Chemical compositions of hardwood and softwood pulps employing photoacoustic Fourier transform infrared spectroscopy in combination with partial least-squares analysis

In the present study, hardwood and softwood pulps were characterized by employing Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS). The pulp samples examined originated from Swedish sulfite and kraft pulp mills, which utilize different cooking processes and modern bleaching technologies. Partial least-squares (PLS) analysis was used to correlate the spectral data obtained with the kappa (K) numbers and carbohydrate compositions of the pulp samples determined by enzymatic hydrolysis and subsequent capillary zone electrophoresis. Using four principal components, the present PLS model based on photoacoustic FT-IR spectra could explain 85% of the variance in the X matrix and 81% of the variance in the Y matrix. The FT-IR-PAS technique in combination with PLS was found to accurately predict the contents of carbohydrates, i.e., xylose, glucose, mannose, arabinose, galactose, and hexenuronic acid residues, as well as the content of lignin measured in terms of K numbers and corrected K numbers of the pulps. From these predictions, the contents of xylan, glucomannan, and cellulose can also be predicted. The content of 4-O-methylglucuronic acid residues is, however, more difficult to predict accurately, using this approach.     

Comparison of the characteristics of hydrothermal carbons derived from holocellulose and crude biomass

The effects of lignin removal on hydrochar were investigated by comparing the structural, chemical, and thermal characteristics of holocellulose and wood powder-derived carbon materials (hydrochar). The hydrochar samples were obtained from hydrothermal carbonization (HTC) of holocellulose and wood powder at 210–230 °C for 9 h. The characteristics of the obtained products were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The observations reveal that the onset temperature of the HTC of holocellulose is lower than that of wood powder. The holocellulose-derived hydrochar samples exhibit higher carbon content and thermal stability with higher coalification degree and less complex chemical composition compared with resultant products based on wood powder. These results reveal that the holocellulose is easier to be disintegrated and hydrocarbonized without the shielding effects of lignin and suggest that the lignin removal is beneficial for increasing the rate and efficiency of the polysaccharide in biomass converting into hydrochar.     

模塑制品热压过程中木素结构变化研究

目的探讨以高得率浆(HYP)为原料制备模塑制品过程中木素结构的变化规律,为研究以HYP为代表的高木素含量原料制备模塑制品的强度形成机理提供理论依据,为逐步构建纸浆模塑技术纤维结合强度形成理论奠定基础。方法采用相对分子质量测定(GPC)、红外光谱分析(FT-IR)、二维核磁共振谱图(2D-HSQC)、定量磷谱分析(³¹P-NMR)等手段,通过模拟纸浆模塑热压干燥过程前后木素结构的对比,研究热压过程对木素结构的影响。结果基于落叶松HYP为原料的热压过程,模塑浆板(MPB)中的磨木木素(MWL)分子质量由5216 g/mol提高到6132 g/mol;FT-IR分析证实MPB-MWL的非共轭羰基减少,共轭羰基增加;从HYP-MWL到MPB-MWL的过程中,2D-HSQC解析证实树脂醇(B)结构百分比由8.66%减少到6.68%(以芳环为内标,下同),而苯基香豆满(C)结构百分比由15.45%增加到20.88%;由³¹P-NMR定量结果可知,MPB-MWL中脂肪族羟基、G型酚羟基结构、对-羟基酚羟基均较HYP-MWL有所降低。结论 MPB-MWL相对分子质量的提高说明木素在热压过程中发生了聚合反应;FT-IR分析证实非共轭羰基(C=O)化学键的断裂、共轭羰基(C=O)化学键的生成在热压过程中共存;2D-HSQC和³¹P-NMR分析证实木素解聚反应和聚合反应同时发生,是一对竞争性的反应,但聚合反应的程度大于解聚反应。     

Quantitative analysis of detailed lignin monomer composition by pyrolysis-gas chromatography combined with preliminary acetylation of the samples

Detailed quantitative analysis of lignin monomer composition comprising p-coumaryl, coniferyl, and sinapyl alcohol and p-coumaraldehyde, coniferaldehyde, and sinapaldehyde in plant has not been studied from every point mainly because of artifact formation during the lignin isolation procedure, partial loss of the lignin components inherent in the chemical degradative methods, and difficulty in the explanation of the complex spectra generally observed for the lignin components. Here we propose a new method to quantify lignin monomer composition in detail by pyrolysis-gas chromatography (Py-GC) using acetylated lignin samples. The lignin acetylation procedure would contribute to prevent secondary formation of cinnamaldehydes from the corresponding alcohol forms during pyrolysis, which are otherwise unavoidable in conventional Py-GC process to some extent. On the basis of the characteristic peaks on the pyrograms of the acetylated sample, lignin monomer compositions in various dehydrogenative polymers (DHP) as lignin model compounds were determined, taking even minor components such as cinnamaldehydes into consideration. The observed compositions by Py-GC were in good agreement with the supplied lignin monomer contents on DHP synthesis. The new Py-GC method combined with sample preacetylation allowed us an accurate quantitative analysis of detailed lignin monomer composition using a microgram order of extractive-free plant samples.     

醋化级竹浆粕的制备及醋化性能

以竹材为原料制备出醋化级的竹浆粕。采用FT-IR、X-ray以及HPLC对竹浆粕的物理化学性质进行了表征,开展了以竹浆粕为原料的醋化反应实验,并与木浆进行了比较。研究结果表明,竹浆粕中的α-纤维的含量能够满足醋化级浆粕的要求,并且由于其中纤维素的结晶度低,竹浆粕的醋化反应活性比木浆粕更高。以竹浆粕为原料合成的醋酸纤维素在丙酮中具有与木浆醋片相似的溶解性能。开发以竹材为原料制备竹浆,合成醋酸纤维素的工艺是完全可行的。     

Spectroscopic analysis of carbonization behavior of wood,cellulose and lignin

The surface and bulk chemistry of Japanese cedar (Cryptomeria Japonica), cotton cellulose and lignin samples carbonized at 500–1,000 °C was investigated by elemental analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and micro-Raman spectrometry. The objective was to link the original wood components to the final carbonized wood microstructures. The carbonized samples show increasing degrees of order from cellulose to wood to lignin. The cellulose component in the wood strongly affects the ordering of polyaromatic carbons in carbonized wood; this ordering is attributed primarily to the difference in ratio between aromatic and aliphatic carbons and to the amount of cross-linking by ether and carboxylic groups up to 500 °C.     

Expanding the library of secondary ions that distinguish lignin and polysaccharides in time-of-flight secondary ion mass spectrometry analysis of wood

Extracted pine (Pinus spp.) wood and the holocellulose and cellulose fractions of pine were analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The main sources of variation among wood constituents were elucidated by principal component analysis (PCA). Peaks characteristic of lignin or polysaccharides were identified through the combination of high mass resolution analyses of pine fractions and high lateral resolution image analyses distinguishing the lignin-rich middle lamella from the secondary cell wall layers in solid wood cross-sections. A collection of peaks was compiled which (1) extends the library of characteristic lignin and polysaccharide secondary ions in wood, (2) can be applied to both high and nominal mass resolution spectra, and (3) is free from peaks that contraindicate between wood components. The removal of additional peaks to avoid mass interferences with common contaminants was also successful. Many of the characteristic peaks were high-intensity fingerprint ions below m/z 100, which provided for rapid analysis of the lignin and polysaccharide biopolymers in woody samples. The analysis also identified important mass interferences with previously reported wood ions.     

合成革用麦草微晶纤维素的制备及其表征

微晶纤维素（MCC）可作为PU合成革湿法生产中优良的微孔剂和增稠剂使用,并能赋予合成革良好的手感和弹性,但国内外生产合成革用MCC多以棉浆粕和木浆粕为原料,资源少,成本高。以漂白麦草浆为原料,通过化学处理、生物酶处理和机械处理等工艺过程制备出了麦草MCC。重点探讨了酸处理工艺条件与产品性能的关系,并优化确定了最佳酸处理工艺。并利用SEM、XRD、TGA等手段分别对麦草MCC的微观形貌、结晶结构和热稳定性等性能进行了表征。研究结果表明,麦草MCC性能指标达到《合成革用微晶纤维素》行业标准要求,可以替代目前棉浆粕和木浆粕为原料生产的PU合成革用MCC产品。     

Identification of chlorinated dimethoxystilbene isomers and homologues in bleached paper products

We report here the identification of a novel class of compounds, the chlorinated dimethoxystilbenes (pinosylvins), in bleached paper products. Pinosylvins are naturally occurring compounds in wood that deter infections and predators. These compounds are being chlorinated during the pulp bleaching process. Two dichlorinated pinosylvins have previously been identified in bleached paper pulp, but we have identified other isomers and more highly chlorinated homologues in various bleached paper products. These compounds are present at concentrations on the order of hundreds of ppb. On the basis of the mass spectra of synthesized standards, we can distinguish the isomers in which the chlorines are located on the ethylene moiety from those in which the chlorines are located on the aromatic ring with the methoxy groups. In addition, we can predict the chlorine substitution patterns on both rings for these compounds using linear relationships between retention indexes and calculated dipole moments. The toxicity of these compounds is not known; however, isomers related to the pesticide methoxychlor are proestrogenic.     

Analysis of stress relaxation on the basis of isolated relaxation spectrum for wet wood

In this study, we investigated the relaxation properties of wet wood based on spectra isolated from the whole wood relaxation spectrum, calculated using Alfrey’s approximation at temperatures ranging from 25 to 85 °C. Three relaxation processes were identified, I, II, and III, in the order of low to high temperature, and these were attributed to local molecular motions of hemicellulose, lignin, and cellulose, respectively. Processes I and II (but not III) depended on temperature and the apparent activation energy, which was calculated from the temperature dependence of their relaxation time and was approximately 85 kJ/mol (20 kcal/mol) for both processes. The peak positions and intensity of the isolated relaxation spectra indicated that the molecular motion of the relaxation processes in the temperature range studied represent not whole molecular motion, but rather local molecular motion of the hemicellulose and lignin matrix. This study also demonstrated that the isolation procedure using a Gaussian function can be used to analyze the relaxation process of wood.     

Chemical analysis of wood chips in motion using thermal-emission mid-infrared spectroscopy with projection to latent structures regression.

The opacity and random surface orientation of process streams of solids complicates the application of spectroscopy to on-line analysis of solid streams. We have used a specialized form of thermal-emission mid-infrared spectroscopy, called transient infrared spectroscopy, combined with PLS regression to analyze a moving stream of wood chips for lignin, hemicellulose, glucan, and extractives content. Sixty-eight softwood samples from 6 species were analyzed using one regression, and 28 hardwood samples from 14 species were analyzed with another. Root-mean-square errors of prediction for the properties varied from 0.8 to 1.9 wt %, depending on property and wood type, with lignin and hemicellulose being the most accurately determined and glucan being the least.     

Ultra violet resonance Raman spectroscopy in lignin analysis: determination of characteristic vibrations of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures

Raman spectroscopy of wood and lignin samples is preferably carried out in the near-infrared region because lignin produces an intense laser-induced fluorescence background at visible excitation wavelengths. However, excitation of aromatic and conjugated lignin structures with deep ultra violet (UV) light gives resonance-enhanced Raman signals while the overlapping fluorescence is eliminated. In this study, ultra violet resonance Raman (UVRR) spectroscopy was used to define characteristic vibration bands of model compounds of p-hydroxyphenyl, guaiacyl, and syringyl lignin structures at three excitation wavelengths (229, 244, and 257 nm). The intensities of each band, relative to the intensity of the aromatic vibration band at 1600 cm-1, were defined and the most suitable excitation wavelength was suggested for each structure. p-Hydroxyphenyl structures showed intensive characteristic bands at 1217-1214 and 1179-1167 cm-1 with excitation at 244 nm, whereas the bands of guaiacyl structures were more intensive with 257 nm excitation. Most intensive characteristic bands of guaiacyl structures were found at 1289-1279, 1187-1185, 1158-1155, and 791-704 cm-1. Syringyl structures had almost identical spectra with 244 and 257 nm excitations with characteristic bands at 1514-1506, 1333-1330, and 981-962 cm-1. The characteristic bands of the three structural units were also found from the compression wood, softwood, and hardwood samples, indicating that UVRR spectroscopy can be applied for the determination of chemical structures of lignin.     

天然纤维素均相对甲苯磺酰化研究

以二甲基乙酰胺（DMAc）／LiCl为溶剂体系、以三乙胺（TEA）为催化剂，将完全溶解的不同种类的天然纤维素原料和对甲苯磺酰氯（Tos—Cl）在均相条件下进行对甲苯磺酰化反应。优化了反应条件．对产品进行了元素分析、红外光谱分析和X射线衍射分析。研究了纤维素葡萄糖残基与对甲幕磺酰氯的摩尔比、纤维素原料（软木纤维素，棉纤维素以及蒸汽闪爆处理的软木纤维素、棉纤维素）种类及溶解方法对合成产物取代度的影响。     

Application of time-of-flight-secondary ion mass spectrometry for the detection of enzyme activity on solid wood substrates

Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) is a surface analysis technique that is herein demonstrated to be a viable tool for the detection of enzyme activity on solid substrates. Proof-of-principle experiments are presented that utilize commercial cellulase and laccase enzymes, which are known to modify major polymeric components of wood (i.e., cellulose and lignin, respectively). Enzyme activity is assessed through principle component analysis (PCA) as well as through peak ratios intended to measure selective enzymatic wood degradation. Spectral reproducibility of the complex wood substrates is found to be within 5% relative standard deviation (RSD), allowing for relative quantification of changes in wood composition. Procedures are also presented to identify and avoid the influence of mass interferences from protein adsorption by the enzyme solutions. The activity of a cellulase cocktail is clearly evident through the TOF-SIMS spectra and is supported by high-pressure liquid chromatography (HPLC) measurements of sugar release and by complementary X-ray photoelectron spectroscopy (XPS) measurements of the wood surfaces. Laccase activity, which is mediated through small organic molecules, can be detected in the TOF-SIMS spectra through a decrease in G and S lignin peaks. This work has positive implications for the development of qualitative, high-throughput screening assays for enzyme activity on industrially relevant, lignocellulosic substrates.     

Physicochemical characterization of pulp and nanofibers from kenaf stem

The aim of this study was to isolate cellulose nanofibers from kenaf (Hibiscus cannabinus) stem using chemo-mechanical treatments. The fiber purification method included pulping and bleaching processes whereas the mechanical treatments employed to isolate kenaf nanofibers were grinding and high pressure homogenizing. Kenaf nanofibers were found to have diameters in the range of 15-80 nm while most nanofibers have diameters within the range 15-25 nm. Fourier transform infrared spectroscopy (FTIR) showed that the chemical treatments removed lignin and most of the hemicelluloses from the fibers. The thermal characteristics of the fibers were analyzed using the technique of thermogravimetric analysis (TGA) which demonstrated that these characteristics were enhanced noticeably both for the bleached pulp and nanofibers. On the other hand, the X-ray analysis indicated that both chemical and mechanical treatments can improve the crystallinity of fibers.     

Magnetic composite Ca(OH)2/Fe3O4 for highly efficient flocculation in papermaking black liquor without pH neutralization

Industrially, lignin in pulp liquor not only obstructed the realization of value-added products, but also threatened the aquatic ecosystem. A magnetic composite Ca(OH)₂/Fe₃O₄, combining the eco-friendliness of Ca-based flocculants with the convenience of magnetic flocculation, was simply compounded to efficiently flocculate lignin from papermaking black liquor. Morphologic and structural features of the flocculant before and after flocculation were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The flocculant Ca(OH)₂/Fe₃O₄ presented mesoporous and core-shell structure, which acted directly in the sodium lignin aqueous solution without pH neutralization, maintaining high lignin removal between 91% and 95%. Ca(OH)₂/Fe₃O₄ showed a wider salts (0–1 mol/L NaCl) and pH (9–12.5) tolerance. In actual pulp black liquor, Ca(OH)₂/Fe₃O₄ exhibited high removal of 90.16% and 85.93% for lignin and chemical oxygen demand (COD), respectively. The flocculation performance of Ca(OH)₂/Fe₃O₄ outdistanced that of the traditional flocculant polyacrylamide (PAM). It displayed magnetically separable with a good reusability. The removal of lignin could attain 90.54% even after 6 cycles. Charge neutralization, micro-bridging, destabilization and sedimentation were involved in the process of lignin flocculation. Consequently, Ca(OH)₂/Fe₃O₄ presented huge potential in papermaking black liquor treatment.     

Development and morphological characterization of wood pulp reinforced biocomposite fibers

Biocomposite fiber has been developed from wood pulp and polypropylene (PP) by an extrusion process and the generated biocomposite fibers were characterized to understand the nature of interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Fiber length analysis showed that most of the fiber lengths lie within the range of 0.2–1.0 mm. Changes in absorption peaks were observed in Fourier transform infrared spectroscopy of biocomposite fibers as compared to the virgin wood pulp, which indicated possible chemical linkages between the fiber and polymer matrix. SEM study was carried out to observe fiber–matrix adhesion at the interface within the composite and MAPP treatment was found to be effective in increasing reinforcing fibers–matrix compatibility. X-ray computed tomography was conducted to understand the internal architecture of the biocomposite fiber and the results showed that with incorporation of additional wood pulp content, the fiber becomes more aligned along length axis possibly due to compression and die geometry of the extruder.     

凹凸棒石的提纯及其在魔芋葡甘聚糖中的应用

采用悬浮液法对江苏省盱眙县凹凸棒石高粘矿原矿进行提纯。利用正交实验考察了凹凸棒石原矿(AT)矿浆浓度、搅拌时间、聚丙烯酸钠用量对提纯凹凸棒石(PAT)膨胀容的影响。试验结果表明:AT矿浆浓度为5%、搅拌时间90min、聚丙烯酸钠用量0.6%时,PAT的膨胀容最大,凹凸棒石提纯效果最佳。XRD和FT-IR分析结果也同样表明,提纯后的凹凸棒石黏土纯度明显提高。以PAT为原料,以魔芋葡甘聚糖(KGM)为基体,采用共混法制备了魔芋葡甘聚糖/凹凸棒石纳米复合膜,并用FT-IR、SEM对复合膜进行了表征。结果表明:凹凸棒石的引入,KGM分子某些特征峰的波数发生了明显变化,此外复合材料的力学性能有所提高。     

Dimensional instability of cement bonded particleboard: behaviour of wood chips from various stages of manufacture of CBPB

A technique for the dissection and measurement of wood chips used in cement bonded particleboard (CBPB) removed from the unpressed mat and the pressed board has been developed. The prepared chips were subjected to changing relative humidity (RH) conditions. The results illustrated the contribution of wood chips to the performance of CBPB. The trend in change of dissected chips was similar to that of CBPB but to a different degree under both a single and cyclic change in RH. However, the compression, contortion and chemical degradation of, and the inclusion of cement in, wood chips within CBPB resulted in an increase in mass change but decrease in dimensional change of dissected chips which were about 0.7, 3.0 and 1.3 times the change of raw wood chips respectively in mass, length and thickness over period tested. The combined effects of anisotropic characteristic, distribution and orientation of wood chips within CBPB brought about a significantly different ratio between length and thickness change of dissected chips to CBPB, having a ratio of about 2.5 for length and 15 for thickness. The nature of hysteresis loop for dissected chips was also very close to that of CBPB but dissimilar to that of raw wood chips. Chips from the various stages of the production process showed very different responses to RH due to the effect of the processing parameters (pressure, curing temperature and time) on the nature of wood chips. The chips coated without any curing treatment were the most resistant to changing RH while raw wood chips had the greatest change in mass and the chips dissected from final product had the greatest change in dimensions. With the exception of raw wood chips, all types of chips showed a consistent increase in mass and a slight decrease in dimension with increasing number of cycles. This revised version was published online in September 2006 with corrections to the Cover Date.     

Fourier transform-infrared and optical studies on sol-gel synthesized SrTiO3 precursor films

SrTiO₃ precursor thin films were deposited on KBr single crystals and fused silica substrates by the sol-gel technique. Fourier transform-infrared (FT-IR) spectra, ultraviolet-visible spectra and X-ray diffraction spectra were recorded after the samples were cured at various temperatures. FT-IR spectra showed a gradual decrease in -OH concentration indicating removal of hydroxyls and reduction in peaks belonging to organic groups indicating the removal of organics. After annealing at 500 °C, the peak due to SrTiO₃ crystallites (500 cm^–1) began to appear, indicating crystallization. The optical spectra showed an increase in refractive index due to densification as the curing temperature increased. With increase in curing temperature, the thickness of the film decreased, indicating densification due to pore collapse. The optical band gap also changed with annealing due to the structural transformation from amorphous to crystalline phase. X-ray diffraction spectroscopy confirmed the structural changes.