温度对二氧化碳酸析提取黑液中木质素的影响

以碱法制浆的松木黑液为原料,用二氧化碳酸化黑液提取其中的木质素,考察了反应温度(40~80℃)对酸析木质素产率及其无机盐和糖分等含量的影响,采用凝胶渗透色谱(GPC)、离子色谱仪(IC)、元素分析仪和热重分析仪(TG)对木质素产物进行结构表征。结果表明,温度升高不利于木质素析出,产率下降;但较高温度下制备的木质素中无机盐、糖分及硫含量低,纯度高;同时温度越高,木质素相对分子质量越大,甲氧基含量增大,但酚羟基含量减小。TG和DTG曲线显示,反应温度升高木质素最大失重速率增加,残余量减少。

Effect of Temperature on Lignin Precipitation via Carbon Dioxide Acidification

A softwood Kraft black liquor was acidified with carbon dioxide at different temperatures. The effect of temperature on the recovery yield, the content of inorganics and carbohydrates was investigated. The chemical structure of lignin was determined by GPC, IC, elemental analyzer and TG analyzer. The results showed that a higher temperature was negative to lignin precipitation. The recovery yield of lignin decreased with the temperature increase. However, the lignin, obtained at the higher temperature, had lower ash and carbohydrate contents, and a higher purity. With the increase of temperature, the molecular weight and methoxyl group content of lignin increased, while the phenolic hydroxyl group decreased. TG and DTG curves indicated that the higher acidification temperature resulted in the larger weight loss rate and smaller solid residue mass.