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采用密度泛函理论方法,对半纤维素的模化物木聚糖在典型温度范围(700-1 500 K)内进行了高温纯蒸汽气化反应机理研究。设计了8条反应路径,木聚糖开环形成链状结构IM1,经过脱水和降解等一系列过程最终得到2-糠醛、乙酸、甲醇、CO等产物。研究表明:在一定温度范围内,各反应路径的吉布斯自由能变随温度升高而增大,当温度超过1 300 K时吉布斯自由能开始逐渐减小;在同样温度下路径4的吉布斯自由能变小于其它路径,且路径4的反应势垒最小,为183 k J/mol,因此反应路径4是木聚糖气化的最优路径。
The density functional theory (XRD) method was used to study the mechanism of high-temperature pure steam gasification of hemicellulose xylan in a typical temperature range (700-1 500 K). Eight reaction paths were designed. The open chain of xylan was formed into chain structure IM1. The products of 2-furfural, acetic acid, methanol and CO were finally obtained through a series of processes such as dehydration and degradation. The results show that the Gibbs free energy of each reaction path increases with increasing temperature at a certain temperature range, Gibbs free energy begins to decrease when the temperature exceeds 1300 K, and at the same temperature, path 4 Gibbs free energy becomes smaller than that of other pathways, and path 4 has the smallest reaction barrier of 183 kJ / mol. Therefore, reaction path 4 is the optimal path for xylan gasification.