| In the traditional chemical pulping process,20～30%of the plant fiber raw materials dissolved in the waste water in the form of hemicellulose and lignin. Combined with the concept of biomass refining, the plant fiber raw materials can be pretreated before pulping and extract part of the hemicellulose. In this paper the combination of pulp and paper and biomass refining is a starting point, the isolation and purification of hemicellulose by alkaline from corn stover and the characterization and structure identification of hemicellulose were studied systematically.With corn straw as raw material, two comparison of NaOH and KOH alkali extraction effect of maize straw hemicellulose, most of the alkaloid extract of hemicellulose in the form of chitosan, monosaccharide content is very low. Two extract contained in the chitosan is the same, the kinds of different concentration, the concentration of poly xylose is highest, compared with other chitosan concentration is very low. In the same concentration of OH-1, liquid ratio, temperature and time, the two kinds of alkali extract of xylose relative to the raw material of xylose in dissolution rate has reached more than forty percent, extract of KOH of xylose dissolution rate is about6%higher than NaOH. In triploid product in the process of ethanol precipitation of hemicellulose, method of KOH alcohol sink rate around10%higher than the NaOH method and two kinds of alkali-ethanol prepared samples of hemicellulose, although the total sugar content of KOH method without NaOH method is high, but both quite containing xylose content. Method of benzyl alcohol extraction of alkali-ethanol had no effect on the separation of hemicellulose.By condition experiments to optimize the conditions for KOH extracting maize straw hemicellulose, found a significant turning point near the alkali concentration6%, temperature, liquid ratio, time at85℃respectively,7:1and120min after xylose dissolution rate into balance. Orthogonal experiment data show that in appropriate range, the influence of temperature on xylose dissolution rate is the largest, followed by alkali concentration, liquid ratio and time for the influence of xylose on dissolution rate is small. Compared with the raw material without the extracted hemicellulose, after alkali extraction of corn straw material about the percentage of glucose is increased by17%, results show that at low temperature with alkali extraction of hemicellulose can guarantee the raw material of cellulose content is almost not affected, most of the lignin in the process of alkaline extraction and dissolved with hemicellulose in the extract. After the optimization condition of KOH was prepared under the condition of extraction extract, extract of calculated according to the standard curves of lignin lignin concentration is45.614g/L. Through acid out most of the methods to extract lignin lignin removal.Fractional precipitation with ethanol and purification of hemicellulose, through the analysis of the yield, sugar grading composition, molecular weight distribution, infrared spectra, nuclear magnetic, thermogravimetric analysis, found in the process of ethanol precipitation classification of hemicellulose, ethanol concentration was30%by average molecular weight distribution in40568samples of hemicellulose, followed by ethanol concentration was40%, the average molecular weight distribution in18685samples of hemicellulose, isolated from the other conditions are low molecular weight of the sample. Mri of the results showed that ethanol concentration of40%get corn straw alkaline hemicellulose F40structure for poly-O-acetyl-4-O-methyl glucuronic acid xylose.After extraction of hemicellulose of maize straw can reduce subsequent when boiled pulp cooking with alkaline, reduce the pollution to the environment at the same time. Copy of paper strength declined, but in addition to the degree of folding, other index decline is not obvious. |
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