排序方式: 共有8条查询结果,搜索用时 15 毫秒
1
1.
Claudia Barba Daniel Montané Marguerite Rinaudo Xavier Farriol 《Cellulose (London, England)》2002,9(3-4):319-326
This paper explores the production of carboxymethylcellulose (CMC) fromseveral bleached cellulose pulps obtained from non-wood species. The chemicalcomposition (-cellulose, hemicellulose and lignin content), the degreeofswelling, viscosity, solubility in concentrated NaOH and crystallinity ofsoda/AQ cellulose pulps from abaca, jute, sisal, linen and Miscanthussinensis were determined. The pulps were carboxymethylated by one andtwo successive reaction steps in aqueous medium under identical conditions. Thedegree of substitution (DS) of CMC was found to be dependent upon the source ofthe cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second. The molar mass of CMC was found to bedependent on the initial intrinsic viscosity of the cellulose pulp. The weightaverage molar mass of our CMCs ranged from 1.5×105 to2.8×105. Increasing the DS up to 2 improved the CMC solubility, butviscosity slightly decreased due to a slight degradation of the polymer. 相似文献
2.
Bernhard Peters 《Journal of Analytical and Applied Pyrolysis》2011,91(2):352-358
The objective of this contribution is to describe thermal degradation of Miscanthus giganteus by a detailed reaction mechanism. It includes degradation kinetics for cellulose, hemicellulose and lignin which constitute the major mass fractions of M. giganteus. Furthermore, the mechanism yields a detailed composition of product gases, and is therefore well-suited to predict evolution of both thermal decomposition and products. Therefore, the reaction mechanism was introduced to the Discrete Particle Method (DPM) that solves the coupled differential conservation equations for mass, momentum, species, and energy for a M. giganteus particle. Predicted results were compared to experimental data and yielded good agreement. 相似文献
3.
Flavonoids in the grasses (Poaceae family), Arthraxon hispidus (Thunb.) Makino and Miscanthus tinctorius (Steudel) Hackel have long histories of use for producing yellow dyes in Japan and China, but up to now there have been no analytical procedures for characterizing the dye components in textiles dyed with these materials. LC-MS analysis of plant material and of silk dyed with extracts of these plants shows the presence, primarily, of flavonoid C-glycosides, three of which have been tentatively identified as luteolin 8-C-rhamnoside, apigenin 8-C-rhamnoside and luteolin 8-C-(4-ketorhamnoside). Two of these compounds, luteolin 8-C-rhamnoside (M=432), apigenin 8-C-rhamnoside (M=416), along with the previously known tricin (M=330) and several other flavonoids that appear in varying amounts, serve as unique markers for identifying A. hispidus and M. tinctorius as the source of yellow dyes in textiles. Using this information, we have been able to identify grass-derived dyes in Japanese textiles dated to the Nara and Heian periods. However, due to the high variability in the amounts of various flavonoid components, our goal of distinguishing between the two plant sources remains elusive. 相似文献
4.
Caroline Vanderghem Aurore Richel Nicolas Jacquet Christophe BleckerMichel Paquot 《Polymer Degradation and Stability》2011,96(10):1761-1770
Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 °C and 80 °C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 °C. The effects of these fractionation processes on chemical structure, physico-chemical properties and antioxidant activity of extracted lignins were investigated. Lignins were characterized by their purity, carbohydrate composition, thermal stability, molecular weight and by Fourier transform infrared (FTIR), 1H and quantitative 13C nuclear magnetic resonance (NMR), adiabatic broadband {13C-1H} 2D heteronuclear (multiplicity edited) single quantum coherence (g-HSQCAD). The radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) was also investigated. Formic/acetic acid pretreatment performed in milder conditions (80 °C for 3 h) gave a delignification percentage of 44.7% and soaking in aqueous ammonia 36.3%.Formic/acetic acid pretreatment performed in harsh conditions (107 °C for 3 h) was more effective for extensive delignification (86.5%) and delivered the most pure lignin (80%). The three lignin fractions contained carbohydrate in different extent: 3% for the lignin obtained after the formic/acetic acid pretreatment performed at 107 °C (FAL-107), 5.8% for the formic/acetic acid performed at 80 °C (FAL-80) and 13.7% for the ammonia lignin (AL). The acid pretreatment in harsh conditions (FAL-107) resulted in cleavage of β-O-4′ bonds and aromatic C-C. Repolymerisation was thought to originate from formation of new aromatic C-O linkages. Under milder conditions (FAL-80) less β-O-4′ linkages were broken and repolymerisation took place to a lesser extent. Ammonia lignin was not degraded to a significant extent and resulted in the highest weight average 3140 g mol−1. Despite the fact of FAL-107 repolymerisation, significant phenolic hydroxyls remained free, explaining the greater antioxidant activity. 相似文献
5.
Biochar derived from reproducible massive biomasses presents the advantages of low cost and renewable resources. In this work aiming to solve the existing problems of the lithium-sulfur battery, sulfur@biochar (S@biochar) composite cathode materials with high capacity and good cycle performance were developed. Specifically, four kinds of biochar prepared from rice husk, miscanthus, fir, and pomelo peel were used as host matrices for the Li-S battery. Among them, the S@biochar derived from rice husk delivered the highest specific capacity and the best cycle stability according to electrochemical tests. To further optimize its performance, we prepared a highly porous rice husk derived biochar (HPRH-biochar) using silica gel as the template. The S@HPRH-biochar composite (60% (w, mass fraction) S) enables the homogeneous dispersion of amorphous sulfur in the carbon matrix and its porous structure could effectively suppress the dissolution of the polysulfide. As a result, its electrochemical performance improved, achieving a high initial charge capacity of 1534.1 mAh·g-1 and maintaining a high capacity of 738.7 mAh·g-1 after 100 cycles at 0.2C (1C corresponds to a current density of 1675 mA·g-1). It also gives a capacity of 485.3 mAh·g-1 at 2.0C in the rate capacity test. 相似文献
6.
我国生物质能源产业近年来得到快速发展,但对能源草的研究还处于初级阶段,如果能建立全面的能源植物木质素、纤维素、半纤维素的近红外预测模型数据库,将有助于优良品种的筛选、能源植物能用性能的评价及生物质能源产业在线控制。本研究采用傅里叶变换近红外光谱(FT-NIR)技术结合偏最小二乘法(PLSR)建立了荻、南荻、奇岗、芒四种芒属能源植物品质指标(纤维素,半纤维素,木质素和灰分)近红外预测模型,并在此基础上研究了样本粒度对模型的影响。研究结果表明:(1)四种芒属能源植物茎秆中纤维素,半纤维素和木质素含量误差均方根(RMSECV)分别为1.35%(R2=0.88),0.39%(R2=0.91)和0.35%(R2=0.80),叶片中纤维素,半纤维素和木质素含量误差均方根(RMSECV)分别为0.72%(R2=0.88),0.85%(R2=0.85)和0.44 (R2=0.87),所建的纤维素,半纤维素和木质素的近红外校准模型在预测未知样品含量时效果较好,但灰分含量预测效果不理想;(2)2和0.5 mm粒度样品所建近红外模型均满足样品检测精度要求,但考虑到时间和人工成本,建议在工厂对能源植物原料品质进行分析时,采用2 mm样品建模。 相似文献
7.
Michel Bergs Yulia Monakhova Bernd W. Diehl Christopher Konow Georg Vlkering Ralf Pude Margit Schulze 《Molecules (Basel, Switzerland)》2021,26(4)
As a low-input crop, Miscanthus offers numerous advantages that, in addition to agricultural applications, permits its exploitation for energy, fuel, and material production. Depending on the Miscanthus genotype, season, and harvest time as well as plant component (leaf versus stem), correlations between structure and properties of the corresponding isolated lignins differ. Here, a comparative study is presented between lignins isolated from M. x giganteus, M. sinensis, M. robustus and M. nagara using a catalyst-free organosolv pulping process. The lignins from different plant constituents are also compared regarding their similarities and differences regarding monolignol ratio and important linkages. Results showed that the plant genotype has the weakest influence on monolignol content and interunit linkages. In contrast, structural differences are more significant among lignins of different harvest time and/or season. Analyses were performed using fast and simple methods such as nuclear magnetic resonance (NMR) spectroscopy. Data was assigned to four different linkages (A: β-O-4 linkage, B: phenylcoumaran, C: resinol, D: β-unsaturated ester). In conclusion, A content is particularly high in leaf-derived lignins at just under 70% and significantly lower in stem and mixture lignins at around 60% and almost 65%. The second most common linkage pattern is D in all isolated lignins, the proportion of which is also strongly dependent on the crop portion. Both stem and mixture lignins, have a relatively high share of approximately 20% or more (maximum is M. sinensis Sin2 with over 30%). In the leaf-derived lignins, the proportions are significantly lower on average. Stem samples should be chosen if the highest possible lignin content is desired, specifically from the M. x giganteus genotype, which revealed lignin contents up to 27%. Due to the better frost resistance and higher stem stability, M. nagara offers some advantages compared to M. x giganteus. Miscanthus crops are shown to be very attractive lignocellulose feedstock (LCF) for second generation biorefineries and lignin generation in Europe. 相似文献
8.
Erika Mészáros Emma Jakab G. Várhegyi P. Tóvári 《Journal of Thermal Analysis and Calorimetry》2007,88(2):477-482
The aim of this work was to study the thermal
decomposition of different plant species obtained from energy plantations.
Thermogravimetry/ mass spectrometry (TG/MS) experiments have been performed
with two herbaceous crops (Miscanthus sinensis,
pelletized energy grass) and two wood samples (willow, water locust) in inert
and oxidative atmospheres. Owing to the large number of data obtained in the
experiments, a chemometric tool, principal component analysis (PCA) has been
used to help the interpretation of the results. It has been found that the
thermal decomposition of the studied wood species is similar, whereas that
of the studied herbaceous samples exhibits significant differences. PCA has
been found to be useful for finding correlations between the various experimental
data. 相似文献
1