Made available in DSpace on 2014-12-17T15:42:07Z (GMT). No. of bitstreams: 1 MarconiSFO_DISSERT.pdf: 4822002 bytes, checksum: 2debc2b37aed6dad6d1e0bb06a153e64 (MD5) Previous issue date: 2013-07-31 / The underground natural gas found associated or not with oil is characterized by a mixture of hydrocarbons and residual components such as carbon dioxide (CO2), nitrogen gas (N2) and hydrogen sulfide (H2S), called contaminants. The H2S especially promotes itself as a contaminant of natural gas to be associated with corrosion of pipelines, to human toxicity and final applications of Natural Gas (NG). The sulfur present in the GN must be fully or partially removed in order to meet the market specifications, security, transport or further processing. There are distinct and varied methods of desulfurization of natural gas processing units used in Natural Gas (UPGN). In order to solve these problems have for example the caustic washing, absorption, the use of membranes and adsorption processes is costly and great expenditure of energy. Arises on such findings, the need for research to active processes of economic feasibility and efficiency. This work promoted the study of the adsorption of sulfide gas in polymer matrices hydrogen pure and modified. The substrates of Poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA) and sodium alginate (NaALG) were coated with vanadyl phosphate compounds (VOPO4.2H2O), vanadium pentoxide (V2O5), rhodamine B (C28H31N2O3Cl) and ions Co2+ and Cu2+, aiming to the adsorption of hydrogen sulfide gas (H2S). The adsorption tests were through a continuous flow of H2S in a column system (fixed bed reactor) adsorption on a laboratory scale. The techniques used to characterize the adsorbents were Infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), X-ray fluorescence (XRF), the X-ray diffraction (XRD) electron microscopy (SEM). Such work indicates, the results obtained, the adsorbents modified PMMA, PVC and NaALG have a significant adsorptive capacity. The matrix that stood out and had the best adsorption capacity, was to ALG modified Co2+ with a score of 12.79 mg H2S / g matrix / O g?s natural encontrado no subsolo associado ou n?o ao petr?leo se caracteriza por uma mistura de hidrocarbonetos e componentes residuais tais como o di?xido de carbono (CO2), o g?s nitrog?nio (N2) e o sulfeto de hidrog?nio (H2S), denominados de contaminantes. O H2S em especial se promove como contaminante do g?s natural por estar associado ? corros?o de dutos (gasodutos), ? toxidade humana e a aplica??es finais do G?s Natural (GN). O teor de enxofre presente no GN deve ser totalmente ou parcialmente removido, visando atender as especifica??es de mercado, seguran?a, transporte ou processamento posterior. H? distintos e variados m?todos de dessulfuriza??o do g?s natural usados nas Unidades de Processamento do G?s Natural (UPGN). Visando solucionar tais problemas temos como exemplo a lavagem c?ustica, a absor??o, o uso de membranas e a adsor??o, sendo processos onerosos e com grande disp?ndio energ?tico. Surge, diante de tais constata??es, a necessidade de pesquisa de processos ativos de viabilidade econ?mica e efici?ncia. O presente trabalho promoveu o estudo da adsor??o do g?s sulfeto de hidrogr?nio em matrizes polim?ricas puras e modificadas. Os substratos de Poli(cloreto de vinila) (PVC), Poli(metacrilato de metila) (PMMA) e alginato de s?dio (NaALG), foram recobertos com os compostos de fosfato de vanadila (VOPO4.2H2O), pent?xido de van?dio (V2O5), rodamina B (C28H31N2O3Cl) e os ?ons Co2+ e Cu2+, objetivando-se a adsor??o do g?s sulfeto de hidrog?nio (H2S). Os ensaios de adsor??o se deram atrav?s de um fluxo cont?nuo de H2S em um sistema de coluna (reator de leito fixo) de adsor??o em escala de laborat?rio. As t?cnicas utilizadas para a caracteriza??o dos adsorventes foram ? espectroscopia de infravermelho (FTIR), a an?lise termogravimetria (TG), a fluoresc?ncia de raios X (FRX), o difra??o de raios X (DRX), a microscopia eletr?nica de varredura (MEV). Tal trabalho indica, pelos resultados obtidos, que os adsorventes modificados de PMMA, PVC e NaALG t?m uma capacidade adsortiva significativa. A matriz que se destacou e apresentou a melhor capacidade de adsor??o, foi a de ALG modificada com Co2+ tendo um resultado de 12,79 mg de H2S/g de matriz

This study explores the possibility of prediction and modification of some of the physicochemical properties of non-metallic inclusions by considering top slag-steel-ladle equilibria in an ASEA-SKF ladle furnace. To test the reliability of an available computational thermodynamic computer program, the first sub project was done. It was concluded that LiMeS, an interface for Thermo-Calc, is a useful tool for slag-steel equilibrium calculations. The second sub project was set out to find some model/s that could calculate the most accurate oxygen activity of molten steel compared to the measured one. This study concluded that both Wagner’s and Turkdogan's equations are useful. It was further seen that increasing the Al contents in the molten steel, increasing the CaO/Al2O3 ratio in the top slag, and reducing the temperature, resulted in reduction of the oxygen activity of the molten steel. In the third sub project a comparison was made between measured CaO and Al2O3 (normalised to CaO-Al2O3) in top slag, calcium aluminate inclusions, and the results of theoretical calculations. The average contents of CaO and Al2O3 in all inclusions were close to the composition of the phase Ca12Al14O33 and the contents of CaO and Al2O3 in the slags were close to the composition of the phase Ca3Al2O6 in the binary phase diagram of CaO-Al2O3. The forth sub project set out to study the effect of vacuum degassing time on non-metallic inclusions. It was concluded that during the vacuum degassing process the share of calcium aluminates compared to spinels, Ca content of the oxides, and the average equivalent circle diameters of the oxides were increasing, and oxides tended to form spherical shapes. Finally, based on the preceding four sub projects, the fifth sub project aimed to optimize the steel treatment in an ASEA-SKF ladle furnace. The final results showed that by adding 200 kg fluorite to the top slag of 1200 kg, it was possible to achieve a sulphur content of less than 10 ppm in the steel and a sulphur ratio between slag and steel of 1570, and at the same time reduce the oxygen activity of the molten steel and the degassing time. / <p>QC 20120917</p>

Australia has the largest economical lignite resources in the world. However, the utilisation of lignite is faced with a number of technical, economical and environmental problems due to its high moisture content and some of the deposits containing high sulphur and high inorganic matter. During pyrolysis, the first step of any thermochemical conversion processes of coal, some of the sulphur in lignite evolves as sulphur-bearing volatiles while others are retained in the solid phase of the lignite char. The present research aims to study the sulphur transformation during pyrolysis of Australian lignite. The specific objectives of this research include a study on the transformation of pyrite, sulphate and organic sulphur during lignite pyrolysis as well as an investigation of the effect of inorganic matter on the sulphur transformation during lignite pyrolysis. To help the interpretation of sulphur transformation, the lignite samples were characterised using a combination of analytical techniques, i.e. X-ray diffraction (XRD), X-ray fluorescent (XRF), ion chromatography (IC), Scanning electron microscope equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infra red (FTIR), solid state 13C nuclear magnetic resonance (NMR) and petrographic analysis. Pyrolysis was carried out in a thermogravimetric analyser (TGA) and fixed bed reactor. The lignites and their chars were analysed for sulphur forms using a carbon sulphur (CS) analyser. To study the volatiles released during pyrolysis, experiments were also performed using a TGA coupled to a mass spectrometer (TGA-MS). Eleven (11) Australian lignite samples, denoted as L1 to L11, respectively, from the same lignite deposit but with different sulphur and inorganic matter concentrations were employed in this study. They are categorised as of low quality since they contain high Executive Summary Sulphur Transformation during Pyrolysis of an Australian Lignite v moisture, very high ash, low fixed carbon and thus they have low calorific value, except for L1. The lignites contain considerable amount of total sulphur, except for L1. Mineralogy of the lignites showed that the lignites contain extremely high sodium and chlorine. FTIR and solid state 13C NMR spectroscopy confirmed that oxygenated functional structures are significantly present in the lignites.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / No presente estudo foram preparados materiais carbonosos modificados mediante a impregnaÃÃo de metais (cobre, prata e palÃdio) para a remoÃÃo de enxofre a partir de soluÃÃes sintÃticas de benzotiofeno numa concentraÃÃo de 50 a 400ppm em iso-octano e em amostras de gasolina comercial. A adsorÃÃo do benzotiofeno em soluÃÃo de iso-octano (mistura modelo) foi avaliada atravÃs de experimentos em coluna de leito fixo recheada com carbonos ativados com e sem impregnaÃÃo de metais em trÃs temperaturas distintas: 30, 45 e 60ÂC. Curvas de breakthrough foram simuladas de acordo com um modelo matemÃtico que considera operaÃÃo isotÃrmica, equilÃbrio de adsorÃÃo nÃo linear, fluxo com dispersÃo axial e transferÃncia de massa descrita por uma aproximaÃÃo de forÃa motriz linear (LDF). Os resultados confirmaram a eficiÃncia da utilizaÃÃo dos carbonos ativados em processos de adsorÃÃo de compostos sulfurados, principalmente quando se modifica sua superfÃcie com metais. Foram obtidas capacidades mÃximas de adsorÃÃo significativas para os materiais utilizados de 1,08 mmol S/gads para o carbono ativado GF45; 2,00 mmolS/gads para o carbono ativado GF45/CuCl2; 2,38 mmolS/gads para o carbono ativado GF45/AgCl e 2,71 mmolS/gads para o carbono ativado GF45/PdCl2, quando se utilizou a mistura modelo. Para a gasolina real, obtiveram-se 0,14 mmolS/gads para o carbono ativado GF45/AgCl, 0,23 mmolS/gads para o carbono ativado GF45, 0,30 mmolS/gads para o carbono ativado GF45/CuCl2 e 1,00 mmolS/gads para o carbono ativado GF45/PdCl2, evidenciando uma melhoria ao se trabalhar na adsorÃÃo com materiais impregnados com metais. Em termos de seletividade foi observado um maior valor para este parÃmetro nos estudos realizados com o carbono impregnado com palÃdio. Com relaÃÃo à reversibilidade do processo foi observado que a quantidade adsorvida foi, em geral, o dobro da quantidade dessorvida quando da passagem de solvente puro sem mudanÃa da temperatura para todos os materiais estudados. Este fato demonstra que o carbono ativado nÃo possui uma boa regenerabilidade, ou seja, o carbono ativado retÃm parte do adsorbato mesmo apÃs a purga, o que acaba diminuindo a quantidade de sÃtios ativos do mesmo ao longo de ciclos sucessivos de adsorÃÃo/dessorÃÃo, embora se espere uma melhor recuperaÃÃo a temperaturas mais elevadas. O modelo de transporte dispersivo foi empregado para reproduzir o comportamento das curvas breakthrough e estimar parÃmetros de transferÃncia de massa, utilizando o solver comercial gPROMS. Assim, processos adsortivos para a remoÃÃo de componentes sulfurados a baixas concentraÃÃes podem ser uma alternativa viÃvel como complemento à unidades de hidrodessulfuraÃÃo (HDS). / In this study, modified carbonaceous materials were prepared by metals impregnation (copper, silver and palladium) for removing sulfur from synthetic solutions of benzothiophene in iso-octane solutions and also in commercial gasoline. Benzothiophene adsorption of iso-octane solutions (mixture model) was measured by fixed bed experiments filled with activated carbons with and without metal impregnation in three different temperatures: 30, 45 and 60ÂC. Breakthrough curves were simulated according to a mathematical model that considers operation nonlinear isothermal adsorption equilibrium, axial dispersion flow and mass transfer described by Linear Driving Force model (LDF). The LDF model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. The results confirmed the efficiency of activated carbons used in sulfur compounds adsorption, especially when its surface is modified with metals. Adsorption capacities, qm, were significant obtained for materials used, values in order of 1.08 mmol S/gads for GF45 activated carbon, 2.00 mmol S/gads for GF45/CuCl2 activated carbon, 2.38 mmol S/gads for GF45/AgCl activated carbon and 2.71 mmol S/gads to GF45/PdCl2 activated carbon to the mixture model and 0.14 mmol S/gads for GF45/AgCl activated carbon, 0.23 mmol S/gads to GF45 activated carbon, 0.30 mmol S/gads for GF45/CuCl2 activated carbon and 1.00 mmol S/gads for GF45/PdCl2 activated carbon, showing an improvement when working with materials impregnated with metals. In terms of selectivity, there was a better value for this parameter studies in material impregnated with palladium. With respect to process reversibility, it was observed that adsorption area was twice value of desorption area for all materials. This demonstrates that activated carbon has no good reversibility, ie, activated carbon retains part of adsorbate even after purging, which will ultimately decreasing the amount of same active sites over successive cycles of adsorption/desorption. Adsorptive processes for removing sulfur components can be a viable alternative to complement the HDS process.

Heightened concerns for cleaner air and increasingly more stringent regulations on sulphur content in transportation fuels will make desulphurization more and more important. The sulphur problem is becoming more serious in general, particularly for diesel fuels as the regulated sulphur content is getting an order of magnitude lower, while the sulphur contents of crude oils are becoming higher. This thesis aimed to develop a desulphurisation process (based on oxidation followed by extraction) with high efficiency, selectivity and minimum energy consumption leading to minimum environmental impact via laboratory batch experiments, mathematical modelling and optimisation. Deep desulphurization of model sulphur compounds (di-n-butyl sulphide, dimethyl sulfoxide and dibenzothiophene) and heavy gas oils (HGO) derived from Libyan crude oil were conducted. A series of batch experiments were carried out using a small reactor operating at various temperatures (40 ¿ 100 0C) with hydrogen peroxide (H2O2) as oxidant and formic acid (HCOOH) as catalyst. Kinetic models for the oxidation process are then developed based on `total sulphur approach¿. Extraction of unoxidised and oxidised gas oils was also investigated using methanol, dimethylformamide (DMF) and N-methyl pyrolidone (NMP) as solvents. For each solvent, the `measures¿ such as: the partition coefficient (KP), effectiveness factor (Kf) and extractor factor (Ef) are used to select the best/effective solvent and to find the effective heavy gas oil/solvent ratios. A CSTR model is then developed for the process for evaluating viability of the large scale operation. It is noted that while the energy consumption and recovery issues could be ignored for batch experiments these could not be ignored for large scale operation. Large amount of heating is necessary even to carry out the reaction at 30-40 0C, the recovery of which is very important for maximising the profitability of operation and also to minimise environmental impact by reducing net CO2 release. Here the heat integration of the oxidation process is considered to recover most of the external energy input. However, this leads to putting a number of heat exchangers in the oxidation process requiring capital investment. Optimisation problem is formulated using gPROMS modelling tool to optimise some of the design and operating parameters (such as reaction temperature, residence time and splitter ratio) of integrated process while minimising an objective function which is a coupled function of capital and operating costs involving design and operating parameters. Two cases are studied: where (i) HGO and catalyst are fed as one feed stream and (ii) HGO and catalyst are treated as two feed streams. A liquid-liquid extraction model is then developed for the extraction of sulphur compounds from the oxidised heavy gas oil. With the experimentally determined KP multi stage liquid-liquid extraction process is modelled using gPROMS software and the process is simulated for three different solvents at different oil/solvent ratios to select the best solvent, and to obtain the best heavy gas oil to solvent ratio and number of extraction stages to reduce the sulphur content to less than 10 ppm. Finally, an integrated oxidation and extraction steps of ODS process is developed based on the batch experiments and modelling. The recovery of oxidant, catalyst and solvent are considered and preliminary economic analysis for the integrated ODS process is presented.

Na matriz energética brasileira, o óleo diesel tem lugar de destaque, porém ainda é comercializado com teores de compostos sulfurados e nitrogenados considerados altos para as legislações ambientais que entrarão em vigor nos próximos anos. Tradicionalmente, a remoção desses compostos de enxofre de correntes de petróleo é realizada por processos de hidrotratamento (HDT). No entanto, devido as características do diesel brasileiro, se faz necessária maior severidade para atingir as novas especificações dos combustíveis. Isto implica em investimentos e custos operacionais crescentes para atender a demanda que se instala. Neste contexto, a adsorção está sendo estudada para a purificação da corrente de óleo diesel oriunda da etapa de hidrotratamento como polimento final para alcançar as especificações mais exigentes. Sabe-se que os adsorventes comerciais apresentam limitações na remoção destes contaminantes e uma alternativa que tem se mostrado promissora é a incorporação de metais de transição na estrutura do sólido. No presente trabalho foram modificados adsorventes comerciais, tais como aluminas, sílica-aluminas e argilas pela introdução dos elementos níquel, colbalto e molibdênio e testado o desempenho dessas modificações frente à adsorção de compostos sulfurados e nitrogenados presentes em um diesel hidrotratado. Foram feitas caracterizações químicas, físicas, texturais e morfológicas dos sólidos com e sem incorporação de metais de transição na estrutura original. Os experimentos de adsorção foram realizados a 40C. Avaliando todos os sólidos, o adsorvente que mostrou o melhor desempenho na remoção de compostos sulfurados e nitrogenados por massa de adsorvente foi a sílica-alumina sem modificações, que foi capaz de remover em torno de 90% de compostos nitrogenados e 55 % de sulfurados para 2 g de sólido / 10 mL de diesel. Para os materiais modificados, observou-se que a incorporação dos metais de transição ocasionou redução da sua área superficial e do volume total de poros. Desta maneira, os efeitos esperados pelas interações entre o sítios metálicos e os compostos de nitrogênio e enxofre foram reduzidos / Diesel oil has a prominent role in the Brazilian energy matrix, but is still marketed with high levels of sulfur and nitrogen compounds compared to the next years ongoing environmental legislation. Traditionally, the removal of sulfur compounds from petroleum streams is performed by the hydrotreating processes (HDT). However, due to the Brazilian diesel characteristics, more stringent operation conditions are necessary to achieve new fuel specifications. This involves investment and operating costs rising to meet demand that is installed. In this context, adsorption is being studied for the purification of HDT diesel oil as a final polishing to meet the specifications. It is known that the commercial adsorbents have limitations in removing these contaminants and an alternative that has been shown promising is the incorporation of transition metal in the solid structure. In this work we modified commercial adsorbents such as alumina, silica-aluminas and clays by the introduction of the elements nickel, colbalto, and molybdenum and the behavior of theses modifications was testes against adsorption of sulfur and nitrogen present in HDT diesel oil. Physical, textural, and morphological characterizations of the solids were performed with and without addition of transition metals in its structure original. The adsorption experiments were performed at 40C. Evaluating all the solids, the adsorbent that showed the best performance in the removal of sulfur compounds and nitrogen per mass of adsorbent was the silica-alumina without modification, which was able to remove around 90% of nitrogen and 55% of sulfur with 2 g of solid / 10 mL of diesel. For the modified materials, it was observed that incorporation of transition metals led to reduction of its surface area and total pore volume. Thus, the expected effects of interactions between the metal sites and nitrogen and sulfur compounds were reduced

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-05-09T20:05:40Z No. of bitstreams: 1 2016 - Melise Ferreira de Aguiar.pdf: 5763969 bytes, checksum: 9dcc7682d7ffab0b0a6ce4d1db704c10 (MD5) / Made available in DSpace on 2017-05-09T20:05:40Z (GMT). No. of bitstreams: 1 2016 - Melise Ferreira de Aguiar.pdf: 5763969 bytes, checksum: 9dcc7682d7ffab0b0a6ce4d1db704c10 (MD5) Previous issue date: 2016-12-12 / CAPES / Natural gas is extensively used in industries as well as in other sectors as an energy resource and, sometimes, it needs to undergo processes for the removal of impurities present in its composition. Among them are the sulfur compounds, which can cause damages to pipes and catalysts, making it necessary to develop and/or improve deep desulfurization methods. In this context, granular activated carbon was modified through two methods, oxidation using nitric acid, and impregnation using a ferric chloride solution. The resulting adsorbents were evaluated for their capacity of adsorbing seven sulfur compounds present in the synthetic natural gas sample, through their rupture curves. Afterwards, the adsorbents desorption was performed by using supercritical carbon dioxide under the conditions of 60?C at 100 bar, 150 bar and 200 bar. The results indicate that all the modification methods improved the sulfur compounds retention when compared to virgin activated carbon. The compound that had the greatest increase in the adsorption capacity after iron impregnation was the tert-butyl mercaptan (TBM), and with the activated carbon oxidized by HNO3 it was the dimethyl sulfide (DMS). Nevertheless, the supercritical conditions studied in the desorption stage were efficient only for the unmodified activated carbon. The adsorption capacities of both modified adsorbents after the regeneration were inferior to those capacities obtained in the first adsorption, then two hypotheses were investigated: (1) destruction of the newly created sites after regeneration; and (2) incomplete desorption in the studied supercritical conditions. Through other experiments it was proved that, after regeneration, there was no destruction of the newly created sites; therefore, further studies on the operating conditions are required in order to the modified adsorbents to achieve high regeneration capacities. / O g?s natural ? utilizado nas ind?strias e em outros setores como fonte de energia e necessita, por vezes, de processos de remo??o das impurezas presentes em sua composi??o. Dentre elas est?o os compostos de enxofre, que provocam danos em tubula??es e catalisadores, sendo necess?rio o desenvolvimento e/ou o aperfei?oamento de m?todos para a dessulfuriza??o profunda. Nesse contexto, um carv?o ativado granular foi modificado por meio de dois m?todos, oxida??o utilizando ?cido n?trico e por impregna??o usando uma solu??o de cloreto de ferro III, os adsorventes resultantes foram avaliados quanto ? sua capacidade para adsorver sete compostos de enxofre presentes em uma amostra de g?s natural sint?tica, atrav?s das curvas de rupturas. Posteriormente, foi realizada a dessor??o dos adsorventes utilizando di?xido de carbono supercr?tico nas condi??es de 60 ?C a 100 bar, 150 bar e 200 bar. Os resultados indicam que todos os m?todos de modifica??o melhoraram a reten??o dos compostos sulfurados individuais em compara??o com o carv?o ativado virgem. O composto que obteve maior aumento da capacidade de adsor??o ap?s a impregna??o com ferro foi o terc-butilmercaptana (TBM), e com o carv?o ativado oxidado pelo HNO3 foi o metiletilsulfeto (DMS). J? as condi??es supercr?ticas estudadas na etapa de dessor??o foram eficientes somente para o carv?o ativado n?o modificado. As capacidades de adsor??o dos dois adsorventes modificados ap?s a regenera??o foram inferiores aos obtidos na primeira adsor??o, ent?o duas hip?teses foram investigadas: (1) destrui??o dos novos s?tios criados ap?s a regenera??o; e (2) dessor??o incompleta nas condi??es supercr?ticas estudadas. Atrav?s de outros experimentos comprovou-se que n?o houve ? destrui??o dos novos s?tios criados ap?s a regenera??o, sendo necess?rio um estudo mais profundo em rela??o ?s condi??es operacionais, a fim de alcan?ar altas capacidades de regenera??o dos adsorventes modificados.

Na matriz energética brasileira, o óleo diesel tem lugar de destaque, porém ainda é comercializado com teores de compostos sulfurados e nitrogenados considerados altos para as legislações ambientais que entrarão em vigor nos próximos anos. Tradicionalmente, a remoção desses compostos de enxofre de correntes de petróleo é realizada por processos de hidrotratamento (HDT). No entanto, devido as características do diesel brasileiro, se faz necessária maior severidade para atingir as novas especificações dos combustíveis. Isto implica em investimentos e custos operacionais crescentes para atender a demanda que se instala. Neste contexto, a adsorção está sendo estudada para a purificação da corrente de óleo diesel oriunda da etapa de hidrotratamento como polimento final para alcançar as especificações mais exigentes. Sabe-se que os adsorventes comerciais apresentam limitações na remoção destes contaminantes e uma alternativa que tem se mostrado promissora é a incorporação de metais de transição na estrutura do sólido. No presente trabalho foram modificados adsorventes comerciais, tais como aluminas, sílica-aluminas e argilas pela introdução dos elementos níquel, colbalto e molibdênio e testado o desempenho dessas modificações frente à adsorção de compostos sulfurados e nitrogenados presentes em um diesel hidrotratado. Foram feitas caracterizações químicas, físicas, texturais e morfológicas dos sólidos com e sem incorporação de metais de transição na estrutura original. Os experimentos de adsorção foram realizados a 40C. Avaliando todos os sólidos, o adsorvente que mostrou o melhor desempenho na remoção de compostos sulfurados e nitrogenados por massa de adsorvente foi a sílica-alumina sem modificações, que foi capaz de remover em torno de 90% de compostos nitrogenados e 55 % de sulfurados para 2 g de sólido / 10 mL de diesel. Para os materiais modificados, observou-se que a incorporação dos metais de transição ocasionou redução da sua área superficial e do volume total de poros. Desta maneira, os efeitos esperados pelas interações entre o sítios metálicos e os compostos de nitrogênio e enxofre foram reduzidos / Diesel oil has a prominent role in the Brazilian energy matrix, but is still marketed with high levels of sulfur and nitrogen compounds compared to the next years ongoing environmental legislation. Traditionally, the removal of sulfur compounds from petroleum streams is performed by the hydrotreating processes (HDT). However, due to the Brazilian diesel characteristics, more stringent operation conditions are necessary to achieve new fuel specifications. This involves investment and operating costs rising to meet demand that is installed. In this context, adsorption is being studied for the purification of HDT diesel oil as a final polishing to meet the specifications. It is known that the commercial adsorbents have limitations in removing these contaminants and an alternative that has been shown promising is the incorporation of transition metal in the solid structure. In this work we modified commercial adsorbents such as alumina, silica-aluminas and clays by the introduction of the elements nickel, colbalto, and molybdenum and the behavior of theses modifications was testes against adsorption of sulfur and nitrogen present in HDT diesel oil. Physical, textural, and morphological characterizations of the solids were performed with and without addition of transition metals in its structure original. The adsorption experiments were performed at 40C. Evaluating all the solids, the adsorbent that showed the best performance in the removal of sulfur compounds and nitrogen per mass of adsorbent was the silica-alumina without modification, which was able to remove around 90% of nitrogen and 55% of sulfur with 2 g of solid / 10 mL of diesel. For the modified materials, it was observed that incorporation of transition metals led to reduction of its surface area and total pore volume. Thus, the expected effects of interactions between the metal sites and nitrogen and sulfur compounds were reduced

>Magister Scientiae - MSc / Coal combustion accounts for over 40 % of the world's energy production and this figure is projected to increase with increasing human population and industrialization. The combustion of coal leads to the generation of waste products such as fly ash (FA), brine from water treatment, bottom ash, slag, flue gas desulphurization products (FGD) and gas emissions such as N20, and C02. The emissions contribute to air pollution and global warming, while FA, brines, and FGD are possible soil and water pollutants. In order to minimize the environmental impact of coal combustion, mitigation of the effects of coal burning processes such as the waste products (FA, brine, bottom ash, slag and FGD) and gas emissions is required. This study investigated utilization of the Secunda FA (class F) and reverse osmosis (RO) Tutuka brine to sequester C02 in an attempt to make coal power production more environmentally sustainable. It was hypothesized that South African FA and brine could sequester C02 through mineral carbonation. A statistical approach was undertaken to optimize the % CaC03 formed from FAlbrine/C02 interaction with input parameters of temperature, pressure, particle size and solid/liquid ratio (S/L) being varied. The ranges adopted for the input parameters were: temperature of 30°C or 90 °C; pressure of 1 Mpa or 4 Mpa; four particle sizes namely bulk ash, > 150 11m, < 20 11m and 20 urn- 150 11m particle size range; S/L ratios ofO.1, 0.5 or 1. The FA! brine dispersions were carbonated in a high pressure reactor varying the above mentioned input parameters. The fresh Secunda FA of various size fractions was characterized morphologically using scanning electron microscopy, chemically using X-ray fluorescence and mineralogically using qualitative X-ray diffraction. The carbonated solid residues on the other hand were characterized using quantitative X-ray diffraction, scanning electron microscopy, thermal gravimetic analysis and Chittick tests. The raw brine from Tutuka together with the carbonation leachates were characterized using inductively coupled mass spectrometry and ion chromatography. Total acid digestion was carried out to evaluate the differences in the total elemental content in both the fresh ash and the carbonated solid residues. The results suggested that South African FA from Secunda belongs to class F based on the CaO content as well as the total alumina, silica and ferric oxide content, while the RO brine from Tutuka were classified as NaS04 waters. Mineral carbonation occurred and ranged between 2.75 % and 6.5 % of CaC03 depending on the input parameters. Two polymorphs of CaC03 were identified in the carbonated residues i.e. calcite and aragonite. The carbonated ash/brine leachates were cleaner with respect to major and trace element concentration compared to raw brine thus the carbonation process could be used to improve the quality of brines generated in the power industry. Removal of the major elements from brine was as follows Ca-74.8 %, Na- 28.7 %, Mg- 98 %, K- 82.9 %, S04- 20.8 %. Hundred percent removal was observed for traces of Fe, Al, Mn, Cu, Zn, Pb, Ni, As, Ti, Sr, Se, Si and N03. However Mo, V, B, and Cl concentrations increased by 72.5 %, 94 %,48.2 % and 7.2 % respectively after carbonation at 90°C, 4 Mpa, S/L ratio of 1 using the bulk ash. The parameters found to be of most significance in the carbonation process were the main effects of temperature, particle size and S/L ratio while the interactions of temperature and particle size as well as the interaction of temperature with S/L ratio were also found to be significant. The statistical approach led to a clear understanding of the effect of each input parameter as well as the ansmg interactions. The conditions of 90°C, 4 Mpa, using bulk ash at a S/L ratio of 1 resulted in the highest yield of % CaC03 with a value of 6.5 %. Theoretically one ton of Secunda FA containing 9.2 % of CaO could sequester 0.083 tons of C02. With the optimized protocol developed in this study bearing in mind that the carbonation efficiency is 75.54%, 1 ton of Secunda FA could sequester 0.062 tons of CO2. This translates to 0.65 % of CO2 produced annually at Secunda plant being sequestered in the FAlbrine dispersions. In other words, 16 tons of FA are required to sequester a ton of C02 annually. It was also observed that carbonation using brine resulted in higher carbonation efficiency than carbonation using water as the Ca2+ component in the brine contributed towards the Ca 2+concentration.

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / This thesis presents a slight on desulphurization process of the commercial diesel fuel using the carbon-based metal oxide nanocomposites such as graphene oxide, ZnO, rGO as a nano-adsorbent, activated carbon (PAC and AC) and charcoal Granular active carbon (GAC) to produce a fuel of less than 10 ppm sulphur content. Due to the high percentage of sulphur compounds in the fuel causing air pollution, acid rain and other problems related to combustion process. The synthesised of sorbents were achieved using incipient impregnation, microwaved-assisted and chemical exfoliation methods. The materials were characterized using Thermogrametric Analyzer (TGA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD), Brunauer, Emmett and Teller (BET). The examination effect of operating conditions on the adsorption capacity with DBT and Sulphur compounds adsorption, the isotherms and the adsorption kinetic models were evaluated. The experimental data for PAC and AC were well suited to Freundlich isotherm and pseudo second-order kinetic models. The results shown that the sulphur feed concentration, the space velocity and the functional groups of the adsorbents have a considerable effect on the adsorption. In addition, it was observed that the temperature in the range of 30 to 80oC has a significant effect on the adsorption of Sulphur compounds from diesel fuel using 20 wt.% of sorbents. The rGO substrate which contained abundant oxygen functional groups was confirmed to promote the dispersion metal oxide and increased the adsorption efficiency of sulphur compounds (H2S and SO2) by providing oxygen ions weakly bound to the sulphur molecules. For the desulfurization process by adsorption, PAC and AC exhibited a better affinity for 80% removal of sulphur compared to the GAC and GO. The effects of metal species such as zinc oxide (ZnO) and reduced graphite oxide (rGO) composite on the adsorption capacity of hydrogen sulphide (H2S) were investigated. It was found that depending on the copper load, the adsorption capacity of H2S increased up to 20 times compared to pure ZnO. To study the oxidation changes on copper and zinc oxides, crystallite analysis by XRD and chemical state analysis by XPS were performed.