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首页> 外文OA文献 >Autohydrolysis and aqueous ammonia extraction of wheat straw: effect of treatment severity on yield and structure of hemicellulose and lignin
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Autohydrolysis and aqueous ammonia extraction of wheat straw: effect of treatment severity on yield and structure of hemicellulose and lignin

机译：小麦秸秆的自水解和氨水萃取：处理强​​度对半纤维素和木质素产量和结构的影响

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The objective of this study was to elucidate the impact of autohydrolysis severity on the yield and structure of wheat straw hemicellulose and lignin. The autohydrolysis treatments were carried out at maximum temperatures between 170 °C and 200 °C. The autohydrolysis liquors were separated and the solids were successively extracted with aqueous ammonia either in moderate or high intensity extraction conditions to dissolve lignin for analysis. Increasing autohydrolysis severity decreased the molar mass of the aqueous ammonia extracts from 5450 g mol−1 to 1810 g mol−1, and carbohydrate content from 6% to 0.1%. The optimum autohydrolysis severity (log R0 = 3.81) for xylan recovery released mainly oligomeric arabinoxylans at 66% xylan recovery yield. Drastic degradation of pentoses occurred beyond the optimum severity. As an indication of accumulation of “pseudo-lignin” during autohydrolysis, decreasing relative aromaticity in the aqueous ammonia extracts as a function of autohydrolysis severity was shown. The finding was confirmed by quantitative analysis of the cupric oxide oxidation products of lignin suggesting up to 55% decrease in the relative amount of native lignin at the highest severity. These results show the importance of distinguishing between lignin and “pseudo-lignin” in fractions obtained from lignocellulosic materials subjected to acidic pretreatment.
机译：这项研究的目的是阐明自水解程度对小麦秸秆半纤维素和木质素产量和结构的影响。自动水解处理是在170°C至200°C的最高温度下进行的。分离自水解液，并在中等或高强度提取条件下依次用氨水提取固体，以溶解木质素进行分析。自水解的严重程度增加，氨水提取物的摩尔质量从5450 g mol-1降低到1810 g mol-1，碳水化合物含量从6％降低到0.1％。木聚糖回收的最佳自动水解强度（log R0 = 3.81）主要释放寡聚阿拉伯木聚糖，木聚糖回收率为66％。戊糖的急剧降解超出了最佳严重程度。作为自动水解过程中“伪木质素”积累的指示，氨水提取物中的相对芳香度随自动水解程度的降低而降低。通过对木质素的氧化铜氧化产物的定量分析证实了这一发现，表明在最高严重性下天然木质素的相对量最多降低了55％。这些结果表明，区分木质素和“假木质素”的重要性在于从经过酸预处理的木质纤维素材料中获得的馏分。

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