Abstract: Process and kinetics of thermal decomposition of humic acid were studied with TG-DTG techniques. Thermal decomposition temperature of humic acid was in the range of 284.65-417.16℃. The structure of humic acid was characterized with FT-IR, ¹H NMR and ¹³C NMR. The kinetic parameters, including activation energy and pre-exponential factor of the thermal decomposition process of humic acid were calculated with the Flynn-Wall-Ozawa (FWO), Kissinger and Šatava-Šesták method respectively. Activation energy and logarithmic value of pre-exponential factor were found to be 210.83 kJ·mol^-1 and 17.55, respectively. Moreover, reaction order and mechanism of thermal decomposition and thermodynamic parameters were also studied. Thermal decomposition of humic acid was a second-order reaction, and the mechanism of the decomposition process was obtained. The maximal used temperature of humic acid maintaining one-minute lifetime in N₂ atmosphere was 278℃. Meanwhile, the thermodynamic paramaters of ΔH^≠, ΔS^≠ and ΔG^≠ were calculated as 67.99 kJ·mol^-1, -164.83 J·(mol·K)^-1 and 176.36 kJ·mol^-1, respectively.

Key words: humic acid, thermal decomposition, kinetics, mechanism, enthalpy, NMR

摘要： 采用热重分析法（DTA-TGA）研究了腐殖酸的热分解过程及其动力学，分析其DTA-TGA曲线可得：热分解反应发生在284.65～417.16℃； 用红外光谱（FT-IR）、核磁氢谱（¹H NMR）、核磁碳谱（¹³C NMR）对腐殖酸结构进行表征，用Flynn-Wall-Ozawa（F-W-O）法、Kissinger法及Šatava-Šesták法计算出腐殖酸热分解反应的表观活化能为210.83 kJ·mol^-1，指前因子对数为17.55；确定了其热分解反应的级数和动力学参数，且热分解反应机理为二级反应；腐殖酸在氮气氛围下维持1min寿命的最高使用温度为278℃；同时，计算出腐殖酸样品热力学参数焓变、熵变及摩尔自由能变分别为67.99 kJ·mol^-1、-164.83 J·（mol·K）^-1 和176.36 kJ·mol^-1。

关键词: 腐殖酸, 热分解, 动力学, 机理, 焓, 核磁共振