Engineered zeolitic materials : synthesis and application

Tableau d'honneur de la Faculté des études supérieures et postdoctorales, 2016-2017Les zéolithes étant des matériaux cristallins microporeux ont démontré leurs potentiels et leur polyvalence dans un nombre très important d'applications. Les propriétés uniques des zéolithes ont poussé les chercheurs à leur trouver constamment de nouvelles utilités pour tirer le meilleur parti de ces matériaux extraordinaires. Modifier les caractéristiques des zéolithes classiques ou les combiner en synergie avec d'autres matériaux se trouvent être deux approches viables pour trouver encore de nouvelles applications. Dans ce travail de doctorat, ces deux approches ont été utilisées séparément, premièrement avec la modification morphologique de la ZSM-12 et deuxièmement lors de la formation des matériaux de type coeur/coquille (silice mésoporeuses@silicalite-1). La ZSM-12 est une zéolithe à haute teneur en silice qui a récemment attiré beaucoup l’attention par ses performances supérieures dans les domaines de l'adsorption et de la catalyse. Afin de synthétiser la ZSM-12 avec une pureté élevée et une morphologie contrôlée, la cristallisation de la zéolithe ZSM-12 a été étudiée en détail en fonction des différents réactifs chimiques disponibles (agent directeur de structure, types de silicium et source d'aluminium) et des paramètres réactionnels (l'alcalinité, ratio entre Na, Al et eau). Les résultats présentés dans cette étude ont montré que, contrairement à l’utilisation du structurant organique TEAOH, en utilisant un autre structurant, le MTEAOH, ainsi que le Al(o-i-Pr)3, cela a permis la formation de monocristaux ZSM-12 monodisperses dans un temps plus court. L’alcalinité et la teneur en Na jouent également des rôles déterminants lors de ces synthèses. Les structures de types coeur/coquille avec une zéolithe polycristalline silicalite-1 en tant que coquille, entourant un coeur formé par une microsphère de silice mésoporeuse (tailles de particules de 1,5, 3 et 20-45 μm) ont été synthétisés soit sous forme pure ou chargée avec des espèces hôtes métalliques. Des techniques de nucléations de la zéolithe sur le noyau ont été utilisées pour faire croitre la coquille de façon fiable et arriver à former ces matériaux. C’est la qualité des produits finaux en termes de connectivité des réseaux poreux et d'intégrité de la coquille, qui permet d’obtenir une stéréosélectivité. Ceci a été étudié en faisant varier les paramètres de synthèse, par exemple, lors de prétraitements qui comprennent ; la modification de surface, la nucléation, la calcination et le nombre d’étapes secondaires de cristallisation hydrothermale. En fonction de la taille du noyau mésoporeux et des espèces hôtes incorporées, l'efficacité de la nucléation se révèle être influencée par la technique de modification de surface choisie. En effet, les microsphères de silice mésoporeuses contenant des espèces métalliques nécessitent un traitement supplémentaire de fonctionnalisation chimique sur leur surface externe avec des précurseurs tels que le (3-aminopropyl) triéthoxysilane (APTES), plutôt que d'utiliser une modification de surface avec des polymères ioniques. Nous avons également montré que, selon la taille du noyau, de deux à quatre traitements hydrothermaux rapides sont nécessaires pour envelopper totalement le noyau sans aucune agrégation et sans dissoudre le noyau. De tels matériaux avec une enveloppe de tamis moléculaire cristallin peuvent être utilisés dans une grande variété d'applications, en particulier pour de l'adsorption et de la catalyse stéréo-sélective. Ce type de matériaux a été étudié lors d'une série d'expériences sur l’adsorption sélective du glycérol provenant de biodiesel brut avec des compositions différentes et à des températures différentes. Les résultats obtenus ont été comparés à ceux utilisant des adsorbants classiques comme par exemple du gel de sphères de silice mésoporeux, des zéolithes classiques, silicalite-1, Si-BEA et ZSM-5(H+), sous forment de cristaux, ainsi que le mélange physique de ces matériaux références, à savoir un mélange silicalite-1 et le gel de silice sphères. Bien que le gel de sphères de silice mésoporeux ait montré une capacité d'adsorption de glycérol un peu plus élevée, l'étude a révélé que les adsorbants mésoporeux ont tendance à piéger une quantité importante de molécules plus volumineuses, telles que les « fatty acid methyl ester » (FAME), dans leur vaste réseau de pores. Cependant, dans l’adsorbant à porosité hiérarchisée, la fine couche de zéolite silicalite-1 microporeuse joue un rôle de membrane empêchant la diffusion des molécules de FAME dans les mésopores composant le noyau/coeur de l’adsorbant composite, tandis que le volume des mésopores du noyau permet l’adsorption du glycérol sous forme de multicouches. Finalement, cette caractéristique du matériau coeur/coquille a sensiblement amélioré les performances en termes de rendement de purification et de capacité d'adsorption, par rapport à d'autres adsorbants classiques, y compris le gel de silice mésoporeuse et les zéolithes.Zeolites as microporous crystalline materials have shown competence and versatility in a huge number of applications. Their unique properties have persuaded researchers to constantly look for novel pathways to get the most out of these extraordinary substances. Modifying the properties of classical zeolites or combining them synergistically with other materials are found to be two viable techniques to attain efficient zeolitic materials with improved characteristics. In this dissertation, these two approaches were separately used to study, first, the morphological modification of ZSM-12 and second, the formation of mesoporous silica@silicalite-1 core-shell materials. ZSM-12 is a high silica zeolite which has recently attracted much attention owing to its superior performance in adsorption and catalysis. In order to synthesize ZSM-12 with high purity and controlled size and morphology, the crystallization behavior of ZSM-12 zeolite was thoroughly studied by screening different commercially available chemical sources (structure-directing agents, silicon and aluminum source types) and compositions (alkalinity and Na, Al and water contents). The results presented in this study showed that, in contrast to TEAOH organic template, using MTEAOH and Al(o-i-Pr)3 could lead to the formation of mono-sized ZSM-12 single crystals in a shorter time. Alkalinity and Na+ contents were found to be playing the major roles. Following the second approach, zeolitic core-shell composites with a polycrystalline silicalite-1 shell, enclosing a mesoporous silica microsphere core (particle sizes of 1.5, 3 and 20-45 μm) in either pure form or loaded with metal guest species, were synthesized. Seeded growth technique was used as one of the reliable ways for the synthesis of such a material. The quality of the final products in terms of the pore network connectivity and shell integrity, which, together, ensure the shape-selective capability, was studied by varying synthesis parameters, such as core pre-treatments which include surface modification, seeding and calcination steps and the number of secondary hydrothermal crystallization steps. Depending on the core size and the presence of guest species, the quality of the seeding step was found to be influenced by the surface modification technique used, i.e., mesoporous silica microspheres which contain guest species need an additional treatment of chemical functionalization of the external surface with species such as APTES, rather than using a simple surface modification with ionic polymers. It was also shown that depending on the core size, two to four short hydrothermal treatments are required to fully cover the core, with no aggregation and core dissolution. Such materials with a molecular sieve crystalline shell can be used in a wide variety of applications, particularly for shapeselective adsorption and catalysis purposes. Selective adsorption capability of the final product was investigated by conducting a series of batch glycerol adsorption experiments from crude biodiesel with different compositions at different temperatures. Glycerol content of the purified biodiesel by using the core@shell material was compared to those purified by using conventional adsorbents including bare mesoporous silica gel spheres, classical zeolites, e.g., silicalite-1, pure siliceous β-zeolite (Si-BEA) and ZSM-5(H+) crystals as well as a physical mixture of the constitutive materials, i.e., equally mixed silicalite-1 and silica gel spheres. Although mesoporous silica gel spheres showed slightly higher glycerol adsorption capacity, the study revealed that the mesoporous adsorbents tended to trap a significant number of bulkier molecules, such as FAMEs, in their large pore networks (dpore> 6 nm). However, the silicalite-1 shell provided a microporous membrane which hindered the diffusion of FAME into the mesopores while the composite adsorbents benefited from large pore volume of mesoporous silica as core compartment, allowing a multi-layer glycerol adsorption. This feature of the synthesized core@shell material considerably enhanced the dry washing performance in terms of purification yield and adsorption capacity, in comparison to other conventional adsorbents including mesoporous silica gel and classical zeolites

Using Zeolitic Core@Shell Adsorbents for the Selective Removal of Free Glycerol from Crude Biodiesel

Selective adsorption of free glycerol from crude biodiesel mixture has been investigated using mesoporous silica spheres coated with a thin shell of microporous silicalite-1. Various types of mesoporous silica spheres with different sizes (commercial silica gel spheres: 20-45 μm and 3 μm, HMS spheres: ~1.5 μm) were used as core templates. A polycrystalline silicalite-1 shell was formed upon first covering the external surface of the core templates with discrete silicalite-1 nanocrystals via electrostatic attractions, followed by short hydrothermal treatments in silica/TPAOH-containing gel to ensure shell coverage and uniformity. The synthesized materials were characterized SEM, TEM, XRD and nitrogen physisorption. Series of batch glycerol adsorption experiments were conducted to evaluate the ability of the final product in the selective removal of free glycerol from crude biodiesels with different compositions at various temperatures. Glycerol contents of the produced biodiesel were compared to those purified by using conventional adsorbents including bare mesoporous silica gel spheres, conventional zeolites, e.g. silicalite-1, pure siliceous beta (Si-BEA) and ZSM-5 (H) crystals as well as physical mixture of the constitutive materials, i.e., equally mixed silicalite-1 and silica gel spheres. Although mesoporous silica gel spheres showed slightly higher glycerol adsorption capacity, the mesoporous adsorbents tend to trap a significant amount of bulkier molecules (e.g., FAME) in their large pore network (dpore= 7nm). However, the silicalite-1 shell provided a microporous membrane which hindered FAME diffusion into the mesopores of the composite adsorbent, while the large pore volume of the mesoporous core enabled a multi-layer glycerol adsorption. This property of the core@shell material significantly enhanced the dry washing performance in terms of purification yield and adsorption capacity, in comparison to other conventional sorbents (Glycerol:FAME ratio in sorbent improved from ~0.65 for silica gel up to 5.2 for core@shell particles).Facultad de Ciencias Exacta

Synthesis of microporous/mesoporous core-shell materials with crystalline zeolitic shell and supported metal oxide silica core

An engineered material, possessing a hierarchical porosity in a shape selective manner, was synthesized by placing a microporous silicalite-1 shell over silica microspheres embedded with various guest species. Core materials were prepared by dispersing catalytically important metallic species comprising Co, Mn or Ti, within the mesoporous structure of the silica microspheres with different particle and pore sizes. The connectivity of the micro- and mesopore networks and shell integrity of the final core@shell products were studied as the main quality control criteria by varying synthesis parameters, such as core pre-treatments which include surface modification, seeding and calcination steps and by varying the number of secondary hydrothermal treatments. Depending on the core size and the presence of the guest species, the effectiveness of core seeding is found to be influenced by the chosen surface modification technique, i.e., mesoporous silica microspheres which contain guest species need an additional treatment of chemical functionalization of the external surface with species such as (3-aminopropyl)triethoxysilane, rather than using a simple surface modification with ionic polymers. It is believed that using such a chemical treatment can strengthen the adhesion of the seeds to the core surface by providing some additional silanol groups and facilitating hydrogen bonding interactions. It is also shown that depending on the core size, two to four short hydrothermal treatments are required to turn the coated seed crystals into a uniform intergrown shell of silicalite-1 around the mesoporous silica microspheres and to avoid aggregation and core dissolution. Such materials with a molecular sieve crystalline shell can be used in a wide variety of applications, particularly for shape-selective adsorption and catalysis purposes.Centro de Tecnología de Recursos Minerales y Cerámic

Synthesis of microporous/mesoporous core-shell materials with crystalline zeolitic shell and supported metal oxide silica core

An engineered material, possessing a hierarchical porosity in a shape selective manner, was synthesized by placing a microporous silicalite-1 shell over silica microspheres embedded with various guest species. Core materials were prepared by dispersing catalytically important metallic species comprising Co, Mn or Ti, within the mesoporous structure of the silica microspheres with different particle and pore sizes. The connectivity of the micro- and mesopore networks and shell integrity of the final core@shell products were studied as the main quality control criteria by varying synthesis parameters, such as core pre-treatments which include surface modification, seeding and calcination steps and by varying the number of secondary hydrothermal treatments. Depending on the core size and the presence of the guest species, the effectiveness of core seeding is found to be influenced by the chosen surface modification technique, i.e., mesoporous silica microspheres which contain guest species need an additional treatment of chemical functionalization of the external surface with species such as (3-aminopropyl)triethoxysilane, rather than using a simple surface modification with ionic polymers. It is believed that using such a chemical treatment can strengthen the adhesion of the seeds to the core surface by providing some additional silanol groups and facilitating hydrogen bonding interactions. It is also shown that depending on the core size, two to four short hydrothermal treatments are required to turn the coated seed crystals into a uniform intergrown shell of silicalite-1 around the mesoporous silica microspheres and to avoid aggregation and core dissolution. Such materials with a molecular sieve crystalline shell can be used in a wide variety of applications, particularly for shape-selective adsorption and catalysis purposes.Fil: Masoumifard, Nima. Laval University; CanadáFil: Kim, Kyoungsoo. Institute for Basic Science; Corea del SurFil: Kaliaguine, Serge. Laval University; CanadáFil: Arnal, Pablo Maximiliano. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Kleitz, Freddy. Laval University; Canad

A Novel Swing Adsorption Reactor Cluster (SARC) for cost effective post-combustion CO2 capture: A thermodynamic assessment

The SARC consists of a number of standalone reactors where a solid sorbent is carbonated by a flue gas and regenerated by a combination of vacuum and temperature swing. Efficiency is maximized through heat integration between carbonation and regeneration using a heat pump. Initial power plant simulations showed 9.4%-points energy penalty when integrated into a pulverized coal plant. This is in-line with reported energy penalty for MEA and VPSA technologies, but great potential for further efficiency improvements exists. Future studies will investigate the effect of SARC process parameters and sorbent material selection on the energy penalty

Gas adsorption and framework flexibility of CALF-20 explored via experiments and simulations

In 2021, Svante, in collaboration with BASF, reported successful scale up of CALF-20 production, a stable MOF with high capacity for post-combustion CO2 capture which exhibits remarkable stability towards water. CALF-20’s success story in the MOF commercialisation space provides new thinking about appropriate structural and adsorptive metrics important for CO2 capture. Here, we combine atomistic-level simulations with experiments to study adsorptive properties of CALF-20 and shed light on its flexible crystal structure. We compare measured and predicted CO2 and water adsorption isotherms and explain the role of water-framework interactions and hydrogen bonding networks in CALF-20’s hydrophobic behaviour. Furthermore, regular and enhanced sampling molecular dynamics simulations are performed with both density-functional theory (DFT) and machine learning potentials (MLPs) trained to DFT energies and forces. From these simulations, the effects of adsorption-induced flexibility in CALF-20 are uncovered. We envisage this work would encourage development of other MOF materials useful for CO2 capture applications in humid conditions

Zeolitic core@shell adsorbents for the selective removal of free glycerol from crude biodiesel

Selective adsorption of free glycerol from crude biodiesel was investigated by using mesoporous silica spheres coated with a thin shell of microporous silicalite-1. A polycrystalline silicalite-1 shell was formed upon first covering the external surfaces of various core templates with discrete silicalite-1 nanocrystals, and this was followed by short hydrothermal treatment to ensure shell uniformity. Batch glycerol adsorption experiments were conducted to evaluate the ability of the sorbents to remove free glycerol selectively from crude biodiesel mixtures at various temperatures, also in comparison to that of conventional sorbents, for example, bare mesoporous silica gel spheres and zeolites. The silicalite-1 shell provided a microporous membrane that hindered the diffusion of fatty acid methyl esters into the mesopores of the composite sorbent, whereas the large pore volume of the mesoporous core enabled multilayer glycerol adsorption; this ultimately substantially enhanced the performance in terms of purification yield and adsorption capacity.Fil: Masoumifard, Nima. Laval University; CanadáFil: Arnal, Pablo Maximiliano. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Tecnología de Recursos Minerales y Cerámica; ArgentinaFil: Kaliaguine, Serge. Laval University; CanadáFil: Kleitz, Freddy. Laval University; Canad

Synthesis of microporous/mesoporous core-shell materials with crystalline zeolitic shell and supported metal oxide silica core

An engineered material, possessing a hierarchical porosity in a shape selective manner, was synthesized by placing a microporous silicalite-1 shell over silica microspheres embedded with various guest species. Core materials were prepared by dispersing catalytically important metallic species comprising Co, Mn or Ti, within the mesoporous structure of the silica microspheres with different particle and pore sizes. The connectivity of the micro- and mesopore networks and shell integrity of the final core@shell products were studied as the main quality control criteria by varying synthesis parameters, such as core pre-treatments which include surface modification, seeding and calcination steps and by varying the number of secondary hydrothermal treatments. Depending on the core size and the presence of the guest species, the effectiveness of core seeding is found to be influenced by the chosen surface modification technique, i.e., mesoporous silica microspheres which contain guest species need an additional treatment of chemical functionalization of the external surface with species such as (3-aminopropyl)triethoxysilane, rather than using a simple surface modification with ionic polymers. It is believed that using such a chemical treatment can strengthen the adhesion of the seeds to the core surface by providing some additional silanol groups and facilitating hydrogen bonding interactions. It is also shown that depending on the core size, two to four short hydrothermal treatments are required to turn the coated seed crystals into a uniform intergrown shell of silicalite-1 around the mesoporous silica microspheres and to avoid aggregation and core dissolution. Such materials with a molecular sieve crystalline shell can be used in a wide variety of applications, particularly for shape-selective adsorption and catalysis purposes. © 2016 The Royal Society of Chemistry1

Designed Synthesis of Mesoporous Solid-Supported Lewis Acid Base Pairs and Their CO2 Adsorption Behaviors

Conventional amines and phosphines, such as diethylenetriamine, diphenylpropylphosphine, triethylamine, and tetramethylpiperidine, were grafted or impregnated on the surface of metalated SBA-15 materials, such as Ti-, Al-, and Zr-SBA-15, to generate air-stable solid supported Lewis acid base pairs. The Lewis acidity of the metalated materials before and after the introduction of Lewis bases was verified by means of pyridine adsorption-Fourier transform infrared spectroscopy. Detailed characterization of the materials was achieved by solid-state C-13 and P-31 MAS NMR spectroscopy, low-temperature N-2 physisorption, Xray photoelectron spectroscopy, and energy-dispersive X-ray mapping analyses. Study of their potential interactions with CO2 was performed using CO2 adsorption isotherm experiments, which provided new insights into their applicability as solid CO2 adsorbents. A correlation between solid-supported Lewis acid base pair strength and the resulting affinity to CO2 is discussed based on the calculation of isosteric enthalpy of adsorption © 2018 American Chemical Society