Abstract Cellulose and hemicelluloses were isolated from birch wood using a dilute alkaline solution and then consolidated into pellets as model compounds of cellulose and hemicelluloses in the wood cell wall. The purity of isolated cellulose and hemicelluloses was examined by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The density, thermal diffusivity, heat capacity, and thermal conductivity were experimentally determined for consolidated birch powder, cellulose, and hemicelluloses in over-dry condition. The thermal degradation kinetic parameters of these materials were successfully calculated using a conversion rate step of 0.01, and the relationship with conversion rate was established. The results show that cellulose and hemicelluloses consolidated under 25 MPa had densities of 1362 kg/m3 and 1464 kg/m3, respectively. The cell wall of birch powder in the oven-dry state was not collapsed under 25 MPa. The thermal diffusivity of consolidated birch powder, cellulose, and hemicelluloses linearly decreased with temperature, with values of 0.08, 0.15, and 0.20 mm2/s at room temperature, respectively. The specific heat capacity (1104, 1209, and 1305 J/(kg·K) at 22 °C, respectively) and thermal conductivity (0.09, 0.24, and 0.38 W/(m·K) at 22 °C, respectively) linearly increased with temperature, except for those for hemicelluloses which exhibited a nonlinear relationship with temperature above 120 °C, and their linear experimental prediction equations were given. Birch cellulose was more thermally stable than hemicelluloses. The thermal degradation kinetic parameters including activation energy and pre-exponential factor of birch powder, cellulose, and hemicelluloses varied with the conversion rate and calculation methods, with average activation energy in a conversion rate range of 0.02–0.15 of 123.2, 159.0, and 147.2 kJ/mol, respectively (using the Flynn–Wall–Ozawa method), for average natural logarithm pre-exponential factors of 25.0, 33.1, and 28.7 min−1, respectively. Linear and quadratic equations were fitted to describe the relationship between the kinetic parameters and conversion rates. These results give comprehensive thermal properties of the densified cellulose and hemicelluloses isolated from a specific wood.

中文翻译：

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碱溶液分离桦木及其纤维素和半纤维素的热特性

摘要 使用稀碱性溶液从桦木中分离纤维素和半纤维素，然后将其固结成颗粒，作为木材细胞壁中纤维素和半纤维素的模型化合物。分离出的纤维素和半纤维素的纯度通过傅里叶变换红外光谱和热重分析进行检测。密度、热扩散率、热容量和热导率通过实验确定在过干条件下固化的桦木粉、纤维素和半纤维素。使用0.01的转化率步长成功计算了这些材料的热降解动力学参数，并建立了与转化率的关系。结果表明，在 25 MPa 下固结的纤维素和半纤维素的密度分别为 1362 kg/m3 和 1464 kg/m3，分别。桦木粉在烘箱干燥状态下的细胞壁在 25 MPa 下没有塌陷。固化的桦木粉、纤维素和半纤维素的热扩散率随温度线性下降，在室温下分别为 0.08、0.15 和 0.20 mm2/s。比热容（分别为 1104、1209 和 1305 J/(kg·K) 在 22 °C 下）和热导率（在 22 °C 下分别为 0.09、0.24 和 0.38 W/(m·K)）线性除半纤维素在 120°C 以上与温度呈非线性关系外, 均随温度升高而增加, 并给出了它们的线性实验预测方程。桦木纤维素比半纤维素更热稳定。桦木粉、纤维素、和半纤维素随转化率和计算方法而变化，转化率范围为 0.02-0.15 的平均活化能分别为 123.2、159.0 和 147.2 kJ/mol（使用 Flynn-Wall-Ozawa 方法），对于平均天然对数指数前因子分别为 25.0、33.1 和 28.7 min-1。拟合线性和二次方程来描述动力学参数和转化率之间的关系。这些结果给出了从特定木材中分离的致密纤维素和半纤维素的综合热性能。分别为 25.0、33.1 和 28.7 min-1 的平均自然对数指数前因子。拟合线性和二次方程来描述动力学参数和转化率之间的关系。这些结果给出了从特定木材中分离的致密纤维素和半纤维素的综合热性能。分别为 25.0、33.1 和 28.7 min-1 的平均自然对数指数前因子。拟合线性和二次方程来描述动力学参数和转化率之间的关系。这些结果给出了从特定木材中分离的致密纤维素和半纤维素的综合热性能。