The description ofP, T, X-phase diagrams in systems with clathrate formation where the guest-guest interaction is taken into account. Hydroquinone-noble gas systems

Experimental Determination of Phase Equilibria and Occupancies for CO2, CH4, and N2 Hydroquinone Clathrates

“…Note that no uncertainty was given by vdW-P for their value. Our experimental value of the occupancy for the Ar–HQ clathrate is consistent with that found (by modeling) by Belosludov et al at the same temperature.…”

“…Equilibrium curve is specific to the guest enclosed. For xenon and krypton HQ α –HQ β –G equilibrium data are available in literature in the range of temperature from ambient to the HQ fusion point (i.e., 446 K). − For other gases such as argon (Ar), methane (CH 4 ), or nitrogen (N 2 ), only a few equilibrium points are available and only for some very limited ranges of temperature. − Very surprisingly, no data exist or have been published to date for carbon dioxide (CO 2 ).…”

Revisiting the thermodynamic modelling of type I gas–hydroquinone clathrates

“…For type I HQ clathrates, considering that Dm ab 0 , DH ab 0 and DV ab 0 are the same, whatever the guest, as the b-HQ structure is the same for all the guests, the only leverage in the theory to obtain an occupancy function of the guest is to include the influence of guest-guest interactions. Belosludov and co-workers [42][43][44][45] studied the importance of these interactions in the clathrate equilibrium. They have shown that in HQ clathrates (especially at high temperature) the guest-guest interaction is weaker than in other clathrates since the cages are relatively small and the volume of the cages is a small part of the whole crystal volume but that, even in these systems, the guest-guest interaction is rather clearly revealed.…”

“…The second group of modifications is not focused solely on hydrates but concerns all types of clathrate compounds. It was performed by Belosludov and coworkers who proposed a non-ideal version of vdWP theory essentially by including: (i) guest-guest interactions to take into account the cooperative behaviour of the guests that participate in the stabilization of the structure [41][42][43] and (ii) the possibility of the a-HQ phase to dissolve guests. 44,45 These improvements, contrary to what has been done in the case of hydrate modelling during the last few decades, have not been widely compared to experimental results of the authors.…”

“…Solely the whole phase diagram of the Xe-HQ system and the nonvariant point or ambient temperature for few noble gas-HQ systems have been explored. 42 In this work, following some ideas developed by Belosludov and coworkers such as the inclusion of guest-guest interactions and the solubility of the guests in the a-HQ phase, we propose a modified version of vdWP theory suitable for all type I gas-HQ clathrates. We propose a strategy to obtain some reference properties of the model in order to accurately compute both the triphasic equilibrium coexistence line (a-HQ, b-HQ and free gas) and the clathrate occupancy of type I gas formers.…”