The purpose of this research was to directly compare the behavior of zeolites containing rhodium with that of homogeneous rhodium species as catalysts for liquid phase hydroformylation of 1-hexene in order to study the effects of zeolite immobilization. NaX zeolite was cation exchanged with several rhodium salts and used as hydroformylation catalysts at 50°C and 125°C in the presence of: triphenylphosphine (PPh₃), dimethylphenylphosphine (PMe₂Ph), and the poison for zeolite surface and solution rhodium: triphenylmethylmercaptan (Ph₃CSH). The results of these experiments were compared with those of several homogeneous catalysts under similar conditions. It was found that previously reported results of intrazeolitic activity with RhNaX at 50°C were probably incorrect, since, the addition of PMe₂Ph, Ph₃CSH, or both, virtually halted all reactivity of RhNax. The catalytic results at 125°C did not conclusively indicate the location of the active rhodium. Thus, intrazeolitic activity at 125°C may or may not have been observed, and needs further investigation. Reaction profiles were obtained for several of the catalyst systems, using an automatic sampling system. From these profiles, it was found that the addition of excess PMe₂Ph halted isomerization of 1-hexene to 2-hexenes for the zeolite-supported rhodium, and hindered, but did not stop isomerization for the homogeneous catalysts. Also, as expected, it was observed that the homogeneous catalysts reacted to completion faster than the heterogeneous catalyst. In addition, the effects of such treatments as preheating in air and precarbonylation of the heterogeneous catalysts were studied. Pretreatments had no effect upon the catalysis. Also, no activity was observed from the heterogeneous catalysts at 125°C unless phosphines were present. Finally, the hydrogenation of 1-hexene was studied. Heterogeneous and homogeneous rhodium catalysts showed hydrogenation activity which was accompanied by isomerization at 60°C and 125°C. / Master of Science

Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. X-ray diffraction, oxygen adsorption, FTIR and SEM were utilized to evaluate crystal purity. X-ray photoelectron spectroscopy (XPS), chemical analysis and electron microprobe analysis were performed in order to ascertain the position (intrazeolitic versus surface) and homogeneity of the transition metal. It was concluded that intrazeolitic transition metals were produced by the novel procedure presented in this work. 1-Hexene hydroformylation by rhodium zeolite A showed intrazeolitic rhodium to migrate to the external surface of the zeolite. However, in the presence of a solution and surface rhodium poison, intrazeolitic rhodium was found to hydroformylate 1-hexene exclusively to heptanal. Ruthenium containing zeolite A was evaluated under CO-hydrogenation conditions. No migration of intrazeolitic ruthenium to the external surface of the zeolite was observed over the course of the reaction. The product distribution obtained for this catalyst did not follow a log normal behavior. Also, loss of zeolite crystallinity was observed following the reaction. Cobalt ZSM-5 was evaluated under CO-hydrogenation conditions. No migration of cobalt to the external surface of the zeolite occurred. XPS analysis of the catalyst following various stages of the reaction indicated that intrazeolitic cobalt was not reduced to the zero valent state. Consequently, the non-zero valent cobalt was not capable of hydrogenating carbon monoxide. / Ph. D.

A number of investigations have been undertaken with the object of replacing the present water treatment system at the Virginia Polytechnic Institute Power Plant. / Master of Science

<p dir="ltr">Metal speciation and structure can be influenced by the deposition method used during synthesis, interactions with the support, and by post-deposition treatments and reaction conditions experienced during its lifetime of carrying out a catalytic reaction. Supported metal particles of different size contain different surface structures and coordination environments, which may not only influence reaction rates but also the interconversion between agglomerated metallic domains and dispersed metal atom or ion sites. Here, we address the influence of post-deposition treatments and support properties on the structural interconversion of Pd and Cu on aluminosilicate chabazite (CHA) zeolites, Pt on gamma-alumina (γ-Al2O3), and Pd on amorphous oxides (γ-Al2O3, La-doped Al2O3, ΘΔ-Al2O3). The fundamental insights from these studies can be used to design catalysts used widely in automotive exhaust aftertreatment systems, including Pd-exchanged zeolites for passive NOx (x = 1,2) adsorbers (PNA), Cu-exchanged zeolites for NOx (x = 1,2) selective catalytic reduction (SCR), Pt/Al2O3 for NH3 oxidation, and Pd/oxides for three-way catalysts (TWC). Incipient wetness impregnation (IWI) and colloidal methods were used to prepare Pd nanoparticles deposited on CHA zeolites with distinct Pd nanoparticle sizes and distributions. These Pd-CHA samples were used to investigate the effects of Pd particle size distribution on structural interconversion between ion-exchanged Pd and agglomerated Pd domains under realistic operating conditions. Smaller Pd nanoparticles had larger fractions of agglomerated Pd that converted to ion-exchanged Pd2+ sites at fixed air treatment temperatures (598–973 K) and H2O pressures (2–6 kPa H2O), consistent with thermodynamic predictions from DFT calculations. Furthermore, the addition of H2O during air treatment of different Pd nanoparticles (2–14 nm) inhibited the formation of ion-exchanged Pd2+ (thermodynamics), but not the rate of redispersion (kinetics). This demonstrates that, regardless of Pd nanoparticle size, water vapor in automotive exhaust streams facilitate metal sintering in PNA applications. Aqueous-phase exchange of Cu on CHA zeolites with varying support properties (i.e., number of paired Al sites in the 6 membered ring) were used to prepare materials with distinct types and numbers of extraframework Cu species (Cu2+, CuOH+). These Cu-CHA materials were used to analyze Cu structural changes before and after exposure to hydrothermal aging conditions. In the absence of H2O, some Cu2+ sites condense to form binuclear Ox-bridged Cu species that can be reduced with H2 to form Cu-hydride sites and reject H2O, leading to a sub-stoichiometric H2 consumption (H2/Cu < 0.5). In the presence of H2O, all nominally isolated Cu2+ species convert to [CuOH]+ structures, which can subsequently be reduced by H2 to form a Cu-hydride and reject H2O, leading to stoichiometric H2 consumption (H2/Cu ~ 0.5). Furthermore, the presence of H2O led to reduction features in H2 temperature programmed reduction (TPR) profiles that were similar among Cu-CHA materials, regardless of the initial Cu2+ speciation, further supporting the proposal that all nominally isolated Cu2+ sites convert to a similar [CuOH]+ motif. This demonstrates how water influences Cu speciation on CHA materials of varying origin or treatment history, aiding in quantifying SCR-active isolated Cu ions and SCR-inactive Cu species (e.g., CuO, CuAl2O4). Pt supported on γ-Al2O3 were prepared with different average Pt particle sizes (2–13 nm) by increasing the temperature of post-deposition air treatment (523–873 K). This suite of materials was interrogated to isolate the effects of Pt particle size on NH3 oxidation rates and selectivities during conditions relevant to NH3 slip applications in diesel exhaust aftertreatment. For all Pt particle sizes, NH3 oxidation rates displayed a hysteresis with temperature, with high rates measured during temperature decreases than during temperature increases. Smaller Pt particles (2 nm) had lower rates (per surface Pt, quantified by CO chemisorption) than larger Pt particles (13 nm), signifying that NH3 oxidation is a structure-sensitive reaction. Furthermore, surfaces of Pt particles restructure under NH3 oxidation reaction conditions, influencing effective Pt oxidation states, surface structures (numbers and types of exposed Pt sites), and surface coverages of intermediates leading to the observed hysteresis in rate. These findings demonstrate that Pt particles undergo dynamic structural changes during reaction, influencing their ability to convert NH3 to environmentally benign products in NH3 slip applications. The influence of treatment conditions, support properties, and initial Pd particle size and distribution on the kinetics of nanoparticle sintering were investigated to identify which material properties allow maintaining high dispersion to maximize metal utilization for three way catalysts (TWC) during the conversion of regulated pollutants (CO, hydrocarbons, NOx). Pd was deposited by IWI methods to generate polydiserse particle size distributions, and using colloidal Pd nanoparticle solutions to generate monodisperse size distributions, onto various supports (γ-Al2O3, La-doped Al2O3, ΘΔ-Al2O3) and subjected to aging under oxidative and reductive conditions relevant for TWC operation. The average Pd particle size for all materials increased with treatment time under both reductive and oxidative environments. For samples prepared with IWI (i.e., log normal distribution of Pd particle sizes), reductive aging treatments led to higher sintering rates than oxidative treatments. In contrast, for samples prepared using colloidal Pd solutions (i.e., normal distribution of Pd particle sizes), oxidative aging treatments led to higher sintering rates than reduction treatments. Furthermore, after the same treatment condition and time, samples prepared with IWI resulted in higher average Pd particle sizes. These results indicate that more monodisperse initial Pd particle size distributions lead to lower sintering rates, providing guidance to design of supported metal TWCs with improved metal utilization during their lifetimes. Here, the combination of synthesis approaches to prepare a suite of model (e.g., powder) supported metal catalysts of varying structure and composition, interrogated using site and structural characterizations and steady-state and transient kinetic measurements, along with predictions from theoretical calculations, enabled unraveling the influence of material properties and gas environments that affect metal speciation, structure, and oxidation state in real-world aftertreatment systems that use more complex catalytic architectures (e.g., layered washcoats) and reactor designs (e.g., monoliths). This approach provides insights into the fundamental thermodynamic and kinetic factors influencing metal restructuring and interconversion under realistic conditions encountered in automotive exhaust aftertreatment applications, and the kinetic and mechanistic factors that underlie complex phenomena (e.g., reaction rate hysteresis) from data measured in the absence of hydrodynamic artifacts. The overall approach used in this work enabled development of synthesis-structure-function relationships on various metal supported catalysts for automotive exhaust aftertreatment applications, which can provide guidance for material design and treatment strategies to form and retain desired metal structures throughout the material lifetime, including synthesis, reaction, and regeneration treatments.</p>

En el presente trabajo se ha estudiado la actividad catalítica de diferentes tamices moleculares sólidos con acidez de Lewis, sintetizados en el Instituto de Tecnología Química, utilizándolos como catalizadores en reacciones de Mukaiyama y de tipo Mukaiyama, que son reacciones con formación de enlaces C-C de gran interés en catálisis i química fina. Los catalizadores desarrollados han sido diversos tamices moleculares microporosos como zeolitas, mesoporosos del tipo MCM-41 i macroporosos como zeolitas deslaminadas, todos ellos con diferentes metales con propiedades de ácido Lewis incorporados en la red. Los resultados obtenidos, rendimientos prácticamente cuantitativos en tiempos de reacción muy cortos, son de especial interés en catálisis i química fina ya que los materiales desarrollados permitirían llevar a cabo reacciones con formación de enlaces C-C de forma sencilla, en condiciones heterogéneas muy suaves i con reutilización del catalizador, cumpliendo en gran medida los criterios de la química verde. Este hecho posibilitaría la aplicación industrial del proceso así como abriría una puerta hacia el desarrollo de nuevos materiales catalíticos todavía más activos y selectivos. / Garro Martínez, R. (2007). Catalitzadors sòlids àcids de Lewis en reaccions de mukaiyama i de tipus mukaiyama. Un exemple d'aproximació a la química verda [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1835

[ES] Las zeolitas han destacado por sus aplicaciones en procesos catalíticos y de adsorción/separación de gases de alto impacto industrial. Esto es debido a que presentan propiedades de tamiz molecular como consecuencia de sus estructuras microporosas y, además es posible ajustar sus propiedades catalíticas variando su composición química, presencia de defectos estructurales, tamaño promedio de cristal, etc. Hasta el momento se han reconocido 255 estructuras zeolíticas diferentes, pero la obtención de zeolitas con nuevas estructuras es un aspecto muy relevante dentro de la ciencia de materiales ya que permite ampliar el rango de aplicaciones de estos materiales. Por ello, el objetivo fundamental de esta tesis doctoral es la obtención de nuevos materiales zeolíticos, empleándose para ello, cationes orgánicos que actuarán como agentes directores de estructura (ADEs) en la cristalización de zeolitas. Así, se ha estudiado el empleo cationes derivados de biciclopirrolidina como ADEs sintetizados mediante reacciones orgánicas de cicloadición [3+2]. Estos ADEs han sido efectivos en la síntesis de zeolitas, obteniéndose diversos sólidos microporosos cuya preparación había sido descrita anteriormente con otros cationes orgánicos. Sin embargo, uno de los cationes empleados ha dado lugar a la cristalización de una nueva zeolita, denominada ITQ-69, que presenta un sistema tridireccional de canales rectos, de poro pequeño (8 x 8 x 8 R) y ausencia de cavidades. Este material ha sido efectivo en la separación selectiva de propileno de propano en su forma de germanosilicato. La síntesis de zeolitas quirales, es sin duda el objetivo más ambicioso propuesto. En esta tesis se ha explorado el empleo de derivados de azúcares como parte fundamental en la síntesis de ADEs. En concreto, se ha explorado la isomanida como unidad sintética quiral en la preparación de dicationes quirales. Cuando la isomanida se combina con la presencia de imidazolios (altamente selectivos hacía la estructura STW) se ha obtenido un material STW en forma de germanosilicato. Este sólido cristaliza formando cristales de tamaño suficientemente grande como para realizar estudios de difracción de Rayos X en monocristal, y determinar el exceso enantiomérico de distintas preparaciones. En todos los casos, se obtiene cristales S-STW homoquirales enantimórficamente puros, constituyendo el primer ejemplo de obtención selectiva quiral de una zeolita reportado hasta la fecha. En esta parte de la tesis, también se obtuvieron zeolitas con topología STW empleando ADEs no quirales. Algunos de estos sólidos, se evaluaron en la separación de hidrocarburos con diferentes grados de ramificación (zeolita STW puramente silícea) y en la reducción selectiva de NO con propano (zeolita Al-STW intercambiadas con Cu). Finalmente, se han estudiado diferentes cationes organofosforados como ADEs. La elevada estabilidad de estos cationes en el medio de síntesis, ha permitido la obtención de una nueva zeolita, ITQ-70, que presenta un elevado grado de defectos de conectividad y una muy baja densidad de red. La estructura de la zeolita ITQ-70 presenta un sistema de supercavidades con ventanas interconectadas de acceso a las mismas (20 x 20 x 18 R) y cristaliza con un grupo de simetría proquiral. / [CAT] Zeolites are well-known for their industrial applications. The presence of pores of molecular dimensions forming a structured channels system confers them the property of performing as a molecular sieve. This characteristic of zeolites, combined with the possibility of modifying their chemical composition, structural defects, average crystal size, etc., provides them with exceptional properties for catalytic and separation processes. Up to now, 255 different zeolitic structures have been compiled. However, obtaining zeolites with new structures remains an important challenge in materials science and broadening their applications. Therefore, the main objective of this doctoral thesis is the obtention of new zeolitic materials using organic cations as structure-directing agents (SDAs) in the crystallization process. Thus, the use of bicyclopyrrolidine-derived cations as ADEs, synthesized by organic cycloaddition reactions [3+2], has been studied. Several microporous solids whose preparation had been previously described using other organic cations have been obtained by utilizing these bicyclopyrrolidine-derived cations as ADEs. In addition, the crystallization of a new zeolite, ITQ-69, has been reached. This structure presents a tridirectional system of straight small pore size channels (8 x 8 x 8 R) and the absence of cavities. ITQ-69, in its germanosilicate form, has been proved to be significantly effective for the separation of propylene from propane. Obtaining chiral zeolite is undoubtedly one of the most ambitious objectives proposed in the field of zeolite synthesis. In this thesis, sugar derivatives have been specifically considered as starting molecules for the synthesis of chiral ADEs. Particularly, the synthesis of dicationic ADEs starting from isomannide as a chiral synthetic unit has been explored. When isomannide was combined with imidazole (highly selective towards the STW structure), a STW-structure material in the form of germanosilicate was obtained. This solid crystallizes forming sufficiently large crystals to perform single-crystal X-ray diffraction studies and determine the enantiomeric excess of different preparations. In all cases, enantiomorphically pure homochiral S-STW crystals are obtained, constituting the first reported example of chiral selective synthesis of a zeolite. Zeolites with STW structure were also obtained using non-chiral ADEs. The properties of these microporous solids were evaluated in the separation of hydrocarbons with different branching, in the form of purely siliceous STW, and in the selective reduction of NO with propane using Cu-exchanged Al-STW zeolites. Finally, different organophosphorus cations have been studied as ADEs. The high stability of these cations in the zeolites crystallization medium has allowed the isolation of a new zeolite, ITQ-70, which presents a high number of connectivity defects and a very low lattice density. The structure of the ITQ-70 zeolite possesses a super-cavity system with interconnected access windows (20 x 20 x 18) and crystallized with a prochiral symmetry group. / [EN] Les zeolites han destacat per les seues aplicacions en processos catalítics i processos d'adsorció/separació de gasos d'alt impacte industrial. Açò és degut al fet que presenten propietats de tamís molecular a conseqüència de les seues estructures microporoses i, a més és possible ajustar les seues propietats catalítiques variant la seua composició química, presència de defectes estructutals, grandària del cristall, etc. Fins al moment es reconeixen 255 estructures zeolítiques diferents, però l'obtenció de zeolites amb noves estructures és un aspecte molt rellevant dins de la ciència de materials, ja que permet ampliar el rang d'aplicacions d'aquests materials. Per tant, l'aspecte fonamental d'aquesta tesi doctoral és l'obtenció de nous materials zeolítics empleant cations orgànics que actuaran com a agents directors d'estructura (ADEs) en la cristal·lització de zeolites. Així, s'ha explorat l'us de cations derivats de biciclopirrolidina com ADEs sintetitzats mitjançant reaccions orgàniques de cicloadició [3+2]. Aquests ADEs han sigut efectius en la síntesis de zeolites, obtenint-se diversos sòlids microporosos, la preparació dels quals havia sigut descrita anteriorment amb altres cations orgànics. No obstant, un dels cations empleats ha donat lloc a la cristal·lització d'una nova zeolita, denominada ITQ-69, que presenta un sistema tridireccional de canals rectes, porus xicotets (8 x 8 x 8 R) i absència de cavitats. Aquest material ha sigut efectiu en la separació selectiva de propilé de propà en la seua forma de germanosilicat. Dins de la síntesi de zeolites, la síntesi de zeolites quirals, és sens dubte un dels objectius més ambiciosos proposats. En aquesta tesi s'ha explorat l'ús de derivats de sucres com a part fonamental en la síntesi de ADEs. En concret, s'ha explorat la isomanida com a unitat sintètica quiral en la preparació de dications quirals. Quan la isomanida es combina amb la presència de imidazolios (altament selectius feia l'estructura STW) s'ha obtingut un material STW en forma de germanosilicato. Aquest sòlid cristal·litza formant cristalls de grandària prou gran com per a realitzar estudis de difracció de Raigs X en monocristall, i determinar l'excés enantioméric de diferents preparacions. En tots els casos, s'obté cristalls S-STW homoquirals enantimórficament purs, constituint el primer exemple d'obtenció selectiva quiral d'una zeolita reportat fins a la data. En aquesta part de la tesi, també es van obtindre zeolites amb topologia STW empleant ADEs no quirals. Alguns dels materials STW es van avaluar les propietats d'aquests sòlids microporosos en la separació d'hidrocarburs amb diferents graus de ramificació amb STW purament silici i en la reducció selectiva de NO amb propà empleant zeolites Al-STW intercanviades amb Cu. Finalment, s'han estudiat diferents cations organofosforats com ADEs. L'elevada estabilitat d'aquests cations en el mitjà de cristal·lització de zeolites ha permés aïllar una nova zeolita, ITQ-70, que presenta un elevat grau de defectes de connectivitat i una molt baixa densitat de xarxa. L'estructura de la zeolita ITQ-70 té un sistema compost per supercavitats amb finestres interconnectades d'accés a les mateixes (20 x 20 x 18) i cristal·litza amb un grup de simetria proquiral. / Al Ministerio de Economía, Industria y Competitividad por concederme la Beca BES-2016-078684 que ha permitido la realización de esta tesis doctoral, junto a la ayuda económica proporcionada en los proyectos MAT2015-71842 y RTI2018-101784-B-100. A la Generalitat Valenciana su financiación a través del proyecto PROMETEO/2021/07 y por último a la Universidad Politécnica de Valencia (UPV), al Consejo Superior de Investigaciones Científicas (CSIC) y al Instituto de Tecnología Química (ITQ) por proporcionar las instalaciones y equipamiento necesarios para llevar a cabo el trabajo de investigación. / Sala Gascón, A. (2022). Síntesis y caracterización avanzada de materiales zeolíticos mediante el empleo de nuevos agentes orgánicos directores de estructura [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/186873

Zeolites are among the least-known products for environmental pollution control, separation science and technology. Due to their unique porous properties, they are used in various applications in petrochemical cracking, ion-exchange and separation and removal of gases and solvents. The preparation of synthetic zeolites from chemical reagents is expensive. Therefore, in order to reduce costs, zeolite researchers are seeking cheaper aluminosilicate bearing raw materials, such as clay minerals, to produce synthetic zeolites. This research concerns the synthesis of zeolites and zeotypes derived from low-cost materials like kaolinite (KAO), natural clinker (NC) and fly ash (FA). The motivation for using these sources as the starting materials in zeolite synthesis is driven by factors, such as they are cheap and available in bulk quantities, are currently under-utilized, have high workability, and require less water (or solution) for activation. The raw materials were activated by two different routes: (1) classic alkaline hydrothermal synthesis and (2) alkaline fusion prior to hydrothermal synthesis. In the first method, the synthesis of zeolitic materials was carried out generally in alkaline media, although KAO or its calcination product, metakaolinite (MTK), was also activated in the presence or absence of structure directing agents (SDAs) and additional silica (precipitated SiO2), with the last one determining the SiO2/Al2O3 ratio of the reaction mixture and the time given for zeolitization. Synthesis in fluoride- and calcium-bearing media was also used to activate kaolinite. The process of synthesis was optimized by applying a wide range of experimental conditions with a wide range of reaction temperature, time, mineralizer concentration and solid/solution ratio. In the second approach, an alkaline fusion step was conducted prior to hydrothermal treatment, because it plays an important role in enhancing the hydrothermal conditions for zeolite synthesis. On the other hand, this approach was adopted because it can dissolve more aluminosilicates. The main synthesis products obtained after activation of KAO in NaOH solutions included zeolite LTA (LTA), sodalite (SOD), cancrinite (CAN), faujasite (FAU), zeolite Na-P1 (GIS), JBW-type zeolite (JBW), analcime (ANA), whereas the activation of KAO in KOH solutions produced chabazite (CHA), zeolite Barrer-KF, phillipsite (PHI) and K-feldspar. The hydrothermal conversion of kaolinite in fluoride media did not produce successful results, although traces of FAU, GIS, CHA, SOD and CAN crystallized. The activation of KAO in the system CaO-SiO2-Al2O3-H2O promoted the formation of different calcium silicate hydrate (C-S-H) phases, including hydrogarnet (HYD) and tobermorite (TOB). Following the fusion approach, the main zeolitic phases obtained using NaOH as mineralizer were LTA and CAN. The main as-synthesized zeolites obtained from NC by the conventional hydrothermal treatment method include PHI, SOD and CAN. Using the fusion approach, FAU and LTA were obtained with NaOH as an activator, whereas non-zeolitic material crystallized when KOH was used. The main as-synthesized zeolitic materials obtained by hydrothermal reaction of FA include PHI, zeolite Barrer-KF, CHA and SOD with traces of TOB, ANA, zeolite LTF (LTF) and herschelite (HER), appearing occasionally. By the fusion approach, FAU was obtained with NaOH as activator, whereas no zeolitic material crystallized using KOH. Experimental results indicate that the method, mineralizer, concentration and time have strong effects on the type and degree of crystallinity of the synthesis products. On the other hand, the type and chemical composition of the as-synthesized products are strongly dependent on the chemical composition of the starting material. The chemistry of zeolite synthesis was subject to perturbations caused by the presence of impurities in the raw materials, which may remain insoluble during crystallization and cause undesired species to nucleate, developing mixtures of different types of zeolites. However, other physicochemical factors may play a very important role in the thermodynamics and kinetics of zeolite formation. The raw materials have very high contents of SiO2 and Al2O3, with SiO2/Al2O3 ratios appropriate for the synthesis of low-Si zeolitic materials with high crystallinity and cation exchange capacity (CEC). However, although zeolites’ CEC represents a very important characteristic quality in the removal of undesired species from polluted effluents, it is not the deciding factor in determining zeolite performance during ion exchange processes, since numerous other factors also need to be considered. Finally, the potential application of the raw materials and their as-synthesized products as low-cost sorbents in the remediation of metal ions and ammonium from wastewater effluents was investigated. PHI showed a lower efficiency than FAU. Selectivity of FAU for metal removal was, in decreasing order, Fe>As>Pb>Zn>Cu>Ni>Cr. Based on these results, the use of these materials has the potential to provide improved methods for the treatment of contaminated effluents.

The goal of this research was to identify and fabricate zeolitic membranes that can separate radioisotope krypton-85 (half-life 10.72 years) and xenon gas released during spent nuclear fuel reprocessing. In spent nuclear fuel reprocessing, fissionable plutonium and uranium are recovered from spent nuclear fuel and recycled. During the process, krypton-85 and xenon are released from the spent nuclear fuel as process off-gas. The off-gas also contains NO, NO2, 129I, 85Kr, 14CO2, tritium (as 3H2O), and air and is usually vented to the atmosphere as waste without removing many of the radioactive components, such as 85Kr. Currently, the US does not reprocess spent nuclear fuel. However, as a member of the International Framework for Nuclear Energy Cooperation (IFNEC, formerly the Global Nuclear Energy Partnership), the United States has partnered with the international nuclear community to develop a “closed” nuclear fuel cycle that efficiently recycles all used nuclear fuel and safely disposes all radioactive waste byproducts. This research supports this initiative through the development of zeolitic membranes that can separate 85Kr from nuclear reprocessing off-gas for capture and long-term storage as nuclear waste. The implementation of an 85Kr/Xe separation step in the nuclear fuel cycle yields two main advantages. The primary advantage is reducing the volume of 85Kr contaminated gas that must be stored as radioactive waste. A secondary advantage is possible revenue generated from the sale of purified Xe. This research proposed to use a zeolitic membrane-based separation because of their molecular sieving properties, resistance to radiation degradation, and lower energy requirements compared to distillation-based separations. Currently, the only commercial process used to separate Kr and Xe is cryogenic distillation. However, cryogenic distillation is very energy intensive because the boiling points of Kr and Xe are -153 °C and -108 °C, respectively. The 85Kr/Xe separation step was envisioned to run as a continuous cross-flow filtration process (at room temperature using a transmembrane pressure of about 1 bar) with a zeolite membrane separating krypton-85 into the filtrate stream and concentrating xenon into the retentate stream. To measure process feasibility, zeolite membranes were synthesized on porous α-alumina support discs and permeation tested in dead-end filtration mode to measure single-gas permeance and selectivity of CO2, CH4, N2, H2, He, Ar, Xe, Kr, and SF6. Since the kinetic diameter of krypton is 3.6 Å and xenon is 3.96 Å, zeolites SAPO-34 (pore size 3.8 Å) and DDR (pore size 3.6 Å) were studied because their pore sizes are between or equal to the kinetic diameters of krypton and xenon; therefore, Kr and Xe could be separated by size-exclusion. Also, zeolite MFI (average pore size 5.5 Å) permeance and selectivity were evaluated to produce a baseline for comparison, and amorphous carbon membranes (pore size < 5 Å) were evaluated for Kr/Xe separation as well. After permeation testing, MFI, DDR, and amorphous carbon membranes did not separate Kr and Xe with high selectivity and high Kr permeance. However, SAPO-34 zeolite membranes were able to separate Kr and Xe with an average Kr/Xe ideal selectivity of 11.8 and an average Kr permeance of 19.4 GPU at ambient temperature and a 1 atm feed pressure. Also, an analysis of the SAPO-34 membrane defect permeance determined that the average Kr/Xe selectivity decreased by 53% at room temperature due to unselective defect permeance by Knudsen diffusion. However, sealing the membrane defects with polydimethylsiloxane increased Kr/Xe selectivity by 32.8% to 16.2 and retained a high Kr membrane permeance of 10.2 GPU at ambient temperature. Overall, this research has shown that high quality SAPO-34 membranes can be consistently fabricated to achieve a Kr/Xe ideal selectivity >10 and Kr permeance >10 GPU at ambient temperature and 1 atm feed pressure. Furthermore, a scale-up analysis based on the experimental results determined that a cross-flow SAPO-34 membrane with a Kr/Xe selectivity of 11.8 and an area of 4.2 m2 would recover 99.5% of the Kr from a 1 L/min feed stream containing 0.09% Kr and 0.91% Xe at ambient temperature and 1 atm feed pressure. Also, the membrane would produce a retentate stream containing 99.9% Xe. Based on the SAPO-34 membrane analysis results, further research is warranted to develop SAPO-34 membranes for separating 85Kr and Xe.

Dans le cadre du concept français de stockage géologique profond des déchets radioactifs, ilest envisagé de stocker les colis vitrifiés de déchets de Moyenne Activité à Vie Longue au sein de surconteneurs en béton. La chimie de l'eau interstitielle étant susceptible de modifier la durabilité chimique des matrices vitreuses, cette étude a été menée afin d'appréhender la phénoménologie d'altération du verre au contact d'eaux cimentaires. Des solutions représentatives des deux premiers stades de dégradation d'un ciment Portland et d'un ciment bas pH ont été étudiées. Les conditions dans lesquelles le rapport S/V (surface de verre sur volume de solution) et la chimie de la solution pilotent les mécanismes d'altération du verre sont clairement établies.Si le flux d'éléments relâchés par le verre est suffisant pour atteindre et maintenir un état de sursaturation qui permette la nucléation de phases secondaires (C-S-H et zéolithes), alors la précipitation de ces phases pilote la dissolution du verre. Les rôles antagonistes du calcium ont été mis en évidence en fonction du régime d'altération du verre. A faible rapport S/V, l'incorporationdu calcium au sein de la pellicule d'altération augmente ses propriétés passivantes. A l'inverse, àfort rapport S/V, le calcium précipite sous forme de phases cimentaires consommatrices d'élémentsréticulants de la pellicule d'altération, ce qui engendre le maintien d'une vitesse d'altération élevée.Le rôle bénéfique d'un ciment bas pH vis-à-vis de l'altération du verre est expliqué à partir de cesrésultats. Ce travail constitue une première étape visant à la compréhension fine des mécanismesd'altération du verre en milieu cimentaire. / In the French deep geological repository concept, intermediate-level vitrified wastepackages could be disposed of concrete medium. Chemical composition and pH of the interstitialleaching water are expected to influence the chemical durability of glass. Investigations have thusbeen carried out to study glass dissolution mechanisms and kinetics in contact with cement waters.Three cement pore waters were studied: the first two correspond to two stages of the Portlandcement aging and the third corresponds to equilibrium with a low pH concrete. The S/V ratio(glass-surface-area-to-solution-volume ratio) and the chemistry of cement waters are the two mainparameters that control glass alteration mechanisms.If the leaching flow from the glass allows a degree of supersaturation to be reached and maintainedwhich leads to nucleation of secondary phases, then precipitation of these phases drives glassdissolution. At a very low S/V ratio, the calcium uptake into the alteration layer increases itspassivating properties. Conversely, at a high S/V ratio, the calcium precipitates as cementitiousphases consuming elements which form the alteration layer. The glass dissolution is maintained ata high rate.This study contributes to highlighting the beneficial role of low pH cement in glass alteration, andis a first step towards understanding the mechanisms between the glass and the cement medium.

L’incinération des ordures ménagères entraîne la formation de dioxines. Ces composés sont reconnus comme toxiques voire cancérigènes. La connaissance des quantités émises en temps réel est donc nécessaire.Ces travaux de thèses s’inscrivent dans une étude globale d’un dispositif permettant l’analyse en ligne des dioxines grâce à un système pré-concentrateur utilisant l’adsorption sélective de congénères toxiques sur des zéolithes, supportant la thermo-désorption, et un analyseur en masse.Dans un premier temps, les enjeux sont exposés. Puis une étude des écoulements dans les milieux poreux a pour but de déterminer quelle est la meilleure mise en forme des zéolithes pour favoriser l’adsorption en phase gazeuse dynamique. Ensuite, la mise en place et la caractérisation d’un système de génération de dioxines en phase gazeuse sont détaillées. Cette source est ajustable en concentration et en débit, permettant des études d’adsorption en laboratoire.Les premiers essais d’adsorption en phase gazeuse montrent, en accord avec les prédictions de la première étude, l’importance d’un adsorbant régulier de faible granulométrie. L’analyse par thermodésorption des dioxines piégées sur des grains de FAU [NaX] est réalisée en quelques heures.La facilité d’utilisation de zéolithes dans un système de prélèvement comme adsorbants et leur analyse par les méthodes de la norme EN 1948 a été prouvée lors de deux campagnes sur une unité d’incinération d’ordures ménagères.Ces travaux ont montré que l’analyse quotidienne en ligne des dioxines est d’actualité et pertinente. / The waste incineration leads to the formation of dioxins. These compounds are known to be toxic, even carcinogenic. Therefore, the emitted amounts have to be monitored.This work is part of a comprehensive study of a device for the online analysis of dioxins by means of a pre-concentrator using selective adsorption of toxic congener upon zeolites, allowing thermal desorption and a mass spectrometer.At first, the stakes are exposed. Then a study of flow in porous media aims to determine the best shape of zeolites to promote dynamic gas-phase adsorption. Then the establishment and characterization of a system for gas phase dioxins generation are detailed. This source is adjustable both in concentration and flow, allowing laboratory adsorption studies.The first gas phase adsorption tests show, in agreement with the predictions of the first study, the importance of a regular-shaped adsorbent with small particle sizes. The analysis by thermal desorption of dioxins trapped on grains FAU [NaX] is carried out in a few hours.The ease of use of zeolites in sampling train as adsorbent and their analysis according to EN 1948 standards has been proved during two campaigns at a waste incinerator facility.