Consistent Description of Hydrogen Hydrates and of their Properties in Mixtures with Multiple Hydrate-Forming Components

拟议项目的目的是建立一个水合物模型，准确地描述纯形式和与其他水合物形成成分混合的水合物的形成，并与流体相的准确经验混合模型相一致。由于这个原因，由申请人和与申请人合作的团体在过去几年中开发的模型需要得到实质性的扩展。例如，氢需要考虑四倍占据空腔，而其他水合物形成者不显示超过两倍占据空腔。在与其他水合物形成成分的混合物中形成水合物的氢是特别相关的。该模型由申请人和合作小组开发，基于单一物质特定参数的线性混合规则，以纯粹预测的方式准确描述混合水合物。然而，这种方法需要用于不同水合物形成物的模型具有相同的结构；由于小腔和大腔的多次占用，氢将不满足这一条件。因此，需要一种全新的方法来描述混合水合物。氢与某些促进剂结合形成sH水合物，而纯氢形成sII水合物，这一事实要求将氢的模型参数调整为含有不同水合物形成物的混合物中竞争性水合物形成的数据，这种方法在数值上要求很高。在模型参数的调整方面需要开辟新的途径。然而，如果成功的话，这种新方法也可以用来改善含有某些其他水合物形成成分的水合物混合物的相平衡描述。最后，水合物形成过程的动力学与氢水合物特别相关。基于新的水合物模型和已建立的水合物形成动力学方法，将根据所涉及相的化学势的差异来描述动力学。长期以来，申请人与捷克科学院热力学研究所Václav Vinš博士密切合作开发水合物模型。Vinš博士将以墨卡托研究员的身份参与拟议的项目。

The aim of the proposed project is to develop a hydrate model, which accurately describes the formation of hydrogen hydrates in pure form and in mixtures with other hydrate forming components, and which is consistent to accurate empirical mixture models for the fluid phases. For this reason, a model that has been developed by the applicant and by groups cooperating with the applicant over the last few years needs to be extended substantially. For example, a quadruple occupation of cavities needs to be considered for hydrogen, while other hydrate formers do not show more than double occupation of cavities. The formation of hydrogen hydrate in mixtures with other hydrate forming components is particularly relevant. The model that has been developed by the applicant and cooperating groups accurately describes mixed hydrates in a purely predictive manner based on a linear mixing rule for a single substance specific parameter. However, this approach requires an identical structure of the models used for the different hydrate formers; this condition will not be fulfilled for hydrogen due to multiple occupation of small and large cavities. Therefore, a completely new approach for the description of mixed hydrates will become necessary. The fact that hydrogen forms sH hydrates in combination with certain promoters, while pure hydrogen forms sII hydrates, will require the adjustment of model parameters for hydrogen to data for competing hydrate formation from a mixture containing different hydrate formers – an approach that is numerically very demanding. New ways need to be established with regard to the adjustment of model parameter. However, if successful this new approach can be used to improve the description of phase equilibria of mixtures containing hydrates of certain other hydrate forming components as well. Finally, the kinetics of the hydrate formation process is particularly relevant for hydrogen hydrates. Based on the new hydrate model and on established approaches for the kinetics of hydrate formation, the kinetics will be described based on differences of the chemical potential of the involved phases. For a long time, the applicant closely cooperates with Dr. Václav Vinš from the Institute Thermomechanics of the Czech Academy of Sciences on the development of hydrate models. Dr. Vinš will be involved in the proposed project as Mercator Fellow.