小桐子壳热解及其挥发性产物特性分析

Analysis of pyrolysis and volatile products characteristics of Jatropha curcas shell

选用小桐子壳作为原料,采用热重-红外联用(TG-FTIR)和热裂解-气相色谱质谱联用(Py-GC/MS)技术,研究小桐子壳的热解特性以及300~800℃热解过程中产物的组分信息和有机化合物中官能团随温度的变化情况,同时利用Coast-Redfern积分法求解不同升温速率下的动力学参数。结果表明,小桐子壳的热解过程分为干燥(30~100℃)、预热解(100~258℃)、热解(258~420℃)和炭化(420~900℃)四个阶段。随升温速率升高,小桐子壳的最大质量损失率依次增加,升温速率的升高对小桐子壳热分解速率具有促进作用。随热解温度升高,吸收峰处存在明显的强度变化,CO_(2)、醛酮类等化合物的吸收峰强度逐渐降低甚至消失;小桐子壳热解过程中的气体产物成分主要为CO,CO_(2),H_(2)O等,主要挥发性有机产物为苯酚、羰基化合物、愈创木酚类等,热解温度由400℃升至700℃时,酚类化合物的峰面积比例从35.94%升至59.59%、羰基化合物的峰面积比例从36.90%降到11.87%。小桐子壳热解动力学参数n=1时,其反应表观活化能最大为61.34 kJ/mol,且三个升温速率的拟合相关系数均在98%以上。小桐子壳热解动力学参数n≠1时,选取相关系数最大时的n值为反应级数,则n=0.2,反应活化能E为47.64 kJ/mol,指数前因子A为0.83。随升温速率的升高表观活化能依次递减,且拟合相关系数均在97%以上。

The pyrolysis characteristics of the Jatropha curcas shell were investigated using thermogravimetric Fourier transform infrared spectrometry(TG-FTIR)and pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS).The component information of pyrolysis products and the change of functional groups in organic compounds with temperature 300~800℃were studied.The Coast-Redfern integral method was used to solve the kinetic parameters at different heating rates.The results showed that the pyrolysis process of the Jatropha curcas shell can be divided into four stages:drying(30~100℃),preheating(100~258℃),pyrolysis(258~420℃)and carbonization(420~900℃).With the increase of heating rate,the maximum mass loss rate of the Jatropha curcas shell increased,and the increase of heating rate promote the thermal decomposition rate of the Jatropha curcas shell.With the increase of pyrolysis temperature,the intensity of absorption peak changed obviously,and the intensity of absorption peak of CO_(2),aldehydes and ketones gradually decreased or even disappeared.The main gas products were CO,CO_(2),H_(2)O,etc.,and the main volatile organic products were phenol,carbonyl compounds,guaiacol,etc.When the pyrolysis temperature increased from 400℃to 700℃,the peak area ratio of phenolic compounds increased from 35.94%to 59.59%,the peak area ratio of carbonyl compounds decreased from 36.90%to 11.87%.When the reaction order n=1,the maximum apparent activation energy(E)was61.34 kJ/mol,and the fitting correlation coefficients of the three heating rates were all above 98%.When the reaction order n≠1 and the n value of the maximum correlation coefficient were selected as the reaction order,then n=0.2,the activation energy(E)was 47.64 kJ/mol,and the pre-exponential factor(A)was 0.83.The apparent activation energy decreased with the increase of heating rate,and the fitting correlation coefficient was above 97%.