超声波处理对麦草碱木质素结构特性的影响

EFFECTS OF ULTRASONIC PROCESSING ON STRUCTURE OF ALKALI LIGNIN OF WHEAT-STRAW

采用超声波作用于麦草碱木质素,探讨了超声波对碱木质素的活化作用,用化学法 对超声波作用前后碱木质素官能团进行了定量测定,用凝胶色谱(GPC)测定了木质素相对分 子质量的变化,用1H NMR光谱对化学结构进行了分析。结果表明:超声波可以显著提高碱木 质素酚羟基和醇羟基含量,当作用时间20 min、作用功率200W、液料质量比100:1时,醇羟 基含量从1．99 mmol／g上升为4．14 mmol／g,酚羟基含量从1．88 mmol／g上升为2．54 mmol／g,羧基含量从 0．59 mmol／g下降为0．29 mmol／g。羰基含量从2．16 mmol／g上升为2．68 mmol／g。1H NMR分析表明,愈创木 基和紫丁香基峰面积与总峰面积的比值分别从3．61％和0．77％下降为0,甲氧基峰面积与总峰面积的比值 从11．50％下降为8．90％。敷均分子质量(Mn)和重均分子质量(Mw)分别从1 179和10250上升为5031 和11 605,分散度(Mw／Mn)从8．69下降为2．31．

Alkali lignin of wheat-straw from black liquor was processed by ultrasonic wave and the activation effect of ultrasonic wave on the alkali lignin was discussed. Functional group of alkali lignin was measured by chemical methods, molecular weight was measured by GPC and chemical structure was analysed by mH NMR. Results indicated that ultrasonic processing was very effective. At ultrasonic processing time 20 min, power 200 W, and mass ratio （0.2 mol/L NaOH ： lignin solution） 100 ： 1, the contents of phenolic hydroxyl, aliphatic hydroxyl, carboxyl and aldehyde of the alkali lignin are from 1.88 mmol/g to 2.54 mmol/g, from 1.99 mmol/g to 4.14 mmol/g, from 0. 59 mmol/g to 0. 29 mmol/g, and from 2.16 mmol/g to 2. 68 mmol/g, respectively. From the spectrum of LH NMR, G-lignin percentage （ the ratio of area of G-lignin peak to sum of all peaks＇area） is from 3.61% to 0. S-lignin percentage is from 0. 77 % to 0, OCH3 percentage is from 11.50 % to 8.90 %. The numerical-average molecular weight （Mn） is from 1 179 to 5 031, the weight-average molecular weight （Mw） is from 10 250 to 11 605, dispersiveness（Mw/Mn） is from 8.69 to 2.31.