摘要
为了提高碱木质素的反应活性,以Pd/C为催化剂,采用微波法进行了碱木质素与H2的还原反应。运用1H-NMR分析了碱木质素的结构变化,且利用凝胶渗透色谱(GPC)测定了碱木质素的分子量和分子量分布。结果表明:较佳的碱木质素加氢还原反应条件是负载量为3%的Pd/C催化剂用量为10%、温度为95℃、时间为30min、氢气流速为20mL/min。1H-NMR分析显示:羰基和羧基含量减少,代表酚羟基和醇羟基的质子吸收增加。GPC分析显示:反应后碱木质素的分子量降低,而多分散性增大。元素分析显示:C和H含量在反应后都有所增加,而O含量则降低了,表明碱木质素发生了还原反应。与常规加热方式相比,微波法合成有利于提高酚羟基含量,缩短反应时间,而在提高碱木质素的总体反应活性方面没有表现出特殊的效应。
In order to improve the reaction activity of alkali lignin,we investigated the deoxidization of alkali lignin with H2 by a microwave method using Pd/C as a catalyst.Characterization was performed using proton nuclear magnetic resonance spectrometry（^1H-NMR） to analyze the chemical structure and gel permeation chromatography（GPC） to determine the molecular weight and molecular weight distribution of alkali lignin.The results show that the best reaction condition is as follows：a 3% Pd loading with a 10% of catalyst dosage,20 mL/min of hydrogen flow at a reaction temperature 95℃ and a reaction time of 30 min.The ^1H-NMR analysis showed that the content of carbonyl and carboxyl both decreased,while proton absorptions belonging to phenolic hydroxyl and alcoholic hydroxyl both increased.GPC analysis showed that the molecular weight of alkali lignin decreased,while the polydispersity increased after the reaction.Element analysis（EA） showed the content of C and H both increased,while O fell,indicating that the alkali lignin had suffered a deoxidization reaction.Compared to the normal method of heating, the synthesis by microwave was benefit in improving the content of phenolic hydroxyl and shortening the reaction time,while not showing a special effect on improving total reaction activity of alkali lignin.
出处
《北京林业大学学报》
CAS
CSCD
北大核心
2010年第2期171-176,共6页
Journal of Beijing Forestry University
基金
国家自然科学基金项目(30471363)
浙江林学院创新团队支持计划项目(2006B03)
浙江林学院科学研究发展基金
关键词
微波法
PD/C催化剂
碱木质素
加氢
microwave method
Pd/C catalyst
alkali lignin
hydrogenation
