基于等转化率法和生物炭性质揭示稻草秸秆的热解特性  

Pyrolytic behavior of rice straw based on the detailed analysis of isoconversional method and biochar characterization

作　　者：张梦垚 汪家乐 张源 朱泽涛 刘艳伟[1] 陶文梅 ZHANG Mengyao;WANG Jiale;ZHANG Yuan;ZHU Zetao;LIU Yanwei;TAO Wenmei(Faculty of Morden Agricultrual Engineering,Kunming University of Science&Technology,Kunming,650500,China)

机构地区：[1]昆明理工大学现代农业工程学院,昆明650500

出　　处：《环境化学》2024年第9期2978-2987,共10页Environmental Chemistry

基　　金：国家自然科学基金(42207286);云南省基础研究计划项目(202201BE070001-041,202101AT070125);昆明理工大学高层次人才平台建设项目资助.

摘　　要：对稻草秸秆在氮气气氛下的热解进行热重分析.基于等转化率方法和生物炭表征,揭示稻草秸秆的热解机理.结果表明:(1)热解区间划分为4个阶段,第一阶段是水分蒸发和易挥发有机物的挥发,纤维素和半纤维素的解聚;第二阶段为主热解阶段,纤维素和半纤维素发生剧烈的脱水和还原反应;第三阶段主要是木质素的热解,炭的芳香性进一步增加;第四阶段为剩余物质继续热解成炭,生物炭高度碳化;(2)在主热解阶段,∆H、∆G和∆S均大于0,表明纤维素和半纤维素的热分解反应是吸热、非自发的、熵增大的反应;(3)热解温度低于250℃时,木质素是稻草秸秆生物炭PFR生成的主要贡献者,g值大于2.004,是以氧为中心的自由基;随着热解温度的升高,g值有所降低但始终位于2.003—2.004之间,稻草秸秆生物炭的自由基类型由以氧为中心的自由基为主逐渐转变为以碳为中心的自由基为主,且自由基的种类减少.本研究为稻草秸秆生物质的热解机制和生物炭的制备提供一定的理论支撑.Rice straw was pyrolyzed by thermogravimetric analysis under nitrogen atmosphere.Based on the,The pyrolysis mechanism was elucidated with the analysis of activation energy obtain by Friedman,DAEM method and biochar characterization.Results showed that:(1)the pyrolysis process of rice straw can be divided into four stages.In the first stage,the reaction was mainly composed by the losing moisture and depolymerization of cellulose and hemicellulose.Subsequently,the dehydration and reduction reaction of cellulose and hemicellulose was mostly occurred in the second stage,which is the main pyrolysis stage of rice straw.The main pyrolysis reaction of lignin was mainly located in the third stage.In the last stage,the biochar was highly carbonized.(2)the positiveΔH andΔG values indicated that the pyrolysis reactions for the second stage were endothermic and nonspontaneous.(3)when the pyrolysis temperature is lower than 250℃,lignin is the main contributor to the formation of persistent free radical in rice straw biochar.Additionally,the g value is greater than 2.004,which is the oxygen-centered free radical on.With the increase of pyrolysis temperature,g was decreasing but was still between 2.003 and 2.004,indicating that the free radical type was gradually changing from oxygen-centered free radicals to carbon-centered free radicals.This study provides useful information to understand the thermal pyrolysis process of rice straw and the application of the derived biochar.

关 键 词：Friedman法 活化能 木质素 自由基 

分 类 号：X-1[环境科学与工程] O6[理学—化学]