2022年木质纤维原料预处理技术研究报告现状 .pdf

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1、个人资料整理仅限学习使用木质纤维原料预处理技术的研究现状摘要：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然趋势，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，并对其发展前景作了展望。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预计在数十年左右将会枯竭，因此，石油替代品的开发研究迫在眉睫。目前有很多国家在研究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，纤维素、半纤维素是可发酵糖的来源，含量占66%75%纤维质原料的

2、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，当采用纤维素酶水解木质生物资源制造乙醇时，纤维素酶必须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决定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、木素对纤维素的保护作用以及纤维素被半纤维素覆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S

3、tuart等2,3发明了一种特殊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，但这种结构很不稳定，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215m

4、in使物料的 40%60%溶解，可除去4%22%的纤维素， 35%60%的木素以及所有的半纤维素 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。如果温度降低，分解速度就会减慢，而且还会产生挥发性的副产物。高温分解后的木质纤精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 1 页，共 10 页个人资料整理仅限学习使用维经 0

5、.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、棉杆和杨木锯末等许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，而半纤维素只受到轻微攻击，纤维素几乎不受影响。臭氧预处理的杨木锯末酶法水解得率为057%，木素含量从29%降低为 8%。臭氧分解有下列优点：1）高效脱除木素；2）

6、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 为天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。第二步，把纤维素解聚为葡萄糖。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

7、止酵母发酵生成乙醇。法国在1856年即开始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理想，因此酸法水解正逐渐被生物法所取代。2.3 碱水解某些碱可以用来预处理木质纤维原料，处理效果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

8、是稀 NaOH预处理对于木素含量超过26%的针叶木没有效果。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、CO2爆破法、蒸汽爆裂与乙醇抽提结合法、氨冷冻爆破法等。3.1 蒸汽爆裂法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。此后各国的研究者进一步结合

9、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%。蒸汽爆破的处理效果不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。采用较大的粒度812mm精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 2 页，共 10 页个人资料整理仅限学习使用）不仅可节约能耗，而且可采用较剧烈的操作条件，具有较高的纤维素保留度，较少的半纤维素水解糖类损失，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似

10、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，然后将压力骤然释放，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，氨纤维爆破法可有效提高各种木素含量低的草本科植物、阔叶材和农作物剩余物的糖化率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，氨的水溶液的流速为1ml/cm2min ，反应时间为 14min。结果显示，脱除木素效果好，并且木素脱除的程度可以控制。木素是影响酶解的主要因素之一，因此，脱除木素

11、可以降低酶的量。氨纤维爆破法对半纤维素的去除程度不高，避免了半纤维素损失；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 A M研究了 19种白腐菌预处理麦草效果，发现在5星期内 35%的麦草被糙皮侧耳菌Pleurotus ostreatus）转化成还原糖。为了降低纤维素的损失，可采用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

12、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研究课题，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、减少化学药品用量、无污染、能耗低等优点，是很有发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，占有独特的优势，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

13、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发展趋势。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 fixed stator device having nozzle tool with opposingcoaxial toothed rings to make the biom

14、ass more susceptible tohydrolysisP. US 5498766 ，1996.2 Stuart Earnest D. Treatment of fibrous lignocellulosic biomass byhigh shear forces in a 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 3 页，共 10 页个人资料整理仅限学习使用turbulent couette flow to make the biomassmore susceptible to hydrolysisP. US 5370999，19

15、94.3 Mosier N,Wyman C, Dale B,etal. Features of promising technologies for pretreatment of lignocellulosic biomassJ.Bioresource Technology,2005,96:673-6864 Shafizadeh F, Bradbury A G W. Thermal degradation of cellulose in air and nitrogen at lowtemperaturesJ. Appl. Poly. Sci., 197923 ）: 1431-1442.5

16、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 treatment of cellulose for viscose fiberJ. Chemical Fiber International,1995, 45 1. By the fermen

17、tation 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 cellulose substrate adsorption to the reaction, therefore, cellulose the availability of cell

18、ulose 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 resources, woody biomass resources, multi-component structure of cellulose, lignin and cellulose are

19、 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 pretreatment methods include physical, chemical, physical chemical, biological method. A physical m

20、ethod 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 developed a special high-speed cutting device of cellulose pulp, can effectively undermine the

21、cellulose and hemicellulose and lignin, the 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 5 页，共 10 页个人资料整理仅限学习使用physical, chemical bonding, and significantly reduce the crystallinity of cellulose macromolecules improve the ratio of surface area. Grinding methods are milling, hammer mill, etc., is m

22、ore 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 disadvantages of mechanical and physical methods. Cellulose loose ball and can make micro-fiber and mic

23、ro 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, mechanical energy treatment is high, it will increase production costs. 1.2 The high temperatu

24、re 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% of the cellulose, 35% 60% of lignin and hemicellulose all 3. Sugar produced by acid hydrolys

25、is, 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 and therefore greater production efficiency is low 7. 1.3 Pyrolysis When the raw materials in

26、 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 volatile by-products. After pyrolysis of wood fiber by 0.5mol / L H2SO4, 97 , 2.5h hydrolysis all

27、ows 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 carbonate as a catalyst, can be achieved at lower temperature the decomposition of pure cellulo

28、se. 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 degrade wheat straw, bagasse, hay, peanuts, pine, cotton stalk and poplar sawdust wood fiber r

29、aw 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 poplar wood sawdust enzymatic hydrolysis rate of 0 to 57%, lignin content decreased from 29% to

30、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. Disadvantage is that pre-need a lot of ozone, high production costs 8. 2.2 Acid Hydroly

31、sis 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 6 页，共 10 页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 amount of catalyst, low cost, easy-to-neutral. However, hemicellulose hydrolysates of pento

32、se 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 minutes to several hours. Brink is made of natural cellulose into glucose, a two-step pr

33、ocess. 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. However, the maximum production rate of glucose only 55% of cellulose, and there are more

34、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, and therefore acid hydrolysis is gradually being replaced by biological methods. 2.3 Al

35、kaline 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 of xylan hemicellulose connections and other components within the molecules (such as lign

36、in 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 increased internal surface area, reducing the degree of polymerization, crystallinity decr

37、eased, 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% digestibility of 55%. However, pretreatment of dilute NaOH lignin content for more than 26% of

38、 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 steam burst, ammonia fiber burst, CO2 blasting method, combined with the steam burst and

39、 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 temperature steam treatment before the appropriate time, and then with water vapor from the reac

40、tor 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 degraded easily. But after the steam explosion treatment may improve the crystallization of ce

41、llulose index. The initial steam explosion made by the Mason in 1927 and obtained patents. After the further integration of national chemical treatment researchers to 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 7 页，共 10 页个人资料整理仅限学习使用make more perfect steam explosion technology. Steam explosion an

42、d 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, with the increase of alkali concentration, lignin removal rate can be increased to 90%. Ste

43、am 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 conditions with high degree of fiber retention, less loss of hemicellulose hydrolysis of

44、carbohydrates to improve cellulase The hydrolysis rate. 3.2 ammonia fiber burst Comparison of ammonia fiber explosion similar to the steam explosion, ammonia fiber explosion is the state of the material placed in high temperature and pressure of liquid ammonia, for a period of time, and then suddenl

45、y release the pressure, so that the material burst. Ammonia fiber explosion method is suitable for low lignin content of plant grass course, wide wood and crop residues pretreatment, ammonia fiber explosion method can effectively improve the low lignin content of various undergraduate grass plants a

46、nd crops the remaining hardwood saccharification rate of compounds 20. Yoon and other aqueous solution of ammonia in a continuous reactor for pretreatment of lignocellulosic raw materials to 5% to 15% of the ammonia solution into a column of wood fiber raw materials, reactors, so that the wood fiber

47、 raw material is soaked in ammonia, the reaction temperature of 160 180 , the flow rate of aqueous ammonia 1ml/cm2min, the reaction time was 14min. The results showed that effective removal of lignin, and the extent of lignin removal can be controlled. Lignin is one of the main factors affect the en

48、zyme, therefore, lignin removal can reduce the amount of enzyme. Ammonia fiber explosion method, the removal of hemicellulose is not high, to avoid the loss of hemicellulose 。 damage to the crystal structure of cellulose, cellulose hydrolysis to improve accessibility。 while processing degradation pr

49、oducts produced less inhibition. 4 biological pretreatment In biological pretreatment, the brown rot fungi, white rot fungi and soft rot Jundeng microbial degradation of lignin was used and hemicellulose. Brown rot fungi mainly attack cellulose, white rot fungi and soft rot fungi attack cellulose an

50、d lignin. Biological pretreatment of the most effective is the burden of white-rot fungi fungi. Azzam AM of the 19 species of white-rot fungus pretreatment of wheat straw, and found that 35% in 5 weeks, the straw was ostreatus fungi (Pleurotus ostreatus into sugar. In order to reduce the loss of cel