纤维素快速热裂解机理试验研究 Ⅱ. 机理分析

针对在热辐射反应器上得到的纤维素热裂解实验结果，对左旋葡聚糖、1-羟基-2-丙酮以及乙醇醛等一次产物的生成机理进行了分析研究。在气相产物快速析出并急冷的条件下，乙醇醛和1-羟基-2-丙酮二种产物的生成与LG的生成呈现出竞争反应。基于这一结果，我们建立了竞争反应动力学模型，并分别对乙醇醛和1-羟基-2-丙酮进行了模拟，得出二种产物的生成具有相似的动力学行为，表明这两种竞争化合物具有相同的初始反应。分析认为，纤维素的热裂解通过活性纤维素这一反应前体以异裂和均裂两种热解途径进行分解，其中转糖基作用下糖苷键的异裂断开形成了包括LG以及其同分异构体的脱水糖；缩醛结构的开环以及环内C—C键的断裂形成乙醇醛、1-羟基-2-丙酮以及CO等其它小分子化合物。在Brodio-shafizadeh模型的基础上提出了反应机理模型，并按照该模型对高辐射源温度下纤维素热裂解LG的生成进行了模拟，计算结果与实验数据吻合较好。

MECHANISM OF CELLULOSE RAPID PYROLYSIS Ⅱ. MECHANISM ANALYSIS

According to the experimental result on cellulose pyrolysis in heat radiation reactor, a mechanism of cellulose pyrolysis was studied on primary products formation, such as levoglucosan, glycolaldehyde and acetol etc In the case of rapid devolatilization and following chill, the formation of glycolaldehyde and acetol appeared to compete with that of levoglucosan Then, a kinetic model based on competitive reaction was proposed to simulate the formation of glycolaldehyde and acetol It was concluded that formation of glycolaldehyde was similar with that of acetol in kinetic behavior, showing that there existed two similar initial formation reactions During pyrolysis process, cellulose underwent decomposition through heterolytic or homolytic fission of some reaction precursors, which could be called as active cellulose Anhydrosugars, including levoglucosan and its isomeric compounds, were formed by heterolytic fission of glucosidic bond under transglycosylation reaction While small molecular compounds, such as glycolaldehyde, acetol and CO, were formed by acetal open-loop and following C-C bond rupture On the basis of Brodio-shafizadeh model, a mechanism model was proposed to simulate levoglucosan formation at high temperature of thermal radiation source The calculation result was consonant well with experimental value