In dieser Dissertation wurden Verfahren für die konvergente Synthese von Peptide entwickelt. Für die erweiterte native chemische Ligation kamen bisher raumbeanspruchende Auxiliare zum Einsatz, die anspruchsvolle Ligationen behinderten. Zudem waren die drastischen säure-basierten Abspaltbedinungen mit vielen post-translationalen Modifikationen nicht vereinbar. In dieser Arbeit wurde ein neuartiges Auxiliargerüst mit geringerem Raumanspruch untersucht, dass eine erheblich mildere Abspaltung unter basischen Bedingungen ermöglichte. Dazu wurde ein kleiner Elektronenakzeptorsubsituent eingeführt, durch den nach der Ligation eine das Zielpeptid freisetzende Eliminierungsreaktion induziert werden konnte. Weiterhin konnte die Verwendung des kommerziell verfügbaren Penicillamins als Vorläufer in der Ligations-Entschwefelungs-Strategie demonstriert werden. Abschließend wurde die Ligation mit sequenz-internem Cystein untersucht. Hierbei zeigte sich, dass Peptide mit Cystein in einer bestimmten Position bevorzugt in thioester-basierten Kondensationen reagierten. / In this thesis approaches for convergent synthesis of peptides have been developed. In the extended native chemical ligation so far space demanding auxiliaries encumbered challenging condensations. Furthermore the required drastic acidolytic cleavage conditions were furthermore incompatible with many post-translational modifications. In the thesis a nouvelle less space demanding scaffold was scrutinized which allowed a milder basic cleavage. Therefore a small electron-accepting substituent was introduced that enabled the induction of an elimination reaction liberating the target peptide after the peptide ligation had taken place. Furthermore the applicability of the commercially available penicillamine as precursor of valine in the ligation-desulfurization strategy could be demonstrated. Finally the ligation with sequence internal cysteines was scrutinized. Herein it could be shown that certain peptides with cysteine in a distinctive position of the sequence preferable reacted in thioester-based condensation reactions.

Made available in DSpace on 2014-12-17T15:41:53Z (GMT). No. of bitstreams: 1 JoseABLRA_DISSERT.pdf: 2347923 bytes, checksum: 6e0dcb6d004a500ef5b9305459cc4e95 (MD5) Previous issue date: 2010-05-27 / Mesoporous molecular sieves of MCM-41 type are considered as promising support for metal in the refining processes of petroleum-based materials as catalysts and adsorbents for environmental protection. In this work, mesoporous molecular sieves MCM-41 were modified with different rare earth ions (La, Eu e Yb) for the obtaining nanostrutured materials with catalytic properties. The catalysts were synthesized by the hydrothermal method at 100oC for 120 h, presenting, all the samples, in the gel of synthesis molar ratio Si/Ln = 50. The obtained materials after calcination at 500oC for 2 h were characterized by XRD, surface area BET, TG/DTG, FTIR, and hydrothermal stability at 700?C. The XRD analysis of the catalysts indicated that the materials containing rare earth presented characteristic hexagonal structure of the mesoporous materials of the type MCM-41. The TG curves showed that the decomposition of the structural template occurs in the materials at temperatures lower than 500oC. The samples presented variations as the specific superficial area, average diameter of pores and thickness of the silica wall, as a function of the nature of the rare earth impregnated in the mesoporous material. Hydrotermal stability was evaluated through the exposition of the materials to water vapour at 700?C. The thiophene adsorptions reach a maximum at 80% of conversion and incorporation of the rare earths showed influence in the process. Adsorption capacity followed the sequence: Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41 / As peneiras moleculares mesoporosas do tipo MCM-41 s?o consideradas promissoras como suporte para metais em processos de refino de materiais a base de petr?leo, como catalisadores e como adsorventes para prote??o ambiental. Neste trabalho a peneira molecular mesoporosa tipo MCM-41 foi modificada com diferentes terras raras (La, Eu e Yb) para a obten??o de materiais nanoestruturados com propriedades catal?ticas. Os catalisadores foram sintetizados pelo m?todo hidrot?rmico a 100 oC por 120 horas, apresentando, todas as amostras, no gel de s?ntese raz?o molar Si/Ln = 50. Os materiais resultantes, ap?s calcina??o a 500 oC por 2 horas, foram caracterizados por: DRX, ?rea superficial pelo m?todo de BET, TG/DTG, FTIR e testes hidrot?rmicos a 700oC. As an?lises de DRX dos catalisadores indicaram que os materiais contendo as terras raras apresentaram estrutura hexagonal caracter?stica do material mesoporoso tipo MCM-41. As curvas TG mostraram que a decomposi??o do direcionador estrutural ocorre nos materiais em temperaturas inferiores a 500oC. As amostras apresentaram varia??es quanto ? ?rea superficial espec?fica, di?metro m?dio de poros e espessura da parede de s?lica, em fun??o da natureza da terra rara impregnada no material mesoporoso. A estabilidade hidrot?rmica foi avaliada atrav?s da exposi??o dos materiais a vapor d ?gua a 700oC. A adsor??o de tiofeno atingiu valores m?ximos de 80% e a incorpora??o das terras raras influenciaram no processo. A ordem crescente de capacidade de adsor??o seguiu a seguinte seq??ncia: Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41

Made available in DSpace on 2014-12-17T15:42:00Z (GMT). No. of bitstreams: 1 Mariele ISM_DISSERT.pdf: 4704397 bytes, checksum: 9fa1538bc3d6948d492f9a6c378eaf62 (MD5) Previous issue date: 2012-07-20 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The oxidative desulfurization process (ODS) of a commercial diesel fuel was performed under mild conditions in the presence of catalysts based on vanadium or manganese, supported on alumina, clays (commercial, natural and pillared) and zeolites (NaX, NaY, beta, mordenite and ZSM-5). The catalysts were synthesized by wet impregnation and characterized by X-ray diffraction, textural analysis by N2 adsorption and scanning electron microscopy. The dibenzothiophene (DBT) was used as sulfur compound in catalytic evaluation. The reactions were performed using acetonitrile as solvent and the hydrogen peroxide as oxidant at 55?C. The reaction products were analized by gas chromatography (GC-FID). In the studied conditions, the process was efficient due to the DBT was converted to its corresponding sulfone. Both DBT and corresponding sulfone were extracted by the solvent. Removals and oxidations up to 100% of sulfur compound were achieved. The catalysts supported on ZSM-5 zeolite showed are more effective for oxidation reaction of sulfur compound, presenting the best results. It was observed for oxidation reaction, that vanadium catalysts were more effective and manganese catalysts showed best results for removal of sulfur compounds / O processo de Dessulfuriza??o Oxidativa (ODS) de um diesel comercial foi realizado em condi??es suaves na presen?a de catalisadores ? base de van?dio ou mangan?s, suportados em aluminas, argilas (comerciais, naturais e pilarizadas) e ze?litas (NaX, NaY, beta, mordenita, ZSM-5). Os catalisadores foram sintetizados via impregna??o ?mida e caracterizados por difra??o de raios-X, an?lise textural por adsor??o e dessor??o de nitrog?nio e microscopia eletr?nica de varredura. O dibenzotiofeno (DBT) foi utilizado como o composto de enxofre nos testes catal?ticos. As rea??es foram realizadas usando como solvente acetonitrila e como oxidante o per?xido de hidrog?nio a temperatura de 55?C. Os produtos de rea??o foram analisados por cromatografia gasosa (CG-FID). Nas condi??es estudadas o processo mostrouse eficiente, o DBT foi convertido para sua respectiva sulfona. Ambos DBT e a sulfona foram extra?dos pelo solvente. Remo??es e oxida??es de 100% do composto de enxofre foram alcan?adas. Os catalisadores suportados na ze?lita ZSM-5 mostraram-se mais efetivos para a rea??o de oxida??o do composto sulfurado, apresentando os melhores resultados. Observa-se para a rea??o de oxida??o que os catalisadores de van?dio foram mais efetivos, e os catalisadores de mangan?s apresentaram melhores resultados na extra??o dos compostos sulfurados

Experiments with both quantitative and qualitative factors always complicate the selections of experimental settings and the statistical analysis for data. Response surface methodology (RSM) provides the systematic procedures such as the steepest ascent method to develop and improve the response models through the optimal settings of quantitative factors. However the sequential method lacks of exploring the direction of the maximum increase in the response among the qualitative levels. In this dissertation the optimal designs for experiments with both qualitative and quantitative factors are investigated. Focused on the second-order response surface model for quantitative factors, which is widely used in RSM as a good approximation for the true response surface, the approximate and exact D-optimal designs are proposed for the model containing the qualitative effects. On spherical design regions, the D-optimal designs have particular structures for considering the qualitative effects to be fixed or random. In this study, the exact D-optimal designs for a second-order response surface model on a circular design region with qualitative factors are proposed. For this model, the interactions between the quantitative and qualitative factors are assumed to be negligible. Based on this design region, an exact D-optimal design with regular polygon structure is made up according to the remainder terms of the numbers of experimental trials at each qualitative levels divided by 6. The complete proofs of exact D-optimality for models including two quantitative factors and one 2-level qualitative factor are presented as well as those for a model with only quantitative factors. When the qualitative factor has more than 2 levels, a method is proposed for constructing exact designs based on the polygonal structure with high efficiency. Furthermore, a procedure for minimizing the number of support points for the quantitative factors of exact D-optimal designs is also proposed for practical consideration. There are no more than 13 support points for the quantitative factors at an individual qualitative level. When the effects between the quantitative and qualitative factors are taken into consideration, approximate D-optimal designs are investigated for models in which the qualitative effects interact with, respectively, the linear quantitative effects, or the linear effects and 2-factor interactions of the quantitative factors or quadratic effects of the quantitative factors. It is shown that, at each qualitative level, the corresponding D-optimal design consists of three portions as a central composite design but with different weights on the cube portion, star portion and center points. Central composite design (CCD) is widely applied in many fields to construct a second-order response surface model with quantitative factors to help to increase the precision of the estimated model. A chemical study is illustrated to show that the effects of the qualitative factor interacts with 2-factor interactions of the quantitative factors are important but absent in a second-order model including a qualitative factor treated as a coded variable. The verification of the D-optimality for exact designs has become more and more intricate when the qualitative levels or the number of quantitative factors increase, even when the patterns of the exact optimal designs have been speculated. The efficient rounding method proposed by Pukelsheim and Rieder (1992) is a model-free approach and it generates an exact design by apportioning the number of trials on the same support points of a given design. For constructing the exact designs with high efficiencies, a modified efficient rounding method is proposed and is based on the polygonal structure of the approximate D-optimal design on a circular design region. This modification is still based on the same rounding approach by apportioning the number of trials to the concentric circles where the support points of the given design are standing on. Then a regular polygon design will be assigned on the circles by the apportionments. For illustration, the exact designs for a third-order response surface model with qualitative factors are presented as well as those for the second-order model. The results show that nearly D-optimal designs are obtained by the modified procedure and the improvement in D-efficiency is very significant. When the factors with the levels selected randomly from a population, they are treated as with random effects. Especially for the qualitative effects caused by the experimental units that the experimenter is not interested in, one should consider the model with random block effects. In this model, the observations on the same unit are assumed to be correlated and they are uncorrelated between different units. Then the mean response surface is still considered as second-order for quantitative factors but the covariance matrix of the observations is different from the identity matrix. In the fourth part of this dissertation, the locally D-optimal designs on a circular design region are proposed for given the value of the correlations. These optimal designs with the structures based on the regular polygons are similar to the D-optimal designs for the uncorrelated model.

Made available in DSpace on 2014-12-17T14:07:01Z (GMT). No. of bitstreams: 1 KarlaSMGS_partes_autorizadas_pelo_autor.pdf: 1248832 bytes, checksum: 6139c9f98f965322e719dfe4f7274a99 (MD5) Previous issue date: 2009-03-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The mixed metal oxides constitute an important class of catalytic materials widely investigated in different fields of applications. Studies of rare earth nickelates have been carried by several researchers in order to investigate the structural stability afforded by oxide formed and the existence of catalytic properties at room temperature. So, this study aims synthesize the nanosized catalyst of nickelate of lanthanum doped with strontium (La(1-x)SrxNiO4-d; x = 0,2 and 0,3), through the Pechini method and your characterization for subsequent application in the desulfurization of thiophene reaction. The precursor solutions were calcined at 300?C/2h for pyrolysis of polyester and later calcinations occurred at temperatures of 500 - 1000?C. The resulting powders were characterized by thermogravimetric analysis (TG / DTG), surface area for adsorption of N2 by BET method, X-ray diffraction (XRD), scanning electron microscopy (HR_SEM) and spectrometry dispersive energy (EDS). The results of XRD had show that the perovskites obtained consist of two phases (LSN and NiO) and from 700?C have crystalline structure. The results of SEM evidenced the obtainment of nanometric powders. The results of BET show that the powders have surface area within the range used in catalysis (5-50m2/g). The characterization of active sites was performed by reaction of desulfurization of thiophene at room temperature and 200?C, the relation F/W equal to 0,7 mol h-1mcat -1. The products of the reaction were separated by gas chromatography and identified by the selective detection PFPD sulfur. All samples had presented conversion above 95% / Os ?xidos met?licos mistos constituem uma importante classe de materiais catal?ticos mundialmente investigados em diferentes campos de aplica??es. Estudos envolvendo niquelatos de terras raras v?m sendo realizados por v?rios pesquisadores no intuito de investigar a estabilidade proporcionada pelo ?xido estrutural formado e a exist?ncia de propriedades catal?ticas, ? temperatura ambiente. Neste contexto, este trabalho tem como objetivo a s?ntese do catalisador nanom?trico de niquelato de lant?nio dopado com estr?ncio (La(1-x)SrxNiO4-d; x = 0,2 e 0,3), atrav?s do m?todo Pechini e caracteriza??o para posterior aplica??o em rea??o de dessulfuriza??o de tiofeno. As solu??es precursoras foram calcinadas a 300?C/2h, para pir?lise do poli?ster e posteriores calcina??es foram realizadas nas temperaturas entre 500 - 1000?C. Os p?s resultantes foram caracterizados por an?lise termogravim?trica (TG/DTG), ?rea superficial por adsor??o de N2 pelo m?todo BET, difra??o de raios x (DRX), microscopia eletr?nica de varredura de alta resolu??o (HR_MEV) e espectroscopia por energia dispersiva (EDS). Com os dados de an?lise t?rmica, foi poss?vel definir as temperaturas e calores envolvidos no processo de decomposi??o dos ?xidos finais. Os resultados de DRX mostraram que as perovisquitas obtidas s?o constitu?das de duas fases (LSN e NiO) e a partir de 700?C apresentaram estrutura cristalina. Os resultados de MEV evidenciaram a obten??o de p?s nanom?tricos. Os resultados de BET mostraram que os p?s obtidos apresentam ?rea superficial dentro da faixa utilizada em cat?lise (5-50m2/g). A caracteriza??o dos s?tios ativos foi realizada atrav?s da rea??o de dessulfuriza??o de tiofeno ? temperatura ambiente e a 200oC, com raz?o F/W igual a 0,7molh-1mcat -1. Os produtos da rea??o foram separados por cromatografia em fase gasosa e identificados por detec??o PFPD seletivo a enxofre. Todas as amostras apresentaram convers?o acima de 95%

Made available in DSpace on 2014-12-17T15:01:19Z (GMT). No. of bitstreams: 1 LuizFSF.pdf: 1747527 bytes, checksum: e75c5e8a2575620cc3a29490253bcad6 (MD5) Previous issue date: 2009-03-05 / Natural gas, although basically composed by light hydrocarbons, also presents in its composition gaseous contaminants such as CO2 (carbon dioxide) and H2S (hydrogen sulfide). Hydrogen sulfide, which commonly occurs in oil and gas exploration and production activities, besides being among the gases that are responsible by the acid rain and greenhouse effect, can also cause serious harm to health, leading even to death, and damages to oil and natural gas pipelines. Therefore, the removal of hydrogen sulfide will significantly reduce operational costs and will result in oil with best quality to be sent to refinery, thereby resulting in economical, environmental, and social benefits. These factors highlight the need for the development and improvement of hydrogen sulfide sequestrating agents to be used in the oil industry. Nowadays there are several procedures for hydrogen sulfide removal from natural gas used by the petroleum industry. However, they produce derivatives of amines that are harmful to the distillation towers, form insoluble precipitates that cause pipe clogging and produce wastes of high environmental impact. Therefore, the obtaining of a stable system, in inorganic or organic reaction media, that is able to remove hydrogen sulfide without forming by-products that affect the quality and costs of natural gas processing, transport and distribution is of great importance. In this context, the evaluation of the kinetics of H2S removal is a valuable procedure for the treatment of natural gas and disposal of the byproducts generated by the process. This evaluation was made in an absorption column packed with Raschig ring, where natural gas with H2S passes through a stagnant solution, being the contaminant absorbed by it. The content of H2S in natural gas in column output was monitored by an H2S analyzer. The comparison between the obtained curves and the study of the involved reactions have not only allowed to determine the efficiency and mass transfer controlling step of the involved processes but also make possible to effect a more detailed kinetic study and evaluate the commercial potential of each reagent / O g?s natural, embora seja composto basicamente de hidrocarbonetos leves, apresenta tamb?m em sua composi??o gases contaminantes como o CO2 (Di?xido de carbono) e o H2S (Sulfeto de hidrog?nio). O H2S, que comumente ocorre nas atividades de explora??o e produ??o de ?leo e g?s, al?m de estar entre os respons?veis pela chuva ?cida e pelo efeitoestufa, causa s?rios danos ? sa?de, levando inclusive ? morte, e danifica as tubula??es de transporte do petr?leo e do g?s natural. Por isso, eliminando-se o g?s sulf?drico haver? significativa redu??o dos custos de opera??o e uma melhor qualidade do ?leo destinado ? refinaria, resultando assim num beneficio econ?mico, ambiental e social. Tudo isso demonstra a necessidade do desenvolvimento e aprimoramento de seq?estrantes que removam o sulfeto de hidrog?nio da ind?stria de petr?leo. Atualmente existem v?rios processos para o tratamento do g?s natural utilizados pela ind?stria petrol?fera para remo??o do H2S, no entanto eles produzem derivados de aminas prejudiciais ?s torres de destila??o, precipitados insol?veis que provocam entupimento dos dutos e originam res?duos de grande impacto ambiental. Por isso, a obten??o de um sistema est?vel em meio reacional inorg?nico ou org?nico capaz de remover o g?s sulf?drico sem formar subprodutos que afetem a qualidade e o custo do processamento, transporte e distribui??o do g?s natural ? de grande import?ncia. Nesse contexto a avalia??o da cin?tica de remo??o do H2S surge como um procedimento valioso para o tratamento do g?s natural e destino dos subprodutos do processo. Esta avalia??o foi feita numa coluna de absor??o recheada com an?is de Raschig, por onde o g?s natural contaminado com H2S atravessava uma solu??o estagnada, sendo por esta absorvida. Na sa?da da coluna o teor de H2S no g?s era monitorado por um analisador de H2S. A compara??o das curvas obtidas e o estudo das rea??es permitiram n?o somente determinar a efici?ncia e a etapa controladora da transfer?ncia de massa dos processos envolvidos como tamb?m efetuar um estudo cin?tico mais aprofundado e avaliar o potencial comercial de cada reagente

Fluorinated nucleosides, especially the analogues with fluorine atom(s) in the ribose ring, have been known to exert potent biological activities. The first part of this dissertation was aimed at developing oxidative desulfurization-fluorination and reductive desulfonylation-fluorination methodologies toward the synthesis of 2'-mono and/or 2',2'-difluoro pyrimidine nucleosides from the corresponding 2'-arylthiopyrimidine precursors. Novel oxidative desulfurization-difluorination methodology was developed for the synthesis of α,α-difluorinted esters from the corresponding α-arylthio esters, wherein the arylthio group is present on a secondary internal carbon. For the reductive desulfonylation studies, cyclic voltammetry was utilized to measure the reduction potentials at which the sulfone moiety of substrates can be cleaved. The 5-bromo pyrimidine nucleosides and 8-bromo purine nucleosides act as crucial intermediates in various synthetic transformations. The second part of the present dissertation was designed to develop a novel bromination methodology using 1,3-dibromo-5,5-dimethylhydantoin (DBH). Various protected and deprotected pyrimidine and purine nucleosides were converted to their respective C5 and C8 brominated counterparts using DBH. The effect of Lewis acids, solvents, and temperature on the efficiency of bromination was studied. Also, N-bromosuccinimide (NBS) or DBH offered a convenient access to 8-bromotoyocamycin and 8-bromosangivamycin. Third part of this research work focuses on the design and synthesis of 6-N-benzylated derivatives of 7-deazapurine nucleoside antibiotics, such as tubercidin, sangivamycin and toyocamycin. Target molecules were synthesized by two methods. First method involves treatment of 7-deazapurine substrates with benzylbromide followed by dimethylamine-promoted Dimroth rearrangement. The second method employs fluoro-diazotization followed by SNAr displacement of the 6-fluoro group by a benzylamine. The 6-N-benzylated 7-deazapurine nucleosides showed type-specific inhibition of cancer cell proliferation at micromolar concentrations and weak inhibition of human equilibrative nucleoside transport protein (hENT1). In the fourth part of this dissertation, syntheses of C7 or C8 modified 7-deazapurine nucleosides, which might exhibit fluorescent properties, were undertaken. 8-Azidotoyocamycin was synthesized by treatment of 8-bromotoyocamycin with sodium azide. Strain promoted click chemistry of 8-azidotoyocamycin with cyclooctynes gave the corresponding 8-triazolyl derivatives. Alternatively, 7-benzotriazolyl tubercidin was synthesized by iodine catalyzed CH arylation of tubercidin with benzotriazole.

Le remplacement des solvants organiques classiques par une nouvelle génération de solvants moins toxiques, moins inflammables et moins polluants est un défi majeur pour l'industrie chimique. Les liquides ioniques, sels liquides qui satisfont ces critères, sont envisagés comme alternatives. Le but de ce travail est d'évaluer le comportement des liquides ioniques en présence de gaz à effet de serre (CO2, N2O et CH4) ou de composés organiques. Dans un premier temps, une étude théorique présente les performances du modèle thermodynamique PC-SAFT sur la représentation des équilibres liquide-vapeur de systèmes constitués de dioxyde de carbone et de liquide ionique. Ensuite, l'étude de la solubilité du méthane, du dioxyde de carbone et du protoxyde d'azote dans divers liquides ioniques a été effectuée sous basse ou haute pression. Ce travail propose un modèle basé sur le concept de contribution de groupes afin de prédire la constante d'Henry du CO2 dans les liquides ioniques. Enfin, une étude sur les équilibres liquide-vapeur des systèmes binaires rencontrés dans la désulfuration des essences a été effectuée. Les données expérimentales ont permis d'évaluer les performances de l'équation PC-SAFT à représenter les équilibres entre phases de systèmes {composés soufrés / aromatiques + liquide ionique} / The replacement of conventional organic solvents by a new generation of solvents less toxic, less flammable and less polluting is a major challenge for the chemical industry. Ionic liquids have been widely promoted as interesting substitutes for traditional solvents. The purpose of this work is to evaluate the behavior of ionic liquids in the presence of greenhouse gases (CO2, CH4 and N2O) or organic compounds. Firstly, a theoretical study presents the performance of the thermodynamic model PC-SAFT in the representation of vapor-liquid equilibrium of systems containing ionic liquids and carbon dioxide. Then, the solubility study of methane, carbon dioxide and nitrous oxide in various ionic liquids was performed at high or low pressure. The group contribution concept is proposed in this study in order to predict the Henry's law constant of carbon dioxide in ionic liquids. Finally, a study on the vapor-liquid equilibrium of binary systems encountered in gasoline desulfurization was carried out. Experimental data were used to evaluate the performance of PC-SAFT equation of state to represent phase equilibrium of systems {sulfur / aromatic compounds + ionic liquid}

[pt] SO2 é conhecido com um grande contaminante ambiental e muitos países estabeleceram regras para o controle da sua emissão para a atmosfera. Como resultado a maioria das plantas fornecedoras de energia foram equipadas com instalações de dessulfurização de gases de combustão. Embora esta tecnologia seja bem sucedida no abate de SO2, ela gera uma grande quantidade de gesso FGD (flue gas desulfurization) como resíduo. Grandes esforços estão sendo feitos para aproveitar este resíduo (gesso FGD). No presente estudo o gesso FGD foi avaliado como aditivo retardador do tempo de pega substituindo o gesso natural na fabricação do cimento Portland (CP II E-32). Os resultados da caracterização físico-química e morfológica do gesso natural e de gesso FGD identificam um material de alta pureza, sulfato de cálcio di-hidratado para o gesso natural, e presença principalmente de bassanita (CaSO4.0,6H2O) e hannebachite (CaSO3.0,5H2O) com baixas concentrações de impurezas no gesso FGD. Baseado nos resultados, o gesso FGD é uma alternativa adequada para substituir o gesso natural. O tempo de pega mostrou cerca de uma hora de retardo em comparação com gesso natural e seu efeito sobre a resistência à compressão para as amostras de 3, 7 e 28 dias depende da composição das misturas, atingindo um valor máximo para a argamassa com 2,1 porcento de gesso FGD e 1,4 porcentode gesso natural. Também foi estimado o impacto ambiental do gesso FGD, examinando a liberação de seus constituintes inorgânicos seguindo a norma ABNT NBR 10004:2004 e classificando o resíduo como não perigoso e não inerte. / [en] The SO2 is well known as an important environmental contaminant and many countries have established rules to control its emission to the atmosphere and as result most of power supply plants were equipped with flue gas desulfurization systems. Although this technology is successful in the discharge of SO2, its generates a large amount of gypsum FGD (flue gas desulfurization) as a residue. Great efforts are being made to find destinations for this residue. In the present study, the FGD gypsum was evaluated as setting retarder to replace the natural gypsum in the production of Portland cement (CP II E-32). The results of physical-chemistry and morphological characterization of both products, natural and FGD gypsum showed a material of high purity, calcium sulfate dehydrate for natural gypsum, and the presence of bassanite (CaSO4.0,6H2O) and hannebachite (CaSO3.0,5H2O) with low concentrations of impurities for FGD gypsum. Based on the results, the FGD gypsum is a suitable alternative to replace natural gypsum. The setting time with FGD gypsum showed about 1 hour delay compared with natural gypsum and its effect on compressive strength, for samples of 3, 7 e 28 days, depend the composition of the mixtures, reaching the maximum value for the mixture of 1,4 weight percent natural gypsum and 2,1 weight percent FGD gypsum. The FGD gypsum environmental impact was evaluated by determining its potential in releasing inorganic constituents, following the standard ABNT NBR 10004:2004, and it was classified as a non-hazardous and non-inert.

No description available.