醇水体系下尾巨桉抽出物的热解特性研究

Leaching Law and Pyrolysis Characteristics of Extractives from Eucalyptus grandis Pretreatment under Ethanol/Water Solution System

采用回转式密封炉在醇水体系下,分别采用水及乙醇-水混合液(醇水体积比1:4、1:2、1:1)4种溶剂对桉木片进行抽提预处理,制得4种不同的抽提物。通过元素分析、溶出物微粒子粒径分析对其进行了基本溶出规律的研究,抽提液中所含的糖类化合物通过HPLC测定,设计TG与Py-GC/MS实验,对不同方式获得的抽出物进行了热分析,对其受热分解特性以及产物的分布进行了考查。结果发现,醇水体系中不同乙醇浓度下抽提液中糖类化合物的GC含量类似,并且抽提物总量也相近;元素分析的结果表明不同浓度醇水抽提物的化学元素含量并没有明显的差异,而与水抽提物相比存在较大的区别,醇水抽提物相对于水抽提物具有较高的C含量及较低的O含量;不同乙醇浓度抽提物溶液之间的微粒子直径也不存在较大的差异,而与水抽提溶液中微粒子的尺寸差别明显。由此推断醇水溶剂中乙醇和水对尾巨桉木片的抽提作用是相对独立的。对于抽提物的热分析表明,不同体系下抽提物所表现出的热解特性存在较大差异,而醇水体系下3种抽提物的热解特性类似;水抽提物(WE)的热解产物主要是酮类、酚类和酸类;醇水抽提物(EWE)的热解产物主要是呋喃、糠醛(醇)、酚类和酮类。

Eucalyptus grandis chips were pretreated under ethanol/water solution system with a sealed helicoid furnace and four extractives were obtained by pure water and ethanol/water mixtures with ratio of 1 ： 4, 1 ： 2, 1 ： 1 ,respectively. Basic leaching rule was studied through ultimate analysis and micro particle size detection. Sugar content in each extractive was determined by ionic chromatograph analysis, meanwhile TG and Py-GC/MS reveal were designed to reveal the pyrolysis properties of extractives. The results showed that all three extractives from ethanol/water extraction had similar total extractive quality and sugar content. Very few differences were observed in view of the element content among ethanol/water extractives （EWE） , but for water extractive （ WE）, it had more O content and less C content. Micro particle distribution of all EWE were similar, but remarkable difference could be found WE was compared with EWE. It could be concluded that roles of ethanol and water in extraction were indepen- dent. Pyrolysis properties of the WE and EWE extractives were quiet different, but for three EWEs, they showed similar pyrolysis characteristics. The main pyrolisis products of WE were ketones, phenols and acids. However, for EWE, furans, furfurals, phe- nols and ketones were found.