在氮气氛和不同的加热速率下对三种木材(马尾松、棉杆和杉木)进行了热重分析。同时研究了碳酸钠对这三种木材热解的催化效应。运用Popescu法从22种动力学机理函数中寻求裂解的最概然机理函数并计算裂解的动力学参数。结果表明,Zhuralev,Lesokin and Tempelmen(Z-L-T)方程为最概然机理函数。根据Z-L-T方程计算的动力学参数表明,在裂解的低转化率范围,碳酸钠可以降低表观裂解活化能,而在裂解的高转化率范围,碳酸钠可以增加表观裂解活化能。根据木材的结构成分对碳酸钠的催化行为进行了分析。
The pyrolysis behavior of two kinds of typical biomass (pine wood and cotton stalk) was studied in nitrogen atmosphere at various heating rates by thermogravimetric analysis (TGA). The pyrolysis process can be divided into three stages: evolution of moisture (<200 ℃), devolatilization (200～400℃) and carbonization (>400 ℃). The comparison of DTG curves of two biomass materials show that the higher the hemicellulose content of biomass, the more evident the shoulder peak of DTG curve. The weight loss process of two materials was simulated by the kinetic model assuming cellulose, hemicellulose and lignin pyrolyzing independently and in parallel, obeying first-order reactions. The pyrolysis kinetic parameters corresponding to the three components were estimated by the nonlinear least square algorithm. The results show that their fitting curves are in good agreement with the experimental data. Their activation energy values for pine wood and cotton stalk are in the range of 188～215, 90～102, 29～49 and 187～214, 95～101, 30～38 kJ/mol, respectively. The corresponding pre-exponential factors are in the range of 1.8×1015～2.0×1016 , 1.6×107～7.1×108 , 9.3×101～1.5×103 and 1.2×1015～6.7×1017 , 1.2×108～1.4×109 , 1.4×102～4.6×102 min-1 , respectively. In addition, the activation energy of cellulose and lignin increased and their contributions to volatile tended to fall, whereas the activation energy of hemicellulose decreased and its contribution to volatile tended to rise with increasing of heating rate.
