The metabolism of propylene in Xanthobacter autotrophicus occurs via epoxypropane formation and subsequent metabolism by a three-step, four-enzyme pathway, utilizing the atypical cofactor Coenzyme M (CoM) to form acetoacetate. The last step in the epoxide carboxylase pathway is catalyzed by a distinctive member of the disulfide oxidoreductase (DSOR) family of enzymes, NADPH:2-ketopropyl CoM oxidoreductase/carboxylase (2-KPCC). 2-KPCC catalyzes the unorthodox cleavage of a thioether bond and successive carboxylation of the substrate. The focus of the research presented in this dissertation aims to elucidate the details of 2-KPCC that allow it to perform chemistry unconventional for typical DSOR members. Sitedirected mutagenesis was used to mutate specific active site residues and to examine the catalytic properties of 2-KPCC upon these changes. Mutation of His137, the proximal histidine that directly coordinates the water molecule, eliminated essentially all redox-dependent activity of the enzyme while mutation of His84, the distal histidine that coordinates the water molecule through His137, diminished redoxdependent enzymatic activity to approximately 25% that of the wild type enzyme, confirming the respective roles of the histidine residues in stabilizing the enolate intermediate formed upon catalysis. Neither mutation of either histidine residue, nor mutation of either redox active cysteine residue had any negative effect on the rate of the redox-independent reaction catalyzed by 2-KPCC, the decarboxylation of acetoacetate. Mutation of Met140 resulted in an enzyme with drastically altered kinetic parameters and suggests Met140 plays a role in shielding the substrate from undesired electrostatic interactions with the surroundings. The inhibitory properties of the structural CoM analogs, 2- bromoethanesulfonate (BES) and 3-bromopropanesulfonate (BPS), were examined and exploited to provide further detail on the active site microenvironment of 2- KPCC. Modification by BES results in a charge transfer complex between the thiolate of Cys87 and the oxidized flavin. The spectral features of this charge transfer complex have allowed the determination of the pKa of the Cys87 to be significantly higher than the flavin thiol in other DSOR enzymes. BPS has been shown to be a competitive inhibitor of 2-KPCC with an inhibition constant over two orders of magnitude lower than for that of BES.

Efficient propylene and propane separation is a major challenge in the modern chemical industry. With current separation methods being highly energy-intensive, there is a pressing need to find alternative green technology. Membrane separation emerged as a promising candidate for propylene and propane separation. Their small footprint, low cost, reliability, and environmental friendliness give membrane separation systems a competitive edge in the race towards sustainable development. The continuous advancements in material science created avenues for new membrane materials such as carbon molecular sieve (CMS) membranes which exhibit exceptional gas separation performances for challenging applications due to their strong size-sieving capabilities. In this work, a carbon molecular sieve (CMS) membrane derived from a polymer of intrinsic microporosity (TPE-PIM) has been investigated for propylene/propane separation made by pyrolysis at 400, 450, 500, 550, 600, 650, and 700 ºC. TPE-PIM-derived CMS films showed excellent pure and mixed-gas permeability and selectivity, exceeding the upper bound limits for propylene and propane. Observed in this work was the presence of an optimal pyrolysis temperature at 600 ºC, where the film showed the best performance with a permeability of 41.6 Barrer and a selectivity of 197 based on pure-gas measurements but dropping to 34 Barrer and selectivity of 33 under equimolar mixed-gas conditions. Such performance could be attributed to the unique internal structural changes that occurred during the pyrolysis. In addition, propane permeability though the CMS films was slow and required long times to reach steady-state values. Such slow kinetics illustrates the molecular sieving capabilities of CMS membranes for bigger and more condensable gases. Several characterization techniques have been performed on the films to confirm CMS formation and showcase deeper molecular structure insights. X-ray diffraction of all TPE-PIM films showed a broad spectrum at each peak due to the material’s amorphous nature. Diffraction patterns also revealed a gradual peak shift for the (002) plane towards smaller values closer to that of pure graphite. Raman spectra showed the characteristic D and G peaks for carbon films prepared at 500 ºC and above. FTIR analysis was also performed to investigate the potential formation of triazine crosslinks in the thermally treated samples, but no conclusive results were obtained.

No description available.

[ES] El actual enfoque hacia la desfosilización de la industria química acentúa la necesidad de desarrollar procesos químicos medioambientalmente más sostenibles. El diseño de sistemas catalíticos en tándem para llevar a cabo reacciones mecanísticamente desacopladas en un solo reactor, representa una estrategia prometedora para potencialmente reducir el tamaño de las instalaciones y alcanzar mayores eficiencias energéticas y económicas. El gas de síntesis y sus derivados directos C1 (metanol, DME) representan una atractiva fuente de carbono no derivada del petróleo para la producción de productos químicos. La propagación selectiva de cadena desde compuestos C1 hasta específicamente productos sigue siendo un desafío importante en el campo de la catálisis heterogénea. En esta tesis, se presenta cómo el diseño racional de un sistema catalítico en tándem, multifuncional y heterogéneo, proporciona una ruta novedosa y alternativa para la síntesis directa de productos C3 de interés a partir de compuestos C1. En este trabajo, se ha estudiado la integración en tándem de la reacción de carbonilación de compuestos metoxi (DME) con CO, con la posterior cetonización de los productos carboxílicos C2 intermedios correspondientes en un sistema catalítico multifuncional. La integración de los catalizadores Ag/MOR y Pd/ZrCeOx respectivamente, permite la síntesis directa de acetona a partir de mezclas de DME/gas de síntesis a 548 K y 20 bares. La incorporación de H-FER nanocristalina en un catalizador multifuncional metal/óxido/zeolita Pd/ZrCeOx:FER, como funcionalidad específica de hidrólisis del acetato de metilo, ha permitido la obtención de rendimientos a acetona hasta tres veces mayores en comparación con los obtenidos utilizando solamente el catalizador metal/óxido. La funcionalidad específica de hidrólisis se ha incorporado en base a los resultados de estudios cinéticos realizados para las etapas de reacción por separado, que revelan una limitación general de la velocidad de cetonización a partir del paso de hidrólisis ácida del intermedio acetato de metilo. A una distancia intercatalítica en el rango de micrómetros, se ha mantenido una conversión de DME estable (superior al 94%), junto con una selectividad de acetona del 65-70% (entre los productos orgánicos) durante al menos 10 días de operación continua. Además, la atmósfera de gas de síntesis a alta presión permite la integración de la hidrogenación de grupos carbonilo, abriendo la puerta para la producción de 2-propanol en un solo reactor. En particular, la incorporación del catalizador de hidrogenación Ag-Pt/¿-Al2O3 ha permitido alcanzar una selectividad de 2-propanol del 51% dentro de la fracción de productos C3. Finalmente, el concepto de conversión en tándem mencionado anteriormente se ha extendido a la conversión directa de mezclas de DME/gas de síntesis a propileno. Con este fin, se han desarrollado catalizadores basados en Ag/SiO2 como una funcionalidad de hidrodeshidratación de acetona y se han acoplado al sistema catalítico multifuncional en tándem desarrollado para la producción de acetona. A una temperatura de reacción en el rango de 548-578 K y una presión total de 15 bares, el sistema catalítico en tándem proporciona ratios propileno-a-etileno en el rango 6-9, y selectividades de propileno de hasta el 40%, para una conversión de DME >97%, demostrando que esta ruta de producción es intrínsecamente más selectiva hacia propileno que la mayoría de los procesos de metanol-a-propileno reportados. Además, la temperatura de reacción relativamente suave y el carácter reductor de la atmósfera de gas de síntesis inhiben la deposición de coque, proporcionando un comportamiento estable durante períodos de operación superiores a 214 horas. Aunque se requiere mayor optimización en cuanto al rendimiento a propileno, los resultados abren la puerta a un nuevo proceso para la producción de propileno a partir de materias primas C1, alternativo a los procesos de metanol-a-hidrocarburos. / [CA] L'actual enfocament cap a la desfossilització de la indústria química accentua la necessitat de desenvolupar processos químics mediambientalment més sostenibles. En aquest context, el disseny de sistemes catalítics en tàndem per a dur a terme reaccions mecanísticamente desacoblades en un sol reactor, representa una estratègia prometedora per potencialment reduir la grandària de les instal·lacions i aconseguir majors eficiències energètiques i econòmiques. El gas de síntesi i els seus derivats directes C1 (metanol, DME) representen una atractiva font de carboni no derivada del petroli. La propagació selectiva de cadena des de compostos C1 fins específicament productes C3 continua sent un desafiament important en el camp de la catàlisi heterogènia. En aquesta tesi, es presenta com el disseny racional d'un sistema catalític en tàndem, multifuncional i heterogeni, proporciona una ruta nova i alternativa per a la síntesi directa de productes C3 d'interés a partir de compostos C1. En aquest treball, s'ha estudiat la integració en tàndem de la reacció de carbonilació de compostos metoxi (DME) amb CO, amb la posterior cetonització dels productes carboxílics C2 intermedis corresponents en un sistema catalític multifuncional. La integració dels catalitzadors Ag/MOR i Pd/ZrCeOx respectivament, permet la síntesi directa d'acetona a partir de mescles de DME/gas de síntesi a 548 K i 20 bars. La incorporació d'H-FER nanocristalina en un catalitzador multifuncional metall/òxid/zeolita Pd/ZrCeOx:FER, com a funcionalitat específica d'hidròlisi de l'acetat de metil, intermedi en el procés global, ha permés l'obtenció de rendiments a acetona fins a tres vegades majors en comparació amb els obtinguts utilitzant solament el catalitzador metall/òxid, Pd/ZrCeOx. La funcionalitat específica d'hidròlisi s'ha incorporat sobre la base dels resultats d'estudis cinètics realitzats per a les etapes de reacció per separat, que revelen una limitació general de la velocitat de cetonització a partir del pas d'hidròlisi àcida de l'intermediari acetat de metil. A una distància intercatalítica en el rang de micròmetres, s'ha mantingut una conversió de DME estable (superior al 94%), juntament amb una selectivitat d'acetona del 65-70% (entre tots els productes orgànics) durant almenys 10 dies d'operació contínua. A més, l'atmosfera de gas de síntesi a alta pressió permet la integració de la hidrogenació de grups carbonil, obrint la porta per a la producció no sols d'acetona, sinó també de 2-propanol en un sol reactor. En particular, la incorporació del catalitzador d'hidrogenació Ag-Pt/¿-Al2O3 ha permés aconseguir una selectivitat de 2-propanol del 51% dins de la fracció de productes C3 (és a dir, acetona, 2-propanol, propà i propilé). Finalment, el concepte de conversió en tàndem esmentat anteriorment s'ha estés a la conversió directa de mescles de DME/gas de síntesi a propilé. A aquest efecte, s'han desenvolupat catalitzadors basats en Ag/SiO2 com una funcionalitat de hidro-deshidratació d'acetona i s'han acoblat al sistema catalític multifuncional en tàndem desenvolupat per a la producció d'acetona. A una temperatura de reacció en el rang de 548-578 K i una pressió total de 15 bars, el sistema catalític multifuncional en tàndem proporciona ràtios propilé-a-etilé en el rang 6-9, i selectivitats de propilé de fins al 40%, per a una conversió de DME >97%, demostrant que aquesta ruta de producció és intrínsecament més selectiva cap a propilé que la majoria dels processos de metanol-a-propilé reportats. A més, la temperatura de reacció relativament suau i el caràcter reductor de l'atmosfera de gas de síntesi inhibixen la deposició de coc, proporcionant un comportament estable durant períodes d'operació superiors a 214 hores. Encara que es requereix una major optimització quant al rendiment a propilé, els resultats obrin la porta a un nou procés per a la producció de propilé a partir de matèries primeres C1, alternatiu als processos de metanol-a-hidrocarburs. / [EN] The present focus on advancing towards a defossilized chemical industry underscores the need for developing more environmentally sustainable chemical processes. In this context, the design of tandem-catalytic systems to steer mechanistically decoupled reactions in a cascade fashion, in a single reactor, represents a promising strategy for potentially reduce the installed size of chemical processes and attain higher energy- and cost-efficiencies. Synthesis gas and its direct C1 derivatives (methanol, DME), represent an attractive non-petroleum derived carbon source for the production of commodity chemicals. The selective chain propagation from C1 building blocks to specifically C3 compounds has been demonstrated through biocatalytic routes, however it remains an important challenge for heterogeneous catalysis. In this thesis, we report how the design and engineering of a multifunctional, heterogeneous tandem-catalytic system provides a novel and alternative route for the direct synthesis of C3 compounds from C1 building blocks. The selective obtention of C2+ products with specific chain lengths, surpassing the inherently non-selective C-C chain propagation characteristic of Fischer-Tropsch polymerization reactions, poses a significant challenge. In this work, the tandem integration of the reaction of carbonylation of methoxy compounds (DME) with CO, with subsequent ketonisation of the corresponding C2 carboxylic intermediate products on a multifunctional catalytic system is reported. The integration of an optimized Ag/MOR and Pd/ZrCeOx catalysts, respectively, allows the direct synthesis of acetone from DME/syngas mixtures at 548 K and 20 bar. Enhanced acetone time-yields, i.e. by a factor greater than three, have been obtained by incorporation of nanosized H-FER, as a specific ester hydrolysis functionality in a Pd/ZrCeOx:FER metal/oxide/zeolite multifunctional ketonisation composite catalyst. The specific hydrolysis functionality was implemented based on insights from kinetic studies on the individual reaction steps revealing overall ketonisation rate limitation from the methyl acetate intermediate acid-catalysed hydrolysis step. At the micro-meter range carbonylation/ketonisation intercatalysts spacing, a noticeably stable DME conversion (of >94%), alongside ca. 65-70% acetone selectivity (within all organic products) has been sustained for at least 10 days on-stream. Furthermore, the high-pressure syngas atmosphere allows integrating the hydrogenation of carbonyl groups therefore opening the door for the production of not only acetone but also 2-propanol in a single reactor. Particularly, Ag-Pt/¿-Al2O3 hydrogenation catalyst afforded reaching a 2-propanol selectivity of 51% within the C3 products fraction (i.e. acetone, 2-propanol, propane and propylene). Finally, the above tandem conversion concept has been extended to the direct conversion of DME/syngas mixtures to propylene. To this end, Ag/SiO2 catalysts have been developed as an acetone hydrodehydration functionality and coupled to the multifunctional catalytic-tandem system developed for acetone production from DME/syngas mixtures. At a reaction temperature in the range of 548-578 K and a total pressure of 15 bar, the multifunctional catalytic system affords a remarkably high propylene-to-ethylene molar ratio of 6-9 and overall propylene selectivities up to 40%, at essentially full DME conversion (>97%), proving this production route intrinsically more selective to propylene than most of methanol-to-propylene processes. Moreover, the comparatively mild reaction temperature and the reducing character of the syngas atmosphere inhibit coke deposition, leading to stable performance for times-on-stream in excess of 214 hours. While future improvements in propylene time-yield will be required, the results open the door to a new process for propylene production from C1 feedstocks, alternative to methanol-to-hydrocarbons processes. / I would like to thank the Spanish Ministry of Science, Innovation and Universities (MCIU) for my FPU fellowship (FPU17/04751) and the European Research Council (ERC) under the Horizon 2020 research and innovation program (ERC-CoG- TANDEng; grant agreement 864195), which have made possible the realization of this thesis. BASF SE (Ludwigshafen, Germany) is gratefully acknowledged for their support to fundamental research efforts in catalysis, a portion of which has contributed to the outcomes presented in this PhD thesis. I would also like to thank the Spanish Research Council (CSIC) and, particularly, the Institute of Chemical Technology (ITQ), for providing the infrastructure where I have developed my PhD work. Next, I want to thank the Massachusetts Institute of Technology (MIT) for giving me access to their facilities during my short PhD research stay, and to the ALBA synchrotron, especially to the CLÆSS beamline, for the several beamtimes granted. Finally, I would like to thank the department of Chemical and Nuclear Engineering (DIQN) of the Polytechnic University of Valencia (UPV), for hosting me as a teaching assistant over these years / Andrés Marcos, E. (2024). Tandem Catalysis for Selective C1-to-C3 Chain Propagations towards Platform Chemicals Production [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204891

Amphiphilic tri- and penta-block copolymers containing a polyurethane central block with pendant carboxylic acid groups flanked by hydroxyl functional polyether tails were synthesized. Our intention was to investigate the activities of these copolymers as dispersants for magnetite nanoparticles in biological media. A benzyl alkoxide initiator was utilized to prepare poly(ethylene oxide) (BzO-PEO-OH), poly(propylene oxide) (BzO-PPO-OH) and poly(ethylene oxide-b-propylene oxide) (poly(BzO-EO-b-PO-OH)) oligomeric tail blocks with varying lengths of PEO and PPO. The oligomers had a hydroxyl group at the terminal chain end and a benzyl-protected hydroxyl group at the initiated end. The polyether oligomers were incorporated into a block copolymer with a short polyurethane segment having approximately three carboxylic acid groups per chain. The block co-polyurethane was then hydrogenated to remove the benzyl group and yield primary hydroxyl functionality at the chain ends. End group analysis by 1H NMR showed the targeted ratio of PEO to PPO demonstrating control over block copolymer composition. Number average molecular weights determined by both 1H NMR and GPC were in agreement and close to targeted values demonstrating control over molecular weight. Titrations of the pentablock copolymers showed that the targeted value of approximately three carboxylic acid groups per chain was achieved. Heterobifunctional poly(ethylene oxide) (PEO) and poly(ethylene oxide-b-propylene oxide) (PEO-b-PPO) copolymers were synthesized utilizing heterobifunctional initiators to yield polymers having a hydroxyl group at one chain end and additional moieties at the other chain end. For PEO homopolymers, these moieties include maleimide, vinylsilane, and carboxylic acid functional groups. Heterobifunctional PEO oligomers with a maliemide end group were synthesized utilizing a double metal cyanide coordination catalyst to avoid side reactions that occur with a basic catalyst. PEO oligomers with vinylsilane end groups were synthesized via alkoxide-initiated living ring-opening polymerization, and this produced polymers with narrow molecular weight distributions. Heterobifunctional PEO-b-PPO block copolymers were synthesized in two steps where the double metal cyanide catalyst was used to polymerize propylene oxide (PO) initiated by 3-hydroxypropyltrivinylsilane. The PPO was then utilized as a macroinitiator to polymerize ethylene oxide (EO) with base catalysis. Heterobifunctional PEO and PEO-b-PPO block copolymers possessing carboxylic acid functional groups on one end were synthesized by reacting the vinyl groups with mercaptoacetic acid via an ene-thiol addition. / Ph. D.

The structure property behavior of an ethylene-propylenediene ionic terpolymer containing varying amounts of ZnSt was investigated. Studies show that ZnSt acts as a reinforcing filler under ambient conditions. Stress-strain behavior, percent relaxation, hysteresis and permanent set were all found to increase with increasing ZnSt content. Increases in stress values upon annealing for all samples were attributed to increased ionic domain formation and growth. Aging was found to alter stress values at elongations beyond the elastic region. SAXS data indicates that structural rearrangement occurs with aging. DSC studies confirmed the effects of aging in that a difference occurred in thermal behavior between 1st and 2nd meltings. DSC also indicated the presence of an impurity, which is believed to be stearic acid. Water absorption studies conducted on the aged systems suggested that ZnSt either interacts with the Zn salt group tying up absorption sites or diffuses towards Zn salt groups as possible nucleation sites and forms a water barrier. Water negatively affects ZnSt's ability to act as a reinforcing filler. A rise in SOC values indicated non-Gaussian behavior for all samples. WAXS indicates that a portion of the ZnSt crystals hold their orientation upon stress release. The ZnSt loaded and unloaded systems had distinctly different morphologies. Both SEM and WAXS studies of the 303-50 sample indicated small ZnSt particles of less than 400°A in size. Comparison with modulus studies of other hard phase systems lent major support to the postulation of very small ZnSt crystals. / Master of Science

The reactions which give the products ethylene oxide, vinyl alcohol, vinyl aldehyde and vinyl radical for ethylene oxidation and the reactions which give propylene oxide, propanal, acetone and pi-allyl radical for propylene oxidation were investigated by using Density Functional Theory (DFT) method with B3LYP/LanL2DZ and 6-31g(d,p) basis sets in Gaussian&rsquo / 03 software. Silver and silver oxide were used as catalyst surface cluster models. Surface comparison was made for silver (111), (110) and (100) surfaces. Ethylene oxidation reaction was studied on these silver surfaces. Oxygen effect on ethylene oxide formation reaction was also investigated on silver (111) surface. Ethylene and propylene oxidation reactions were completed on both Ag13(111) and Ag14O9(001) surface clusters. VASP software which utilizes periodic plane wave basis sets was also used to compare trends of reactions for ethylene and propylene oxidations obtained by using Gaussian&rsquo / 03 software. According to results, silver (110) surface is more active for ethylene oxide formation than (111) and (100) surfaces. Hill site of (110) surface is much more active than hollow site of (110) surface since oxygen atom weakly adsorbed on hill site. Ethyl aldehyde and vinyl alcohol can not be formed on Ag(111) surface because of those higher activation barriers while ethylene oxide can be formed on cluster. Activation barrier for ethylene oxide formation decreases with increasing oxygen coverage on Ag(111) surface. Ethylene oxametallocycle intermediate molecule was not formed on Ag2O(001) surface while it is formed on surface oxide structure on Ag(111). Ethyl aldehyde and vinyl alcohol are not formed on silver oxide (001) surface. For propylene oxidation, &amp / #928 / -allyl formation path has the lowest activation barrier explaining why silver is not a good catalyst for the propylene oxide formation while it is a good catalyst for the ethylene oxide formation. This situation is valid for silver oxide. Propylene oxide selectivity increased in the gas phase oxidation. The qualitative relative energy trend obtained by VASP software is the similar with that of calculations obtained by using GAUSSIAN&rsquo / 03 software.

>Magister Scientiae - MSc / These days there are deep concerns over the environmental consequences of the rate of consumption of energy from non-renewable sources because of the accelerated increase in greenhouse effect. There is, therefore, increasing interest in research activities on renewable energy systems (e.g., supercapacitors, batteries, fuel cells and photovoltaic cells) and their materials. Supercapacitor materials have attracted much attention because of their high energy storage capacity, large surface area, high specific power density (watts/kg) and low cost. The development of advanced supercapacitor devices requires active electrode materials with high storage capacity and dispensability. Graphene oxide-dendritic star copolymer nanocomposites are fascinating as electrode materials, both scientifically and technologically, due to their exceptional properties, including light weight and high potential. / 2020-08-31

This dissertation discusses the polymorphism, crystallization and melting behavior of propylene-ethylene random copolymers. It also discusses the results of studies of the miscibility and the competitive liquid-liquid demixing and crystallization processes in blends of poly(propylene) and poly(1-butene). In the first part of this study, polymorphism of propylene-ethylene copolymers is studied by wide angle X-ray diffraction. By comparing the a and y crystal phase contents in samples with different ethylene content as well as samples isothermally crystallized at different temperatures, it was shown that increasing ethylene content as well as increasing crystallization temperature promotes the formation of the y-phase. Comparison of the results from fractionated samples and unfractionated samples with similar ethylene contents reveals that in propylene-ethylene copolymers with similar micro-structure, the polymorphism, crystallization and melting behavior are mainly determined by their ethylene content. The issue of co-unit inclusion and its effect on crystallization and melting behavior are also discussed. In the second part of this dissertation, the miscibility behavior of atactic - poly(propylene) (at-PP) and atactic poly(1-butene) (ai-P1B) with different molecular weights is investigated by differential scanning calorimetry. The phase diagram of at-PP and at-P1B blend of molecular weight (87K/48.5K) shows a upper critical solution temperature (UCST) behavior. The UCST behavior is consistent with predictions by the group contribution method. Miscibility behavior of high molecular weight isotactic poly(propylene) (it-PP) and isotactic poly(1-butene) (it-P1B) blend is investigated by a combination of optical microscopy and scanning electron microscopy, differential scanning calorimetry and dynamic mechanical analysis. These studies reveal that for the molecular weights investigated, it-PP and it-P1B form blends that are partially miscible in the liquid state. Liquid-liquid demixing is observed by optical microscopy at temperatures above the melting temperature of the it-PP component and is also inferred from scanning electron micrographs of the freeze fracture surface of quenched blends after extraction of the it- P1B component with cyclohexane. It-PP spherulites grow through both liquid phases at relative rates that depend markedly on the crystallization temperature. The complex multiple-melting behavior of the it-PP component in the blend is explained in terms of a bimodal distribution of it-PP lamellar crystals which result from crystal growth in the phase-separated liquid. Finally, the dynamic mechanical analysis data are explained in terms of a liquid-liquid demixing process that results in a significant degree of phase mixing. / Ph. D.

Nanocomposites have been receiving a lot the attention in the last decade from both industry and academia, since a small amount of nanofiller can significantly improve the materials properties. In the field of thermoplastics, polypropylene (PP) is one of the most used materials , due its easy processability, good balance of mechanical properties, and low cost. However, PP has certain shortcomings such as poor gas barrier and low thermal stability which limit its application. In order to be classified as nanocomposite the material needs to have at least one phase with one dimension less than 100nm. The properties achieved by nanocomposites will depend on the type of polymer, type of dispersed phase (filler), surface interaction between filler and polymer, and the production method. Nanofillers present many shapes and sizes, but they can be grouped in nanoparticles, nanotubes and nanoplates. Montmorillonite (MMT) is a clay that has been extensively studied to produce PP nanocomposites, due to its availability, high aspect ratio, high modulus and high cation exchange capacity, characteristics that result in composite with improved properties. Three different morphologies can be observed in PP/MMT nanocomposites: agglomerates (similar to the conventional composites); intercalated; or exfoliated. Among these morphologies, exfoliation is the most desirable and the hardest to be achieved in PP/MMT nanocomposites. Several methods have been used to produce PP nanocomposites. They can be grouped in three main groups: solution blending; melt processing; and in situ polymerization. In order to produce an exfoliated nanocomposite, some methods have assisted the exfoliation using supercritical fluids. Supercritical carbon dioxide is by far the most explored one. Polypropylene is a semi-crystalline polymer and its properties rely on amount of its crystallinity, which is related to its stereochemical configurations. Isotactic PP and syndiotactic PP result in a semi-crystalline polymer while atactic results in an amorphous polymer. Two catalyst systems can be used to produce isotactic PP: Metallocene and Ziegler-Natta (ZN). This research study was carried out in order to develop an appropriated process to produce PP/MMT nanocomposites with a high level of exfoliation using in situ polymerization assisted by supercritical propylene. The main idea is to use supercritical propylene to treat the montmorillonite before polymerization. In this process, the small molecules of propylene diffuse inside the clay galleries under supercritical conditions (high pressure and temperature) until reaching complete saturation. Once this saturation is reached the mixture of polypropylene and clay is catastrophically decompressed and fed into an autoclave reactor. The propylene polymerization reaction is them catalyzed by ZN catalyst. The pressure of the mixture of propylene-montmorillonite from the supercritical condition to the reactor autoclave decreased significantly, allowing propylene to expand and exfoliate the clay as it was fed in the reactor. Propylene in supercritical conditions was used in this works because it is the monomer for the subsequently polymerization and because its good properties at supercritical conditions. In order to evaluate the results the following methods were used: transmission electron microscopy (TEM) to investigate the nanoscale sample morphology and evaluate the clay exfoliation, X-ray diffraction (XRD) to determine interlamellar distance, d001, of the clay, differential scanning calorimetry (DSC) to determine the amount of crystallization of polymer and composite, thermogravimetric analysis (TGA) to determine composite clay content, scanning electron microscopy (SEM) to evaluate the morphology, and clay swelling test to evaluate the compatibility among various pairs clays-solvent. The first part of this work evaluated the interaction and swelling effects of different pairs of clay-solvent with or without sonication. This was necessary in order to choose the best clay to carry out the study. Four solvents with different polarity (chlorobenzene, toluene, cyclohexane and hexane) and eight clays (seven organically modified and one unmodified) were evaluated with or without sonication. Closite 15A and 93A presented the best results with different solvents and they were selected for further experiments. The experiments also showed that sonication improves the swelling of the clay. Initial screening of the polymerization reaction was carried out using two conditions: feeding supercritical propylene without clay and adding clay without the addition of supercritical fluid. The addition of supercritical propylene did not modify the morphology and properties of PP in comparison to the normal polymerization. The addition of Cloisite 15A or Cloisite 93A (pre-treated with toluene, not with supercritical propylene) produced nanocomposites. Although Cloisite 15A showed better results on the swelling tests, Cloisite 93A presented much better polymerization yield, therefore it was selected for further investigation using treatment with supercritical propylene. Cloisite93A was submitted to a treatment under four different supercritical propylene conditions (temperature and pressure) for thirty minutes. Each mixture was subsequently fed to the reactor through a catastrophic expansion inside an autoclave reactor running a propylene polymerization reaction. The results from XRD and TEM show a significant improvement on the exfoliation when treating the clay under supercritical propylene conditions followed by in situ polymerization, as compared to the in situ polymerization without treating the clay with supercritical propylene. In conclusion, the utilization of supercritical propylene has improved the dispersion of the clay at the nanoscale during the preparation of these nanocomposites by in situ polymerization.