Production of xylose,furfural, fermentable sugars and ethanol from agricultural residues

With the developing shortage of petroleum, reliance on biomass as a source of chemicals and fuels will increase. In the present work, bagasse and rice husk were subjected to dilute acid (H₂SO₄) hydrolysis using pressurised water to obtain furfural and fermentable sugars. Various process conditions such as particle size, solid-liquid ratio, acid concentration, reaction time and temperature have been studied to optimise yields of furfural, xylose and other fermentable sugars. The use of particle sizes smaller than 495 μm did not further increase the yield of reducing sugars. A solid-liquid ratio of 1:15 was found to be the most suitable for production of reducing sugars. Hydrolysis using 0.4% H₂SO₄ at 453 K resulted in selective yields (g per 100 g of dried agricultural residues) of xylose from bagasse (22.5%) and rice husk (21.5%). A maximum yield of furfural was obtained using 0.4% H₂SO₄ at 473 K from bagasse (11.5%) and rice husk (10.9%). It was also found that hydrolysis using 1% H₂SO₄ at 493 K resulted in maximum yields of total reducing sugar from bagasse (53.5%) and rice husk (50%). The reducing sugars obtained were fermented to ethanol after removal of furfural. The effect of furfural on the fermentation of sugars to ethanol was also studied. Based on these studies, an integrated two-step process for the production of furfural and fermentable sugars could be envisaged. In the first step, using 0.4% H₂SO₄ at 473 K, furfural could be obtained, while in the second step, the use of 1% H₂SO₄ at 493 K should result in the production of fermentable sugars.     

Systematic Isolation and Utilization of Lignocellulosic Components from Sugarcane Bagasse

Lignocellulosic constituents as renewable feedstock can be utilized for various applications. A systematic procedure for separation of cellulose and lignin followed by hydrolysis of hemicelluloses was proposed in this study. Sugarcane bagasse was first subjected to alkaline hydrolysis to remove lignin and hemicelluloses. Then cellulose was separated from the alkali pretreatment residue and further purified. Meanwhile, the obtained pre-hydrolysis liquor (PHL) was acidified to precipitate lignin, and the filtrate was hydrolyzed with 1-methylimidazolium hydrogen sulfate ([Hmim]HSO₄) to prepare furfural. Response surface methodology (RSM) was employed to determine optimal conditions for isolation of cellulose. The sequential treatments resulted in a total release of over 77.3% of the original cellulose and 84.5% of the original lignin. In particular, 7.5% yield of furfural was obtained. The structures of the isolated cellulose and lignin were elucidated with Fourier transform infrared spectroscopy (FT-IR).     

Optimization of Sugarcane Bagasse Hydrolysis by Microwave‐Assisted Pretreatment for Bioethanol Production

Sugarcane bagasse hydrolysis was optimized by dilute‐acid pretreatment and subsequent enzymatic treatment. The studied parameters were microwave heating temperature, residence time, and enzyme dosage as the main factors in a central composite design. The amount of released total reducing sugars, glucose, pentose, phenolic compounds, and furfural were measured after each stage. The optimum conditions with suitable concentrations of inhibitors and reducing sugars were applied for bioethanol production. As an example, ethanol was obtained from reducing sugars by Pichia stipitis without detoxification.     

醋酸水解玉米芯中木聚糖的动力学

利用醋酸作为催化剂水解玉米芯中半纤维素来制备还原糖,测定了温度在160-200℃、固液质量比为1∶15、搅拌速度为500 r/min下,不同水解时间水解液中还原糖的收率以及副产物糠醛的收率.利用半纤维素高温液态水的Garrote模型拟合还原糖生成过程.实验表明,该模型能够较好地描述还原糖生成过程以及副产物糠醛的产生过程...     

发酵抑制物对葡萄糖发酵产乙醇的影响

在纤维素乙醇研究中,木质纤维原料在酸性预处理过程中会产生甲酸、乙酸、乙酰丙酸、糠醛和5-羟甲基糠醛等发酵抑制物,这些发酵抑制物会影响葡萄糖发酵生产乙醇的收率。本文考察了发酵液中各种发酵抑制物含量对高温超级酿酒酵母发酵乙醇收率的影响。研究结果表明,多种发酵抑制物的协同作用对乙醇发酵的影响要高于单一种类发酵抑制物对乙醇发酵的影响。发酵液中发酵抑制物总量一般控制在3.0g/L以内时,对葡萄糖发酵生产乙醇的抑制作用不明显。     

三苯基磷在玉米芯制备糠醛中的应用

研究了三苯基磷在稀硫酸法水解玉米芯制备糠醛中的应用。在三苯基磷用量占玉米芯总量的0.05%～0.5%范围内,考察了三苯基磷的量对糠醛收率的影响。实验结果表明：随着三苯基磷用量的增加,糠醛收率明显提高,当三苯基磷加入量为玉米芯总量的0.25%时,糠醛收率升至86.0%,同传统工艺相比,糠醛收率提高20%～25%。由此可见,通过添加三苯基磷的途径可大幅度提高糠醛收率,在稀硫酸法水解玉米芯制备糠醛工艺中将具有良好的应用前景。     

Low-Temperature Dilute Acid Hydrolysis of Oil Palm Frond

Oil palm frond (OPF) fiber, a lignocellulosic waste from the palm oil industry, contains high cellulose and hemicellulose content, thus it is a potential feedstock for simple sugars production. This paper describes the two-stage hydrolysis process focusing on the use of low-temperature dilute acid hydrolysis to convert the hemicellulose in OPF fiber to simple sugars (xylose, arabinose, and glucose). The objective of the present study was to evaluate the effect of operating conditions of dilute sulfuric acid hydrolysis undertaken in a 1 L self-built batch reactor on xylose production from OPF fiber. The reaction conditions were temperatures (100–140°C), acid concentrations (2–6%), and reaction times (30–240 min). The mass ratio of solid/liquid was kept at 1:30. Analysis of the three main sugars glucose, xylose, and arabinose were determined using high-pressure liquid chromatography. The optimum reaction temperature, reaction time, and acid concentration were found to be 120°C, 120 min, and 2% acid, respectively. Based on the potential amount of xylose (10.8 mg/mL), 94% conversion (10.15 mg/mL) was obtained under the optimum conditions with small amount of furfural (0.016 mg/mL). To enhance the effectiveness of dilute acid hydrolysis, the hydrolysis of OPF fiber was also performed using ultrasonic-pretreated OPF fiber. The effects of ultrasonic parameters power (40–80%) and ultrasonication times (20–60 min) were determined on sugar yields under optimum hydrolysis conditions (2% acid sulfuric, 120°C and 120 min). However, the use of ultrasonication was found to have detrimental effect on the yield of simple sugars due to the 10-fold increase in the formation of furfural.     

糠醛生产工艺的研究进展

糠醛不仅是生产各类精细化学品的平台化合物,而且可以作为能源前体,生产运输燃料.在分析糠醛生产现状基础上,详细介绍了近年来糠醛清洁生产工艺的最新研究成果,并比较各种工艺改进的优缺点.指出两相法生产糠醛并联产纤维乙醇及高附加值化学品等,提高资源综合利用率,减少三废是具有工业化前景、环境友好的糠醛生产技术.     

Furfural production by acid hydrolysis and supercritical carbon dioxide extraction from rice husk

The aim of this research was to study the effect of furfural production from rice husk by hydrolysis accompanying supercritical CO₂ (SC-CO₂) extraction. The two-level fractional factorial design method was used to investigate the production process carried out with respect to furfural yield. The process variables are temperature range of 373–453 K, pressure 9.1–18.2 MPa, CO₂ flow rate 8.3 × 10⁻⁵–1.7 × 10⁻⁴ kg/s (5–10 g/min), sulfuric acid concentration 1 to 7 (%wt) and ratio of liquid to solid (L/S) 5 : 1 to 15 : 1 (vol/wt). The results obtained from the experimental design showed that increasing temperature, pressure, CO₂ flow rate and sulfuric acid concentration but decreasing ratio of liquid to solid would improve furfural yield. Moreover, furfural production by two-stage process (pre-hydrolysis and dehydration) can improve furfural yield further to be around 90% of theoretical maximum.     

糠醛的生物炼制技术研究进展

生物炼制是新时代应对能源危机和环境污染的极佳策略,基于生物炼制可以将低值的生物质资源转化为各类高附加值产品。糠醛是一种来自生物质资源的高附加值平台化合物,在能源、医药、化工等领域具有重要应用。糠醛的工业生产已经近一个世纪,工业生产技术已经比较成熟,但是目前工业生产过程中还存在不少问题。为解决糠醛工业生产中存在的问题,研究者对制备糠醛的新技术和新工艺进行了研究与探索。本文首先介绍了糠醛的性质及应用,分析了糠醛的工业生产技术现状和所面临的问题,如利用无机酸作催化剂时会腐蚀设备,催化剂不易回收,存在污染水源等问题。然后详细叙述了水解法和热解法制备糠醛的技术研究现状以及微波加热辅助新工艺的特点,最后展望了糠醛制备技术的未来发展方向。     

生物质转化制糠醛及其应用

在一步法糠醛生产技术的基础上重点对两步法糠醛生产技术,糠醛生产流程及糠醛的应用进行了综述。由于两步法糠醛生产技术结合两段水解工艺,在生产糠醛的同时可获得燃料乙醇,得率可以达到70%以上,同时提高了原料的利用率。所以两步法必将成为糠醛生产的重要研究方向。     

高温液态水条件下木糖直接转化制备糠醛的工艺

使用自制的高温高压反应釜,在高温液态水（HTW）的条件下对木糖直接转化制备糠醛的过程进行了研究。考察了HTW作为反应介质对木糖转化率和糠醛产率的影响,并与文献中所采用催化剂的催化效果进行了对比,探索了不同的溶剂对反应产物中糠醛的萃取效果。研究结果表明：HTW作为反应介质对木糖直接转化制备糠醛具有优良的反应性能,可以替代液体酸和固体酸作用于木糖制糠醛,在优化的工艺条件下,当木糖初始浓度为10%（g/g）、反应温度为200 ℃、反应时间为3 h时,糠醛的产率高达78%。此外,乙酸丁酯作为萃取剂对于糠醛的萃取具有良好的萃取效率。所得结果为工业化生产糠醛奠定了实验基础和理论依据。     

Utilization of Black Liquor for Production of Antimicrobial Substance by Streptomyces Species

Utilization of black liquor hydrolyzates, obtained from different sources, for the growth of different Streptomyces species and production of antimicrobial substance was studied. Streptomyces violaceoniger, which exhibited good growth and production of the antimicrobial substance, was chosen for further studies. Removal of aldehydes, lactones, and furfural from the liquor resulted in a considerable increase in biomass and yield.     

Production of Xylooligosaccharides from Waste Xylan,Obtained from Viscose Fiber Processing,by Selective Hydrolysis Using Concentrated Acetic Acid

Xylooligosaccharides (XOS) were prepared by selective hydrolysis of the waste xylan, obtained from viscose fiber plants, using concentrated acetic acid. The influences of acetic acid concentration, reaction temperature, and reaction time on the yield and component profiles of XOS product were investigated. These results were further ascertained by designing orthogonal experiments. The hydrolysis of xylan residue was selective, since mainly xylooligosaccharide components were formed, with hardly any impure ingredients, except for a small amount of xylose and traces of furfural, in the hydrolyzed product. Reaction temperature was found to be the most significant factor, influencing the XOS yield. Accurate HPAEC–PAD analysis of component profiles indicated that a maximum XOS yield of 45.86% was achieved on hydrolysis of 33.77 g/L waste xylan using 20% acetic acid for 20 min at 140°C. The main XOS components obtained were xylobiose, xylotriose, and xylotetraose, which were more than xylopentaose and xylohexaose.     

糠醛渣直接同步糖化发酵生产乙醇过程比较研究

以糠醛渣为原料,直接同步糖化发酵(SSF)生产乙醇,并与水洗糠醛渣生产乙醇进行对比。通过考察不同条件来优化同步糖化发酵生产工艺条件,并分析表征了SSF过程中乙醇浓度和副产物浓度变化。优化条件为:糠醛渣底物质量分数10%,纤维素酶用量12%,无患子皂素质量浓度0.5g/L,酵母接种量7g/L,同步糖化发酵乙醇得率达到其理论得率的93.1%。与水洗糠醛渣相比,糠醛渣直接SSF过程可将原料吸附的5.50%葡萄糖部分转化为乙醇。水洗糠醛渣SSF生产乙醇所产生的副产物要远低于糠醛渣直接生产所产生的副产物,添加无患子皂素可有效抑制糠醛渣同步糖化发酵过程中副产物的产生。     

Reaction extraction of furfural from pentose solutions in a modified Scheibel column

Furfural, which is one of the most promising platform chemicals derived from biomass, has the potential for the production of biofuels and biochemicals. However, the current industrial furfural production process relies on relatively old and inefficient technology, which has some problems such as low production yields, environmental pollutions, and lack of biomass comprehensive utilization. The main contribution of this paper is the use of a modified Scheibel column to improve the furfural recovery. Integration of pentose dehydration to furfural and the solvent phase extraction of furfural occurred simultaneously in this column. Compared with the prevailing batch biphasic reactor, the use of this modified column intensified the extraction efficiency as well as the furfural recovery. Process parameters including organic feed flow rate, reaction temperature, and stirring speed were evaluated and turned out to be significant. In order to achieve the optimal operating conditions, the CCD design was used to optimize the process parameters, and the maximum furfural yield of 80.5% was obtained.     

生物质快速热解制糠醛的实验研究及理论探讨综述

糠醛是生物质快速热解的重要产物之一,通过对生物质进行定向热解可实现糠醛的选择性制备,从而获得一种新型的糠醛制备方法,实现生物质的高值化利用。概述了国内外对纤维素和半纤维素热解形成糠醛机理的实验研究和密度泛函理论分析,总结了生物质选择性热解制备糠醛的工艺技术,指出了今后的研究需要,明确糠醛的热解形成机理以及优化糠醛选择性制备的技术。     

Laser-assisted preparation of monolithic acidic catalysts for biomass conversion

5-(Hydroxymethyl)furfural (5-HMF) is a vital platform molecule from which a variety of high-value-added fine chemicals and polymerizable monomers can be prepared. The use of solid acids to catalyze the conversion of biomass into 5-HMF is environmentally friendly and economical. However, exploiting the high yield of 5-HMF in a highly concentrated reactant system is challenging. Herein, we present a laser-assisted method for preparing highly acidic monolithic acidic catalysts. A monolithic acidic catalyst based on metal Zr sheets was synthesized and used to catalytically convert 30 wt% fructose into 5-HMF (conversion rate: 96%; yield: 95%). The catalyst was immediately separated from the reaction solution by direct removal at the end of the reaction. Catalytic efficiency was largely unaffected after 10 cycles of use, and the same catalytic efficiency was observed after laser-regeneration, highlighting the potential industrial applicability of the developed catalyst.     

糠醛和呋喃的生产、合成进展

主要介绍了国内外糠醛和呋喃生产的现状,以及糠醛脱羰制呋喃的研究进展。目前生产糠醛的方法主要是一步法和两步法。一步法中以酸催化和改良后的酸催化法为主,酸催化法主要缺点是腐蚀设备,产生的废弃物难以处理;改良法则有效的减少了废弃物的产生。目前呋喃的主要合成方法有5种,工业中主要使用的则是在催化剂的作用下,糠醛分别在液相和气相状态下脱羰制备呋喃。催化剂主要以贵金属和金属氧化物为主。     

Hemicellulose Removal from Hardwood Chips in the Pre-Hydrolysis Step of the Kraft-Based Dissolving Pulp Production Process

Abstract

A pre-hydrolysis step to remove hemicelluloses from mixed hardwood chips consisting of maple, aspen, and birch with a ratio of 7:2:1 has been carried out. The effects of parameters on the pre-hydrolysis such as time, temperature, acetic acid addition, and raw material species, were determined. Different sugars, acetic acid, and furfural formation in the pre-hydrolysis liquor were quantified. The results showed that the pre-hydrolysis is a dynamic process, in which the removal of hemicelluloses increased with time while the conversion of extracted hemicelluloses to monosaccharides due to acid hydrolysis increased and part of the xylose was converted to furfural. The maximum temperature was the most critical parameter for hemicelluloses extraction and conversion, and a temperature of 170°C was the optimum for hemicelluloses extraction with relatively low conversion of xylose to furfural. About 11% of the xylan (in both monomeric and oligomeric forms) was removed at 170°C. Due to the presence of a high amount of xylan, birch produced the highest amount of xylose, followed by maple, and then aspen.