Hydrate growth at the interface between water and CO2/CH4 gas mixtures: influence of pressure, temperature, gas composition and water soluble surfactants

Two major bottlenecks must be overcome when exploiting gas hydrate formation to capture CO2 from natural or flue gases: selectivity, i.e., the CO2 content of the enclathrated gas, which should be as high as possible, and kinetics, which is the focus of this paper. Anionic surfactants such as SDS (sodium dodecyl sulfate) are known to be much more efficient at speeding up gas hydrate formation in the case of methane-rich gases than in the case of CO2-rich gases. To assess the kinetic efficiency of a given surfactant additive, a simple experimental method has been devised, in which hydrate formation is triggered at the top of a sessile water drop by contact with the hydrate phase, and the ensuing hydrate growth is visualized. Depending on the surfactant and gas type, very different gas hydrate growth mechanisms are observed

Hydrate growth at the interface between water and pure or mixed CO2/CH4 gases: Influence of pressure, temperature, gas composition and water-soluble surfactants

The morphology and growth of gas hydrate at the interface between an aqueous solution and gaseous mixtures of CO2 and CH4 are observed by means of a simple experimental procedure, in which hydrate formation is triggered at the top of a sessile water drop by contact with another piece of gas hydrate and the ensuing hydrate growth is video-monitored. The aqueous solution is either pure water or a solution of a nonionic or anionic surfactant at low concentration (in the 100–1000 ppmw range). In agreement with previously published data, hydrates formed from pure water and aqueous solutions of non-ionic surfactant grow rapidly as a low-permeable polycrystalline crust along the water/gas interface, which then inhibits further growth in a direction perpendicular to the interface. Lateral growth rates increase strongly with subcooling and CO2 content in the gas mixture. Similar lateral growth rates, but varying morphologies, are observed with the non-ionic surfactants tested. In contrast, the two anionic surfactants tested, sodium dodecyl sulfate (SDS) and dioctyl sodium sulfosuccinate (AOT), promote in the presence of CH4 (but not in the presence of CO2) a rapid and full conversion of the water drop into hydrate through a ‘capillary-driven’ growth process. Insights are given into this process, which is observed with AOT for an unprecedented low concentration of 100 ppmw

Characterization Study of CO2, CH4, and CO2/CH4 Hydroquinone Clathrates Formed by Gas–Solid Reaction

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO2 and CH4. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO2, pure CH4, and an equimolar CO2/CH4 mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and 13C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications

Creating innovative composite materials to enhance the kinetics of CO 2 capture by hydroquinone clathrates

This study addresses both the preparation of a reactive medium composed of porous particles impregnated with hydroquinone (HQ), an organic compound capable of forming gas clathrates, and an evaluation of the kinetic performance of these composite materials for CO2 capture. Two types of porous silica particles of different sizes and pore diameters were tested. The porous particles were impregnated with HQ by a dry impregnation (DI) method in a fluidized bed, and by a wet impregnation (WI) method. The impregnation effectiveness of the two methods is discussed, and the reactivity of the composite materials formed in terms of CO2 capture and storage capacity is studied experimentally. The experimental results showed that the HQ adheres well on the silica without any chemical modification of the deposit’s structure. We demonstrated that the impregnation technique plays a very important role in the kinetics of CO2 capture. A series of experiments performed using a magnetic suspension balance at 3.0 MPa and 323 K showed that the silica-based impregnated particles reversibly capture and store CO2, and that the CO2 capture kinetics are significantly enhanced compared to the results obtained with pure powdered HQ. Finally, we demonstrated that CO2 capture is faster with dry-impregnated particles

CATHY : une plateforme expérimentale multi-échelles pour l'étude et la CAracTérisation d'HYdrates de gaz

Les hydrates de gaz sont des structures cristallines, composées d’un réseau tridimensionnel de molécules d’eau pouvant emprisonner sous certaines conditions de pression et température des molécules de gaz comme par exemple le méthane ou le dioxyde de carbone (CO2). Les recherches menées sur ces composés ont de nombreuses applications pratiques à fort impact économique dans les domaines du flow-assurance (prévention de la formation d'hydrates de gaz pour assurer la production de gaz ou de pétrole), du captage/stockage du CO2 (traitement et/ou stockage de gaz sous pression), de l’environnement (production d'énergie propre, transport et stockage de gaz), de l’énergie (exploitation des dépôts naturels d’hydrates représentant une source colossale de gaz naturel), et de l’industrie du froid (utilisation en tant que nouveaux Matériaux à Changement de Phase (MCP)). La plateforme CATHY met en synergie trois laboratoires (le LFC-R, le LaTEP et l’IPREM-ECP) de l’Université de Pau et des Pays de l’Adour (UPPA) pour l’étude et la caractérisation expérimentale des hydrates de gaz par plusieurs techniques complémentaires, mises en œuvre à différentes échelles, dans les domaines suivants : - micro et macro spectroscopie RAMAN pour l’analyse cinétique et structurale in-situ; - synthèse d’hydrates à échelle pilote et à l’échelle de la goutte ; - micro et macro calorimétrie (un brevet déposé) sous pression pour la détermination de propriétés thermodynamiques (diagrammes d’équilibre de phases, enthalpies, etc). Les différents équipements de la plateforme ainsi que des résultats expérimentaux caractéristiques de chaque technique seront illustrés et présentés pour l’hydrate de CO2

Installation d'une plate-forme d'imagerie à l'Université de Pau et des Pays de l'Adour

International audienceUne plate-forme Imagerie est en cours d'installation sur le site de l'Université de Pau et des Pays de l'Adour. Elle comprend deux tomographes à rayons X permettant des acquisitions en micro et nano tomographie. Cette plate-forme sera également équipée de périphériques permettant d'effectuer des acquisitions in situ (dans des cellules d'essai) sous pression et sous température avec circulation de fluides, ainsi que d'équipements informatiques pour le traitement et l'analyse des images obtenues (post-traitement, segmentation, quantification, etc.). Ces équipements permettront d'obtenir des images présentant une résolution comprise entre quelques dizaines de microns et environ 0,7 microns et ce dans des conditions statiques ou dynamiques (si les contraintes liées à l'échantillon l'autorisent). Outre les applications de caractérisation de géomatériaux, ces équipements ont pour objet de fournir des données expérimentales permettant en particulier de faire progresser la compréhension des écoulements complexes en milieux poreux, la caractérisation des microstructures et de leur évolution liées aux divers processus de vieillissement. Nous ferons ici une présentation de cette nouvelle plate-forme

Novel hydroquinone-alumina composites stabilizing a guest-free clathrate structure: applications in gas processing

International audienceOrganic clathrates formed by hydroquinone (HQ) and gases such as CO2 and CH4 are solid supramolecular host–guest compounds in which the gaseous guest molecules are encaged in a host framework of HQ molecules. Not only are these inclusion compounds fascinating scientific curiosities but they can also be used in practical applications such as gas separation. However, the development and future use of clathrate-based processes will largely depend on the effectiveness of the reactive materials used. These materials should enable fast and selective enclathration and have a large gas storage capacity. This article discusses the properties and performance of a new composite material able to form gas clathrates with hydroquinone (HQ) deposited on alumina particles. Apart from the general characterization of the HQ-alumina composite, one of the most remarkable observations is the unexpected formation of a guest-free clathrate structure with long-term stability (>2 years) inside the composite. Interestingly enough, in addition to a slight improvement in the enclathration kinetics of pure CO2 compared to powdered HQ, preferential capture of CO2 molecules is observed when the HQ-alumina composite is exposed to an equimolar CO2/CH4 gas mixture. In terms of gas capture selectivity toward CO2, the performance of this new composite exceeds that of pure HQ and HQ-silica composites developed in a previous study, opening up new opportunities for the design and use of these novel materials for gas separation

Characterization Study of CO₂, CH₄, and CO₂/CH₄ Hydroquinone Clathrates Formed by Gas–Solid Reaction

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO₂ and CH₄. This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO₂, pure CH₄, and an equimolar CO₂/CH₄ mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and ¹³C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications