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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。
This paper reviews the results of a series of thermochemical studies on porous materials that Navrotsky’s group at the Academy of Sciences of the University of California, Davis, has made over the years. The effects of thermochemistry on the structural stability and the synthesis of microporous and mesoporous materials are discussed. The enthalpy, thermal entropy and free energy influencing the skeleton structure were systematically measured and calculated by means of various measurement methods. The data show that a series of pure silica molecular sieves, mesoporous materials, and aluminophosphate porous materials are at most 15 kJ · mol-1 higher in energy than the corresponding quartz phase and block feldspar phases. The entropy of a series of pure molecular sieves is 3.2-4.2 J.K-1.mol-1 higher than that of the quartz phase. There is almost no difference between the corresponding free energies in the range of 0-12.6 J.K-1.mol-1. Therefore, for different microporous, mesoporous materials, the skeleton structure is almost indistinguishable in energy. In addition, this paper introduces a new type of calorimetry --- in situ calorimetry, revealing the kinetics and nucleation / crystallization mechanism in the molecular sieve synthesis process.