Monovalent and bivalent cations exchange isotherms for faujasites X and Y.

International audienceThis study addresses the modeling of exchange isotherms for faujasite-type zeolites X and Y with K+, Cs+, Ca2+ and Ba2+ cations based on a large experimental dataset obtained under operating conditions of 0.5 N total normality and an exchange temperature of 80 1C. The isotherm models are based on the mass action law. Ideal solution phase is assumed. Heterogeneity of the solid phase is taken into account by using Barrer and Klinowski´s approach to multi-site exchange. Three types of exchange sites are identified on these zeolites. To each exchange site j corresponds a fitted selectivity coefficient Kj. These parameters, estimated by least square method, evaluate the affinity of the studied cations for the identified exchange site. Globally, these fitted coefficients show that the cations considered present better affinity than Na+, especially for type III sites in faujasite X and type II sites in faujasite Y. For bivalent cations, an exchange with Ba2+ is always more favorable than with Ca2+. On faujasite X, type II sites are more strongly preferred by monovalent cations (with the exception of Cs+) than by bivalent ones. The opposite trend is observed on faujasite Y, even for Cs+. These conclusions have been confirmed and are supported by bibliographic data

Synthesis of hollow Y zeolites

SSCI-VIDE+ING+CPG:DFA:ATUNational audienceNon

Synthesis of hollow Y zeolites

SSCI-VIDE+ING+CPG:DFA:ATUNational audienceNon

Lanthanide-Based Metal Organic Frameworks: Synthetic Strategies and Catalytic Applications

SSCI-VIDE+ING+CPGInternational audienceThis short critical review outlines the main synthetic strategies used in the designed synthesis of lanthanide-based metal organic frameworks (Ln-MOFs). It explains the impact of the choice of organic linker on the final network topology, and it highlights the applications of Ln-MOFs in the catalysis of organic reactions

Lanthanide-Based Metal Organic Frameworks: Synthetic Strategies and Catalytic Applications

SSCI-VIDE+ING+CPGInternational audienceThis short critical review outlines the main synthetic strategies used in the designed synthesis of lanthanide-based metal organic frameworks (Ln-MOFs). It explains the impact of the choice of organic linker on the final network topology, and it highlights the applications of Ln-MOFs in the catalysis of organic reactions

Synthesis of hollow Y zeolite for catalytic applications

SSCI-VIDE+ING+CPG:DFA:ATUInternational audienceMainly motivated by catalytic applications, the design of zeolites with diverse and well controlled morphologies remains a topic of intense research and development. In this sense, it is worth highlighting FAU-type materials that are extensively used in industrial catalytic and adsorption processes. The design of multimodal pore Y zeolite materials have been then emerging in order to combine the catalytic features of the zeolite and improved transport properties. In the literature, we can distinguish between two different approachesfor multimodal pore systems: creation of hierarchical structures with intraparticle mesopores and synthesis of nanocrystals (< 100 nm) with interparticle mesopores. Both approaches yield Y zeolite materials with smaller zeolite domains and concomitant larger external surface area.Here, we propose an alternative approach that consists in synthesizing a new class of crystalline materials: hollow Y zeolite crystals which possess a large central cavity and similar size and shape to the parent crystals. In contrast to classical hierarchical zeolite materials, following this procedure, it can be obtained a smaller zeolite domain, i.e. the walls are thinner while the external surface remains approximatively the same. So far,hollow single crystals have mainly been created from MFI-type zeolites thanks to a natural gradient of composition. The dissolution/recrystallization approach cannot be directly applied to as-synthesized Y zeolites, because the homogeneous distribution of aluminum throughout the crystals prevents a preferential dissolution of the core as opposed to the surface.We report for the first time, a top-down pathway for the synthesis of original hollow Y zeolite from parent crystals in which a gradient of composition has been artificially created. Materials were obtained by a three-step process based on successive dealumination/realumination reactions followed by a selective dissolution of crystal cores.See this article for further informations : Pagis et al., CrystEngComm, 2018, 20, 1564 - 157

Synthesis of hollow Y zeolite for catalytic applications

SSCI-VIDE+ING+CPG:ATU:DFAInternational audienceHighly crystalline hollow Y zeolite capsules have been obtained for the first time. Starting from clas-sical NaY, the three-step process involves the formation of an artificial composition gradient within the crystals followed by a selective dissolution of crystal cores. Hollow Y zeolite crystals contain a single large internal cavity, a wall thickness of about 0.15 μm and an overall size similar to that of the starting materials. The well-defined Y zeolite capsules provide an alternative design to hierar-chical and nanosized zeolites for adsorption and catalysis. They shall offer fastest transport compared to the bulk due to the thin walls. Moreover, the effect of hollow structures on mass transport by transient adsorption methods (TAP measurements) and catalytic tests (hydrogenation of alkenes) will be reported in the basis of Thiele modulus and effectiveness factor studies

Synthesis of hollow Y zeolite for catalytic applications

SSCI-VIDE+ING+CPG:DFA:ATUInternational audienceMainly motivated by catalytic applications, the design of zeolites with diverse and well controlled morphologies remains a topic of intense research and development. In this sense, it is worth highlighting FAU-type materials that are extensively used in industrial catalytic and adsorption processes. The design of multimodal pore Y zeolite materials have been then emerging in order to combine the catalytic features of the zeolite and improved transport properties. In the literature, we can distinguish between two different approachesfor multimodal pore systems: creation of hierarchical structures with intraparticle mesopores and synthesis of nanocrystals (< 100 nm) with interparticle mesopores. Both approaches yield Y zeolite materials with smaller zeolite domains and concomitant larger external surface area.Here, we propose an alternative approach that consists in synthesizing a new class of crystalline materials: hollow Y zeolite crystals which possess a large central cavity and similar size and shape to the parent crystals. In contrast to classical hierarchical zeolite materials, following this procedure, it can be obtained a smaller zeolite domain, i.e. the walls are thinner while the external surface remains approximatively the same. So far,hollow single crystals have mainly been created from MFI-type zeolites thanks to a natural gradient of composition. The dissolution/recrystallization approach cannot be directly applied to as-synthesized Y zeolites, because the homogeneous distribution of aluminum throughout the crystals prevents a preferential dissolution of the core as opposed to the surface.We report for the first time, a top-down pathway for the synthesis of original hollow Y zeolite from parent crystals in which a gradient of composition has been artificially created. Materials were obtained by a three-step process based on successive dealumination/realumination reactions followed by a selective dissolution of crystal cores.See this article for further informations : Pagis et al., CrystEngComm, 2018, 20, 1564 - 157

Hollow Zeolite Structures: An Overview of Synthesis Methods

SSCI-VIDE+ING+CPG:DFA:ATUInternational audienceHollow capsules with dimensions below 1 mu m have recently attracted much attention due to their potential applications as catalysts as well as biomedical and pharmaceutical vectors for controlled drug delivery. Among them, hollow zeolites are particularly interesting because they possess (0 a crystalline structure, which greatly improves their hydrothermal and chemical stability as compared to amorphous silica analogs and (ii) a microporous network that acts as a shape-selective membrane. Moreover, their properties can be continuously tuned by changing their composition, in particular the framework aluminum content. In this perspective review, we examine the recent progress in the development of synthetic methods for the preparation of hollow zeolite and zeotype structures, from templating routes providing large polycrystalline capsules to controlled dissolution methods leading to nanometer-sized hollow single crystals. The applications of these materials will be illustrated and discussed, namely their main potential as catalytic nanoreactors, these being materials particularly adapted for the encapsulation and the confinement of metal nanoparticles. Critical perspectives on future materials with specific properties are also addressed, particularly those with less common zeolite structures and/or compositions

Influence of crystal size and mesopores connectivity on adsorption/diffusion properties of silicalite-1 crystals

SSCI-VIDE+ING+CPG:DLP:ATU:FRM:DFANational audienceIt is well know that the auxiliary network in hierarchical zeolites alleviates diffusional transport limitation. However, the study of connectivity between pores in the secondary network, is not straight forward. Here, we report the influence of the crystal size and the type of additional porosity on the adsorption and diffusion properties of silicalite-1 crystals. We have prepared a series of five model porous silicalite-1 with well controlled mesopore connectivity.The scanning isotherm method by using N2 adsorption/desorption isotherms has been carried out for the determination of possible connections between mesoporous cavities. In addition, the effect of mesopores connections on transport has been measured by DRIFTS and ZLC methods. For instance, we have shown that the transport was mostly limited by surface effects in the case of small crystals, while it was not the case for much larger crystals. The presentation will show correlations between transport and the pore network / size of the crystals