正己烷转化为丙烷的反应调控与研究

分别在反应温度(T)为420和500℃下，通过调整正己烷在HZSM-5分子筛催化剂表面的停留时间对正己烷转化为丙烷反应进行了研究，并利用分子模拟对脱氢和氢转移反应进行了模拟，明确了获得理想丙烷选择性的关键因素和原因。实验结果和模拟结果表明：T为420℃时丙烷选择性最高，可达49.70%;此时丙烷的生成主要发生在正己烷活化阶段，以及停留时间m_cat/F>172 (g·h)/mol时中间产物丁烷的活化阶段。T为500℃时丙烷选择性较小的原因，一方面是因为脱氢反应为强吸热反应，氢转移反应为微放热反应，热力学上高温有利于脱氢反应的发生；另一方面T为500℃和m_cat/F>30 (g·h)/mol的反应条件将引发丙烷的再转化。因此，在反应温度T为420℃时保证m_cat/F>172 (g·h)/mol是获得理想丙烷选择性的关键因素。

Reaction Regulation and Study on Conversion of n-hexane to Propane

The conversion of n-hexane to propane was studied by adjusting the residence time of n-hexane on the surface of HZSM-5 zeolite catalyst at 420 and 500 ℃, respectively. The dehydrogenation and hydride transfer reactions were simulated by molecular simulation. The key factors and causes for obtaining ideal propane selectivity were clarified. The experimental and simulation results show that the propane selectivity hit the peak at the reaction temperature of420 ℃, reaching up to 49.70%; the propane is mainly formed in the activation stage of n-hexane, as well as the activation stage of the intermediate product butane when the residence time (mcat/F) is greater than 172 (g·h)/mol. As for why the propane selectivity is smaller at the reaction temperature of 500 ℃, on one hand, it is because dehydrogenation is classified as a highly endothermic reaction, while hydride transfer is classified as a slightly exothermic reaction, and high temperature is conducive to the occurrence of dehydrogenation reaction in thermodynamics; on the other hand, the conditions of T=500 ℃ and mcat/F＞30 (g·h)/mol will trigger the reconversion of propane. Therefore, ensuring the residence time mcat/F＞172 (g·h)/mol at 420 ℃ is the key factor to obtain an ideal propane selectivity.