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

拟议项目的目的是开发一种水合物模型，该模型准确地描述了纯形式和与其他水合物形成组分的混合物中氢水合物的形成，并且与流体相的准确经验混合物模型一致。因此，申请方和与申请方合作的团体在过去几年中制定的模式需要大量推广。例如，对于氢，需要考虑空穴的四重占据，而其他水合物形成剂不显示超过两倍的空穴占据。在与其它水合物形成组分的混合物中形成氢水合物是特别相关的。由申请人和合作小组开发的模型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了混合水合物。然而，这种方法需要用于不同水合物形成物的模型的相同结构;由于小腔和大腔的多个占据，对于氢将不满足该条件。因此，一个全新的方法来描述混合水合物将成为必要的。氢与某些促进剂组合形成sH水合物，而纯氢形成sII水合物的事实将需要将氢的模型参数调整为从含有不同水合物形成剂的混合物竞争水合物形成的数据-一种在数值上非常苛刻的方法。在模型参数的调整方面需要建立新的方法。然而，如果成功的话，这种新的方法也可以用于改进含有某些其他水合物形成组分的水合物的混合物的相平衡的描述。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水合物形成动力学的既定方法，将基于所涉及的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的Václav Vingles博士在水合物模型的开发方面密切合作。Vinegar博士将作为墨卡托研究员参与拟议的项目。

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.