林产化学与工业
林產化學與工業
림산화학여공업
CHEMISTRY AND INDUSTRY OF FOREST PRODUCTS
2014年
2期
33-39
,共7页
熊果酸%咖啡酸%热重-红外联用%热降解机理%分解动力学
熊果痠%咖啡痠%熱重-紅外聯用%熱降解機理%分解動力學
웅과산%가배산%열중-홍외련용%열강해궤리%분해동역학
ursolic acid%caffeic acid%TG-FT-IR%thermal decomposition mechanism%decomposition kinetics
采用热重-傅里叶红外光谱联用技术( TG-FT-IR)对杜仲中的两种天然有机酸熊果酸和咖啡酸进行了非等温热分析。结合量子化学GAMESS软件分子模拟计算、热失重和热解逸出气体红外光谱分析,对两种有机酸化学键的断裂情况进行了推断和验证。使用积分Coats-Redfern法、微分Achar法以及Malek法等3种热分析动力学方法对热重实验数据进行了分析,推断了各步分解最概然机理函数,得到相应的动力学参数---表观活化能(Ea)和指前因子(A),并推断其贮存期。研究表明,各步失重、分子模拟推断和逸出气体红外光谱解析,这三者能够对热分解过程的化学键断裂情况进行判断；熊果酸的热分解自236.8℃至431.2℃,且一步完成,为二维扩散控制机制(圆柱形对称型),符合Valensi方程,Ea为228.26 kJ/mol,lnA为39.56；咖啡酸在153.0℃后发生了两步分解,第一步热分解为二维扩散控制机制,符合Jander方程,Ea1为111.28 kJ/mol, lnA1为25.78,而第二步热分解为三维扩散控制机制,符合 Z.-L.-T.方程, Ea2为231.75 kJ/mol, lnA2为43.50；熊果酸和咖啡酸在室温(25℃)的贮存期分别为4~5年和3年。
採用熱重-傅裏葉紅外光譜聯用技術( TG-FT-IR)對杜仲中的兩種天然有機痠熊果痠和咖啡痠進行瞭非等溫熱分析。結閤量子化學GAMESS軟件分子模擬計算、熱失重和熱解逸齣氣體紅外光譜分析,對兩種有機痠化學鍵的斷裂情況進行瞭推斷和驗證。使用積分Coats-Redfern法、微分Achar法以及Malek法等3種熱分析動力學方法對熱重實驗數據進行瞭分析,推斷瞭各步分解最概然機理函數,得到相應的動力學參數---錶觀活化能(Ea)和指前因子(A),併推斷其貯存期。研究錶明,各步失重、分子模擬推斷和逸齣氣體紅外光譜解析,這三者能夠對熱分解過程的化學鍵斷裂情況進行判斷；熊果痠的熱分解自236.8℃至431.2℃,且一步完成,為二維擴散控製機製(圓柱形對稱型),符閤Valensi方程,Ea為228.26 kJ/mol,lnA為39.56；咖啡痠在153.0℃後髮生瞭兩步分解,第一步熱分解為二維擴散控製機製,符閤Jander方程,Ea1為111.28 kJ/mol, lnA1為25.78,而第二步熱分解為三維擴散控製機製,符閤 Z.-L.-T.方程, Ea2為231.75 kJ/mol, lnA2為43.50；熊果痠和咖啡痠在室溫(25℃)的貯存期分彆為4~5年和3年。
채용열중-부리협홍외광보련용기술( TG-FT-IR)대두중중적량충천연유궤산웅과산화가배산진행료비등온열분석。결합양자화학GAMESS연건분자모의계산、열실중화열해일출기체홍외광보분석,대량충유궤산화학건적단렬정황진행료추단화험증。사용적분Coats-Redfern법、미분Achar법이급Malek법등3충열분석동역학방법대열중실험수거진행료분석,추단료각보분해최개연궤리함수,득도상응적동역학삼수---표관활화능(Ea)화지전인자(A),병추단기저존기。연구표명,각보실중、분자모의추단화일출기체홍외광보해석,저삼자능구대열분해과정적화학건단렬정황진행판단；웅과산적열분해자236.8℃지431.2℃,차일보완성,위이유확산공제궤제(원주형대칭형),부합Valensi방정,Ea위228.26 kJ/mol,lnA위39.56；가배산재153.0℃후발생료량보분해,제일보열분해위이유확산공제궤제,부합Jander방정,Ea1위111.28 kJ/mol, lnA1위25.78,이제이보열분해위삼유확산공제궤제,부합 Z.-L.-T.방정, Ea2위231.75 kJ/mol, lnA2위43.50；웅과산화가배산재실온(25℃)적저존기분별위4~5년화3년。
Two kinds of natural organic acid, ursolic acid and caffeic acid were analyzed under the nitrogen atmosphere by thermogravimetry combined fourier transform infrared spectroscopy ( TG-FT-IR) . Experimental data of TG were computationally processed by three kinds of thermal analysis kinetics methods ( Coats-Redfern, Achar and Malek methods) , through which the most probable mechanisms and functions of each stage were inferred and the values of apparent activation energy Ea and pre-exponential factor A were also obtained. The results showed that according to percentage of weight loss, molecular simulation and infrared spectrum of evolved gases, the cracking of chemical bonds was confirmed. Thermal decomposition of ursolic acid began at 236. 8 ℃ and ended at 431. 2 ℃ with a complete mass loss while after 153. 0 ℃ caffeic acid underwent the two-stage thermal decomposition. The most probable mechanisms of ursolic acid and caffeic acid at the first stage and the second stage were two-dimension diffusion, two-dimension diffusion and three-dimension diffusion, corresponding with Valensi equation, Jander equation and Z.-L.-T. equation, respectively. Ea of ursolic acid and caffeic acid at first stage and second stage were 228. 26, 111. 28 and 231. 75 kJ/mol while their lnA were 39. 56, 25. 78 and 43.50, respectively. According to kinetic parameters, shelflives of ursolic acid and caffeic acid at 25 ℃ were 4-5 years and 3 years, respectively.
