The effective separation of ammonia from the synthesis loop in ammonia synthesis plants is an important step in its manufacture. This work presents the use of nanocomposite MFI zeolite membranes prepared by a pore-plugging method for this separation process. Performance of a zeolite membrane is highly dependent on the operating conditions. Therefore, the influences of differential pressure, temperature, sweep gas flow, feed gas flow and gas composition are studied experimentally. Transport of NH3 in this membrane is by surface diffusion in the intracrystalline (zeolite) pores in parallel with capillary condensation in the intercrystalline (non-zeolite) pores. The separation of NH3 from a mixture with H2 and N2 is by preferential adsorption of NH3, which hinders the permeation of weakly adsorbed H2 and N2. Differential pressure has only relatively small effects in the pressure range 300kPa – 1550kPa. Increase in sweep flow rate has little effect on NH3 gas permeance, but H2 and N2 permeances increase thereby decreasing the selectivities. Increase in feed flowrate also has little effect on NH3 permeance. However, the N2 and H2 permeances increase and there is a subsequent decrease in selectivities. Membrane performance was found to be highly dependent on temperature. NH3 permeance in the mixture increases linearly with temperature. NH3 selectivity was found to increase with temperature up to 353K after which it starts to decrease due to N2 and H2 permeances increasing with temperatures beyond 353K (αNH3/N2 = 46 and αNH3/H2 = 15) and is therefore the optimum temperature for separation. A potential barrier model is developed to describe the hindering effect of NH3 on H2 and N2 permeance. The model fails to predict correctly H2 and N2 permeances in the ternary mixture using pure gas (H2 and N2) permeances. Binary mixture permeation H2/N2 studies showed that there are diffusion effects (single file diffusion) that have not been taken into account in the potential barrier model. When permeances of the individual components in the binary mixture are used in the model instead of the pure gas permeances, there is an improved agreement between experimental and predicted results.

Zeolite membrane synthesis is conventionally carried out in batch systems. Recently, several attempts have been performed to synthesize zeolite membranes in flow systems which can allow preparation of membranes with large specific surface areas. Membranes synthesized in the recirculating flow system had comparable N2/SF6 and n- C4H10/i-C4H10 ideal selectivities with the membranes prepared in the batch system, indicating that good quality membranes can be produced by this method. The objective of this study is to separate organic/water mixtures by pervaporation by using MFI type membranes synthesized in the flow system. Effect of number of synthesis steps and synthesis method on the separation factor and flux was investigated. Membranes were synthesized from clear solutions with a molar composition of 80SiO2:16TPAOH:1536H2O at 95oC and atmospheric pressure. The synthesis solution was recirculated through the tubular alumina support with a flow rate of 6 ml/min for 72 h. The membranes were characterized by X-ray diffraction for phase identification and scanning electron microscopy for morphology determination. Single gas permeances of N2, H2, CH4, CO2, n-C4H10 and i-C4H10 were measured between 25 and 200oC. Mixtures of 5 wt% ethanol/water, 2-propanol/water and acetone/water were separated by pervaporation at different temperatures. The single gas permeances decreased with increasing temperature for weakly adsorbed gases. For n-C4H10 the permeance passed through a maximum and i-C4H10 permeance was nearly constant. For a membrane synthesized by two consecutive synthesis steps, the ideal selectivity for n-C4H10/i-C4H10 was 132 at 200oC. The selectivity in the pervaporation separation of ethanol-water mixture was 43 with a permeate flux of 0.2 kg/m2h at 25oC. With increasing temperature, selectivity decreased but the flux increased, the selectivity was 23 and the flux was 1.9 kg/m2h at 85oC. 2-propanol/water and acetone/water separation factors were 36 and 1024 with 0.2 and 0.1 kg/m2h fluxes, respectively. The separation factors and fluxes for membranes synthesized in the flow system were comparable with membranes synthesized in the batch system.

Ces travaux portent sur la conception et le développement d'un procédé membranaire de captage/stockage du CO2 embarqué pour le transport routier. Dans une première partie, nous réalisons la simulation d'un procédé membranaire embarqué de captage du CO2 dans le cas d'un poids lourd (>3500 kg). Ceci comprend l'analyse énergétique de la séparation et de la compression des gaz, l'évaluation des surfaces et volumes requis ainsi que l'autonomie de l'unité de stockage et la surconsommation engendrée par ce dispositif. Nous étudions dans un second temps la relation entre qualité des supports fibres creuses et celle des membranes nanocomposites MFI-alumine synthétisées. Nous nous intéressons ensuite aux performances des membranes nanocomposites dans la séparation CO2/N2 en phase gazeuse. Plus particulièrement nous évaluons l'influence de la substitution isomorphique du silicium par le bore et le germanium, ainsi que l'échange du proton de valence par d'autres atomes, sur la séparation en question. Un chapitre est dédié à l'évaluation des paramètres thermodynamiques (adsorption) et cinétiques (diffusion) de la séparation CO2/N2. Enfin, nous analysons l'influence de la présence de polluants dans le mélange à séparer (eau, NOx, hydrocarbures) sur les performances séparatives des membranes synthétisées.

Ces travaux portent sur la conception et le développement d’un procédé membranaire de captage/stockage du CO2 embarqué pour le transport routier. Dans une première partie, nous réalisons la simulation d’un procédé membranaire embarqué de captage du CO2 dans le cas d’un poids lourd (>3500 kg). Ceci comprend l’analyse énergétique de la séparation et de la compression des gaz, l’évaluation des surfaces et volumes requis ainsi que l’autonomie de l’unité de stockage et la surconsommation engendrée par ce dispositif. Nous étudions dans un second temps la relation entre qualité des supports fibres creuses et celle des membranes nanocomposites MFI-alumine synthétisées. Nous nous intéressons ensuite aux performances des membranes nanocomposites dans la séparation CO2/N2 en phase gazeuse. Plus particulièrement nous évaluons l’influence de la substitution isomorphique du silicium par le bore et le germanium, ainsi que l’échange du proton de valence par d’autres atomes, sur la séparation en question. Un chapitre est dédié à l’évaluation des paramètres thermodynamiques (adsorption) et cinétiques (diffusion) de la séparation CO2/N2. Enfin, nous analysons l’influence de la présence de polluants dans le mélange à séparer (eau, NOx, hydrocarbures) sur les performances séparatives des membranes synthétisées. / This work focuses on the conception and development of a membrane-based process for an on-board CO2 capture/storage application. In a first part, we simulate an on-board CO2 capture unit based on a membrane process for the case study of a heavy vehicle (>3500 kg). This study includes an energy analysis of the impact of gas separation and compression on the required membrane surface and module volume, as well the autonomy of the storage unit and the energy overconsumption involved in the process. In a second part, we study the influence of the hollow-fibre support quality on the final intergrowth level of nanocomposite MFI-alumina membranes. Special attention is devoted to the influence of the isomorphic substitution of silica by boron and germanium, and replacement of the counter-cation (proton) by other elements, on the CO2/N2 separation and permeance properties. Next, a complete chapter has been devoted to the evaluation of the thermodynamic (adsorption) and kinetic (diffusion) parameters in the CO2/N2 separation. Finally, we analyze the influence of standard pollutants (water, NOx, hydrocarbons) on the CO2 separation properties of the synthesized membranes.

Cette étude se situe dans le cadre des recherches menées par le CEAEA sur la production massive d'hydrogène, sans émission de gaz à effet de serre, via un cycle thermo-chimique de décomposition de l'eau couplé à une source de chaleur à haute température d'origine nucléaire. Dans le cas particulier du cycle dit« Iode-Soufre», on doit extraire H2 à partir d'un mélange H2/HI/H20 très corrosif, opération pour laquelle des procédés membranaires ont été proposés. L'objectif de ce travail est le développement de membranes zéolithiques de type MFI susceptibles d'être utilisées dans ce contexte. Nous présentons les différents matériaux utilisés, la méthodologie de synthèse de couches minces de Silicalite-1 et de ZSM-5 synthétisée sans structurant organique, les techniques de caractérisation des membranes. Une étude cinétique nous a permis d'optimiser et de contrôler les conditions d'obtention de ces couches minces déposées sur des substrats tubulaires en Ti02 et plans en Al2O3-α. De nombreuses expériences de perméation ont été réalisées, pour des gaz simples (H2, He, Ar, N 2, C02, SF6) et des mélanges gazeux (H2/H20/Ar) et (H2/H20/HI/Ar). Les effets de la température, de la pression amont, de l'épaisseur et de la longueur de la couche mince ainsi que du gaz vecteur ont été étudiés en détail. Il apparaît que la présence de molécules d'H20 dans le système joue un rôle prépondérant sur la perméation des autres molécules. / In the general context of massive and "carbon free" hydrogen production studies, the aim of this work was the development of zeolitic MFI membranes for hydrogen extraction and separation. The methodology of synthesis, the membranes characterization techniques as well as the permeation experimental setup are presented. Optimization and control of the elaboration of Ti02 supported Silicalite-1 and template free ZSM-5 membranes have been reached. Details of the full kinetic study that we performed are given. Numerous permeation experiments, involving pure gas (H2, He, Ar, N2, C02, SF6) and mixtures (H2/H20/Ar) and (H2/H 20/HI/Ar) have been carried on. The effects of temperature, feed pressure, thickness and length of the membranes, as well as the role of the sweeping gas have been emphasized. In the case of gas mixtures, the presence of H20 molecules appears to be a predominant factor.