共查询到17条相似文献,搜索用时 125 毫秒
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介绍了乙二胺、氢氧化钠和高温等三种不同的纤维素预处理方法。研究预处理后纤维素的结构变化,讨论预处理过程中的转化机理,并通过X射线衍射对纤维素结晶度的变化进行表征,证明乙二胺预处理后纤维素的结晶度下降最大。纤维素经过预处理后可以溶解在DMAc/LiCI中,讨论其溶解机理,通过对比三种预处理纤维素的溶解性能,表明经过乙二胺预处理之后的纤维素在DMAc/LiCI中溶解性能最好,氢氧化钠预处理的纤维素次之,高温预处理的纤维素溶解性能相对较差。 相似文献
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《纤维素科学与技术》2015,(4):37-42
纤维素经过活化、再生后可以溶解在氢氧化钠/尿素体系中。本文研究了乙二胺活化对细菌纤维素结晶度的影响规律,得到最佳活化条件;然后将活化后的细菌纤维素在LiCl/DMAc体系中溶解再生,得到再生细菌纤维素。最后,使用氢氧化钠/尿素溶液作为再生细菌纤维素的复合溶剂,得到的细菌纤维素的水溶液。通过红外光谱、X射线衍射仪、热重分析仪等分析了细菌纤维素不同处理阶段得到产物的性能。溶解与再生并没有发生化学变化,纤维素的结构基本保持不变,但结晶度有所降低,热稳定性有所提高。 相似文献
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《化学与生物工程》2017,(10)
纤维素在小麦秸秆中含量丰富,但因其结晶度高而不易改性。以小麦秸秆为原料,采用NaOH/硫脲/尿素水溶液法和乙二胺法分别对小麦秸秆纤维素进行预处理,采用正交实验对2种化学预处理方法进行优化,通过FTIR、XRD对红外光谱、结晶度、晶型的测定,比较了2种化学预处理方法对小麦秸秆纤维素的影响。结果表明,采用优化的NaOH/硫脲/尿素水溶液法(NaOH、硫脲、尿素的质量分数分别为8%、7%、6%),能使纤维素结晶度降低51%,晶型由纤维素Ⅰ变为纤维素Ⅱ;而采用优化的乙二胺法[乙二胺质量分数70%、液固比16∶1(mL∶g)、处理温度40℃、处理时间4h],纤维素结晶度仅降低36%,且晶型未变,仍为纤维素Ⅰ。 相似文献
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采用不同方法将棉纤维活化并溶解在LiCl/DMAc极性溶液中,研究了活化方法、溶解温度、时间及LiCl浓度对棉纤维素溶解性的影响。结果表明:DMAc热活化法为较好的活化方法;提高溶解温度,延长溶解时间及提高LiCl浓度均有利于棉纤维溶解;棉纤维在LiCl质量分数为12%的LiCl/DMAc溶液中,150℃下搅拌4h,溶解度可达3%。碱活化法使棉纤维素聚合度大幅度降低,可提高棉纤维溶解度至8%。通过扫描电镜和X射线衍射方法研究了棉纤维在前处理和溶解过程中的形态和结构变化,初步揭示了纤维素高温处理后在低温下发生溶解的机理。 相似文献
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木薯酒精渣的处置是制约木薯燃料乙醇大规模产业化的问题之一。本文立足于探索木薯酒精渣利用途径,分析了木薯酒精渣的主要成分,对比了氨水、氢氧化钠、氨水组合稀硫酸3种预处理方式对于木薯酒精渣纤维素和木素含量及纤维素酶水解效率的影响,分析了处理前后木薯酒精渣的表面结构及纤维素结晶度,并以氨水处理后的木薯酒精渣为底物,进行了同步糖化发酵。结果表明,3种预处理方法中组合预处理能更好地增加纤维素含量和提高纤维素酶水解效率,与未处理原料相比,组合预处理后纤维素含量增加了111.26%,木素下降了35.05%,酶水解72h纤维素转化率从42.10%增加到61.71%。氨水预处理后,原料的木素含量降低,处理后木薯酒精渣的表面变得更加粗糙,纤维素结晶度有所增加,以氨水处理后的木薯酒精渣为底物进行分批补料同步糖化发酵,当初始底物浓度为100.0g/L,分别在20h、40h、60h进行补料至最终底物浓度为400.0g/L时,发酵120h乙醇浓度达到51.0g/L。 相似文献
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以N,N二甲基乙酰胺/无水氯化锂(DMAc/LiCl)为溶剂配置聚丙烯腈(PAN)和棉纤维素溶液,采用旋涂法制备不同比例的PAN/棉纤维素薄膜。通过旋转黏度计对PAN/棉纤维素共混溶液的表观黏度进行研究,采用X射线衍射仪、傅里叶红外光谱仪、电子万能试验机以及吸水性能测试对PAN/棉纤维素薄膜的结构和性能进行了研究。结果表明,共混溶液的表观黏度随着纤维素含量的增加逐渐增大;DMAc/LiCl溶剂对PAN和棉纤维素的溶解为直接溶解,没有发生衍生化反应;PAN和棉纤维素均保持各自结晶结构不变;当棉纤维素含量为2.0 %(质量分数,下同)时,复合薄膜的拉伸强度和断裂伸长率达到最大值;棉纤维素含量越高,复合薄膜的吸水性越好。 相似文献
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Novel aerogels (or aerocellulose) based on all‐cellulose composites were prepared by partially dissolving microcrystalline cellulose (MCC) in an 8 wt % LiCl/DMAc solution. During this process, large MCC crystals and fiber fragments were progressively split into thinner crystals and cellulose fibrils. The extent of the transformation was controlled by using cellulose concentrations ranging from 5 to 20 wt % in the LiCl/DMAc solution. Cellulose gels were precipitated and then processed by freeze‐drying to maintain the openness of the structure. The density of aerocellulose increased with the initial cellulose concentration and ranged from 116 up to 350 kg m?3. Aerocellulose with relatively high mechanical properties were successfully produced. The flexural strength of the materials reached 8.1 MPa and their stiffness was as high as 280 MPa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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Large amounts of textile waste are generated every year and disposed of through landfill or incineration, leading to numerous environmental and social issues. In this work, the dissolution of three typical waste cotton fabrics (t-shirts, bed sheets and jeans) in NaOH/urea aqueous solution, H2SO4 aqueous solution, and LiCl/DMAc solution was investigated. Compared to different types of cotton fabrics, the effects of three solvents on the dissolution of fabrics were more obvious, leading to the significant changes in the structure and properties of regenerated cellulose films. Cotton fabrics (about 2%–5%) were rapidly dissolved (8 min) in H2SO4 and NaOH/urea solvents after acid pretreatment, while the dissolution in LiCl/DMAc solvent did not need any pretreatment, but a lower cellulose concentration (1%), higher dissolution temperature (80°C), and longer dissolution time (24 h) were required. The films produced from bed sheets in NaOH/urea solution exhibited the highest tensile strength, thermal stability, and water vapor barrier property. It was because of the stronger cellulose chain entanglement and hydrogen bonds induced by the higher cellulose concentration in NaOH/urea solution. Therefore, this work proves the feasibility to recycle waste cotton fabrics into biodegradable cellulose films, which can be potentially used in various food and agricultural applications. 相似文献
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Michael FitzPatrick Pascale Champagne Michael F. Cunningham Charlene Falkenburger 《加拿大化工杂志》2012,90(5):1142-1152
Rapid and facile screening techniques to determine the effectiveness of solvents for cellulose or biomass dissolution can advance biomass processing research. Here, we report the use of a simple optical microscopy method to screen potential cellulose and lignin solvents. The described methodology was used to screen the dissolution of cellulose and lignin in two imidazolium‐based ionic liquids (ILs), two phosphonium‐based ILs, as well as a N,N‐dimethylacetamide/lithium chloride (DMAc/LiCl) solution in less time than other techniques. The imidazolium‐based ILs and the DMAc/LiCl were found to dissolve both cellulose and lignin. Also, it was observed that one of the phosphonium‐based ILs dissolved lignin and not cellulose, demonstrating a potential for biomass fractionation applications. © 2011 Canadian Society for Chemical Engineering 相似文献
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研究了制备纤维素纤维的新型原料——纤维素氨基甲酸酯(CC)溶液的制备工艺及其稳定性。结果表明:在-5~10℃条件下,用聚合度为350~612的纤维素浆粕(棉浆粕、木浆粕)合成的氮含量(酯化度)为2.34%~3.56%的CC能很好地溶解在质量百分比浓度为8%~11%的NaOH溶液中,形成淡黄色透明溶液,该溶液稳定性良好,可用于纺丝。另外,尿素、AlCl3及ZnCl2在一定范围内对CC有助溶作用。 相似文献
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Shear‐induced morphology changes in N,N′‐dimethylacetamide/lithium chloride pretreated cellulose 下载免费PDF全文
A new mechanochemical treatment was performed on cellulose with the objective of modifying its morphology, reducing its crystallinity, and enabling better dissolution. Cellulose treated with N,N′‐dimethylacetamide (DMAc)/lithium chloride (LiCl) was subjected to shear with natural rubber as the carrier and shear‐transfer medium. When cellulose was subjected to such a mechanochemical treatment, significant changes in its surface morphology and a decrease in crystalline index were observed. The dissolution of the mechanochemically treated cellulose samples in DMAc/LiCl was found to be better compared with the dissolution of samples subjected to either mechanical shear or the chemical action of DMAc/LiCl independently. Chemical interactions between DMAc/LiCl and cellulose were enhanced synergistically under shear‐induced deformation. When shear alone was used in the absence of a DMAc/LiCl treatment, changes in the morphology, crystalline index, and dissolution were found to be negligible. The shear‐induced cellulose samples were characterized with Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and thermogravimetric analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44809. 相似文献