Biomass Conversion Division, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas Norte # 152, C.P. 07730 México City, Mexico.
Biomass Conversion Division, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas Norte # 152, C.P. 07730 México City, Mexico.
Waste Manag. 2020 Apr 1;106:203-212. doi: 10.1016/j.wasman.2020.03.021. Epub 2020 Mar 30.
This study focuses on the thermo-kinetic analysis of solid peanut shell waste, through dependence of the activation energy with the conversion degree. Three model-free kinetics, Kissinger (K), Friedman (Fr) and Kissinger-Akahira-Sunose (KAS), were applied to thermogravimetric (TGA) data to calculate the effective activation energy E during a pyrolysis process. The results obtained by Kissinger's method showed that the pyrolytic breakdown pathway of hemicellulose, cellulose, and lignin in a ligno-cellulosic biomass is independent of the heating rate and can be described through a simple first-order kinetic reaction (f(α) = 1 - α). The thermo-kinetic behavior obtained by isoconversional methods (Fr and KAS) of the hemicellulose degradation shows a progressive and monotonic increase in E with the conversion, between ~140 and ~195 kJ mol with an average value of 172 kJ mol, which reveals the competitive character of the process (multi-step process). Conversely, in the cellulose degradation, the dependence of E on α, shows the typical behavior of a reaction controlled by a single rate-determining step, with constant average E values of ~209 kJ mol. Meanwhile, the lignin pyrolytic degradation shows an increase in E from ~220 up to ~300 kJ mol with the conversion, indicating that this stage is kinetically controlled by an energy barrier that comprises multiple and simultaneous processes. Finally, the kinetic analysis confirmed the absence of autocatalytic reactions (thermally auto-catalyzed process) during the pyrolysis, although the global process is highly exothermic.
本研究专注于固体花生壳废物的热动力学分析，通过依赖于转化率的活化能。应用三种无模型动力学（Kissinger（K）、Friedman（Fr）和 Kissinger-Akahira-Sunose（KAS））对热重分析（TGA）数据进行处理，以计算热解过程中的有效活化能 E。Kissinger 方法得到的结果表明，木质纤维素生物质中半纤维素、纤维素和木质素的热解断裂途径与加热速率无关，可以通过简单的一级动力学反应（f(α) = 1 - α）来描述。通过等转化率方法（Fr 和 KAS）获得的半纤维素降解的热动力学行为表明，E 随着转化率呈递增和单调增加，在 140 到 195 kJ/mol 之间，平均值为 172 kJ/mol，这揭示了该过程的竞争特征（多步过程）。相反，在纤维素降解中，E 对 α 的依赖性表现出由单个速率决定步骤控制的典型行为，平均 E 值约为 209 kJ/mol。同时，木质素热解降解的 E 值从 220 增加到 300 kJ/mol 左右，转化率表明该阶段动力学受到包含多个同时发生过程的能量障碍的控制。最后，动力学分析证实热解过程中不存在自催化反应（热自催化过程），尽管整个过程是高度放热的。
