Clathrates hydrates are crystalline compounds that are increasingly attracting research teams for the development of industrial applications such as carbon dioxide capture and sequestration. Recently, it has been shown that propane may be used as a thermodynamic additive promoting the formation of carbon dioxide hydrates. Opened questions exist regarding the structural properties of mixed carbon dioxide/propane hydrate: is there a single clathrate structure co-including both molecules (so-called type I or type II) or is there a multi-phasic phenomenon occuring (i.e., mixture of two clathrate structures, type I and type II)? This proposal aims at investigating this structural issue by using the powder diffractometer D1B. Such information is crucial for optimizing all promising hydrate processes for gas capture/separation from carbon dioxide using propane as an additive. Especially, it constitutes the basis for developing realistic thermodynamics models predicting not only the gas hydrate stability, but also the gas storage capacities.