本文關(guān)鍵詞：玉米秸稈中半纖維素的提取　出處：《大連工業(yè)大學(xué)》2014年碩士論文　論文類(lèi)型：學(xué)位論文

  更多相關(guān)文章： 玉米秸稈 預(yù)處理 堿液 半纖維素 乙醇分級(jí)沉淀 紙頁(yè)性能

【摘要】：傳統(tǒng)的化學(xué)法制漿過(guò)程中,植物纖維原料的20%～30%會(huì)以半纖維素和木素的形式溶解在廢液中,結(jié)合生物質(zhì)精煉的理念,考慮在原料蒸煮之前預(yù)提取部分半纖維素用作化工原料,預(yù)提取后的植物纖維原料仍用于制漿造紙。本論文以制漿造紙與生物質(zhì)精煉相結(jié)合為出發(fā)點(diǎn),系統(tǒng)的研究了堿法分離純化玉米秸稈半纖維素以及半纖維素的表征和結(jié)構(gòu)鑒定。 以玉米秸稈為原料,KOH和NaOH提取玉米秸稈半纖維素的提取液中,大部分半纖維素是以聚糖的形式存在,其中聚木糖的濃度最高,兩種堿提取液中的聚木糖相對(duì)于原料中木糖的溶出率都達(dá)到了40%以上,KOH提取液中聚木糖的溶出率比NaOH的高6個(gè)百分點(diǎn)左右,醇沉率比NaOH法高10個(gè)百分點(diǎn)左右,兩種堿法制備的半纖維素樣品中,所含木糖含量相當(dāng)。苯醇抽提對(duì)堿-乙醇法分離半纖維素影響很小,可以忽略不計(jì)。 與未提取半纖維素的原料相比,堿提取后的玉米秸稈物料中的葡萄糖的百分含量提高了17個(gè)百分點(diǎn),玉米秸稈物料中的葡萄糖的保留率都接近百分之七十：總木素含量大大降低,堿提取后木素的脫除率達(dá)到了百分之八十以上。 KOH提取玉米秸稈半纖維素的較佳的工藝條件為：在堿濃6%,溫度85℃、液比7：1、保溫時(shí)間120min。溫度對(duì)聚木糖溶出率的影響最大,其次是堿濃,液比和時(shí)間對(duì)聚木糖溶出率的影響都較小。在優(yōu)化的工藝條件下,用KOH提取的半纖維素提取液中木素的濃度為45.614g/L。酸析木素法能有效脫除提取液中的木素。酸析法得到的粗木素中含20.36%的糖類(lèi)組分。 用乙醇分級(jí)沉淀法純化半纖維素,乙醇濃度為30%時(shí)得到了平均分子量分布在40568的半纖維素樣品,其次是乙醇濃度為40%時(shí),得到了平均分子量分布在18685的半纖維素樣品,其它條件下分離出的樣品的分子量都很低。核磁結(jié)果顯示玉米秸稈堿性半纖維素F40的所含的半纖維素主要為聚-O-乙�；�-4-O-甲基葡萄糖醛酸木糖。 提取半纖維素后的玉米秸稈煮漿時(shí)可以減少大量的后續(xù)蒸煮用堿量,抄成的紙張強(qiáng)度有所下降,耐折度、抗張強(qiáng)度、裂斷長(zhǎng)明顯下降很多,其它的指標(biāo)下降均不明顯。
[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.

【學(xué)位授予單位】：大連工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TQ914.3

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