玉米秸秆中半纤维素的提取

发布时间：2018-01-08 00:27

本文关键词：玉米秸秆中半纤维素的提取　出处：《大连工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：传统的化学法制浆过程中,植物纤维原料的20%～30%会以半纤维素和木素的形式溶解在废液中,结合生物质精炼的理念,考虑在原料蒸煮之前预提取部分半纤维素用作化工原料,预提取后的植物纤维原料仍用于制浆造纸。本论文以制浆造纸与生物质精炼相结合为出发点,系统的研究了碱法分离纯化玉米秸秆半纤维素以及半纤维素的表征和结构鉴定。以玉米秸秆为原料,KOH和NaOH提取玉米秸秆半纤维素的提取液中,大部分半纤维素是以聚糖的形式存在,其中聚木糖的浓度最高,两种碱提取液中的聚木糖相对于原料中木糖的溶出率都达到了40%以上,KOH提取液中聚木糖的溶出率比NaOH的高6个百分点左右,醇沉率比NaOH法高10个百分点左右,两种碱法制备的半纤维素样品中,所含木糖含量相当。苯醇抽提对碱-乙醇法分离半纤维素影响很小,可以忽略不计。与未提取半纤维素的原料相比,碱提取后的玉米秸秆物料中的葡萄糖的百分含量提高了17个百分点,玉米秸秆物料中的葡萄糖的保留率都接近百分之七十：总木素含量大大降低,碱提取后木素的脱除率达到了百分之八十以上。 KOH提取玉米秸秆半纤维素的较佳的工艺条件为：在碱浓6%,温度85℃、液比7：1、保温时间120min。温度对聚木糖溶出率的影响最大,其次是碱浓,液比和时间对聚木糖溶出率的影响都较小。在优化的工艺条件下,用KOH提取的半纤维素提取液中木素的浓度为45.614g/L。酸析木素法能有效脱除提取液中的木素。酸析法得到的粗木素中含20.36%的糖类组分。用乙醇分级沉淀法纯化半纤维素,乙醇浓度为30%时得到了平均分子量分布在40568的半纤维素样品,其次是乙醇浓度为40%时,得到了平均分子量分布在18685的半纤维素样品,其它条件下分离出的样品的分子量都很低。核磁结果显示玉米秸秆碱性半纤维素F40的所含的半纤维素主要为聚-O-乙酰基-4-O-甲基葡萄糖醛酸木糖。提取半纤维素后的玉米秸秆煮浆时可以减少大量的后续蒸煮用碱量,抄成的纸张强度有所下降,耐折度、抗张强度、裂断长明显下降很多,其它的指标下降均不明显。
[Abstract]:Chemical pulping process of the traditional plant fiber raw materials from 20% to 30% will be in the form of dissolved hemicellulose and lignin in the waste water, combined with the concept of biomass refining, considered in the pre cooking extraction of hemicellulose used as chemical raw materials, after pre extraction of plant fiber raw material is still used for pulp and paper. In this paper, pulp and paper and biomass refining combined as the starting point, the system of alkali separation and purification of corn straw hemicellulose and hemicellulose characterization and identification.
Using corn straw as raw material, extract KOH and NaOH extraction of corn straw hemicellulose in most of the hemicellulose is in the form of chitosan, poly xylose concentrations were highest in liquid polyxylose compared with raw materials in the xylose dissolution rate has reached more than 40% of the extraction of two kinds of alkali solution, poly xylose the dissolution rate of higher than 6 percentage points of NaOH KOH extraction, alcohol precipitation rate of 10 percentage points higher than the NaOH method, two semi cellulose samples prepared by alkali method, containing xylose content. Benzene alcohol extraction on alkali ethanol separation of hemicellulose is very small, can be neglected.
Compared with non extraction hemicellulose content of raw material, corn straw material after alkali extraction of glucose increased by 17 percentage points, the retention rate of corn straw material in glucose was close to seventy percent: the total lignin content decreased greatly after alkali extraction, lignin removal rate reached more than eighty percent.
The better process conditions of KOH extraction of corn straw hemicellulose was in alkali concentration 6%, 85 degrees Celsius temperature, liquid ratio 7:1, holding time 120min. temperature on xylan dissolution rate of the greatest impact, followed by alkali concentration, liquid ratio and time on xylan dissolution rate had little effect in the process. Under optimum conditions, the hemicellulose extracted by KOH extraction concentration of lignin from black liquor of 45.614g/L. acid precipitation lignin method can effectively remove the extracted lignin. Acid precipitation method of wood containing 20.36% carbohydrate components.
Purification of hemicellulose by ethanol precipitation method, ethanol concentration was obtained in 40568 of the average molecular weight distribution of hemicellulose samples was 30%, followed by ethanol concentration was 40%, the average molecular weight distribution in the 18685 semi cellulose samples, molecular separated sample amount under other conditions are very low magnetic. The results show that the content of hemicellulose of corn straw alkaline hemicellulose F40 was mainly poly -O- acetyl -4-O- methyl glucuronic acid xylose.
Extraction of corn straw hemicellulose after cooking can reduce subsequent cooking with plenty of alkali, the strength of the paper copy into the decline, folding, tensile strength, breaking length was significantly decreased, other index decline was not obvious.

【学位授予单位】：大连工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TQ914.3

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