纤维素蒸汽闪爆改性及其在NaOH溶液中溶解的试验研究

介绍了纤维素结构、纤维素蒸汽闪爆的机理及纤维素蒸汽闪爆的处理过程。对闪爆纤维素的形态、聚合度、超分子结构及其溶解进行了分析。结果表明;高温、高压蒸汽闪爆是对纤维素改性的有效方法。     

天然纤维素蒸汽闪爆改性对其长支链酯合成影响

采用蒸汽闪爆技术对天然纤维素进行改性,并利用改性后的纤维素、乙酸酐和脂肪酸合成长支链纤维素酯。结果表明,蒸汽闪爆处理后纤维素葡萄糖环单元三个羟基的可及性及相对反应性能得到提高,同时缩短了反应周期。     

改性软木纤维素的NaOH水溶液体系成膜性研究

对天然软木纤维素进行了闪爆改性,同时以一定浓度的NaOH溶液为溶剂,采用H2SO4水溶液为凝固剂,制备出再生纤维素膜。分析了NaOH溶液浓度、H2SO4浓度、纤维素—NaOH溶液浓度及温度、时间等条件对成膜的影响,确定最佳软木纤维素闪爆条件。     

NaOH水溶液对改性软木纤维素的超分子结构作用研究

采用高压热蒸汽闪爆技术对天然软木纤维进行物理改性处理，对处理前后的试样进行X－射线衍射表征，溶解度测试，结果表明，在一定的压力及保压时间条件下，软木纤维在9％wt的NaOH水溶液中的溶解度达到100％，本文还就软木纤维的分子结构，超分子结构进行了讨论。     

硬木纤维素蒸汽闪爆处理机理的研究

研究了硬木纤维素在蒸汽闪爆改性过程中的各种状态及蒸汽闪爆对硬木纤维素超分子结构的影响。用SEM、X-射线衍射、FT-IR分析及对聚合度Pv、溶解度Sa的研究结果表明,蒸汽闪爆改性后硬木纤维素的结晶度Xc(X)和微晶尺寸L002有所增加,但其超分子结构遭到破坏,游离羟基和可及度有所增加,尤其是纤维素内部氢键的断裂与纤维素的Sa有十分密切的关系。     

棉纤维蒸汽闪爆改性及其化学反应性能

研究采用高压热蒸汽闪爆技术,对棉纤维进行物理改性,并对闪爆前后棉纤维形态、溶解度、聚合度分析表征。通过改性前后棉纤维合成羧甲基纤维素研究发现,闪爆改性后其反应性能有大的提高。     

天然纤维素蒸汽闪爆改性及其在新型溶剂中溶解与绿色湿纺技术

<正>一、项目简介项目针对目前粘胶纤维工业生产过程存在的污染严重问题,采用自行设计的高压热蒸汽闪爆(Steam Explosion,简称SE)技术,在超分子水平实现对天然木纤维素快速、安全可靠、低污染物理改性并固化其构象,同时利用环保、廉价的新型纤维素溶剂体系,实现温和条件下纤维素的溶解,通过真空脱泡、充氮、喷丝、凝固等工艺的优化获得了纤维素纤     

新型再生纤维素纤维的生产工艺、结构及性能

简述了从NaOH水溶液中通过湿纺技术制得的新型纤维素纤维的原料的处理工艺、纤维结构和性能。通过蒸汽闪爆蒸煮,从木浆可制得碱可溶纤维素,在4℃下可溶于9.1wt%的NaOH水溶液中。通过湿法纺丝技术,从该溶液中可制得具有良好性能的新型纤维素及其织物,性能测试结果表明,这一新型纤维具有良好的柔软性、耐磨性、抗起皱性和尺寸稳定性,是传统粘胶纤维的最佳替代品,其性能／价格比甚至优于NMMO溶剂纺纤维。     

纤维素的溶解与再生及其生物质能利用的新发展

纤维素是一类重要的天然高分子聚合物,具有广阔的应用前景。本文综述了纤维素的溶解与再生技术以及纤维素生物质利用技术的新发展。其中,纤维素的溶解与再生包括NaOH／CS2体系、铜氨溶液、胺氧化合物、NaOH／尿素水溶液以及离子液体,综述了各体系溶解与再生纤维素的技术要点与优缺点;生物质能利用包括从纤维素制备乙醇、氢气以及生物柴油。     

蔗渣闪爆处理及其黄原酸化物的制备和应用

采用热蒸汽适度闪爆及稀碱洗涤等预处理技术对蔗渣进行纯化和活化,利用处理后的蔗渣纤维素合成纤维素基黄原酸酯,对其在水处理中的应用进行了研究。研究优化了闪爆处理的工艺条件,并采用IR、SEM和化学分析技术对闪爆前后蔗渣纤维的形态、结构、a-纤维素的含量进行了分析,对处理前后的蔗渣纤维的碱化和黄原酸化合成条件进行了优化。结果表明,闪爆预处理技术是一种便宜、迅速、无污染的技术,蔗渣纤维素基黄原酸酯对含金属离子的污水有良好的处理效果。     

Characterisation of cellulose treated by the steam explosion method. Part 2: Effect of treatment conditions on changes in morphology,degree of polymerisation,solubility in aqueous sodium hydroxide and supermolecular structure of soft wood pulp during steam explosion

An attempt was made to clarify the effect of steam explosion conditions on the changes in morphology, degree of polymerisation P_v, solubility towards aqueous alkali solution S_a, and supermolecular structure of a soft wood pulp and to elucidate the mechanism by which the steam explosion treatment makes natural cellulose completely soluble in aqueous alkali solution. For this purpose, scanning electron microscopic (SEM) observation and X-ray diffraction, solid-state cross-polarisation/magic-angle sample-spinning (CP/MAS) ¹³C nuclear magnetic resonance (NMR), S_a and P_v measurements were carried out on a series of soft wood pulps treated systematically by the steam explosion method. It was found that (1) the maximum S_a (c. 100%) was obtained when the soft wood pulp was treated under the conditions of steam pressure P = 2.9MPa and treatment time t = 30s, (2) the decrease in P_v of the pulp by the steam explosion resembled conventional acid hydrolysis of cellulose, (3) a higher water content in the sample to be treated gave a lower degree of decrease in P_v, (4) the repeated steam explosion method gave more fibrillated sample with higher S_a than the corresponding batch steam explosion, (5) the amorphous content of the samples as estimated by X-ray analysis decreased by the steam explosion, in spite of an increase in S_a, and (6) the structural parameters expressing the degree of breakdown in the intramolecular hydrogen bonds at the C₃ and C₆ positions, X_am(C₃) and X_am(C₆), of the samples as estimated by CP/MAS ¹³C NMR changed as functions of P and t, being almost parallel to S_a. This suggests that these parameters may be more closely correlated with S_a than with X_am(X) from X-ray analysis.     

Characterisation of cellulose treated by the steam explosion method. Part 3: Effect of crystal forms (cellulose I,II and III) of original cellulose on changes in morphology,degree of polymerisaion,solubility and supermolecular structure by steam explosion

An attempt was made to clarify the effect of the crystal form of untreated cellulose on the morphological and structural changes of cellulose during steam explosion treatment (steam pressure P = 2.9MPa (T = 508K), treatment time t = 15-300 s). For this purpose, the crystal form of soft wood pulp (cellulose I) was converted by solid-to-solid transition, with minimal unavoidable change in other structural characteristics including morphology and average degree of polymerisation, into cellulose II or cellulose III. It was proved by both X-ray and solid-state cross-polarisation/magic-angle sample-spinning (CP/MAS) ¹³C NMR analyses that even a simple addition of water at room temperature brought about a significant structural change in the steam-untreated cellulose samples. The solubility towards 9.1 wt% aqueous sodium hydroxide, S_a, of the cellulose samples of crystal forms I and III could be improved from 31-33% up to almost 100% by selecting appropriate steam explosion conditions (for example, P = 2.9MPa, t = 30 s). Such a magnificent increase in S_a by the steam explosion treatment was not observed for the cellulose II sample, even under the rather severe conditions of the steam explosion treatment at which the cellulose III crystal was converted to a large extent to cellulose I, as confirmed by X-ray diffraction. X-ray diffraction analysis showed that crystallisation of samples with cellulose I or II crystal occurred to some extent during the steam explosion treatment. Contrary to this, the degree of breakdown of the intramolecular hydrogen bond O₃…O'₅, as estimated by CP/MAS ¹³C NMR analysis, significantly increased for cellulose I and I11 during the treatment. The decrease in the viscosity-average degree of polymerisation, P, observed for all treated samples can be roughly categorised into two or three steps of the first-order decomposition reaction with different reaction rates.     

New class of cellulose fiber spun from the novel solution of cellulose by wet spinning method

A novel cellulose solution, prepared by dissolving an alkali-soluble cellulose, which was obtained by the steam explosion treatment on almost pure natural cellulose (soft wood pulp), into the aqueous sodium hydroxide solution with specific concentration (9.1 wt %) was employed for the first time to prepare a new class of multifilament-type cellulose fiber. For this purpose a wet spinning system with acid coagulation bath was applied. The mechanical properties and structural characteristics of the resulting cellulose fibers were compared with those of regenerated cellulose fibers such as viscose rayon and cuprammonium rayon commercially available. X-ray analysis shows that the new cellulose fiber is crystallographically cellulose II, and its crystallinity is higher but its crystalline orientation is slightly lower than those of other commercial regenerated fibers. The degree of breakdown of intramolecular hydrogen bond at C₃[X_am(C₃)] of the cellulose fiber, as determined by solid-state cross-polarization magic-angle sample spinning (CP/MAS) ¹³C NMR, is much lower than other, and the NMR spectra of its dry and wet state were significantly different from each other, indicating that cellulose molecules in the new cellulose fiber are quite mobile when wet. This phenomenon has not been reported for so-called regenerated cellulose fibers.     

不同预处理对剑麻纤维组分和结构的影响

采用机械破碎、酸法蒸煮、氢氧化钠溶液碱法蒸煮、氨水处理和蒸汽爆破等五种不同物理和化学方法对剑麻纤维进行处理。通过化学分析、扫描电镜(SEM)及红外光谱(IR)等手段表征了处理前后剑麻纤维组分和结构的变化。结果表明,不同预处理方法均使剑麻纤维组分分离,杂质含量降低,纤维素含量提高。其表面形态和聚集态结构根据不同的处理方法而发生不同变化。在五种方法中以碱煮和蒸汽爆破处理效果较佳。     

木质纤维原料蒸汽爆破-生物联合预处理及其生物脱毒研究进展

在木质纤维素类生物质结构中,木质素是生物质中纤维素与半纤维素进行生物降解的天然抗性屏障,预处理是打破木质纤维素抗性结构这一阻碍生物转化与利用瓶颈的最主要途径。本文分别概述了木质纤维素蒸汽爆破预处理技术与生物预处理技术的研究现状,介绍了蒸汽爆破-生物联合预处理的研究进展,分析了蒸汽爆破预处理过程中抑制物产生的机理和主要抑制物的种类,并提出了具有脱毒效果的蒸汽爆破-生物联合预处理技术,以及木质纤维素高效预处理技术研究发展方向。     

氯化锌预处理玉米秸秆纤维素

采用新近发展的蒸汽爆破技术对玉米秸秆进行组分结合相分离,再用氯化锌溶液对汽爆后的物料进行纤维素结晶相破坏的预处理方法,运用单因素实验和响应面法获取处理过程中的多因素组合的优化,包括氯化锌质量分数、预处理时间、预处理温度对玉米秸秆纤维素预处理效果的影响,建立并分析了各因素与处理后玉米秸秆纤维素溶解度的数学模型,处理后的物料经X射线衍射(XRD)和扫描电镜(SEM)分析表明,纤维素致密结构被破坏。最佳预处理工艺条件为:氯化锌质量分数87%、预处理温度139℃、预处理时间49 m in,在该条件预处理后1 g玉米秸秆纤维素溶解度最高达0.762 g。     

汽爆预处理技术在纤维素乙醇工业化中的应用及实践

纤维素乙醇技术是推动秸秆高值化利用、缓解环境压力的重要途径之一。在整个工艺过程中,原料预处理对于纤维素乙醇技术的发展起着至关重要的作用。其中,蒸汽爆破是目前应用最广、工业化水平最高的预处理技术之一。综述了汽爆技术在纤维素乙醇工业化装置中的应用,按照汽爆方式、汽爆设备类型、工艺流程和添加的化学试剂的不同,对汽爆工艺和设备分别进行了介绍。综合而言,两段式连续汽爆预处理能够有效的降低半纤维素降解产生的抑制物,提高木糖回收率,降低原料成本,是比较有应用前途的技术之一,对设备的耐压能力和稳定性以及系统控制水平要求较高。从化学试剂的使用来看,中性或低酸汽爆是未来工业发展的方向。