2022年木质纤维原料预处理技术研究报告现状.docx

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1、精选学习资料 - - - - - - - - - 个人资料整理 仅限学习使用木质纤维原料预处理技术的讨论现状摘 要：木质纤维原料作为一种可转化为液体燃料的可再生资源,其转化利用已成为必定趋势,而木质纤维原料的预处理是利用木质生物资源生产乙醇的一个重要环节；文章阐述了木 质纤维原料的常用预处理技术,并对其进展前景作了展望；关键词：木质纤维；预处理；进展作为世界经济支柱的石油资源估计在数十年左右将会枯竭,因此,石油替代品的开发讨论 迫在眉睫；目前有很多国家在讨论以木质生物资源为原料用生物转化法制备燃料乙醇,以 替代或部分替代储量有限的石油；木质生物资源的主要成分是纤维素、半纤维素和木素；其中,纤维

2、素、半纤维素是可发酵糖的来源,含量占66%75%纤维质原料的绝干重量）1 ；由己糖通过酿酒酵母发酵生成乙醇是很成熟的工艺,当采纳纤维素酶水解木质生物资源制造乙醇时,纤维素酶必需接触吸附到纤维素底物上才能使反应进行,因此,纤维素对纤维素酶的可及 性是打算水解速度的关键因素；木素的存在阻碍了纤维素对酶的可及性,且纤维素的结晶 结构以及木质生物资源的表面状态、木质生物资源的多组分结构、木素对纤维素的爱护作 用以及纤维素被半纤维素掩盖等结构与化学成分的因素致使木质生物资源难以水解；目前,木质纤维原料预处理的方法主要有物理法,化学法,物理化学法,生物法等；1 物理方法 常用的物理方法有剪切和研磨,高温液

3、态法,高温分解,微波处理,蒸汽爆破和高能 辐射等；1.1 剪切和研磨Stuart等2,3 创造了一种特别的纤维素浆的高速剪切装置,可有效破坏纤维素与木质素和半 纤维素的物理、化学结合,并显著降低纤维素大分子的结晶度,提高比表面积；研磨的方法有球磨、锤磨等,比较有效的是球磨；1946年有人用球磨制得了完全无定形结构的纤维素,但这种结构很不稳固,很快又重新形成晶态结构,这也是机械物理方法常有的弊端；球磨可使纤维素的结构松散和使微纤中和微纤间晶区间存在的氢键断裂 5,6 ；使用三轮球 磨处理木质纤维素,对糖化反应极为有效；但存在的问题是,机械处理方法的能耗很高,这无疑增加了生产成本；1.2 高温液态

4、法液态热水法是指将物料置于高压状态的热水中,温度为200230,处理物料 215min使物料的 40%60%溶解,可除去 4%22%的纤维素, 35%60%的木素以及全部的半纤维素 3 ；用酸水解生成的糖液,可使以单糖形式存在的半纤维素的回收率高于 90%,并且,可使活性纤维转化率高达 90%,但只能在较低固体含量 20%）下对物料进行处理,因此能耗较大,生产效率较低 7 ；1.3 高温分解当原料在 300以上的高温条件下处理时,纤维素快速分解成为气体和残留固体 8 ；假如温度降低,分解速度就会减慢,而且仍会产生挥发性的副产物；高温分解后的木质纤名师归纳总结 - - - - - - -第 1

5、页,共 10 页精选学习资料 - - - - - - - - - 个人资料整理 仅限学习使用维经 0.5mol/L H2SO4、97、 2.5h水解可使 80%85%的纤维素生成糖,其中葡萄糖占 50%以上 1 ；在热解过程中加入氧会加快分解过程,当用氯化锌或碳酸钠作催化剂时,可以在较低温下实现对纯纤维素的分解；2 化学预处理法常用的化学法有臭氧法、酸水解法、碱法、氧化脱木素法、有机溶剂法等；2.1 臭氧分解法臭氧可以用来降解麦草、甘蔗渣、干草、花生、松木、棉杆和杨木锯末等很多木质纤维原料的木素和半纤维素；该法中 木素受到很大程度的降解,而半纤维素只受到稍微攻击,纤维素几乎不受影响；臭氧预处理

6、的杨木锯末酶法水解得率为 057%,木素含量从 29%降低为 8%；臭氧分解有以下优点：1）高效脱除木素；2）不产生有毒的阻碍生物过程的化合物； 3）反应在室温、常压下进行；缺点是预处理需要大量的臭氧,生产成本昂贵 8；2.2 酸水解主要有浓酸水解和稀酸水解两种；稀酸处理的优点在于半纤维素水解得到的糖量大,催化剂成本低,易于中和；但半纤维素水解产物五碳糖易在催化下进一步降解 糠醛）；稀酸水解过程为多相水解反应,硫酸浓度一般0.5%2%,温度为 180240,时间为几分钟到几小时； Brink 为自然纤维素转化为葡萄糖提出了一个两步法过程；第一步,把半纤维 素解聚为木糖和其他糖类；其次步,把纤维

7、素解聚为葡萄糖；由于酸的浓度低,可以不必进行酸的回收；但葡萄糖的最大产率仅占纤维素的55%,并且有较多的解聚产物会阻挡酵母发酵生成乙醇；法国在 1856年即开头进行了浓硫酸水解法进行乙醇生产；使得乙醇的产量和产率都不是太抱负,因此酸法水解正逐步被生物法所取代；2.3 碱水解某些碱可以用来预处理木质纤维原料,处理成效主要取决于原料中的木素含量；碱水解的机理是基于连接木聚糖半纤维素和其他组分内部分子之间比如木素和其他半纤维素之间）酯键的皂化作用；连接键的脱除增加了木质纤维原料的多孔性；稀 NaOH 处理引起木质纤维原料润胀,结果导致内部表面积增加,聚合度降低,结晶度下降,木素和碳水化合物之间化学键

8、断裂,木素结构受到破坏；随着木素含量从 24% 55%降低到 20%,NaOH 处理的阔叶木消化性从 14%增加到 55%；但是稀 NaOH 预处理对于木素含量超过 26%的针叶木没有成效；对于木素含量低 10%18%）的草类原料,稀 NaOH 预处理是有效的；3 物理化学法常用的物理化学法有蒸汽爆裂法、氨纤维爆裂、合法、氨冷冻爆破法等；3.1 蒸汽爆裂法CO2爆破法、蒸汽爆裂与乙醇抽提结这一方法主要指蒸汽爆破技术；蒸汽爆破是将木质纤维原料先用高温水蒸气处理适当时间,然后连同水蒸气一起从反应釜中急速放出而爆破,由于木质素、半纤维素结合层被破坏,并造成纤维素晶体和纤维束的爆裂,使得纤维素易于被降

9、解利用；但蒸汽爆破处理后可能会提高纤维素的结晶指数；最初的蒸汽爆破由Mason于1927年提出并取得专利；此后各国的讨论者进一步结合化学处理,使蒸汽爆破技术更加完善；蒸汽爆破与酸结合,分 两步预处理；软木质纤维,糖的回收率可大大提高,并可降低后续酶解过程的酶的用量；蒸汽爆破杨木时加入 NaOH ,随碱浓度的增加,木质素脱除率可提高到90%；蒸汽爆破的处理成效不名师归纳总结 仅与使用的化学试剂有关,而且与纤维材料的粒度大小有关；采纳较大的粒度812mm第 2 页,共 10 页- - - - - - -精选学习资料 - - - - - - - - - 个人资料整理 仅限学习使用）不仅可节省能耗,而

10、且可采纳较猛烈的操作条件,具有较高的纤维素保留度,较少的半 纤维素水解糖类缺失,提高纤维素酶的酶解率；3.2 氨纤维爆裂 氨纤维爆破法比较相像于蒸汽爆破法,氨纤维爆破是指将物料置于高温高压状态的液 态氨中,保持一段时间,然后将压力突然释放,使物料爆破；氨纤维爆破法适合于木素含量低的草本科植物、阔材和农作物的剩余物的预处理、阔叶材和农作物剩余物的糖化率,氨纤维爆破法可有效提高各种木素含量低的草本科植物 20； Yoon等以氨的水溶液在连续式反应器中对木质纤维原料进行预处理,把 5%15%的氨的水溶液注入有木质纤维原料的柱式反应器,使木质纤维原料被氨浸泡,反应温度为 160 180,氨的水溶液的流

11、速为 1ml/cm2min ,反应时间为 14min；结果显示,脱除木素成效好,并且木素脱除的程度可以掌握；木素是影响酶解的主要因素之一,因此,脱除木素可以降低酶的量；度不高,防止了半纤维素缺失；氨纤维爆破法对半纤维素的去除程破坏纤维素的结晶结构提高纤维素的酶解可及性；同时处理过程中产生的抑制性降解产物 少；4 生物预处理 在生物预处理法中,褐腐菌、白腐菌和软腐菌等微生物被用来降解木素和半纤维素；褐腐菌主要攻击纤维素,白腐菌和软腐菌攻击纤维素和木素；生物预处理法中最有效的白腐菌是担子菌类；Azzam 5星期内 35%的麦草被糙皮侧耳菌Pleurotus A M 讨论了 19种白腐菌预处理麦草成

12、效,发觉在ostreatus）转化成仍原糖；为了降低纤维素的缺失,可采纳较少纤维素酶变种的侧孢霉属 白腐菌 Pulverulentum 来降解木片中的木素；据报道两种白腐菌对百慕大草有降解作用,用白腐菌 Ceriporiopsis subvermispora 和 Cyathus stercoreus 预处理 6周,生物降解率分别提高到 29%32%和 63%77%；5 结语木质纤维生产燃料酒精已成为一个热门讨论课题,预处理技术作为木质纤维转化为能源 的关键步骤,也成为科研工作者关注的焦点；传统的化学处理、机械处理技术等耗能较多,且不同程度地存在环境污染；蒸汽爆破具有处理时间短、削减化学药品用量

13、、无污染、能耗低等优点,是很有进展前途的预处理新技术；生物处理技术从成本和设备角度考虑,占有特殊的优势,但处理效率较低,利用基因工程和传统的生物技术对菌种和酶进行改造,提高酶活力,降低酶成本,也有望应用于大规模工业生产；利用多种预处理方法相结合,开发更加高效、无污染且成本低的预处理手段,将是今后木质纤维原料预处理的进展趋 势；木质纤维原料预处理问题的解决,将为今后以木质纤维为原料的燃料酒精工业化生产 打下坚实的基础；参考文献1 Stuart Earnest D,et al. Treatment method for fibrous lignocellulosicbiomass using fi

14、xed stator device having nozzle tool with opposingcoaxial toothed rings to make the biomass more susceptible tohydrolysisP. US 5498766 ,1996.2 Stuart Earnest D. Treatment of fibrous lignocellulosic biomass byhigh shear forces in a 名师归纳总结 - - - - - - -第 3 页,共 10 页精选学习资料 - - - - - - - - - 个人资料整理 仅限学习使

15、用turbulent couette flow to make the biomassmore susceptible to hydrolysisP. US 5370999,1994. 3 Mosier N,Wyman C, Dale B,etal. Features of promising technologies for pretreatment of lignocellulosic biomassJ.Bioresource Technology,2005,96:673-686 4 Shafizadeh F, Bradbury A G W. Thermal degradation of

16、cellulose in air and nitrogen at lowtemperaturesJ. Appl. Poly. Sci., 197923 ）: 1431-1442.5 Tossinari T,Macy C,Spano L Energy J. Biotechnology andBioengineering ,1980,22：1689-1705.6 Koshijiima T,Yuka F,Muraki E, et al. J. Journal Applied PolymerSynposium ,1983,37：671-683.7 Hacking A J. Electron treat

17、ment of cellulose for viscose fiberJ. Chemical Fiber International,1995, 45 1. By the fermentation of hexoses to ethanol by Saccharomyces cerevisiae is a very mature technology, when using the enzymatic hydrolysis of woody biomass resources to produce ethanol, the cellulose must have access to the c

18、ellulose substrate adsorption to the reaction, therefore, cellulose the availability of cellulose hydrolysis is a key factor in the decision. The presence of lignin cellulose hinders the accessibility of the enzyme, and the crystal structure of cellulose and wood surface state of biological resource

19、s, woody biomass resources, multi-component structure of cellulose, lignin and cellulose are protective effect hemicellulose structure and chemical composition of coverage and other factors resulted in hydrolysis of woody biomass resources is difficult. Currently, the wood fiber raw material pretrea

20、tment methods include physical, chemical, physical chemical, biological method. A physical method Physical methods commonly used cut-and-grinding, high-temperature liquid method, pyrolysis, microwave treatment, steam explosion, and high-energy radiation. 1.1 Cutting and Grinding Stuart et al 2,3 dev

21、eloped a special high-speed cutting device of cellulose pulp, can effectively undermine the cellulose and hemicellulose and lignin, the 名师归纳总结 - - - - - - -第 5 页,共 10 页精选学习资料 - - - - - - - - - 个人资料整理 仅限学习使用physical, chemical bonding, and significantly reduce the crystallinity of cellulose macromolec

22、ules improve the ratio of surface area. Grinding methods are milling, hammer mill, etc., is more effective milling. 1946 had been used to grind the ball completely amorphous structure of cellulose, but this structure is unstable, quickly re-formed crystalline structure, which is often the disadvanta

23、ges of mechanical and physical methods. Cellulose loose ball and can make micro-fiber and micro fiber in the presence of hydrogen bonds between the crystal fracture interval 5,6. Three rounds of ball milling using wood cellulose, the saccharification reaction is very effective. But the problem is, m

24、echanical energy treatment is high, it will increase production costs. 1.2 The high temperature liquid method Liquid water law refers to the material placed in high pressure hot water, the temperature of 200 230 , 2 15min to make materials handling material 40% to 60% dissolved, remove the 4% to 22%

25、 of the cellulose, 35% 60% of lignin and hemicellulose all 3. Sugar produced by acid hydrolysis, can form a single hemicellulose sugar recovery rate of more than 90% and enable the active fiber 90% conversion rate, but only at low solid content 20% , the processing of materials, energy consumption a

26、nd therefore greater production efficiency is low 7. 1.3 Pyrolysis When the raw materials in more than 300 high temperature processing, rapid decomposition of cellulose into a gas and residual solids 8. If the temperature decreases, the decomposition rate will slow down, but would also produce volat

27、ile by-products. After pyrolysis of wood fiber by 0.5mol / L H2SO4, 97 , 2.5h hydrolysis allows 80% to 85% of the fiber formation of sugar, which accounted for 50% of glucose, 1. In the pyrolysis process will speed up the decomposition process by adding oxygen, when using zinc chloride or sodium car

28、bonate as a catalyst, can be achieved at lower temperature the decomposition of pure cellulose. 2 chemical pretreatment method Commonly used chemical method has ozone, acid hydrolysis, alkaline, oxidative delignification, organic solvent method. 2.1 The decomposition of ozone Ozone can be used to de

29、grade wheat straw, bagasse, hay, peanuts, pine, cotton stalk and poplar sawdust wood fiber raw materials, and many of lignin and hemicellulose. The method of lignin degradation by a large degree, but only by a slight attack of hemicellulose, cellulose is almost unaffected. Ozone pretreatment of popl

30、ar wood sawdust enzymatic hydrolysis rate of 0 to 57%, lignin content decreased from 29% to 8%. Ozone decomposition has the following advantages: 1 efficient removal of lignin； 2 does not produce toxic compounds that hinder the biological process； 3 reaction at room temperature under normal pressure

31、. Disadvantage is that pre-need a lot of ozone, high production costs 8. 2.2 Acid Hydrolysis 名师归纳总结 - - - - - - -第 6 页,共 10 页精选学习资料 - - - - - - - - - 个人资料整理 仅限学习使用Mainly concentrated acid hydrolysis and acid hydrolysis of the two. The advantage is that acid hydrolysis of hemicellulose sugars large a

32、mount of catalyst, low cost, easy-to-neutral. However, hemicellulose hydrolysates of pentose in the catalyst is easy to further degradation furfural. Dilute acid hydrolysis process for the multi-phase hydrolysis, sulfuric acid concentration is generally 0.5% to 2%, temperature 180 240 , 时间 for a few

33、 minutes to several hours. Brink is made of natural cellulose into glucose, a two-step process. The first step, the hemicellulose depolymerization as xylose and other sugars. The second step, the depolymerization of cellulose to glucose. The acid concentration is low, the recovery can not be acid. H

34、owever, the maximum production rate of glucose only 55% of cellulose, and there are more depolymerization will prevent yeast fermentation products to ethanol. France began in 1856 was concentrated sulfuric acid hydrolysis for ethanol production. Make ethanol production and yield that it is not ideal

35、, and therefore acid hydrolysis is gradually being replaced by biological methods. 2.3 Alkaline hydrolysis Some of the alkali pretreatment of lignocellulosic material can be used, the treatment effect depends on the lignin content of raw materials. The mechanism is based on the alkaline hydrolysis o

36、f xylan hemicellulose connections and other components within the molecules such as lignin and hemicellulose between ester bond saponification. Connections increase the removal of key raw materials, porous wood fiber. Dilute NaOH treatment caused swelling of wood fiber raw materials, resulting in in

37、creased internal surface area, reducing the degree of polymerization, crystallinity decreased, lignin and carbohydrates break chemical bonds between the lignin structure has been damaged. As the lignin content from 24% to 55% to 20%, NaOH treatment of the broad-leaved trees increased from 14% digest

38、ibility of 55%. However, pretreatment of dilute NaOH lignin content for more than 26% of the coniferous wood no effect. The lignin content is low 10% to 18% of grass-based raw materials, thin NaOH pretreatment is effective. 3 physical chemistry Physical and chemical methods commonly used method of s

39、team burst, ammonia fiber burst, CO2 blasting method, combined with the steam burst and ethanol extraction method, ammonia refrigerant blasting method. 3.1 Law of the steam burst This method mainly refers to the steam explosion technology. Steam explosion of wood fiber raw material is high temperatu

40、re steam treatment before the appropriate time, and then with water vapor from the reactor together with the rapid release of the bursting of the lignin and hemicellulose binding layer was destroyed, and the crystal and the resulting cellulose fibers the burst, making the use of cellulose is degrade

41、d easily. But after the steam explosion treatment may improve the crystallization of cellulose index. The initial steam explosion made by the Mason in 1927 and obtained patents. After the further integration of national chemical treatment researchers to 名师归纳总结 - - - - - - -第 7 页,共 10 页精选学习资料 - - - -

42、 - - - - - 个人资料整理 仅限学习使用make more perfect steam explosion technology. Steam explosion and acid binding, two-step pretreatment. Soft wood fiber, can greatly improve the recovery rate of sugar, and reduce the subsequent amount of enzyme hydrolysis process. Steam explosion of poplar was added NaOH, wit

43、h the increase of alkali concentration, lignin removal rate can be increased to 90%. Steam explosion treatment effect not only with the use of chemical reagents, but also to the grain size of the fiber material. The use of larger size 8 12mm not only saves energy, but can be more severe operating cond