Comparative study of cellulose isolated by totally chlorine‐free method from wood and cereal straw

Highly purified cellulose preparations were obtained by pretreatment of dewaxed barley straw, oil palm frond fiber, poplar wood, maize stems, wheat straw, rice straw, and rye straw with 2.0% H₂O₂ at 45°C and pH 11.6 for 16 h, and sequential purification with 80% acetic acid–70% nitric acid (10/1, v/v) at 120°C for 15 min. The purified cellulose obtained was relatively free of bound hemicelluloses (2.3–3.2%) and lignin (0.4–0.6%) and had a yield of 35.5% from barley straw, 39.6% from oil palm frond fiber, 40.8% from poplar wood, 36.0% from maize stems, 34.1% from wheat straw, 23.4% from rice straw, and 35.8% from rye straw. The weight‐average molecular weights of the purified cellulose ranged from 39,030 to 48,380 g/mol. The thermal stability of the purified cellulose was higher than that of the corresponding crude cellulose. In comparison, the isolated crude and purified cellulose samples were also studied by Fourier transform IR and cross‐polarization/magic‐angle spinning ¹³C‐NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 322–335, 2005     

Promoting effect of Pd on H2 production from cellulose pyrolysis over mesocellular-foam-supported Ni catalysts

Noble-metal promoters have been added to catalysts for reactions such as steam-methane reforming, but have rarely been applied to systems that produce H₂ from larger, biomass-derived molecules, such as polyols or cellulose. We have previously found that nickel catalysts supported on mesocellular-foam-(MCF)-type silica catalyze H₂ formation during cellulose pyrolysis, and sought to increase their activity. Thus, palladium-promoted nickel catalysts supported on MCF were prepared, and their activities were tested in cellulose pyrolysis (RT → 800 °C, 40 °C/min) under dry argon. A thermogravimetric analyzer–mass spectrometer (TG–MS) was used to semi-quantitatively monitor the gases, especially H₂, that were released during pyrolysis over catalysts with and without Pd promoters. Although the Pd promoters had little impact on the fraction of H₂ in the product gas, adding ≥ 0.4 wt.% Pd enhanced the H₂ yield from cellulose pyrolysis by increasing the total gas yield from the reaction. Thus the promoter improved H₂ yield by enhancing the tar-cracking activity of the catalyst. A 5%Ni/MCF catalyst that was doped with 0.7 wt.% Pd yielded 85 cm³ H₂/g cellulose, which was 15% more H₂ than was obtained when the catalyst was 5%Ni/MCF.     

Catalytic organosolv fractionation of willow wood and wheat straw as pretreatment for enzymatic cellulose hydrolysis

BACKGROUND: Ethanol‐based organosolv fractionation of lignocellulosic biomass is an effective pretreatment technology for enzymatic cellulose hydrolysis to produce sugars and lignin within a biorefinery. This study focuses on the catalytic effect of H₂SO₄, HCl, and MgCl₂ on organosolv pretreatment of willow wood and wheat straw. RESULTS: The use of catalysts improved fractionation of both feedstocks. The maximum enzymatic cellulose digestibility obtained was 87% for willow wood (using 0.01 mol L^?1 H₂SO₄ as catalyst) and 99% for wheat straw (0.02 mol L^?1 HCl). Non‐catalytic organosolv fractionation at identical conditions resulted in 74% (willow wood) and 44% (wheat straw) glucose yield by enzymatic hydrolysis. Application of catalysts in organosolv pretreatment was particularly effective for wheat straw. The influence of the acid catalysts was found to be primarily due to their effect on the pH of the organosolv liquor. Acid catalysts particularly promoted xylan hydrolysis. MgCl₂ was less effective than the acid catalysts, but it seemed to more selectively improve delignification of willow wood. CONCLUSION: Application of catalysts in organosolv pretreatment of willow wood and wheat straw was found to substantially improve fractionation and enzymatic digestibility. The use of catalysts can contribute to achieving maximum utilization of lignocellulosic biomass in organosolv‐based biorefineries. Copyright © 2011 Society of Chemical Industry     

Optimisation of the alkaline peroxide pretreatment for the delignification of rice straw and its applications

Alkaline peroxide pretreatment for the delignification of rice straw was optimised by varying the concentrations of H₂O₂ and NaOH and changing the temperature and duration of the pretreatment. Changes in the lignin content, content of total carbohydrates and weight loss were measured during the pretreatments. Maximum delignification of 62% was obtained by pretreating rice straw at 50°C for 5h with 1.5% (w/v) NaOH and 1% (v/v) H₂O₂, The preferential loss of hemicellulose and lignin from the straw resulted in an increase in the cellulose content of the insoluble residue after pretreatment from 47% (untreated) to 67.79% (treated). The product of this treatment is characterised by having higher cellulose digestibility than untreated rice straw. It also has use as a carbohydrate source in ruminant feed since the in-vivo digestibility by the cow increased from 56.85 % to 76.54% (P < 0.001). The treated rice straw could also be used for commercial process such as the generation of Single Cell Protein. Growth of Sporotrichum pulverulentum on treated rice straw gave a protein product of 24.41 % as compared to 3.8% on untreated rice straw.     

A novel approach for extracting cellulose nanofibers from lignocellulosic biomass by ball milling combined with chemical treatment

Cellulose nanofibers (CNFs) were isolated from kenaf fibers and wheat straw by formic acid (FA)/acetic acid (AA), peroxyformic acid (PFA)/peroxyacetic acid (PAA), hydrogen peroxide (H₂O₂) treatment; and subsequently through ball milling treatment. Characterization of extracted cellulose and cellulose nanofibers was carried out through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). TEM images showed that extracted cellulose nanofibers had diameter in the range of 8–100 nm. FTIR and XRD results implied that hemicellulose and lignin were mostly removed from lignocellulosic biomass with an increase in crystallinity, and isolation of cellulose nanofibers was successful. The TGA results showed that decomposition temperature of cellulose nanofibers increased by about 27°C when compared with that of untreated lignocellulosic biomass. No significant change was observed in the decomposition temperature of bleached celluloses after ball milling. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42990.     

FED-BATCH SIMULTANEOUS SACCHARIFICATION AND FERMENTATION OF MICROWAVE/ACID/ALKALI/H2O2 PRETREATED RICE STRAW FOR PRODUCTION OF ETHANOL

The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H₂O₂ pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H₂O₂ pretreated rice straw.     

Characteristics of hemicellulose,cellulose and lignin pyrolysis

The pyrolysis characteristics of three main components (hemicellulose, cellulose and lignin) of biomass were investigated using, respectively, a thermogravimetric analyzer (TGA) with differential scanning calorimetry (DSC) detector and a pack bed. The releasing of main gas products from biomass pyrolysis in TGA was on-line measured using Fourier transform infrared (FTIR) spectroscopy. In thermal analysis, the pyrolysis of hemicellulose and cellulose occurred quickly, with the weight loss of hemicellulose mainly happened at 220–315 °C and that of cellulose at 315–400 °C. However, lignin was more difficult to decompose, as its weight loss happened in a wide temperature range (from 160 to 900 °C) and the generated solid residue was very high (∼40 wt.%). From the viewpoint of energy consumption in the course of pyrolysis, cellulose behaved differently from hemicellulose and lignin; the pyrolysis of the former was endothermic while that of the latter was exothermic. The main gas products from pyrolyzing the three components were similar, including CO₂, CO, CH₄ and some organics. The releasing behaviors of H₂ and the total gas yield were measured using Micro-GC when pyrolyzing the three components in a packed bed. It was observed that hemicellulose had higher CO₂ yield, cellulose generated higher CO yield, and lignin owned higher H₂ and CH₄ yield. A better understanding to the gas products releasing from biomass pyrolysis could be achieved based on this in-depth investigation on three main biomass components.     

Grafting of N-methylolacrylamide onto flax/polyester fabric using ferrous cellulose thiocarbonate/H2O2 redox system

Graft copolymerization of N-methylolacrylamide onto flax/polyester blend fabric using ferrous cellulose thiocarbonate/H₂O₂ redox system was investigated under different conditions including hydrogen peroxide concentration (1?60 mmol/l), ferrous ammonium sulphate concentration (1?50 mmol/l), N-methylolacrylamide concentration (5?200%, based on weight of sample), polymerization time (10?90 min), temperature (20?50°C), and pH of the medium (1.1?11). The nitrogen content and/or the methylol content were used for calculation of graft yields. Results obtained indicated that graft yields, derived from nitrogen analysis, are higher the greater the H₂O₂ concentration increases till 40 mmol/l, then level off. On the other hand, graft yields derived from methylol content exhibit maximum value at 10 mmol/l H₂O₂. The results indicate also that grafting was highly favoured when it was carried out using 1 mmol/l ferrous ammonium sulphate and pH 4.4 at 30°C for 60 min. The apparent activation energy of the copolymerization reaction amounts to 9.74 kJ/mol. Furthermore, the graft yield increases by increasing N-methylolacrylamide concentration within the range studied. The work was further extended to include a comparison between the polymerization efficiencies of the ferrous cellulose thiocarbonate/H₂O₂ redox system and the ferrous/H₂O₂ redox system in inducing grafting of N-methylolacrylamide onto flax/polyester blend fabric. For this reason, the two systems were studied with respect to graft yield, homopolymer proportion, total conversion, graft efficiency, and homopolymer efficiency.     

Characteristics of cellulose isolated by a totally chlorine‐free method from Caragana korshinskii

The chemical composition and fiber morphology of Caragana korshinskii were investigated in this study. Isolation of cellulose was performed in a nonsulfur acetic acid/nitric acid system under various conditions. The influence of three factors, i.e., nitric acid concentration (0, 2, 4, 6, 8, or 10%), temperature (95, 100, 110, 115, 120, or 130°C), and reaction time (30, 40, 50, 60, or 90 min) on the cellulose properties (viscosity, yield, and molecular weight) was studied. The cellulose isolated was characterized by using Fourier transform infrared, gas chromatography, high performance liquid chromatography, solid‐state cross‐polarization magic angle spinning carbon‐13 nuclear magnetic resonance, wide‐angle X‐ray diffraction, and thermogravimetric analysis/differential scanning calorimetry techniques. The results showed that the treatment using 80% acetic acid and nitric acid as a catalyst under the given conditions resulted in slight acetylation of the cellulose and increased the degree of crystallinity of cellulose except for significant degradation of lignin and hemicellulosic polymers. The thermal stability of the cellulose declined with an increase in nitric acid concentration. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3251–3263, 2006     

The pyrolysis of cellulose derivatives

The thermal degradation in vacuo of ethyl cellulose and cellulose acetate in the form of very thin films or bulk material between 230° and 320°C has been studied. With the ethyl cellulose films, volatilization (as measured by weight loss) was a first-order process up to about 50% reaction, with an activation energy of 208 kJ/mole. This is about the same as that associated with the initial drop in intrinsic viscosity of the solid during bulk pyrolysis, in which very high molecular weight material, probably crosslinked, was formed at a later stage. The volatile products from ethyl cellulose included H₂O, CO, CO₂, C₂H₄, C₂H₆, C₂H₅OH, CH₃CHO, unsaturated aliphatic compounds, and furan derivatives. Acetic acid and acetyl derivatives of D -glucose were produced from cellulose acetate. It is suggested that the polymers degrade by radical chain mechanisms, and a number of possible elementary steps are proposed.     

Direct conversion of cellulose into polyols or H2 over Pt/Na(H)-ZSM-5

The direct conversion of cellulose into polyols such as ethylene glycol and propylene glycol was examined over Pt catalysts supported on H-ZSM-5 with different SiO₂/Al₂O₃ molar ratios. The Pt dispersion, determined by CO chemisorption and transmission electron microscopy (TEM), as well as the surface acid concentration measured by the temperature-programmed desorption of ammonia (NH₃-TPD), increased with decreasing SiO₂/Al₂O₃ molar ratio for Pt/H-ZSM-5. The total yield of the polyols, i.e., sorbitol, manitol, ethylene glycol and propylene glycol, generally increased with increasing Pt dispersion in Pt/H-ZSM-5. The one-pot aqueous-phase reforming of cellulose into H₂ was also examined over the same catalysts. The Pt catalyst supported on H-ZSM-5 with a moderate SiO₂/Al₂O₃ molar ratio and a large external surface area showed the highest H₂ production rate. The Pt dispersion, surface acidity, external surface area and surface hydrophilicity appear to affect the catalytic activity for this reaction.     

Production of furfural and cellulose from barley straw using acidified zinc chloride

An effective fractionation process was sought to produce furfural and cellulose-rich solid from barley straw. Acidified zinc chloride (ZnCl₂) was used as a catalyst in order to achieve hemicellulose recovery in the form of liquid hydrolysate. This fractionation process recovered 55.6% of XM (xylan and mannan) in the untreated barley straw under best reaction conditions (10% acidified ZnCl₂, 150 °C, 30 min, and 1/15 of S/L ratio). Hemicellulose hydrolysate was converted into furfural using hydrothermal reaction without additional catalyst. The furfural conversion yield at various reaction temperatures (150, 180, and 210 °C) was in the range of 59.9–64.5%. The two parameters that affected performance in fractionation processing were reaction temperature and time. Reaction severity (Log R0) was used to evaluate the effects of two processing parameters on hemicellulose recovery. In the ZnCl₂ treatment, the data indicated that the proper range of severity was 2.95–3.07 because the XM recovery yield decreased as the reaction condition became more severe beyond that point.     

Rapid synthesis of cellulose triacetate from cotton cellulose and its effect on specific surface area and particle size distribution

A highly rapid process is described for the preparation of cellulose triacetate and its effect on particle size and surface area of the product. The process involves microwave-assisted rapid synthesis of cellulose triacetate with very low amount of acetic anhydride (10–15% of acetic anhydride is used in conventional methods) in the presence of iodine as a catalyst using a designed reaction vessel. The technique used is simple and rapid; it is also characterized by a high conversion ratio (yield 100%). A small amount of iodine (115 and 230 mg, 1.15 and 2.3% of cellulose weight) was found to be effective in the production of cellulose triacetate using 25, 30 to 40 mL acetic anhydride for 10 g cellulose under microwave irradiation for 2–4 min. The production of cellulose triacetate and the degree of substitution were confirmed by FTIR, Raman, ¹H NMR, and thermogravimetric analysis. The optimal reaction condition was discovered to be 3 min microwave radiation and 30 mL acetic anhydride in the presence of 230 mg iodine for 10 g cellulose. The effects of the amount of acetic anhydride, and amount of catalyst and reaction time on the specific surface area, pore volume, mean pore diameter, and particle size distribution were investigated. The highest surface area obtained was 39.63 m²/g. The specific surface area and particle size distribution are highly dependent on the amount of acetic anhydride and I₂ catalyst. About 10% of the synthesized cellulose acetate showed particle size less than 200 nm.     

Novel regenerated cellulose fibers from rice straw

Regenerated cellulose fibers from rice straws with a diameter of 10 to 25 μm and initial modulus of 11 to 13 GPa were prepared by wet spinning in rice straw/N‐methylmorpholine‐N‐oxide (MMNO) solution. X‐ray diffraction analysis indicates that the rice straw regenerated fibers are classified as cellulose (II). This observation indicates a potential utility of rice straw as an alternative to wood pulp as a cellulose‐based fiber material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1705–1708, 2001     

Synthesis and characterization of the new cellulose derivative films based on the hydroxyethyl cellulose prepared from esparto “stipa tenacissima” cellulose of Eastern Morocco. II. Esterification with acyl chlorides in a homogeneous medium

Esparto “Stipa tenacissima” cellulose esters derivatives: HECA‐COO? C₄H₈? COOC₂H₅, HECA‐COO? C₈H₁₆? COOC₂H₅, and HECA‐COO? C₆H₄? COOC₂H₅ were successfully prepared in Tetrahydrofuran (THF)/triethylamine system with a degree of substitution (DS), respectively, DS_AD‐Et=0.32, DS_SB‐Et=0.22, and DS_TRP‐Et=0.50 using hydroxyethyl cellulose acetate (HECA; DS_AC=0.50) as intermediate product, and we avoided the drawbacks of cellulose solubility. The structural modifications were investigated using Fourier transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance (¹H‐NMR), Carbon‐13 nuclear magnetic resonance (¹³C‐NMR), and Distortionless Enhancement by Polarization Transfer 135° (DEPT‐135). The results from these analyses revealed the presence of the characteristic groups indicating that the grafting reaction was successful. The crystallinity and the structure order changes during the esterification reactions were recorded by X‐ray diffraction (XRD), it is found that the crystallinity degree decrease from 63.1% for Esparto “Stipa tenacissima” cellulose to 27.74% for HECA. The thermal stability of the esterified and unmodified cellulose samples was studied by thermogravimetric analysis (TGA)‐differential thermal analysis (DTA); the modified HECA exhibits a decrease in thermal stability relatively to the unmodified HECA, and this may be related to the groups grafted. The resulted cellulose esters HECA‐P_x (x = 1, 2, or 3) were soluble in THF and present an amorphous structure justified by XRD spectra. It was noted by TGA‐DTA analysis that the cellulose esters with low melting range were proved as thermoplastic polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

秸秆醋酸纤维素的制备

农作物秸秆是自然界中数量极大的可再生资源,本研究以农作物秸秆为反应原料,采用无污染蒸汽爆破技术活化预处理,然后进行乙酰化反应,通过溶剂萃取分离并制备出高附加值的醋酸纤维素。实验结果表明：秸秆汽爆后明显增加了反应活性,制备醋酸纤维素的适宜条件是123℃,2 h,催化剂用量为7％,汽爆秸秆中性洗涤剂处理后的乙酰化结果效果最好,不同汽爆秸秆中小麦秸秆乙酰化效果最佳,优化实验条件下,秸秆醋酸纤维素聚合度均在120以上,取代度2.80以上,并且用红外图谱、1H NMR进行了表征。与目前工业上采用α-纤维素含量较高的高级浆为反应原料相比,不仅原料和预处理成本大大降低,而且工艺流程简单。     

Kinetic study of cellulose hydrolysis with tungsten-based acid catalysts

Tungsten plays an important role in transforming cellulose to C2 C3 polyols. In previous reports, the research focus was mainly on the C C cleavage reactions of cellulose catalyzed by various tungsten-containing catalysts, but less on its catalytic role in cellulose hydrolysis although it is usually considered as the rate-determining step in cellulose conversion. In this article, the method of determining kinetics parameters for hydrolyzing cellulose into glucose was developed. The effects of reaction temperature, different tungsten-based acid catalysts, and H⁺ concentration on reaction rate of hydrolyzing cellulose into glucose were quantitatively addressed. The relevant reaction rate equations with using H₃O₄₀PW₁₂, H₄O₄₀SiW₁₂, and H₂WO₄ as tungsten acid catalysts were obtained in developed batch continuous stirred tank reactors and validated by experimental data. The simulating analysis indicates that the reaction mechanism of cellulose hydrolysis can change with the temperature. H₃O₄₀PW₁₂ is the best candidate catalyst for obtaining the maximum glucose concentration.     

Photodegradation of cellulose under UV light catalysed by TiO2

BACKGROUND: Since natural cellulose is an insoluble, crystalline microfibril, which is difficult to react with other compounds, most reactions related with cellulose are heterogeneous. The methods of cellulose degradation include acid hydrolysis, thermal degradation, alkaline degradation and catalytic degradation. Photocatalysis is a very powerful process. RESULTS: With 10 g cellulose dissolved in 100 mL ZnCl₂ solution (66%), the 5‐hydroxymethyl furfural yield in the corrugated plate photocatalytic reactor reached 3.87 g L^?1 under the following experimental conditions: 2 h irradiation under ultraviolet (UV) lamp (power—21 W), nine TiO₂ coating cycles, and 42° corrugated plate angle. CONCLUSION: Owing to the enhancement of catalyst surface area illuminated by UV light and the large number of photons captured on the catalyst surface, the energy efficiency per mass (EE/M) of the corrugated plate photocatalytic reactor for photocatalytic degradation of cellulose was 10.9 kWh kg^?1. This is therefore an effective technology for 5‐HMF preparation from cellulose. Copyright © 2011 Society of Chemical Industry     

Preparation and characterization of polychloroprene nanocomposites with cellulose nanofibers from oil palm empty fruit bunches as a nanofiller

Cellulose nanofibers (CNFs) from oil palm empty fruit bunches were chemically modified by acetylation with acetic anhydride and pyridine (as the solvent and catalyst). The acetylated CNFs showed good dispersion in a polychloroprene (PCR) matrix. The tensile strength and modulus of neat PCR were improved, whereas its elongation at break decreased with increasing nanofiber content. Above the glass‐transition temperature (T_g), the dynamic mechanical analysis profiles showed that the storage modulus of the PCR–cellulose nanocomposites was higher than that of neat PCR. Meanwhile, the thermal stability was still maintained, and the T_g was close to the neat PCR at the 5 wt % addition level of CNFs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40159.     

Efficient hydrolysis of cellulose over a magnetic lignin-derived solid acid catalyst in 1-butyl-3-methylimidazolium chloride

A green and efficient strategy for the hydrolysis of cellulose was developed by using a magnetic lignin-derived solid acid catalyst (MLC-SO₃H) in the presence of ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). The results indicated that reaction temperature, reaction time, catalyst loading and water content have a big influence on the yield of total reducing sugars (TRS). By optimizing these reaction parameters, 69.3% TRS yield was observed at 140 °C for 150 min with the addition of 40 wt% MLC-SO₃H and 1 wt% water. More importantly, MLC-SO₃H could be easily separated from the reaction mixture with an external magnet and could be repeatedly used five times without an obvious loss of catalytic activity, demonstrating that it possessed excellent recyclability. Furthermore, a plausible mechanism involving three consecutive processes of dissolution, adsorption and catalysis for the hydrolysis of cellulose in [BMIM]Cl over a catalyst of MLC-SO₃H was also proposed.