(261d) Development of a New Volumetric Gravimetric Device of H2 Sorption for the Analysis of Zeolites under Equilibrium Conditions

For the H₂ production, realized by reforming or partially oxidation of hydrocarbons using the Pressure Swing Adsorption (PSA) as key method, the knowledge of thermodynamic parameters of the used adsorbents like selectivity, heat of adsorption and desorption are magnitudes for the efficiency of the process. For the separation of gas mixtures, using zeolites is very interesting because of the surface charges of this material. The aim of this work is the determination of the thermodynamic data obtained from sorption measurements of gases on different zeolites under equilibrium conditions. So, a new experimental setup for the measurement of adsorption by the gravimetric-volumetric method was designed. Intended for the study of thermodynamic gas equilibriums in adsorbents, either in the powder shapes or of pellets, it allows also the study of their equations of state. The device is designed to operate with pure gases until a maximum pressure of 6.9 MPa and temperatures ranging between 273.15 K and 333.15 K. As well the regeneration process is integrated up to 673.15 K at secondary vacuum. The reliability of this device was established by comparison with results obtained in the Claude-Delorme Research Center at Air Liquide (France) and those referred in National Institute of Standards and Technology databases (USA). With our experimental device, we determined isotherms of adsorption of pure gases (H₂, CH₄, CO₂ and N₂) at several temperatures. The analysis of the results enables to conclude that the capacity of adsorption of a material is evaluated in a reliable way only if its true density were determined by helium displacement at high temperature. The considerable influence of the ratio of exchanged cations on hydrogen gas adsorption was highlighted for Ca-LTA exchanged at the rates of: 66%, 77%, 88%, 90% and 94%. Among the considered zeolites, our research study leads to the selection of the best adapted to an effective use for the H₂ purification by PSA process.