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Ethylene and propylene are important chemical feedstocks for the production of polyethylene and polypropylene. Ethylene and propylene can be produced by various methods including steam cracking of liquefied natural gas (LNG), naphta or light olefin fractions. The methanol to olefin (MTO) process provides an alternative means of producing ethylene and propylene, where ZSM-5 is frequently used as catalyst due to its hydrophobicity, strong acidity, molecular sieve properties and low tendency towards coking, which makes ZSM-5 one the most popular zeolite catalysts in the industry. The oil crisis 1973 and the second oil crisis in 1978 caused the development of a commercial MTO process. Mobil Research and Development Corporation built a fixed-bed pilot plant to demonstrate the feasibility of the MTO as well as methanol-to-gasoline (MTG) process. When the oil price dropped again during the 1980’s, further developments of commercial processes were stopped for the time being. However, investigations on a bench scale are still pursued, and applications for patents are still submitted. During this study ZSM-5 was synthesized with a hydrothermal method, which produced agglomerated polycrystalline grains with characteristic ZSM-5 morphology and a Si/Al ratio of approximately 40. The synthesis time, synthesis temperature and aging time were varied while keeping all the other synthesis parameters constant in order to determine their influence on crystallite size. The synthesis time was varied between 12-72 hours, synthesis temperature was varied between 130-170°C and aging time between 30-90 minutes. Using SEM to determine crystal size, it was found that a variation in the aging time produced the largest crystallites (average of 21.6μm ± 10.8μm) while also having the largest influence on crystallite size followed by synthesis temperature (average of 13.1μm ± 4.9μm) and finally synthesis time (average of 5.7μm ± 0.4μm). In all cases XRD and SEM confirmed the formation of ZSM-5. To evaluate the as-synthesized ZSM-5 and compare it to a commercial ZSM-5 catalyst, Catalyst A using the MTO process, ZSM-5 was synthesized for 72 hours at 170°C with an aging time of 60 minutes before synthesis. The as-synthesized as well as Catalyst A’s agglomerated polycrystalline grains were sieved into three size fractions: smaller than 75μm, 75-150μm and 150-300μm. All six ZSM-5 fractions of ZSM-5 were used as catalysts for the MTO process in a fixed bed reactor at 400°C, atmospheric pressure and a 20wt% methanol to water feed. At 3.5 hours time on stream (TOS), the intermediate 75-150μm fraction had the highest light olefin selectivity for both the as-synthesized as well as Catalyst A, followed by the 150-300μm fraction and finally the smaller than 75μm fraction with the lowest light olefin selectivity. From this results it is clear that the as-synthesised ZSM-5 did not perform as well as Catalyst A. While the intercrystalline voids of the agglomerated ZSM-5 form second-order pores where self-diffusion is enhanced, the increased diffusional barriers created by the intercrystalline boundaries reduce the diffusion rate, promoting secondary reactions at the strong Brönsted acid sites thereby reducing ethylene and propylene selectivity. Coking reduces access to the Brönsted acid sites and plays a more influencial role for smaller crystallite sizes. Accordingly, the smaller than 75μm fraction had the lowest light olefin selectivity, while the 150-300μm fraction was probably least influenced by coking. The increased pathways for products and reagents in the 150-300μm fraction resulted in more secondary reactions taking place within this catalyst than the 75-150μm fraction explaining the superior performance of the 75-150μm fraction. Since the grain size determines the ratio of the external to the internal surface areas as well as the amount of intercrystalline boundaries in the catalyst, it follows that the catalytic activity and polycrystalline grain size ratio should actually be tailored when optimising the product distribution of the ZSM-5 catalysed MTO process. The as-synthesized ZSM-5 didn’t perform very well when compared to Catalyst A and modification of the synthesis method is recommended. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Pure fluorocarbon gases can be sold for up to 30 USD/kg, if they were manufactured locally. Due to the absence of local demand, South Africa at present has less than 0.3 % of the fluorochemical market and most fluoro–products used in the South African industry are currently imported. The depolymerisation of waste polytetrafluoroethylene (PTFE or Teflon) filters in a nitrogen plasma reactor results in the mixture of gases which includes N2, CF4 and C3F6. An existing challenge entails the separation of these gases, which is currently attained by an energy intensive cryogenic distillation process. Both the small energy requirements as well as the small process streams required, make a membrane separation an ideal alternative to the current distillation process. Based on our research groups existing expertise in the field of zeolite membranes, it was decided to investigate the separation capability of zeolite (MFI, NaA, NaY, and hydroxysodalite) coated tubular ceramic membranes for the separation of the above mentioned gases. The separation study was subdivided into adsorption studies as well as single and binary component studies. CxFy gas adsorption on MFI zeolites. Tetrafluoromethane (CF4) and hexafluoropropylene (C3F6) were adsorbed on zeolite ZSM–5 and silicalite–1 to help explain permeation results through zeolite membranes. According to the obtained data, the separation of CF4 and C3F6 would be possible using adsorption differences. The highest ideal selectivities (~ 15) were observed at higher temperatures (373 K). While the CF4 adsorption data did not fit any isotherm, the heat of adsorption for C3F6 adsorbed on ZSM–5 and silicalite–1 was calculated as –17 and –33 kJ/mol respectively. Single gas permeation. A composite ceramic membrane consisting of a ceramic support structure, a MFI intermediate zeolite layer and a Teflon AF 2400 top layer was developed for the separation of N2, CF4 and C3F6. The adsorption properties of the Teflon AF 2400 sealing layer was investigated. A theoretical selectivity, in terms of the molar amount of gas adsorbed, of 26 in favour of the C3F6 vs CF4 was calculated, while the N2 adsorption remained below the detection limit of the instrument. While the ideal N2/CF4 and N2/C3F6 selectivities for the MFI coated support were either near or below Knudsen, it was 5 and 8 respectively for the Teflon coated support. Ideal selectivities improved to 86 and 71 for N2/CF4 and N2/C3F6 when using the composite ceramic membrane, while CF4/C3F6 ideal selectivities ranged from 0.9 to 2, with C3F6 permeating faster though the composite ceramic membrane. Zeolite based membrane separation. Inorganic membranes (?–alumina support, NaA, NaY, hydroxysodalite, MFI) and composite membranes (Teflon layered ceramic and composite ceramic membrane) were synthesized and characterized using the non–condensable gases N2, CF4 and C3F6. For the inorganic membranes either near or below Knudsen selectivities were obtained during single gas studies, while higher selectivities were obtained for the composite membranes. Subsequently, the MFI, hydroxysodalite and both composite membranes were chosen for binary mixture separation studies. The membranes exhibited binary mixture permeances in the order Teflon layered ceramic > hydroxysodalite > MFI > composite ceramic, which was comparable to the single gas permeation results. The highest separation for N2/CF4 (4) and N2/C3F6 (2.4) was obtained with the composite ceramic membrane indicating that the Teflon layer was effective in sealing non–zeolitic pore in the intermediate zeolite layer. The aim of this project was met successfully by investigating a method of fluorocarbon gas separation by zeolite based membranes using various inorganic and composite membranes with single and binary mixtures. / Thesis (Ph.D. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Pure fluorocarbon gases can be sold for up to 30 USD/kg, if they were manufactured locally. Due to the absence of local demand, South Africa at present has less than 0.3 % of the fluorochemical market and most fluoro–products used in the South African industry are currently imported. The depolymerisation of waste polytetrafluoroethylene (PTFE or Teflon) filters in a nitrogen plasma reactor results in the mixture of gases which includes N2, CF4 and C3F6. An existing challenge entails the separation of these gases, which is currently attained by an energy intensive cryogenic distillation process. Both the small energy requirements as well as the small process streams required, make a membrane separation an ideal alternative to the current distillation process. Based on our research groups existing expertise in the field of zeolite membranes, it was decided to investigate the separation capability of zeolite (MFI, NaA, NaY, and hydroxysodalite) coated tubular ceramic membranes for the separation of the above mentioned gases. The separation study was subdivided into adsorption studies as well as single and binary component studies. CxFy gas adsorption on MFI zeolites. Tetrafluoromethane (CF4) and hexafluoropropylene (C3F6) were adsorbed on zeolite ZSM–5 and silicalite–1 to help explain permeation results through zeolite membranes. According to the obtained data, the separation of CF4 and C3F6 would be possible using adsorption differences. The highest ideal selectivities (~ 15) were observed at higher temperatures (373 K). While the CF4 adsorption data did not fit any isotherm, the heat of adsorption for C3F6 adsorbed on ZSM–5 and silicalite–1 was calculated as –17 and –33 kJ/mol respectively. Single gas permeation. A composite ceramic membrane consisting of a ceramic support structure, a MFI intermediate zeolite layer and a Teflon AF 2400 top layer was developed for the separation of N2, CF4 and C3F6. The adsorption properties of the Teflon AF 2400 sealing layer was investigated. A theoretical selectivity, in terms of the molar amount of gas adsorbed, of 26 in favour of the C3F6 vs CF4 was calculated, while the N2 adsorption remained below the detection limit of the instrument. While the ideal N2/CF4 and N2/C3F6 selectivities for the MFI coated support were either near or below Knudsen, it was 5 and 8 respectively for the Teflon coated support. Ideal selectivities improved to 86 and 71 for N2/CF4 and N2/C3F6 when using the composite ceramic membrane, while CF4/C3F6 ideal selectivities ranged from 0.9 to 2, with C3F6 permeating faster though the composite ceramic membrane. Zeolite based membrane separation. Inorganic membranes (?–alumina support, NaA, NaY, hydroxysodalite, MFI) and composite membranes (Teflon layered ceramic and composite ceramic membrane) were synthesized and characterized using the non–condensable gases N2, CF4 and C3F6. For the inorganic membranes either near or below Knudsen selectivities were obtained during single gas studies, while higher selectivities were obtained for the composite membranes. Subsequently, the MFI, hydroxysodalite and both composite membranes were chosen for binary mixture separation studies. The membranes exhibited binary mixture permeances in the order Teflon layered ceramic > hydroxysodalite > MFI > composite ceramic, which was comparable to the single gas permeation results. The highest separation for N2/CF4 (4) and N2/C3F6 (2.4) was obtained with the composite ceramic membrane indicating that the Teflon layer was effective in sealing non–zeolitic pore in the intermediate zeolite layer. The aim of this project was met successfully by investigating a method of fluorocarbon gas separation by zeolite based membranes using various inorganic and composite membranes with single and binary mixtures. / Thesis (Ph.D. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 272-288).

A combustão do carvão para a produção de energia elétrica tem como consequência a geração de cinzas, que é um dos maiores resíduos gerados no Brasil, em termos de volume (4.109 dm³/ano). Visando a minimização do impacto ambiental causado pelo mau descarte das cinzas, este trabalho teve como objetivo sintetizar e caracterizar zeólitas obtidas a partir de cinza de carvão e aplicar na agricultura como fertilizante potássico. Para isso a cinza utilizada foi obtida no combustor piloto de leito fluidizado operando com carvão da Mina do Leão/RS e empregada para sintetizar material zeolítico a partir do tratamento hidrotérmico alcalino. Foram realizados ensaios experimentais utilizando razão solução/cinzas constante em 6 L mg-1, variando a concentração de hidróxido de potássio (KOH) entre 3 e 5 M, a temperatura entre 100 e 150 ºC e o tempo de reação entre 24 e 72 h. O material sintetizado e a cinza foram caracterizados quanto a sua composição química, mineralógica, morfologia, área superficial específica e capacidade de troca catiônica. Através da caracterização foi observada a formação de duas fases zeolíticas, a chabazita-K e a merlinoíta. A partir da caracterização do material, foi escolhido um dos produtos zeolíticos obtidos para aplicação em solo, como fertilizante de potássio para o cultivo de trigo (Triticum aestivum L.). A condição experimental escolhida foi de 5 M a concentração da solução de KOH, temperatura de 150 ºC e tempo de reação de 24 h. Nesta condição obteve-se apenas uma fase zeolítica identificada, a zeólita merlinoíta, com uma área superficial de 23,37 m² g e uma capacidade de troca catiônica (CTC) de 2,62 meq g 1. Para fins de comparação foi utilizado o fertilizante comercial, cloreto de potássio (KCl), que contém em torno de 60 % de K2O. Foram realizados 35 ensaios experimentais em casa de vegetação da EMBRAPA, utilizando 7 tratamentos (3 doses diferentes de KCl e zeólita 50, 100 e 150 % da dose máxima recomendada e o solo não tratado (testemunha)) em 5 blocos aleatórios. Os experimentos na casa de vegetação foram concluídos com 59 dias de cultivo de trigo e submetidos às análises como determinação da produção de matéria seca da parte aérea e raízes das plantas e análise química do solo e tecido foliar. Verificou-se que a zeólita merlinoíta obtida a partir da cinza de carvão pode ser utilizada como fertilizante, pois teve um desempenho similar ao KCl no crescimento do trigo, não inibindo seu crescimento. Utilizando o tratamento com zeólita 100 % a produção de matéria seca da parte aérea foi de 1,07 ± 0,09 g e raízes 1,6 ± 0,23 g e na análise do tecido foliar teve uma absorção de 3,39 ± 0,31. / Coal combustion for electricity production results in the generation of ash, which is one of the main waste generated in Brazil in terms of volume. Intending the minimization of the environmental impact caused by poor disposal of ashes, this study aimed to synthesize and characterize zeolites obtained from coal ash and apply in agriculture as potassium fertilizer. For this purpose, coal fly ash was obtained from a fluidized bed pilot combustor operating with coal from Mina do Leão/RS and used to synthesize zeolitic material through the alkaline hydrothermal treatment. Experimental tests were performed using the ratio volume of solution/mass of coal fly ash constant at 6 mL mg -1, varying the concentration of potassium hydroxide (KOH) between 3 and 5 M, temperature between 100 and 150 °C and reaction time between 24 and 72 h. The synthesized and coal fly ash material was characterized by their chemical composition, mineralogy, morphology, specific surface area and cation exchange capacity. With the characterization, it was observed the formation of two phases zeolite K-chabazite and merlinoite. By the characterization of the material, it was chosen one of the zeolitic products obtained for application to soil as a potassium fertilizer for the cultivation of wheat (Triticum aestivum L.). The chosen experimental condition was 5 M KOH solution, temperature of 150 °C and 24 h time of reaction. At this condition, only one zeolitic phase was identified, zeolite merlinoite, with a surface area of 23.37 m² g a cation exchange capacity (CEC) of 2.62 meq g-1. For purposes of comparison, the tests in the soil were performed using also a commercial fertilizer, potassium chloride (KCl), containing about 60 % of K2O. A total of 35 experimental trials were carried out in a greenhouse at EMBRAPA, using 7 treatments in 5 random blocks: 50, 100 and 150 % of the maximum recommended dose for KCl and for zeolite and untreated soil (witness). The experiments in the greenhouse were concluded with 59 days of wheat cultivation. The plants were submitted to analysis for dry matter in aerial parts and roots determination. Likewise, soil and foliar tissue were submitted to chemical analysis. It was found that the zeolite Merlinoite obtained from the coal fly ash can be used as a fertilizer because it had a similar performance to KCl in the wheat growth. The treatment with 100% zeolite presented a dry matter production of 1.07 ± 0.09 g for aerial parts and 1.6 ± 0.23 g for roots. Also, the leaf tissue analysis showed a potassium absorption of 3.39 ± 0.31 % m/m in this treatment.

Synthèses et structures cristallines de nanocomposites polymère/zéolithe obtenus à haute pression. Les nanocomposites polymère/zéolithe forment une classe de matériaux constitués par une chaine de polymère à l’intérieur d’une zéolithe (matériau poreux dont la matrice est principalement formée par des tétraèdres SiO4). Le confinement élevé dans les micropores du matériau stabilise le polymère réactif et améliore les propriétés physiques (électrique, optique,...) tout en permettant leurs exploitations. L’insertion du monomère dans la zéolithe a lieu à haute pression en utilisant une cellule à enclumes de diamant et la polymérisation (suivie par spectroscopie infrarouge) est induite par la pression pour former le polymère confiné dans les pores. Aucune aide externe supplémentaire ou catalyseur n’est nécessaire. Quelques études précédentes ont montré la faisabilité de synthétiser des nanocomposites polymère/zéolithe à partir d’une zéolithe à porosité 3D. Ici on s’intéresse aux zéolithes hôtes à porosité 1D qui, contrairement aux pores tridimensionnels, peuvent induire la formation de chaines polymères linéaires disposant de propriétés directionnelles.Dans cette étude on a travaillé sur la synthèse de polyacétylène/TON et de polycarbonyle/TON, les chaines polymères s’adaptent étroitement avec les pores unidimensionnels de 5.7x4.6 Å de la TON (Theta-1, ZSM-22).La caractérisation par diffraction des rayons X a permis l’affinement de la structure des nanocomposites par méthode de Rietveld et la localisation du polymère grâce aux cartes de différence Fourier, ce qui permet de quantifier le nombre de chaines par maille. Il y en a quatre dans le cas du polyacétylène et une pour le polycarbonyle. Des calculs DFT ont été réalisés dans le cas de la TON, le polyacétylène/TON et le polycarbonyle/TON pour prévoir les propriétés physiques : modification d’un état isolant en semi-conducteur ou métallique. / Synthesis of linear polymer/zeolite nanocomposites under high pressurePolymer/zeolite nanocomposites form a class of materials constituted by polymer chains inside the pores of the zeolite (porous materials with a framework principally built up of SiO4 tetrahedra). Confinement in the microporous material allows reactive polymers to be stabilized, opening the way for the exploitation of their electrical and optical properties. The insertion of monomers in the zeolite takes place in a diamond anvil cell under high pressure, which induces polymerization (monitored by infrared spectroscopy) without any external assistance, avoiding the use of unwanted catalysts. The use of a zeolite host with unidirectional porosity, unlike previously investigated three-dimensional pore systems zeolites, can induce the formation of linear polymers with useful directional properties. In this work, we studied the synthesis of polyacetylene/TON and polycarbonyl/TON composites, as the linear polymers fit in the unidirectional 5.7x4.6 Å micropores of TON (Theta-1, ZSM-22).Characterization by X-ray diffraction allowed us to perform structure refinements of nanocomposites by the Rietveld method and to locate the polymer using difference Fourier maps, which also provide information on the number of chains by unit cell. There are 4 in the case of polyacetylene and 1 for polycarbonyl. DFT calculations were performed for TON, polyacetylene/TON and polycarbonyl/TON to predict their physical properties: transition from an insulating to a semi-conducting or metallic state.

A combustão do carvão para a produção de energia elétrica tem como consequência a geração de cinzas, que é um dos maiores resíduos gerados no Brasil, em termos de volume (4.109 dm³/ano). Visando a minimização do impacto ambiental causado pelo mau descarte das cinzas, este trabalho teve como objetivo sintetizar e caracterizar zeólitas obtidas a partir de cinza de carvão e aplicar na agricultura como fertilizante potássico. Para isso a cinza utilizada foi obtida no combustor piloto de leito fluidizado operando com carvão da Mina do Leão/RS e empregada para sintetizar material zeolítico a partir do tratamento hidrotérmico alcalino. Foram realizados ensaios experimentais utilizando razão solução/cinzas constante em 6 L mg-1, variando a concentração de hidróxido de potássio (KOH) entre 3 e 5 M, a temperatura entre 100 e 150 ºC e o tempo de reação entre 24 e 72 h. O material sintetizado e a cinza foram caracterizados quanto a sua composição química, mineralógica, morfologia, área superficial específica e capacidade de troca catiônica. Através da caracterização foi observada a formação de duas fases zeolíticas, a chabazita-K e a merlinoíta. A partir da caracterização do material, foi escolhido um dos produtos zeolíticos obtidos para aplicação em solo, como fertilizante de potássio para o cultivo de trigo (Triticum aestivum L.). A condição experimental escolhida foi de 5 M a concentração da solução de KOH, temperatura de 150 ºC e tempo de reação de 24 h. Nesta condição obteve-se apenas uma fase zeolítica identificada, a zeólita merlinoíta, com uma área superficial de 23,37 m² g e uma capacidade de troca catiônica (CTC) de 2,62 meq g 1. Para fins de comparação foi utilizado o fertilizante comercial, cloreto de potássio (KCl), que contém em torno de 60 % de K2O. Foram realizados 35 ensaios experimentais em casa de vegetação da EMBRAPA, utilizando 7 tratamentos (3 doses diferentes de KCl e zeólita 50, 100 e 150 % da dose máxima recomendada e o solo não tratado (testemunha)) em 5 blocos aleatórios. Os experimentos na casa de vegetação foram concluídos com 59 dias de cultivo de trigo e submetidos às análises como determinação da produção de matéria seca da parte aérea e raízes das plantas e análise química do solo e tecido foliar. Verificou-se que a zeólita merlinoíta obtida a partir da cinza de carvão pode ser utilizada como fertilizante, pois teve um desempenho similar ao KCl no crescimento do trigo, não inibindo seu crescimento. Utilizando o tratamento com zeólita 100 % a produção de matéria seca da parte aérea foi de 1,07 ± 0,09 g e raízes 1,6 ± 0,23 g e na análise do tecido foliar teve uma absorção de 3,39 ± 0,31. / Coal combustion for electricity production results in the generation of ash, which is one of the main waste generated in Brazil in terms of volume. Intending the minimization of the environmental impact caused by poor disposal of ashes, this study aimed to synthesize and characterize zeolites obtained from coal ash and apply in agriculture as potassium fertilizer. For this purpose, coal fly ash was obtained from a fluidized bed pilot combustor operating with coal from Mina do Leão/RS and used to synthesize zeolitic material through the alkaline hydrothermal treatment. Experimental tests were performed using the ratio volume of solution/mass of coal fly ash constant at 6 mL mg -1, varying the concentration of potassium hydroxide (KOH) between 3 and 5 M, temperature between 100 and 150 °C and reaction time between 24 and 72 h. The synthesized and coal fly ash material was characterized by their chemical composition, mineralogy, morphology, specific surface area and cation exchange capacity. With the characterization, it was observed the formation of two phases zeolite K-chabazite and merlinoite. By the characterization of the material, it was chosen one of the zeolitic products obtained for application to soil as a potassium fertilizer for the cultivation of wheat (Triticum aestivum L.). The chosen experimental condition was 5 M KOH solution, temperature of 150 °C and 24 h time of reaction. At this condition, only one zeolitic phase was identified, zeolite merlinoite, with a surface area of 23.37 m² g a cation exchange capacity (CEC) of 2.62 meq g-1. For purposes of comparison, the tests in the soil were performed using also a commercial fertilizer, potassium chloride (KCl), containing about 60 % of K2O. A total of 35 experimental trials were carried out in a greenhouse at EMBRAPA, using 7 treatments in 5 random blocks: 50, 100 and 150 % of the maximum recommended dose for KCl and for zeolite and untreated soil (witness). The experiments in the greenhouse were concluded with 59 days of wheat cultivation. The plants were submitted to analysis for dry matter in aerial parts and roots determination. Likewise, soil and foliar tissue were submitted to chemical analysis. It was found that the zeolite Merlinoite obtained from the coal fly ash can be used as a fertilizer because it had a similar performance to KCl in the wheat growth. The treatment with 100% zeolite presented a dry matter production of 1.07 ± 0.09 g for aerial parts and 1.6 ± 0.23 g for roots. Also, the leaf tissue analysis showed a potassium absorption of 3.39 ± 0.31 % m/m in this treatment.

Orientador: Antonio Carlos Luz Lisboa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-13T07:12:00Z (GMT). No. of bitstreams: 1 Alves_GiseledeSouza_M.pdf: 3224374 bytes, checksum: 5a827eb875ee4426d3974a21ead44074 (MD5) Previous issue date: 2009 / Resumo: As zeólitas são materiais cristalinos porosos encontrados sob forma natural ou sintética com alto poder adsorvente. O estudo deste material como adsorvente industrial foi iniciado em meados dos anos 50. O campo de aplicações das zeólitas é vasto. Podemos citar seu uso como adsorventes para purificação de gases e líquidos, como catalisadores para refino de petróleo e na síntese de produtos orgânicos. O objetivo deste trabalho consiste da caracterização e simulação do processo de adsorção de nitrogênio de uma zeólita. Análises físicas e químicas foram feitas para a caracterização deste material. Pode-se concluir que a zeólita sob a forma de grãos é higroscópica, similar ao tipo faujasita e possui uma grande área superficial 593 m2 g-1. A partir desta última análise (BET), o modelo sofreu uma adaptação para Langmuir para simular o processo de adsorção de nitrogênio pela zeólita. A simulação de uma unidade de separação de gases (nitrogênio e oxigênio) a partir do ar foi realizada através do processo PSA (pressure-swing adsorption) com o auxílio do software MATLAB. Esse processo consiste da adsorção seletiva de gases por meio dos poros do sólido. O programa mostrou que o processo de adsorção de nitrogênio é rápido com duração de segundos devido à afinidade do gás pelo material e ao tipo de processo envolvido. / Abstract: Zeolites are crystalline porous materials found naturally or synthetically manufactured with high adsorbent power. The study of this material as an industrial adsorbent began in the mid 50's. The fields of zeolite application are rather wide. Zeolites have been used as adsorbents for purification of gases and liquids, as catalysts for petroleum refinig and for synthesis of organic products. The objective of this work was to characterize a sample of zeolite X and to simulate a nitrogen adsorption pilot unit. Physical and chemical analyses were made for the characterization of this material. Its possible to conclude with characterization data that zeolite is higroscopic, similar to faujasite type, and large superficial area 593 m2 g-1. With this last analysis (BET), the model was adapted to langmuir in order to simulate the nitrogen adsorption process onto zeolite. The simulation of a gas separation unity (nitrogen and oxygen) from air was realized through PSA process (pressure-swing adsorption) using the MATLAB software. This process consists selective adsorption of gases through the porous of solid. The program showed that nitrogem adsorption process is fast with seconds of duration due to afinity of the gas for zeolite and the kind of the process involved. / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Os BTEX (benzeno, tolueno, etilbenzeno e xilenos) constituem preocupaÃÃo particular pela sua toxicidade, sendo formados no meio ambiente pela oxidaÃÃo incompleta dos combustÃveis fÃsseis, os quais contaminam a atmosfera; pelo descarte de efluentes industriais, por derrames durante o transporte e por vazamentos em postos de combustÃveis, contaminando o solo e a Ãgua, e acumulando-se, principalmente, nas Ãguas subterrÃneas. Tecnologias convencionais e avanÃadas vÃm sendo utilizadas na tentativa de tratamento e remediaÃÃo de Ãreas contaminadas por BTEX. As zeÃlitas englobam grande nÃmero de minerais naturais e sintÃticos que apresentam caracterÃsticas comuns. O grande potencial de aplicaÃÃo das zeÃlitas sintÃticas na Ãrea ambiental à mundialmente comprovado. Neste trabalho, avaliou-se a modificaÃÃo superficial da zeÃlita sintÃtica Y com surfactante HDTMA-Br e sua aplicaÃÃo para a remoÃÃo de BTEX de amostras aquosa. Foi realizado estudo da capacidade de troca catiÃnica (CTC) da zeÃlita e em seguida foram realizadas trÃs modificaÃÃes da zeÃlita com surfactante, correspondente a 50% da CTC, 100% da CTC e 200% da CTC. A zeÃlita sintÃtica e as modificadas foram submetidas a teste de adsorÃÃo dos BTEX. Os resultados mostraram que dentre as zeÃlitas modificadas, a ZMS-100 se mostrou mais eficiente na remoÃÃo dos BTEX. Este material foi utilizado para estudo de cinÃtica e isoterma de adsorÃÃo. O estudo de cinÃtica indicou que o equilÃbrio de adsorÃÃo multicomponente foi atingido em 6 horas e segue cinÃtica de pseudo-segunda ordem. Foram utilizados os modelos de Langmuir, Freundlich, Redlich-Peterson e Temkin para avaliar o mecanismo de adsorÃÃo dos BTEX pela ZMS-100. O modelo de Temkin foi adequado para todos os BTEX em um sistema multicomponente e os valores de capacidade de adsorÃÃo mÃxima foram de 175, 32; 164,58; 162,22; 152,41; 150,42 mg/g para m,p-xilenos, o-xileno, etilbenzeno, tolueno e benzeno, respectivamente. Foi realizado estudo de ciclos de regeneraÃÃo do material em batelada e os resultados mostraram que o adsorvente sà pode ser utilizado para um ciclo de adsorÃÃo na remoÃÃo do benzeno, para os outros componentes à possÃvel realizar quatro ciclos de adsorÃÃo. / BTEX (benzene, toluene, ethylbenzene and xylenes) are organic compounds of particular concern due to their toxicity. BTEX occur in the environment as products of incomplete oxidation of fossil fuels, thus polluting the atmosphere. Also, the disposal of industrial effluents, oil spills, and fuels leaks at gas stations are sources of BTEX contamination in soil and water, resulting in their accumulation mainly in groundwater. Conventional and advanced technologies have been used for treatment and remediation of contaminated areas. Zeolites include many natural and synthetic minerals that have characteristics in common. The potential application of synthetic zeolites in the environmental field has been reported worldwide. In this work, surface modification of synthetic zeolite Y by Hexadecyltrimethylammonium (HDTMA-Br) was studied, as well as its application for removal of BTEX from aqueous solution. The zeolite cation exchange capacity (CEC) was evaluated and three modifications of the zeolite with surfactant HDTMA-Br were carried out, with results corresponding to 50%, 100%, and 200% of CEC. The results of BTEX adsorption experiments onto both synthetic and modified zeolites showed that the ZMS-100 was the most efficient modified zeolite for BTEX removal. Adsorption isotherms and kinetics study of this material were carried out. Kinetics study indicated that multicomponent adsorption equilibrium was reached in 6 hours and followed pseudo-second order kinetics. Langmuir, Freundlich, Redlich-Peterson and Temkin models were used to evaluate the adsorption capacity of BTEX by ZMS-100. Temkin model was found to be suitable all BTEX in a multicomponent system, and maximum adsorption capacities of 175, 32, 164.58, 162.22, 152.41, and 150.42 mg g-1 were observed for m-xylene, p-xylene, o-xylene, ethylbenzene, toluene and benzene, respectively. Regeneration cycles of the zeolite were also performed and the results showed that the adsorbent can be used only for one adsorption cycle for the removal of benzene, while for the other BTEX up to four regeneration cycles can be achieved.