A study on the recovery of xylitol by batch adsorption and crystallization from fermented sugarcane bagasse hydrolysate

Xylitol was recovered from fermented sugarcane bagasse hemicellulosic hydrolysate by adsorption and crystallization procedures. Silica gel adsorption was employed to purify the broth containing xylitol. In this step, different mixtures of the solvents ethyl acetate, ethanol and acetone were used as eluent, and different proportions of fermented broth volume incorporated per gram of silica gel (V_b/M_sg, varying from 1.0 to 2.0 cm³ g^?1) were used to pack the column employed as stationary phase bed. The xylitol purification efficiency varied for each mixture of solvent, and for each V_b/M_sg ratio used. The purified broth was submitted to different crystallization procedures (cooling, concentration and supplementation with commercial xylitol) aiming to recover xylitol crystals. The best result (60% crystallization yield and 33% total recovery of xylitol from fermented broth) was obtained when the column was packed with a V_b/M_sg ratio of 2 cm³ g^?1, and the broth was purified with a mixture of ethyl acetate and ethanol, concentrated 6.5‐fold, and supplemented with commercial xylitol to force the precipitation. Copyright © 2006 Society of Chemical Industry     

Effect of pH and activated charcoal adsorption on hemicellulosic hydrolysate detoxification for xylitol production

Biotechnological conversion of xylose into xylitol using hydrolysates obtained from the hemicellulosic fraction of lignocellulosic materials is compromised by the presence of compounds released or formed during the hydrolysis process, some of them being toxic to microorganisms. In order to improve the bioconversion of these hydrolysates it is necessary to find methods to reduce their toxicity. In the present work, rice straw hemicellulosic hydrolysate was treated by six different procedures (all of them involving pH adjustment, with or without activated charcoal adsorption), before being used as a fermentation medium for xylitol production. The most effective method of treatment was to increase the initial pH (0.4) to 2.0 using solid NaOH, followed by the addition of activated charcoal (25 g kg^?1) and increase in the pH to 6.5 using solid NaOH. Lignin degradation products were the most inhibitory compounds present in the hydrolysate; their removal was selective and strongly dependent on the pH employed in the treatment. The highest yield of xylitol was 0.72 g g^?1 xylose, with a productivity of 0.55 g dm^?3 h^?1. Copyright © 2004 Society of Chemical Industry     

Effect of glucose:xylose ratio on xylose reductase and xylitol dehydrogenase activities from Candida guilliermondii in sugarcane bagasse hydrolysate

The influence of glucose on xylose reductase (XR) and xylitol dehydrogenase (XDH) enzyme activity was evaluated from sugarcane bagasse hydrolysate fermentations with different glucose:xylose ratios (1:25, 1:12, 1:5 and 1:2.5) by employing an inoculum of Candida guilliermondii grown in media containing glucose, a mixture of glucose and xylose, or only xylose as carbon sources. According to the results, the glucose:xylose ratio affected positively this bioconversion and a correlation was not observed between the favourable conditions for xylitol production and the XR and XDH activities. Also, the results were influenced not only by the glucose:xylose ratio in the fermentation medium, but also by the carbon source employed in the growth medium of the inoculum. The optimum condition for xylitol production by C. guilliermondii in sugarcane bagasse hemicellulosic hydrolysate should use hydrolysate with a 1:5 glucose:xylose ratio and inoculum grown in medium containing xylose as the only carbon source. Copyright © 2006 Society of Chemical Industry     

Detoxification of sugarcane bagasse hemicellulosic hydrolysate with ion‐exchange resins for xylitol production by calcium alginate‐entrapped cells

This study describes the performance of four different resins, in sequence, to detoxify sugarcane bagasse hemicellulosic hydrolysate and to improve xylitol production by calcium alginate‐entrapped Candida guilliermondii FTI20037 cells under conditions of low oxygen concentration. The treatment resulted in a removal of 82.1% furfural, 66.5% hydroxymethylfurfural, 61.9% phenolic compounds derived from lignin degradation, 100% chromium, 46.1% zinc, 28.5% iron, 14.7% sodium and 3.5% nickel. On the other hand, the removal of acetic acid was not significant. A xylitol yield factor (Y_P/S) of 0.62 g g^?1 and a volumetric productivity (Q_p) of 0.24 g dm^?3 h^?1 were attained in the fermentation process for xylitol production from detoxified hydrolysate. Copyright © 2004 Society of Chemical Industry     

降低磷酸生产中硫酸消耗的技术措施

云天化云峰分公司产能为P2O5 280kt／a磷酸装置存在硫酸消耗偏高问题,分析磷酸生产中硫酸消耗偏高的原因,从合理配矿、改善矿浆粒度、控制萃取SO3含量、改善过滤状况等方面提出了降低硫酸消耗的技改措施。技改后,每吨P2O5硫酸消耗由2．628t降为2．512t。     

二水法磷酸生产降低硫酸消耗的几点措施

硫酸消耗是磷酸生产的主要经济技术指标,降低磷酸过滤系统水溶磷的损失是降低硫酸消耗最有效的途径。通过采取改变过滤系统洗涤水水质、改善滤盘上洗涤水分布等措施,提高磷石膏洗涤效果,降低石膏中水溶磷的含量,最终实现55万t／aP20,磷酸装置降低硫酸消耗6．27万t／a。     

Activated carbon from sugar cane bagasse by carbonization in the presence of inorganic acids

Dried ground bagasse, impregnated with 50% inorganic acids and carbonized at 500°C, showed the sequence H₃PO₄ > H₂SO₄ > HCl > HNO₃, with respect to the efficiency of activation. Treatment with phosphoric acid of various concentrations (30–50 wt%) was followed by carbonization at 300–500°C for 3 h. Pore structure parameters were determined from the low-temperature adsorption of nitrogen, by applying the BET and α_s methods. Activated carbons obtained at low temperatures are essentially microporous with a low degree of mesoporosity. At higher temperatures products of higher surface area and total pore volume with developed mesoporosity and low microporosity are formed. An increase in the period of carbonization leads to a small decrease in both surface area and pore volume. Activated carbons with surface areas > 1000 m² g^?1 and mean pore dimensions around 2·0 nm, suitable for various purposes, are thus obtained.     

硫磷混酸分解高镁尾矿渣制取磷镁复合肥的工艺条件研究

介绍了以硫磷混酸和高镁磷尾矿粉为原料制备磷镁复合肥的工艺条件,研究了硫酸用量、磷酸用量、反应时间和反应温度对五氧化二磷、氧化镁转化率的影响。通过单因素实验得到最佳的工艺条件:磷酸用量为110 g、硫酸用量为15 g、反应时间为20 min、反应温度为50℃。在此条件下,磷尾矿渣中五氧化二磷的转化率大于90%,氧化镁转化率大于80%。     

降低湿法磷酸中硫酸含量的工艺技术

采用在湿法磷酸中加入磷矿浆来降低磷酸的硫酸含量。介绍采用磷矿浆脱除硫酸根的反应原理,工艺路线的选择,矿浆添加量的计算及实施效果。通过计算,脱硫后反应、过滤装置生产能力提高,30万t/a磷酸装置每年节省硫酸8 700 t,减少消耗支出300多万元。     

Effect of several factors on peracetic acid pretreatment of sugarcane bagasse for enzymatic hydrolysis

BACKGROUND: Lignocellulose should undergo pretreatment to enhance its enzymatic digestibility before being saccharified. Peracetic acid (PAA) is a strong oxidant that can remove lignin under mild conditions. The sulfuric acid in the PAA solution also can cause degradation of hemicelluloses. The objective of the present work is to investigate the effect of several factors on peracetic acid pretreatment of sugarcane bagasse. RESULTS: It was found that PAA charge, liquid/solid (l/s) ratio, temperature, time, interactions between PAA charge and l/s ratio, temperature and time, all had a very significant effect on the enzymatic conversion ratio of cellulose. The relative optimum condition was obtained as follows: PAA charge 50%, l/s ratio 6:1, temperature 80 °C and time 2 h. More than 80% of the cellulose in bagasse treated under the above conditions was converted to glucose by cellulase of 20 FPU g^?1 cellulose. Compared with H₂SO₄ and NaOH pretreatments under the same mild conditions, PAA pretreatment was the most effective for enhancement of enzymatic digestibility. CONCLUSION: PAA pretreatment could greatly enhance the enzymatic digestibility of sugarcane bagasse by removing hemicelluloses and lignin, but removal of lignin was more helpful. This study can serve as a step to further optimization of PAA pretreatment and understanding the mechanism of enhancement of enzymatic digestibility. Copyright © 2007 Society of Chemical Industry     

鹤峰磷矿在硫、磷混酸中的溶解动力学

对鹤峰磷矿在硫、磷混酸中的溶解动力学进行了研究,考查了硫酸质量分散及反应温度对酸解过程的影响;选用考虑了自阻化因素的德罗兹多夫方程In100/(100-Kp)-βKKp%=kt描述酸解过程的动力学.研究结果表明:鹤峰磷矿在硫、磷混酸中的反应速率常数随温度升高而增加,随硫酸质量分效的增加而减小.该反应属于扩散控制,平均反应活化能约为32.7kJ/mol.     

探讨湿法磷酸生产中节约硫酸的途径

湿法磷酸生产的主要原料之一——硫酸 ,其费用约占磷酸直接成本的 6 0 % ,因此 ,通过讨论影响硫酸消耗的各种因素 (磷矿组成 ,磷酸生产工艺条件 ) ,探讨降低硫酸消耗的途径     

Sugarcane bagasse reinforced phenolic and lignophenolic composites

Lignin, extracted from sugarcane bagasse by the organosolv process, was used as a partial substitute of phenol (40 w/w) in resole phenolic matrices. Short sugarcane fibers were used as reinforcement in these polymeric matrices to obtain fiber‐reinforced composites. Thermoset polymers (phenolic and lignophenolic) and related composites were obtained by compression molding and characterized by mechanical tests such as impact, differential mechanical thermoanalysis (DMTA), and hardness tests. The impact test showed an improvement in the impact strength when sugarcane bagasse was used. The inner part of the fractured samples was analyzed by scanning electron microscopy (SEM), and the results indicated adhesion between fibers and matrix, because the fibers are not set free, suggesting they suffered a break during the impact test. The modification of fiber surface (mercerization and esterification) did not lead to an improvement in impact strength. The results as a whole showed that it is feasible to replace part of phenol by lignin in phenolic matrices without loss of properties. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 880–888, 2002     

我国磷酸生产工艺分析与展望

本文分析并比较了湿法磷酸、热法磷酸和窑法磷酸三种磷酸生产工艺,以及影响生产的关键因素.针对生产工艺中存在的问题,提出了磷酸生产工艺的研究方向和发展趋势.     

氟化氢副产稀硫酸在湿法磷酸中的应用

对湿法磷酸生产中硫酸浓度应考虑的两个因素,以及氟化氢副产稀硫酸加入湿法磷酸生产系统后磷石膏结晶情况和磷损失进行分析。确定了氟化氢副产稀硫酸加入点及生产方法,取得了良好的使用效果。2015年公司使用副产稀硫酸248 279 m~3(w(H_2SO_4)70%),节约浓硫酸使用量173 795.3 m3。     

Peracetic acid pretreatment of sugarcane bagasse for enzymatic hydrolysis: a continued work

Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry     

电渗析技术在木糖醇酸水解法制备中的应用

木糖醇作为一种可作为甜味剂的糖醇具有广泛的应用前景。目前工业上酸水解法制备木糖醇的过程中需要一个脱除水解液中的残酸的工艺步骤。传统的残酸去除方法为饱和石灰水中和法,存在能耗高、消耗的化学试剂多、污染大等缺点。为实验木糖醇的清洁生产,本文采用自我组装的电渗析装置对木糖水解液中的残酸进行了选择性的去除,考察了操作电流对残酸去除及木糖得率的影响。结果表明,当操作电流为30 mA·cm^-2时,电渗析过程对残酸的去除率大于99%,其木糖的得率为84.9%,电渗析工艺处理木糖水解液的能耗为179 kW·h·t^-1,脱酸工序成本为每吨母液139元,具有良好的经济效益和环境效益。由此可见,电渗析工艺在木糖醇酸水解法制备过程中具有广泛的应用前景。