This dissertation research aimed at evaluating a fly ash zeolite (FAZ) catalyst support for use in heterogeneous catalytic processes. Gas phase Fischer-Tropsch Synthesis (FTS) over a fixed-bed of the prepared catalyst/FAZ support was identified as an appropriate process for evaluation, by comparison with commercial catalyst supports (silica, alumina, and 13X). Fly ash, obtained from the Wabash River Generating Station, was first characterized using XRD, SEM/EDS, particle size, and nitrogen sorption techniques. Then, a parametric study of a two-step alkali fusion/hydrothermal treatment process for converting fly ash to zeolite frameworks was performed by varying the alkali fusion agent, agent:flyash ratio, fusion temperature, fused ash/water solution, aging time, and crystallization time. The optimal conditions for each were determined to be NaOH, 1.4 g NaOH: 1 g fly ash, 550 °C, 200 g/L, 12 hours, and 48 hours. This robust process was applied to the fly ash to obtain a faujasitic zeolite structure with increased crystallinity (40 %) and surface area (434 m2/g). Following the modification of fly ash to FAZ, ion exchange of H+ for Na+ and cobalt incipient wetness impregnation were used to prepare a FTS catalyst. FTS was performed on the catalysts at 250 - 300 °C, 300 psi, and with a syngas ratio H2:CO = 2. The HFAZ catalyst support loaded with 11 wt% cobalt resulted in a 75 % carbon selectivity for C5 - C18 hydrocarbons, while methane and carbon dioxide were limited to 13 and 1 %, respectively. Catalyst characterization was performed by XRD, N2 sorption, TPR, and oxygen pulse titration to provide insight to the behavior of each catalyst. Overall, the HFAZ compared well with silica and 13X supports, and far exceeded the performance of the alumina support under the tested conditions. The successful completion of this research could add value to an underutilized waste product of coal combustion, in the form of catalyst supports in heterogeneous catalytic processes.

The primary aim of this thesis is to investigate and quantify the self-diffusion processes of gaseous molecules adsorbed in industrially relevant microporous zeolite materials using Pulsed Field Gradient Nuclear Magnetic Resonance (PFG NMR). The main body of this work involves the use of weakly adsorbing hydrocarbon gases (CH4, C2H6 and C3H¬8) adsorbed in a large pore β-zeolite structure. This thesis describes the development of a solely PFG NMR based technique for measuring the molecular displacements of these species at varying length-scales. This enabled the characterisation of self-diffusion regimes across zeolite beds and within individual zeolite crystallites. The characterisation of self-diffusion processes within single zeolite crystallites was critical with respect to accounting for quantitative discrepancies reported in the literature between PFG NMR and alternative measurement techniques. This approach also revealed that the transitions in the Gaussian probability distributions of the molecular displacements in the aforementioned self-diffusion regimes could be recorded by varying the experimental time-scale for observing molecular motion. This technique was extended to characterise the self-diffusion processes of the aforementioned hydrocarbons in small (≤ 1 μm) and large (≥ 15 μm) zeolite crystallites to investigate the dependence of this technique on zeolite geometry. It was found that the self-diffusion coefficients within single crystallites were in good agreement with one another, despite their differing crystallite geometries. This technique was subsequently used to study the self-diffusion behaviour of two-component hydrocarbon gaseous mixtures with differing sorption properties co-adsorbed in β-zeolite. Excellent chemical shift resolution was obtained for chemically similar species using NMR spectroscopy, relaxometry and diffusometry without the use of Magic Angle Spinning (MAS). This connoted that conventional PFG NMR is capable of precisely characterising individual species in real world multi-component systems. This thesis also describes the self-diffusion of ammonia in small pore chabazite structures, which are typically used in Selective Catalytic Reduction (SCR) processes. It was found that the self-diffusion coefficient of this strongly adsorbing species increased with molecular loading up to a certain point. This peculiar behaviour implied a strong concentration and inter-molecular dependence within the zeolite structure. Lastly, the techniques which were developed at high magnetic field strengths (300 MHz) were transferred to a lower field strength (43 MHz) benchtop spectrometer at the Johnson Matthey Technology Centre (JMTC). This describes the first characterisation of mass transport behaviour of weakly interacting sorbates in zeolites using a portable spectrometer. This presents an excellent opportunity for future off-line molecular displacement measurements to be made for complex and real-world systems in a matter of minutes.

Computational simulations using empirical force fields are frequently used to model guest-host interactions in porous periodic systems, where the interaction energy is broken into electrostatic and van der Waals contributions. While simulations such as these have been instrumental in progressing our understanding of neutral periodic systems, limitations in deriving partial atomic charges has largely contributed to the difficulty in modeling charged periodic frameworks. However, many nanoporous materials possess frameworks that have a net charge, which is balanced by counter-ions that intercalate through the pores. For example, virtually all zeolites used in practice contain a proportion of Al, which bestows the framework with a negative charge. In this respect, we investigate two methods for the generation of partial atomic charges in periodic systems having a net framework charge. First, we examine the validity of generating REPEAT electrostatic potential fitted charges derived from periodic electronic structure calculations, where a constant background charge is added to neutralize the net charge on the framework without adding neutralizing counter-ions. The second method we explore is the split charge equilibration (SQE) method for very rapid charge generation. In its original formulation, the SQE model cannot be applied to systems with a net charge. In this work, we reformulate the SQE method for non-neutral systems to be treated. The new SQE model, which we call SQEAB, was shown to give equivalent results to those of the original SQE model for neutral systems. For charged frameworks, the model was shown to provide partial atomic charges in good agreement with the DFT derived REPEAT method. Taking advantage of that work, we next focus on the development of a force field for modeling CO2, N2, and CH4 gas adsorption in both neutral and charged zeolites, which we call the AMP (Aluminosilicate MicroPorous) force field. Commonly, the electrostatic potential of zeolites is represented through the use of generic charges, where every atom of the same type in the framework is assigned the same atomic charge. Though this model is fast, it fails to account for structural differences between framework geometries. In this work, we have optimized a set of SQEAB parameters to reproduce the DFT derived electrostatic potentials (ESPs) of a structurally representative set of both neutral and charged zeolite frameworks. Comparing with other popular models, the SQEAB-AMP charges are shown to better reproduce the QM ESP by more than 30%, on average. Gas uptakes obtained using SQEAB AMP charges were found to be within 5% of those obtained using DFT derived charges. We have further optimized a set of Lennard-Jones parameters to be combined the SQEAB-AMP charges that reproduce experimental uptake data in zeolites.

Made available in DSpace on 2014-10-09T12:54:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:12Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Ana Paula Ribeiro Povinelli (paulinha-pol@hotmail.com) on 2017-07-26T19:45:49Z No. of bitstreams: 1 Dissertacao_Ana_FINAL.pdf: 3540005 bytes, checksum: d82bc4d015af48c2fda01a4eff17975f (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-07-26T20:13:00Z (GMT) No. of bitstreams: 1 povinelli_apr_me_sjrp.pdf: 3540005 bytes, checksum: d82bc4d015af48c2fda01a4eff17975f (MD5) / Made available in DSpace on 2017-07-26T20:13:00Z (GMT). No. of bitstreams: 1 povinelli_apr_me_sjrp.pdf: 3540005 bytes, checksum: d82bc4d015af48c2fda01a4eff17975f (MD5) Previous issue date: 2017-07-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A substituição da fonte de calor convencional por fontes de radiação de micro-ondas vem sendo bastante explorada na área de síntese de sólidos inorgânicos devido ao seu eficaz mecanismo de entrega de energia que proporciona rapidez no processo de síntese além de gerar materiais com maior pureza de fase. Neste contexto, o presente trabalho visou a otimização das sínteses das zeólitas NaA e NaX utilizando radiação de micro-ondas e a caracterização utilizando as técnicas de DRX (Difração de Raios-X), MEV (Microscopia eletrônica de varredura) e EDS (Energy-dispersive X-Ray Spectrocopy). As zeólitas foram sintetizadas e caracterizadas visando a posterior aplicação como agentes hemostáticos coagulantes. Os experimentos mostraram que a zeólita NaA obtida utilizando radiação de micro-ondas durante 30 minutos possui as mesmas características da zeólita NaA sintetizada utilizando aquecimento convencional por 48 horas, indicando que com a utilização da radiação foi possível alcançar uma redução de 98,96% no tempo de síntese. A aplicação de aquecimento de micro-ondas na síntese da zeólita NaX também provou decréscimo no tempo de síntese quando comparado ao aquecimento convencional, entretanto os dados de microscopia eletrônica revelaram que a zeólita sintetizada pelo aquecimento de micro-ondas estavam aglomeradas. A fim de tornar o coloide mais estável, foi feita a estabilização estérica dessas zeólitas através da esterificação dos grupos silanóis presentes na superfície das mesmas utilizando 1-propanol e 1-butanol. Os dados MEV mostraram que a modificação foi eficiente e que a dispersão foi estabilizada após o tratamento. Em relação ao potencial das zeólitas como agentes hemostáticos coagulantes, os dados de tromboelastografia mostraram que as zeólitas NaA e NaX provocaram diminuição no tempo necessário para a formação e crescimento do coágulo porém, dentre todas as zeólitas avaliadas, a zeólita NaX sintetizada por aquecimento convencional se destacou como agente hemostático apresentando uma redução de 6 minutos no tempo de formação do coágulo. / Conventional heat source has been substituted by microwave heat source in many chemical reactions including inorganic solids syntheses, since the microwave heat source can accelerate the energy delivery. Because of that, it is possible to obtain syntheses in a shorter time and materials obtained have a higher purity phases. Zeolites were synthesized and characterized aiming to zeolites hemostatic agents application. In this context, this work aimed to synthesize NaA and NaX zeolites employing microwave radiation and to characterize materials obtained using XRD (X-Ray Diffraction), SEM(Scanning Electron Microscopy) and EDS (Energy-dispersive X-Ray Spectrocopy) techniques. NaA zeolite obtained by microwave radiation after 30 minutes showed the same characteristics of NaA zeolite obtained by conventional heat after 48 hours. In other words, the substitution of the heat source reduced 98,96% the synthesis time. Related to NaX zeolite, microwave radiation also reduced the synthesis time, however SEM and EDS data showed some differences between NaX obtained by conventional and NaX obtained by microwave heating. It was also observed by SEM that the colloidal system of NaX obtained by microwave radiation has agglomerated. In order to stabilize sterically the colloid, NaX surface was functionalized by silanols groups esterification using 1-propanol and 1-butanol alcohols. SEM data showed that steric stabilization was successful. Regarding the potential of the zeolites as hemostatic coagulating agents, thromboelastography data showed that NaA and NaX zeolites caused decrease in time required for clot formation and growth. However, among all the zeolites evaluated, NaX zeolite synthesized by conventional heating had better results as a hemostatic agent showing a reduction of 6 minutes in clot formation time. / CNPq: 135582/2015-6

Made available in DSpace on 2014-10-09T12:54:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:12Z (GMT). No. of bitstreams: 0 / As cinzas de carvão podem ser convertidas em produtos zeolíticos por tratamento hidrotérmico alcalino. No presente estudo, a capacidade de zeólitas sintetizadas a partir de cinzas de carvão brasileiras (6 amostras da cinza volante do filtro de mangas e 6 amostras da cinza leve do filtro ciclone) na remoção de Zn2+ e Cd2+ de soluções aquosas foi investigada. O tempo de equilíbrio alcançado pela maioria das zeólitas foi de 24 horas. Os dados de equilíbrio obtidos se ajustaram à isoterma de adsorção de Langmuir. As capacidades de troca catiônica máximas estavam entre 25,9 e 39,5 mg g-1 para o Zn2+ e entre 49,5 e 72,3 mg g-1 para o Cd2+. A zeólita sintética (ZM1) apresentou área superficial no valor de 66,38 m2 g-1, baixa relação Si/Al (1,65) e a formação de zeólitas sodalita e faujasita, que contribuíram para seu melhor desempenho. Estudos de adsorção de íons metálicos com a ZM1 indicaram a seguinte seqüência de seletividade: Pb2+ > Cd2+ > Cu2+ > Zn2+ > Ni2+. Para a ZM1, a maior porcentagem de remoção de Zn2+ e Cd2+ foi obtida em pH 5 e a recuperação de metais foi efetivamente realizada com solução de NaCl 2 mol L-1. Comparou-se o desempenho das zeólitas sintetizadas a partir das cinzas de carvão com as zeólitas sintéticas comerciais, bem como o custo de ambas. As zeólitas sintetizadas com cinza de carvão apresentaram melhor eficiência de retenção do zinco e do cádmio do que as zeólitas comerciais. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Orientadores: Bernardino Ribeiro de Figueiredo, Romulo Simões Angelica / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-11T02:16:06Z (GMT). No. of bitstreams: 1 DalBosco_SandraMaria_M.pdf: 475525 bytes, checksum: d539864c9285d28b195d0358b87cc60e (MD5) Previous issue date: 2007 / Resumo: Além do enriquecimento de metais pesados em águas subterrâneas devido aos processos biogeoquímicos que ocorrem na natureza, as atividades industriais, agrícolas e outras têm contribuído para um aumento significativo nas concentrações de íons metálicos em águas, representando importantes fontes de contaminação dos corpos aquáticos e provocando preocupações principalmente quando se considera que tais íons podem ser disseminados via cadeia alimentar. O cromo, objeto deste estudo, é um dos metais potencialmente tóxicos encontrados em água subterrânea. Em águas naturais, o cromo pode ocorrer nas formas químicas Cr(III) e Cr(VI), estáveis em meio aeróbio. A ingestão de águas contaminadas com Cr(VI) pode causar vários danos à saúde como dermatite alérgica, ulcerações na pele, perfurações do septo nasal e câncer. Embora o Cr(III) seja reconhecido como menos móvel e menos tóxico que o Cr(VI), vários processos podem induzir o intercâmbio entre as espécies Cr(VI) e Cr(III) revelando a importância de prevenir concentrações excessivas de cromo em água. Neste trabalho, foi avaliado o comportamento de um arenito contendo zeólita, proveniente da Formação Corda, Bacia do Parnaíba, como trocador catiônico, visando à remoção de cromo de soluções aquosas. A pesquisa restringiu-se ao Cr(III) que, em solução aquosa, ocorre como um cátion, ao contrário do Cr(VI), que ocorre como ânion em solução, necessitando, por isso, de um trocador aniônico ou de uma pré-redução a Cr(III) para ser removido de soluções aquosas. Para os testes de troca iônica, foram utilizadas duas frações granulométricas do material, <250 µm (Zeo60) e <177 µm (Zeo80). A presença de estilbita como a espécie de zeólita predominante nas amostras foi indicada por difratometria de raios X. Os testes foram realizados com 1,0 g da amostra em 60 mL de solução contendo Cr(III) em concentrações conhecidas, submetidos à agitação constante até que a reação atingisse o equilíbrio. O equilíbrio nas reações de troca iônica foi alcançado rapidamente, em cerca de 1 hora para Zeo80 e de 4 horas para Zeo60. A concentração de cromo presente na solução após as reações foi determinada por espectrometria de absorção atômica. Foi demonstrada uma eficiência de 99 % na remoção de cromo de uma solução contendo 10 mg L-1 do metal em ambas as amostras. Nos testes realizados a 25, 40 e 60 ºC, a temperatura não demonstrou influência significativa na remoção do metal de solução. A influência do pH da solução foi avaliada no intervalo de 3,0 a 5,0 e um aumento significativo na remoção de cromo foi registrado em pH = 5 atingindo-se o mesmo total de cromo removido da solução para ambas as amostras. Os testes de dessorção revelaram uma elevada capacidade de regeneração de ambas as amostras: cerca de 90 % do cromo adsorvido na amostra foi liberado para a solução no caso da Zeo60, e 93 % no caso da Zeo80. Os resultados obtidos indicam a possibilidade do uso do material na remoção do cromo de efluentes e água contaminada. Além disso, o fato de se tratarem de amostras naturais, não modificadas e, portanto de baixo custo, encontradas em depósitos sedimentares, ou seja, de fácil obtenção, pode também ser um estímulo para contínuos estudos visando viabilizar a sua aplicação em larga escala / Abstract: Heavy metal enrichment in groundwater can be due to natural biogeochemistry processes as well as to industrial, agricultural and other activities that contribute significantly to groundwater contamination and, hence, giving rise to great concerns when considering the extension of ionic dispersion via food chain. Chromium, object of the present study, is one of these potential toxic metals found in groundwater. In natural water, chromium may be found in the Cr(III) and Cr(VI) chemical forms, stable in aerobic environment. Ingestion of contaminated water for Cr(VI) can lead to health problems such as allergic dermatitis, ulcerate of skin, nasal septum perforation and cancer. Despite of Cr(III) being recognized as less mobile and less toxic than Cr(VI), several natural processes can induce interchange between Cr(VI) and Cr(III) species, revealing the importance of preventing excessive chromium concentration in water. In the present study, zeolite-bearing sandstone, originated from the Parnaiba Paleozoic basin, northeastern Brazil, was tested as a cationic exchange material for chromium removal from aqueous solution. Two grain-size fractions <250 µm (Zeo60) and <177µm (Zeo80) were used. Essays were restricted to removal of Cr(III) species which occur cationic species in aqueous solution whereas the negative charged Cr(VI) species were not considered in the present study. Tests were performed using 1.0 g of each sample in 60 mL of solution with known initial Cr(III) concentrations kept agitated until equilibrium was attained (1 hour for Zeo80 and ca. 4 hours for Zeo60). After reactions, the final Cr concentrations were determined by Atomic Absorption Spectrometry. The material response to ionic exchange showed to be very efficient for Cr(III) removal from solution at around 99 % when the cation initial concentration was 10 mg L-1. Tests were carried out at 25, 40 and 60 ºC but the influence of temperature was not significant. The influence of solution pH was observed in the interval from 3.0 to 5.0 and an increase of Cr removal occurred at pH = 5 of equal amounts of chromium for both samples. The material easily regenerates after the desorption tests: ca. 90 % of adsorbed Cr was released from the Zeo60 sample and ca. 93 % from the Zeo80 sample. All the results support the recommendation of using this material for chromium removal from contaminated water and effluents. In addition, this low-cost material is natural, easily accessed from sedimentary deposits and does not need any previous treatment which can be a stimulus for continuing studies oriented to consider its application in large scale / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

No description available.

One problem of intensive fish culture systems is the progressive build-up of toxic wastes such as ammonia. The possibility of improving aquaculture water quality using two kinds of zeolite is discussed. Zeolites are alumino-silicates whose framework allows them to exchange cations. Ion exchange has been demonstrated to be competitive with other methods of ammonia removal due to the high selectivity for ammonia exhibited by zeolite materials. In this study an unknown Zambian zeolite (identified as laumontite by X-ray diffraction techniques) and Pratley clinoptilolite (a South African zeolite) were tested under laboratory conditions and in a fresh water recirculating system. Ammonia cation exchange capacities (CEC) and suitable application rates for efficient water treatment were determined using the batch and column ion exchange procedures. Estimated ammonia uptake, the most important criterion used to assess performance of zeolite filters was strongly influenced by zeolite type, particle size, pre-treatment, regeneration and ion exchange method used. Statistical analysis showed significant differences in average ammonia CEC values between clinoptilolite (14.94 mg g⁻¹) and laumontite (2.77 mg g⁻¹), with the former displaying a higher Na⁺ ® NH₄⁺ exchange rate especially in the early reaction stages. This difference accords with the higher purity of clinoptilolite, 47% as opposed to 4.7% for laumontite, which makes it a better zeolite for ammonium removal. CEC increased linearly as particle size of the clinoptilolite was reduced resulting in a linear regression model (y = 18.29 – 3.704 x; r² = 74%). Pre-treatment of clinoptilolite using 1N NaCl significantly improved the ammonia CEC of clinoptilolite. Overall performance of both the batch and column methods achieved after regeneration (18.3 mg g⁻¹) was 25% higher than the estimated CEC values (13.0 mg g⁻¹) for the unregenerated samples of clinoptilolite. Comparison of CEC estimates using Pratley clinoptilolite, showed that average batch CEC estimates were significantly lower than the column method estimates. The average ammonia CEC values estimated in a fresh water recirculating system (5.80 mg g⁻¹ and 4.12 mg g⁻¹ for the 0.7-1.0 and 1.0-1.4 mm particle sizes, respectively) were significantly lower than the column and batch estimates for the same particle sizes (P < 0.05). Some nitrite (NO₂) and nitrate (NO3) build up was experienced probably due to the growth of autotrophs in the filters. Mass balance of nitrogen (N) for the three treatments of the fish trial (0.7-1.0 mm, 1.0-1.4 mm and the control treatment that had no zeolite in the filter) indicated that less that 10% of the N was retained for growth. It was found that 60% of the NH₄-N present associated with the soluble N was available for absorption by the zeolite filter or biological nitrification and that a total of approximately 22% of NH₄-N available was absorbed by clinoptilolite. The results indicate that the rate of nitrification can be deductively estimated by allowing a zeolite filter to become a biological filter. It is concluded that water treatment by ion exchange using natural zeolites, provides a reliable and efficient method for ammonia removal and appears to be a viable supplementary water treatment method for fresh water systems.

Silicalite-1 crystals and hollow tube structures were synthesized and functionalized with amine and sulfur containing groups. The adsorption behavior of metal ions (Pb2+, CrO4-) in aqueous solution was investigated on nanocrystalline zeolites functionalized with amines and thiols. Nanocrystalline zeolites with a diameter of 30-50 nm and external surface areas around 100 m2/g were functionalized with 3-aminopropyltriethoxysilane (3-APTES) and 3-mercaptopropyltrimethoxysilane (3-MPTMS). The materials were characterized by 29Si magic angle spinning nuclear magnetic resonance spectroscopy and x-ray diffraction. The adsorption of metal ions from aqueous solutions of Pb (NO3)2 and Na2Cr2O7 was measured by inductively coupled plasma-atomic emission spectroscopy. The effects of various conditions such as pH and concentration were studied to optimize adsorption. Adsorption on functionalized mesoporous silica (MS) was conducted for comparison to the functionalized zeolites. Magnetic zeolite/iron composites were prepared using nanoscale and commercial faujasite zeolites. The composites were functionalized with amine groups to facilitate chromate adsorption under acidic conditions. The materials were characterized using nitrogen adsorption, scanning electron microscopy, thermogravametric analysis, FTIR spectroscopy, and Mossbauer spectroscopy. The adsorption of chromium was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP/OES) to monitor solution chromium quantitatively. The removal of the composites with a magnet was demonstrated. The materials were then evaluated for the adsorption of Cr6+ using ICP-OES to detect chromium. Iron containing zeolite composites were prepared using nanoscale faujasite zeolites. The composites were functionalized with amine groups and Fe ions to facilitate arsenate(As V) adsorption under a variety of pH conditions. The materials were characterized using nitrogen adsorption, X-ray diffraction, thermogravametric analysis and FTIR spectroscopy, and Mossbauer spectroscopy. The adsorption of arsenic was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP/OES) to monitor solution concentration quantitatively. The removal of the composites with a magnet was demonstrated. Kinetics and pH dependence of the adsorption were studied.