Search

The increasing CO2 concentration in the atmosphere has a severe influence on both the environment and human health, resulting in global warming. According to the high adsorption capacity for CO2 removal, zeolites play an important role for CO2 capture and sequestration. However, its powdery form limits their use in adsorption applications. When binding agents are used, the zeolite porosity is partially occluded that compromises the CO2 adsorption capacity severely. How to prepare binder‐free zeolite beads with a certain structure strength and how to keep the high surface area and porosity are a great challenge. In this work, LTA‐5A beads composites (80 wt.%) are prepared via cationic photopolymerization and then calcination is performed to remove organic part to obtain LTA‐5A beads with different sizes (<1.0 mm, 1.0–2.0 mm, and 2.0–3.0 mm). These beads (0.1 g) are characterized by good mechanical strength without any binder (partial bead fragmentation under 200 g‐load) with a preserved zeolite porosity. This method allows to exploit the zeolite beads reaching a high specific surface area (586 688 m2 g−1) and good CO2 adsorption capacity (4.5‐4.9 mmol g−1). These values are higher than those of commercial LTA‐5A beads (515 m2 g−1 and 3.8 mmol g−1, respectively), which is in agreement with their binder‐free structure. [ABSTRACT FROM AUTHOR]

Porous materials play an essential role in chemical processes such as catalysis, adsorption, and in emerging technologies for electronic materials, light harvesting, and energy transfer. By far, zeolites have contributed most to industrial development. Other porous solid such as activated carbon, metal–organic frameworks, covalent organic frameworks, and porous coordination polymers also have been studied by researchers in the past two decades. The use of porous solids is set to grow in the future, and so is the need to fabricate them into more complex and diverse geometries for a variety of applications. Additive manufacturing, also known as 3D printing, has provided the possibility to shape the materials into desired forms, which offers many advantages over their traditional configurations. Structured catalysts, for example, can help to overcome the drawbacks of conventional packed catalyst bed‐like mass or heat transfer limitations and high pressure drop. This review focuses on the latest advances as well as the current challenges in 3D printing of the porous solids. This article aims to contribute to the shape engineering of porous solids and provide a better understanding of their formulations, structures, techniques, properties, and applications. [ABSTRACT FROM AUTHOR]

In recent years, photopolymerization has been found wide applications in industry and daily life, while many defective properties of polymers limit their development, including compressive strength, mechanical properties, and functions. Furthermore, zeolites are microporous solids with many industrial applications. As fillers they can improve mechanical properties of zeolite/polymer composite and transfer their properties to composites. Here the fabrication is reported of composites with very high filler contents (80–95 wt%) under mild photopolymerization conditions (visible LED light irradiation, room temperature, under air). Compared to pure poly(ethylene glycol) diacrylate (PEGDA) polymer, mechanical properties have been greatly improved, and the storage modulus increased by nearly 20‐fold compared to that of pure polymer. After debinding/sintering of composites by high temperature treatment, zeolite porosity is preserved with good adsorption capacities. Some step‐like object with 3D structure is also obtained by an original 3D printing technique noted "layer by layer molding/curing." Hence, as a great breakthrough, this work is expected to lead to a valuable development in the field of photopolymerization in quite highly filled composites. This also will expand their potential applications for 3D printing in the fields of high‐performance lightweight materials and adsorption, and opens the door to a new process of zeolite shaping. [ABSTRACT FROM AUTHOR]

In recent years, hydrogels have been widely applied in daily life and industry. More and more fillers have been combined with hydrogel to broaden their fields of application and improve their mechanical properties. However, there are few works about zeolite‐based hydrogel composites via photopolymerization. Hence, in this work, it is reported that the fabrication of hydrogel composites containing zeolite (FAU‐13X ≈ 40 wt%) under mild photopolymerization conditions (visible LED light irradiation, at room temperature, under air, and without any monomer purification). Markedly, compared to pure hydrogel, the elastic modulus (G′) of hydrogel composite contains 10% FAU‐13X increased by more than 100%. When the zeolite content reached 40%, the water swelling ratio in mass reached 120%, and that in volume remained at 150%. In addition, 3D patterns with flat surface are obtained through direct laser write as a lithography technique. This means these hydrogel composites can be applied in the field of water absorption materials and 3D printing. [ABSTRACT FROM AUTHOR]

Aromatic chlorinated compounds, such as 1,2-dichlorobenzene, are considered as precursors of dioxin formation and their removal from flue gas using adsorption technology could be a solution. Faujasite type zeolites seem to be the most promising adsorbent, as the size of its porosity matches the size of the molecule. Even though the cationic faujasites are hydrophilic, the strength of interaction of chlorinated aromatic compounds adsorbed in porosity are higher than with more silicic faujasite such as FAU-NaY. FAU-NaX commercial beads have been Nd3+ exchanged at different rates. Dichlorobenzene dynamic gas adsorption has been performed via a thermobalance with vapours at concentration of 938 ppm in nitrogen gas flow and the quantities absorbed have been recorded during time. Then, from the coupling of a thermobalance with an in-line mass spectrometer, the desorbed quantities and desorption temperatures have been measured for both water and dichlorobenzene. Total quantities of 1,2-dichlorobenzene adsorbed onto partially exchanged FAU-Nd-NaX zeolites increases with the exchange rate: it has been measured a capacity of 23.3 wt % (relative to activated zeolite) for the most exchanged FAU-Nd-NaX at exchange rate of 53.6 %. For that zeolite, 74.7 % of the 1,2-dichlorobenzene is adsorbed at high-energy bonds with cations, desorbable at temperatures higher than 160 °C. The desorption temperature of dichlorobenzene decreases from 380 to 310 °C for FAU-NaX and the FAU-Nd-NaX at exchange rate of 53.6 % and remains higher than that of water. So that, thermal-desorption remains a separative process between water and chlorinated molecules previously adsorbed on cationic faujasites. [Display omitted] • FAU-NaX beads have been partially exchanged by Nd3+ cations at different rates. • The amounts of 1,2-DCB adsorbed onto the exchanged FAU (X) beads increases with the Nd3+ exchange rate. • The desorption temperature of 1,2-DCB decreases from 380 to 310 °C with the Nd3+ exchange rate from 0 to ca. 54 %. • Different strengths of interaction of 1,2-DCB molecules with the zeolite framework are clearly identified by TG/MS analyses. [ABSTRACT FROM AUTHOR]

Abstract: A new synthesis way to form core/shell Al-ZSM-5/silicalite-1 zeolite composites in one step in fluoride medium is described. The effect of some parameters, such as Si/Al, H2O/SiO2 and F/SiO2 molar ratios, was investigated in order to understand their influence on the features of the products. These ones were systematically characterized by complementary techniques such as thermal analysis, X-ray emission mappings of silicon and aluminum, and in some cases by 27Al, 29Si and 19F MAS NMR.19F liquid state NMR was also performed to detect the presence of fluoro-metal complexes in order to get a better understanding of the crystal growth mechanism. The transposition of the reaction in an alkaline medium was also investigated and this method leads to smaller crystals with a reversed aluminum composition gradient. [Copyright &y& Elsevier]

This work focuses on different ways to improve the yield and/or the crystalline quality of EMT/FAU-type zeolite nanocrystal aggregates obtained in the presence of organic additive triethanolamine (TEA). The increase of the amount of aluminum reagent enhances the synthesis yield by a factor of 2.5 without affecting the crystallization rate and the microporous volume. On the other hand, the increase of the thermal treatment time allows to increase the synthesis yield, the crystallization rate and the microporous volume. Furthermore, addition of EMT zeolite seeds into the starting reaction medium improves the crystallization rate and the microporous volume. [ABSTRACT FROM AUTHOR]

The present study demonstrates an optimized procedure for mass production of EMT-type structure zeolite. The introduction of triethanolamine (TEA) in the synthesis gel leads to the formation of larger and agglomerated nanocrystals. The obtained particles can be easily recovered from the reaction medium by filtration and washing without the use of high speed centrifugation. This simple approach paves a new way for energy-efficient synthesis of nanoporous materials for potential industrial applications. [ABSTRACT FROM AUTHOR]

The objective of this work was to study the adsorption and separation of the most important families of hydrocarbon compounds on metal-organic frameworks (MOFs), in comparison with zeolites. For this purpose, we have selected four probe molecules, each of them representing one of these families, i.e., o- and p-xylene as aromatics, 1-octene as an alkene, and n-octane as an alkane. The separation of these four molecules was studied by binary breakthrough experiments. To represent the large diversity of MOF structures, the experiments were carried out with (i) two MOFs with coordinatively unsaturated metal sites (CUS), i.e., Cu-btc (HKUST-1) and CPO-27-Ni, (ii) a MOF with an anionic framework and extraframework cations, i.e. RHO-ZMOF, and (iii) two rather apolar zeolitic imidazolate framework (ZIF) materials with different pore sizes, i.e. ZIF-8 and ZIF-76. Zeolite NaY and zeolite β were used as polar and apolar reference adsorbents, respectively. The results can be briefly summarized as follows: ZIFs (not carrying any polar functional groups) behave like apolar adsorbents and exhibit very interesting and unexpected molecular sieving properties. CUS-MOFs behave like polar adsorbents but show the specificity of preferring alkenes over aromatics. This feature is rationalized thanks to DFT+D calculations. MOFs with extraframework cations behave like polar (cationic) zeolites. [ABSTRACT FROM AUTHOR]

The separation of paraffin isomers is a very importanttopic inthe petrochemical industry. Zeolite 5A is industrially used to sievealkane isomers, but its pore size does not allow the separation ofmonobranched and dibranched alkanes by a kinetic mechanism. In thispublication, we compare three ZIF materials in the separation of C6-paraffinisomers: ZIF-8, ZIF-76, and a new material called IM-22. The performanceof the materials is evaluated by a breakthrough curve of binary mixturesof n-hexane, 3-methylpentane, and 2,2-dimethylbutane.We show that ZIF-8 is a very attractive alternative to zeolite 5Abecause it exhibits a high (kinetic) selectivity for the adsorptionof linear alkanes and at the same time a high adsorption capacity.The new material IM-22, a ZIF with CHAtopology, seemsto be particularly suited for the separation of mono- and dibranchedparaffin isomers. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the use of the fluoride route in the synthesis of silica-based zeolites and metallophosphates (mainly gallophosphates) microporous materials, with a special emphasis on the work of the Mulhouse''s group during the last recent years. The first part of this account relates to silica-based zeolites and is divided into three sections. The first section is mainly devoted to pure silica and variously substituted MFI-type zeolite (T=Al, Ga, B, Ti….), whereas the second section concerns the synthesis of pure silica or (Si, Al) zeolites with other framework topologies. Among the numerous structure-types so far obtained in fluoride medium, some of them are new and display the small F–-containing double four-ring unit (D4R-F). The formation of this type of unit was first observed in the case of the clathrasil octadecasil (AST-structure-type), and is only possible due to the templating and stabilizing effect of the fluoride anion. Besides, the fluoride route leads to pure silica zeolite samples with very few or no connectivity defects. The resulting hydrophobic character allowed us to develop a new application in the field of energetics, where the systems zeolite-water can be used as molecular springs or bumpers. The third section concerns specifically the recently discovered silicogermanate zeolites with new framework topologies. Germanium acts indeed as a real structure-directing agent, favoring in particular the formation of structures displaying the small D4R or D4R-F unit. The example of IM-10 (IM standing for Institut Français du Pétrole: Mulhouse), with UOZ structure-type, prepared in our laboratory in fluoride medium and from germanium-rich mixtures in the presence of hexamethonium cations, is described. Two other new materials called IM-9 and IM-12, both characterized by the presence of the same D4R-F or D4R unit in their structures, and prepared, respectively, from fluoride-containing or fluoride-free systems in the presence of the (6R,10S)-6,10-dimethyl-5-azoniaspiro [4,5] organic agent, are also presented. The second part concerns the phosphate-based microporous materials prepared in fluoride media and mainly the gallophosphates. As for silica-based zeolites, besides its mineralizing role, F– can play a templating role, being found inside the small D4R units. Thus many fluorogallophosphates of the Mu-n family, with 0-D, 1-D, 2-D or 3-D frameworks (Mu standing for Mulhouse), showing such a building unit were obtained. Specific experiments are reported about the hydrothermal transformation of the fluorogallophosphate Mu-3 (1-D framework) into the fluorogallophosphate Mu-2 (3-D framework), both containing D4R-F units, and a possible mechanism of reaction is suggested. Several examples are also given where fluorine is part of the framework as terminal groups (Ga–F) or bridging species (Ga–F–Ga). Finally the observed variety in the coordination of the gallium atom results in a great flexibility in the building of the framework and thus allows the formation of a large number of different structures. To cite this article: P. Caullet et al., C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

In this paper, the influence of permanent binder was first determined on the photopolymerization process under mild condition (visible LED irradiation, at room temperature and under air) of LTA zeolite/polymer based composites. Different inorganic binders were tested in order to investigate their optical properties and to improve the mechanical properties after polymer removal by thermal treatment. Optimum formulation obtained with poly(ethylene glycol) diacrylate (PEGDA) and colloidal silica demonstrates excellent Depth of Cure (DOC) and good spatial resolution. The monolith obtained after thermal treatment at 600 °C shows hierarchical porosity with high BET surface area and high compressive strength. Furthermore, Ni2+ and Sr2+ ion exchange capacities were evaluated and the effect of colloidal silica as binder was investigated. This work extends our understanding of highly-filled composites (solid content up to 60.8 wt% where zeolite content = 40 wt%/21 vol%) obtained by photopolymerization, and expands their applications for 3D printing of high-performance lightweight materials and ion exchange. [Display omitted] • Excellent DOC for highly filled zeolite/binder/polymer based composite. • Best mechanical properties with 30 dwb% of colloidal silica in composite. • Good spatial resolution by laser write for filled composite. • Silica nanoparticles (binder) contributes to Sr2+ and Ni2+ cation-exchange. [ABSTRACT FROM AUTHOR]

[Display omitted] • Composites containing two types of filler (Al 2 O 3 and LTA-5A) are proposed. • Photocomposites have improved mechanical properties and good depth of cure. • Composites have obviously potential applications in 3D printing and 4D printing. • Calcinated samples keep good porosity for CO 2 adsorption. Normally, 3D printed objects via photopolymerization usually don't have fully optimized mechanical properties and functions. In this context, the addition of single filler usually can improve these properties through the access to composite materials. However, the addition of filler inevitably has a negative influence on the light penetration inside the composites strongly reducing the depth of cure. Hence, the fabrications of photo-composites based on a combination of two inorganic fillers (alumina Al 2 O 3 and zeolite LTA-5A) are reported in this work. Compared to pure poly(ethylene glycol) diacrylate (PEGDA) and its other corresponding single filler-based composites, PEGDA with 25 wt% LTA-5A and 25 wt% Al 2 O 3 -200 had several improved properties: better depth of cure (DOC), good mechanical properties (the storage modulus, tensile strength, the Young's modulus). Direct laser write (DLW) was used to manufacture 3D patterns and 3D cross-shaped objects with good resolution. Under the hydrothermal stimuli, a 4D printing behavior (reversible shape change) was observed on the 3D cross-shaped objects. In addition, the 3D object with the condition of 4D printing had the ability of withstand a heavy stuff (the mass difference was more than 100 times). This is the first time to report the fabrication of the double filler-based (50 wt%) composite (ceramic and zeolite) with 4D printing behavior and good mechanical properties. Interestingly, calcinated composites had a certain structure strength and good CO 2 adsorption performance. Therefore, this work not only paves the way for the investigation of photo-composites filled with multiple fillers combinations (how to improve the mechanical properties and keep good depth of cure for composites via photopolymerization), but also shows us the potential applications in the field of 3D/4D printing, microlithography and functional composites. [ABSTRACT FROM AUTHOR]

Abstract: The present work describes the adsorption and separation of xylene isomers by ZIF-8. Although the formal pore diameter of ZIF-8 is much smaller than the molecular diameter of the xylene isomers, ZIF-8 is able to separate the isomers by molecular sieving. A structural study indicates that the diffusion of the xylenes into the pore structure of ZIF-8 happens via a transitory deformation of the pore aperture which is based on a tilt of the imidazolate linkers, followed by a return to the initial conformation. The rate of adsorption depends on the size of the isomer, i.e. it decreases from para- to meta- and to ortho-xylene. The separation of the xylene isomers is good in the gas phase. In liquid phase breakthrough experiments, the quality of the separation is deteriorated. Moreover, as expected for a separation based on molecular sieving, para-xylene cannot be well separated from ethyl-benzene. [Copyright &y& Elsevier]