超低马来酸水解纤维素的试验研究

以定量滤纸为纤维素模化物,在3种超低酸浓度和4种温度下进行了马来酸水解的多点取样实验,以还原糖收率为指标得到较佳工况,并进一步通过间歇实验确定酸浓度0.1%、液固比20:1、温度220℃、压力4MPa、搅拌速率500r/min、反应时间55min为较优工况,可得到还原糖收率、还原糖转化率和原料转化率分别为32%、66%和48%。硫酸水解的较佳工况比较,发现马来酸存在下还原糖降解较弱,糠醛类的相对含量比硫酸存在时减少24.57%(48.22%:72.79%)。马来酸水解纤维素产糖多为聚糖;残渣依然具有纤维素特性,但结晶度较原料降低17%,对后续的酶解及发酵有利。     

微波促纤维素超稀酸水解研究

将微波加热方法应用于纤维素超稀酸水解。研究了在微波辐射及加压条件下纤维素的超稀酸水解机理,并对超稀硫酸和超稀马来酸的催化水解效果进行了对比研究,通过正交试验考查了固含量、酸浓度、反应压力、反应时间及微波功率对还原糖得率的影响。试验结果表明,对于纤维素超稀酸水解制备还原糖的转化,微波加热法可降低反应压力,缩短反应时间,提高水解液还原糖浓度;在优化工艺条件下,超稀马来酸的催化效果优于超稀硫酸。对纤维素水解残余物的红外分析表明,超稀硫酸和超稀马来酸催化水解残余物均保留了较好的纤维素特征。     

纤维素低浓度酸水解试验及产物分析研究

在自行设计小型间歇生物质水解试验台上,以0.01%~0.10%超低浓度硫酸为催化剂对纤维素进行了高温中压水解,在0.05%硫酸作为催化剂的条件下,于215℃和40atm等优化条件下得到了46.55%的还原糖得率和55.07%的纤维素转化率。并以HPLC、GC-MS、X射线能谱分析和扫描电镜等分析手段对液体产物和固体残渣进行了分析研究,最后对纤维素水解反应途径进行了探讨。     

超低酸催化纤维素醇解制备乙酰丙酸乙酯

乙酰丙酸乙酯（EL）是极具潜力的生物质燃料和添加剂,利用产量丰富的生物质生产EL有利于EL的产业化、大规模化生产。文章利用超低浓度硫酸催化纤维素制备EL,研究了硫酸用量、反应时间、反应温度和底物浓度对EL产率的影响,并利用响应面Box-Behnken模型研究各因素对EL产率的影响。优化EL制取工艺,得到了超低浓度硫酸催化纤维素制取EL的最优工艺条件：硫酸用量为0.5%,反应温度为204℃,反应时间为240 min,底物浓度为29 g/L,EL实际平均产率为66.70%,与理论预测值相对误差为3.25%。利用GC-MS分析了不同反应时间下超低浓度硫酸催化纤维素的醇解产物分布,提出了可能的反应路径。研究结果可为纤维素生物质醇解转化提供借鉴和参考。     

芒草稀硫酸水解工艺条件的正交实验

芒草含有80%以上的可降解的纤维素和半纤维素,仅含有19%的不被酸降解的苯环化合物,木质素,适于作为生产燃料乙醇的原料。通过对芒草稀酸水解工艺的正交实验研究,探讨了反应时间、硫酸浓度、原料与硫酸的固液比等因素对纤维素、半纤维素降解为葡萄糖、木糖及总糖含量的影响。结果表明:在121℃条件下,对于纤维素,影响葡萄糖产量的主要因素是硫酸浓度;而对于半纤维素,1.5%的硫酸就可使之降解完全;但在酸浓度较高时,会产生葡萄糖、木糖以外的杂质。     

2-乙基蒽醌修饰碳电极电芬顿法解聚纤维素

以2-乙基蒽醌修饰的石墨/聚四氟乙烯电极作为阴极,通过电芬顿反应降解纤维素,考察了盐酸浓度、电解电位和氯化亚铁含量等因素对纤维素降解的影响。结果表明,由1 mol/L盐酸和0.4 g氯化亚铁组成的100mL溶液中,在电解电势为-1.2 V(vs.SEC)下,电化学降解4 h,纤维素的解聚率为85.8%。采用苯酚-硫酸法确定了降解产物中可溶性糖的含量,用核磁和质谱对降解液中的提取物进行了表征,分析表明,产物中含有5-羟甲基糠醛。文章把环境友好的电芬顿法引入到纤维素的降解研究中,取得了初步进展,推动了可再生能源纤维素的利用。     

生物质酸催化两步水解反应的研究

以松木木屑为原料,在自行设计的连续水解反应装置中进行稀硫酸催化连续水解的研究。通过正交试验法对木屑水解的反应条件进行优化,得到分别以木糖和葡萄糖为目标产物的较优工艺条件;以正交试验得到的工艺条件为基础,对木屑两步水解反应进行单因素分析,得到的最佳工艺分别为:反应温度170℃,反应时间5min,酸浓度1%,液固比7和反应温度190℃,反应时间7min,酸浓度3%,液固比9;通过分析半纤维素和纤维素的水解情况,探讨半纤维素水解对纤维素水解的促进作用机理。     

混合酸催化水解白酒丢糟的研究

以还原糖浓度和糠醛生成量为指标,通过正交试验方法优化混合酸催化水解白酒丢糟的工艺条件,并分析丢糟酸解前后的结构特性。结果表明,丢糟在温度为100℃、固液比为1:12、混合酸浓度为2.5%的最优条件下催化水解120 min,可获得59.32 g/L还原糖,抑制物糠醛的生成量仅为8.37 g/L。结构特性分析表明,酸水解后的丢糟形态结构变化明显,木质纤维结构被破坏,其中的纤维素和半纤维素组分发生降解,酸解残渣的相对结晶度提高。     

基于高效液相色谱分析的生物质超低酸水解研究

基于自行开发的生物质水解装置,应用高压液态水与超低浓度酸相结合的二步水解的方法,对木聚糖和定量滤纸进行水解试验研究,继而在此基础上研究了3种典型生物质的二步超低酸水解规律。对水解液体产物应用高效液相色谱方法进行定性和定量分析,从而得知3种典型生物质第一步水解产物中主要以木糖和低聚木糖为主,第二步水解产物中主要有纤维二糖,葡萄糖及少量果糖。由于3种原料组成不同,其糖类产物的分布和含量有较大差别。     

木质纤维素两步稀酸低温水解研究

为了降低水解液中抑制剂的浓度,对木质纤维素采用两步稀酸低温水解,通过对两步稀酸水解中重要参数(温度,反应时间,硫酸浓度)的研究,得到第一步水解的最佳条件为:温度135℃,反应时间2h,硫酸1.5%;第二步水解最佳条件为:温度135℃,反应时间2h,硫酸3.0%。以秸秆为原料得到的糖浓度可达5%。采用嗜鞣管囊酵母对水解软木所得水解液进行乙醇发酵实验,24h乙醇产率为0.41g/g,达到最大理论产率的80.4%。乙醇发酵实验证明,两步稀酸低温水解物对乙醇发酵没有抑制作用。     

Experimental study and product analysis of lignocellulosic biomass hydrolysis under extremely low acids

Using our self-designed facility for lignocellulosic biomass hydrolysis under extremely low acid, and under the optimal reaction conditions of hemicellulose and cellulose determined by xylan and quantitative filter paper as the model, two-step dilute acid hydrolysis was carried out in detail on pine, fast-growing poplar and maize straw. The corresponding conversion ratio is 41.78%, 57.84% and 53.44% and the total reducing sugar conversion ratio is 39.28%, 42.83% and 23.82% respectively. Simultaneously, sugar component analysis of the products was performed by high performance liquid chromatography (HPLC) and monosaccharide and oligosaccharide content were compared. Finally, poplar hydrolysis residues were analyzed by proximate and ultimate analysis.     

Experimental study and product analysis of lignocellulosic biomass hydrolysis under extremely low acids

Using our self-designed facility for lignocellulosic biomass hydrolysis under extremely low acid, and under the optimal reaction conditions of hemicellulose and cellulose determined by xylan and quantitative filter paper as the model, two-step dilute acid hydrolysis was carried out in detail on pine, fast-growing poplar and maize straw. The corresponding conversion ratio is 41.78%, 57.84% and 53.44% and the total reducing sugar conversion ratio is 39.28%, 42.83% and 23.82% respectively. Simultaneously, sugar component analysis of the products was performed by high performance liquid chromatography (HPLC) and monosaccharide and oligosaccharide content were compared. Finally, poplar hydrolysis residues were analyzed by proximate and ultimate analysis. __________ Translated from Journal of Engineering Thermophysics, 2006, 27(5): 741–744 [译自: 工程热物理学报]     

水热条件下CO2催化棉纤维水解过程的研究

纤维素是地球上丰富的可再生资源之一,通过水解纤维素可以获得许多有价值的化合物.以脱脂棉为纤维素模型化合物,研究了水热条件下CO2催化脱脂棉的水解过程.试验结果表明:在水热条件下,CO2可以有效地催化脱脂棉进行水解反应.DSC分析表明:水解后棉纤维的软化点向高温区移动,即非晶态纤维减少;SEM图显示:在无CO2催化条件下,脱脂棉的水解反应主要是非晶态纤维的水解;在CO2催化条件下,晶态纤维素也可以被有效地水解.此外,还考察了温度、CO2压力和停留时间对棉纤维水解过程的影响.     

The effect of temperature and hemicellulose-lignin,cellulose-lignin,and cellulose-hemicellulose on char yield from the slow pyrolysis of rice husk

In this work, the effect of temperature on the char yield of untreated rice husk, cellulose removed (hemicellulose + lignin), hemicellulose removed (cellulose + lignin), and lignin removed (cellulose + hemicellulose) is investigated. The work compares the performance of acid and alkaline hydrolysis in the context of lignin removal as well. The effect of hemicellulose-lignin, cellulose-lignin, and cellulose-hemicellulose on char yield during slow pyrolysis of rice husk is also studied. The study reveals that only low temperatures favor char yield. Alkaline hydrolysis effects better lignin removal than acid hydrolysis. The effect of hemicellulose-lignin on char yield is more than cellulose-lignin and cellulose-lignin.     

Increased Saccharification Yield by Cellulases Coupling

In many cellulase preparations the enzymatic activity is not well balanced and the catalytic attack of the cellulose is limited. The purpose of this study was to investigate the possibility of simultaneously using two cellulases from distinct sources for improving the rate of hydrolysis as alternative to other costly techniques which require enzyme separation and purification

A comparative study on the hydrolysis of microcrystalline cellulose (Avicel), amorphous cellulose derivative (CMC) and native cellulose-olive husks, catalyzed by mixtures of cellulase complexes was performed in ultrafiltration and batch reactors. The experiments were carried out varying the percentages of Trickoderma viride and Aspergillus niger in the enzymatic preparation and the effect of enzyme composition on cellulose conversion and glucose selectivity was determined. The use of mixtures of these two enzymes improves cellulose saccharification in a different extent depending on the chemical and physical features of the cellulose and on the biomass particle size. The increase of glucose production is three times as big as with the use of the two enzymes separately. For the olive husks the optimum is attained for a T. viride to A. niger ratio of 2:1. An ultrafiltration-membrane reactor for the hydrolysis of the three substrates can be helpfully adopted since product inhibition is controlled and a higher glucose selectivity is reached in comparison With batch ones.     

Kinetics of the thermal decomposition of cellulose under the experimental conditions of thermal analysis. Theoretical extrapolations to high heating rates

Thermobalance-mass spectrometer (TG-MS) experiments carried out by the authors in a period of 8 years are reviewed and analyzed. Celluloses and lignocellulosic biomass samples were studied. The data are evaluated by the method of least squares. The results indicate that a single rate-controlling reaction step dominates the kinetics of the cellulose decomposition at low heating rates (2–20°C/min) provided that the heat and mass transport problems are experimentally eliminated and the amount of catalytic impurities is reduced by dilute acid or hot water washing treatments. The kinetic parameters obtained from the experiments with different cellulose and biomass samples evidenced only ca 8% scattering. A simple explanation is given for the kinetic compensation effect observed. Theoretical extrapolations are presented to predict the behavior of extremely small, idealized cellulose samples at high heating rates.     

Tight control of cellulose depolymerization towards glucose in organic electrolyte solutions

Organic electrolyte solutions (OES) prepared by combination of an ionic liquid (1-Butyl-3-methylimidadozium chloride) with dimethyl sulfoxide (DMSO) have been tested as reaction media for the controlled hydrolysis of cellulose. The use of these mixtures is justified because of they provide an excellent media for the solubilization of cellulose, while saving a significant fraction of expensive ionic liquids. Cellulose hydrolysis tests performed in presence of these OES media have been used to determine the influence of several important operational reaction variables. These include the determination of the influence of the mineral acid used as catalyst, the reaction temperature, the amount of water as well as the addition rate of the same to the reaction media in the production of glucose. While the presence of mineral acid is mandatory, not only to accomplish cellulose hydrolysis, but to maintain the polysaccharide under solution, the amount of water and its addition rate is crucial to provide a proper control in the hydrolytic cleavage of 1,4-glucoside bondings between glucose units. While low amounts of water hampers the cellulose hydrolysis rate and produces large yields of by products coming from the dehydration of glucose, the opposite leads to the precipitation of the polysaccharide. In both cases a low yield towards glucose is achieved. In this way, the control of the water concentration in the reaction media, together with the use of an appropriate reaction temperature, allows maximizing the production of glucose with an outstanding selectivity towards this monosaccharide, leading to the transformation of more than 90% of the starting dissolved cellulose into glucose. This methodology can be easily adapted to the transformation of other cellulose-based materials, such as biomass-feedstocks like wheat straw or paper-derived materials.