微孔和介孔材料中的热化学

这篇论文综述了美国加州大学戴维斯分校科学院院士Navrotsky课题组多年来在多孔材料上取得的一系列热化学研究结果。讨论了热化学对微孔、介孔材料的结构稳定性和合成过程的影响。借助多种测热手段对影响骨架结构的热焓、热熵和自由能进行了系统的测量和计算。研究数据表明一系列纯硅分子筛、介孔材料和磷酸铝多孔材料同相应的石英相和块磷铝矿相相比能量上最多只高出15 kJ·mol-1。一系列纯硅分子筛的熵值比石英相高出3.2—4.2 J·K-1·mol-1；在0—12.6 J·K-1·mol-1范围内相对应的自由能几乎没有差别。因此，对不同微孔、介孔材料，其骨架结构在能量上是几乎没有区别的。另外，本文通过介绍一种新型测热方法——原位测热，揭示了分子筛合成过程中的动力学和成核/结晶机理。

Thermochemistry of Microporous and Mesoporous Materials

The paper reviews thermochemistry contribution to the stability of frameworks and synthetic progress in microporous and mesoporous materials. Knowledge of enthalpies, entropies and free energies of formation on the framework structure in micorporous and mesoporous materials is systematically summarized via several calorimetric measurements. It is found that a series of pure-silica, mesoporous silicas and AlPO4 polymorphs are energetically, at most, 15 kJ·mol-1 higher than quartz and berlinite, and the entropies of a series of pure silica zeolites span a very narrow range at 3.2-4.2 J·K-1·mol-1 above quartz. Therefore, the Gibbs free energy of transformation calculated for several SiO2 phases have nearly the same ΔG298tran as the values range from 0 to 12.6 J·K-1·mol-1 with respect to quartz. Thus, there is very little energetic limitation to the possibility of synthesizing various micro- and mesoporous framework structures. In addition, a new calorimetric method, in situ calorimetry, is introduced to reveal the kinetics and nucleation/crystallization in the process of the zeolite synthesis.