw and intact rice plant stem and sheath tissue have been investigated using reflectance Fourier transform infrared spectroscopy (FTIR-ATR), electrokinetic analysis (EKA), and scanning electron microscopy (SEM). Klason lignin and Kappa numbers were determined according to TAPPI standard methods. Sohxlet extractions were performed with hexanes, ethyl acetate, chloroform, ethanol-toluene and benzene-ethanol azeotropes. The FTIR reflectance spectra showed differences between the untreated sheath and stem tissues. It was found that the functional groups of the stem interior tissues were masked by another substance, which is proposed to be potassium oxalate monohydrate. This mineral salt, readily removed by water-washing, was affected by the solvent extractions with varying results. The extracted amounts ranged from 1 to 7%. While lipid removal was detectable by the FTIR reflectance method, the streaming potential method showed only slight differences between the curves representing the zeta potential (mV) as a function of pH of the untreated versus extracted samples. Reduced values of the iso-electric points were observed for the extracted samples as compared to the untreated rice straw, indicative of more acidic surface characteristics.     

煤与稻杆共液化性能研究

通过与神府煤和稻杆单独热解和液化的对比,研究了神府煤与生物质稻杆的共热解和共液化行为,考察和揭示了两者之间的协同作用。热重分析表明,稻杆的热解温度较低,在与神府煤共热解时,由于在较低温度下稻杆热解形成的自由基对煤热解的促进作用,使得混合物实际的热解失重高于对应的加权平均计算结果。共液化结果表明,神府煤与稻杆之间存在着明显的协同效应,并因液化反应条件的不同而不同。在较高的液化反应温度和较长的反应时间,由于煤本身的热解速率增加,系统内供氢能力的不足导致逆向缩合反应速率增加,减弱了两者的协同效应。在实验条件范围内,当稻杆配入量为50%,在400℃,60min的反应条件下,神府煤与稻杆共液化时产生的协同效应最大。此时,共液化转化率和正己烷可溶物分别高于对应加权平均计算值的14.8%和9.7%,气体产率也同时降低了2.6%。