In order to decrease our dependence on non-renewable petrochemical resources, it is urgently required to establish sustainable biomass-based biorefineries. Replacing fossil fuels with renewable biomass as a raw feedstock for the production of chemicals and biofuels is a main driving force of biorefinering. Almost all kinds of biomass can be converted to biochemicals, biomaterials and biofuels via continuing advances on conversion technologies. In vitro synthetic biology is an emergent biomanufacturing platform that circumvents cellular constraints so that it can implement some biotransformations better than whole-cell fermentation, which spends a fraction of energy and carbon sources for cellular duplication and side-product formation. In this work, the in vitro synthetic (enzymatic) biosystem is used to produce a future carbon-neutral transportation fuel, hydrogen, and two high-value chemicals, a sugar phosphate and a highly marketable sweetener, representing a new portfolio for new biorefineries. Hydrogen gas is a promising future energy carrier as a transportation fuel, offering a high energy conversion efficiency via fuel cells, nearly zero pollutants produced to end users, and high mass-specific and volumetric energy densities compared to rechargeable batteries. Distributed production of cost-competitive green hydrogen from renewable biomass will be vital to the hydrogen economy. Substrate costs contribute to a major portion of the production cost for low-value bulk biocommodities, such as hydrogen. The reconstitution of 17 thermophilic enzymes enabled to construct an artificial enzymatic pathway converting all glucose units of starch, regardless of the branched and linear contents, to hydrogen gas at a theoretic yield (i.e., 12 H2 per glucose), three times of the theoretical yield from dark microbial fermentation. Using a biomimetic electron transport chain, a maximum volumetric productivity was increased by more than 200-fold to 90.2 mmol of H2/L/h at a high starch concentration from the original study in 2007. In order to promote economics of biorefineries, the production of a sugar phosphate and a fourth-generation sweetener is under development. D-xylulose 5-phosphate (Xu5P), which cannot be prepared efficiently by regular fermentation due to the negatively charged and hydrophilic phosphate groups, was synthesized from D-xylose and polyphosphate via a minimized two-enzyme system using a promiscuous activity of xylulose kinase. Under the optimized condition, 32 mM Xu5P was produced from 50 mM xylose and polyphosphate, achieving a 64% conversion yield, after 36 h at 45 °C. L-arabinose, a FDA-approved zero-calorie sweetener, was produced from D-xylose via a novel enzymatic pathway consisting of xylose isomerase, L-arabinose isomerase and xylulose 4-epimerase (Xu4E). Promiscuous activity of Xu4E, a monosaccharide C4-epimerase, was discovered for the first time. Directed evolution of Xu4E enabled to increase the catalytic function of C4-epimerization on D-xylulose as a substrate by more than 29-fold from the wild-type enzyme. Together, these results demonstrate that the in vitro synthetic biosystem as a feasible biomanufacturing platform has great engineering, and can be used to convert renewable biomass resources to a spectrum of marketable products and renewable energy. As future efforts are addressed to overcome remaining challenges, for example, decreasing enzyme production costs, prolonging enzyme lifetime, engineering biomimetic coenzymes to replace natural coenzymes, and so on. This in vitro synthetic biology platform would become a cornerstone technology for biorefinery industries and advanced biomanufacturing (Biomanufacturing 4.0). / Ph. D.

The environmentally unsafe by-products (CO2, H2S, NOx and SO2 for example) of using carbon-based fuels for energy generation have paved the way for research on cleaner, renewable and possibly cheaper alternative energy production methods. Hydrogen gas, which is considered as an energy carrier, can be applied in a fuel cell setup for the production of electrical energy. Although various methods of hydrogen production are available, sulphur-based thermochemical processes (such as the Hybrid Sulfur Process (HyS)) are favoured as alternative options for large scale application. The SO2 electrolyser is applied in producing H2 gas and H2SO4 by electrochemically converting SO2 gas and water. This study focused firstly on the evaluation of the performance of the SO2 electrolyser for the production of hydrogen and sulphuric acid, using commercially available PFSA (perfluorosulfonic acid) (Nafion®) as benchmark by evaluating i) various operating parameters (such as cell temperature and membrane thickness), ii) the influence of MEA (membrane electrode assembly) manufacturing parameters (hot pressing time and pressure) and iii) the effect of H2S as a contaminant. Subsequently, the suitability of novel PBI polyaromatic blend membranes was evaluated for application in an SO2 electrolyser. The parametric study revealed that, depending on the desired operating voltage and acid concentration, the optimisation of the operating conditions was critical. An increased cell temperature promoted both cell voltage and acid concentration while the use of thin membranes resulted in a reduced voltage and acid concentration. While an increased catalyst loading resulted in increased cell efficiency, such increase would result in an increase in manufacturing costs. Using electrochemical impedance spectroscopy at the optimised operating conditions, the MEA manufacturing process was optimised with respect to hot press pressure and time, while the effect of selected operating conditions was used to evaluate the charge transfer resistance, ohmic resistance and mass transport limitations. Results showed that the optimal hot pressing conditions were 125 kg.cm-2 and 50 kg.cm-2 for 5 minutes when using 25 and 10 cm2 active areas, respectively. The charge transfer resistance and mass transport were mostly influenced by the hot pressing procedure, while the ohmic resistance varied most with temperature. Applying the SO2 electrolyser in an alternative environment to the HyS thermochemical cycle, the effect of H2S on the SO2 electrolyser anode was investigated for the possible use of SO2 electrolysis to remove SO2 from mining off-gas which could contain H2S. Polarisation curves, EIS and CO stripping were used to evaluate the transient voltage response of various H2S levels (ppm) on cell efficiency. EIS confirmed that the charge transfer resistance increased as the H2S competed with the SO2 for active catalyst sites. Mass transport limitations were observed at high H2S levels (80 ppm) while the ECSA (electrochemical surface area obtained by CO stripping) showed a significant reduction of active catalyst sites due to the presence of H2S. Pure SO2 reduced the effective active area by 89% (which is desired in this case) while the presence of 80 ppm H2S reduced the active catalyst area to 85%. The suitability of PBI-based blend membranes in the SO2 electrolyser was evaluated by using chemical stability tests and electrochemical MEA characterisation. F6PBI was used as the PBI-containing base excess polymer which was blended with either partially fluorinated aromatic polyether (sFS001), poly(2,6-dimethylbromide-1,4-phenylene oxide (PPOBr) or poly(tetrafluorostyrene-4-phosphonic acid) (PWN) in various ratios. Some of the blend membranes also contained a cross-linking agent which was specifically added in an attempt to reduce swelling and promote cross-linking within the polymer matrix. The chemical stability of the blended membranes was confirmed by using weight and swelling changes, TGA-FTIR and TGA-MS. All membranes tested showed low to no chemical degradation when exposed to 80 wt% H2SO4 at 80°C for 120 h. Once the MEA doping procedure had been optimised, electrochemical characterisation of the PBI MEAs, including polarisation curves, voltage stepping and long term operation (> 24 h) was used to evaluate the MEAs. Although performance degradation was observed for the PBI membranes during voltage stepping, it was shown that this characterisation technique could be applied with relative ease, producing valuable insights into MEA stability. Since it is expected that the SO2 electrolyser will be operated under static conditions (cell temperature, pressure and current density) in an industrial setting (HyS cycle or for SO2 removal), a long term study was included. Operating the SO2 electrolyser under constant current density of 0.1 A cm-2 confirmed that PBI-based polyaromatic membranes were suitable, if not preferred, for the SO2 environment, showing stable performance for 170 hours. This work evaluated the performance of commercial materials while further adding insights into both characterisation techniques for chemical stability of polymer materials and electrochemical methods for MEA evaluation to current published literature. In addition to the characterisation techniques this study also provides ample support for the use of PBI-based materials in the SO2 electrolyser. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2015

The environmentally unsafe by-products (CO2, H2S, NOx and SO2 for example) of using carbon-based fuels for energy generation have paved the way for research on cleaner, renewable and possibly cheaper alternative energy production methods. Hydrogen gas, which is considered as an energy carrier, can be applied in a fuel cell setup for the production of electrical energy. Although various methods of hydrogen production are available, sulphur-based thermochemical processes (such as the Hybrid Sulfur Process (HyS)) are favoured as alternative options for large scale application. The SO2 electrolyser is applied in producing H2 gas and H2SO4 by electrochemically converting SO2 gas and water. This study focused firstly on the evaluation of the performance of the SO2 electrolyser for the production of hydrogen and sulphuric acid, using commercially available PFSA (perfluorosulfonic acid) (Nafion®) as benchmark by evaluating i) various operating parameters (such as cell temperature and membrane thickness), ii) the influence of MEA (membrane electrode assembly) manufacturing parameters (hot pressing time and pressure) and iii) the effect of H2S as a contaminant. Subsequently, the suitability of novel PBI polyaromatic blend membranes was evaluated for application in an SO2 electrolyser. The parametric study revealed that, depending on the desired operating voltage and acid concentration, the optimisation of the operating conditions was critical. An increased cell temperature promoted both cell voltage and acid concentration while the use of thin membranes resulted in a reduced voltage and acid concentration. While an increased catalyst loading resulted in increased cell efficiency, such increase would result in an increase in manufacturing costs. Using electrochemical impedance spectroscopy at the optimised operating conditions, the MEA manufacturing process was optimised with respect to hot press pressure and time, while the effect of selected operating conditions was used to evaluate the charge transfer resistance, ohmic resistance and mass transport limitations. Results showed that the optimal hot pressing conditions were 125 kg.cm-2 and 50 kg.cm-2 for 5 minutes when using 25 and 10 cm2 active areas, respectively. The charge transfer resistance and mass transport were mostly influenced by the hot pressing procedure, while the ohmic resistance varied most with temperature. Applying the SO2 electrolyser in an alternative environment to the HyS thermochemical cycle, the effect of H2S on the SO2 electrolyser anode was investigated for the possible use of SO2 electrolysis to remove SO2 from mining off-gas which could contain H2S. Polarisation curves, EIS and CO stripping were used to evaluate the transient voltage response of various H2S levels (ppm) on cell efficiency. EIS confirmed that the charge transfer resistance increased as the H2S competed with the SO2 for active catalyst sites. Mass transport limitations were observed at high H2S levels (80 ppm) while the ECSA (electrochemical surface area obtained by CO stripping) showed a significant reduction of active catalyst sites due to the presence of H2S. Pure SO2 reduced the effective active area by 89% (which is desired in this case) while the presence of 80 ppm H2S reduced the active catalyst area to 85%. The suitability of PBI-based blend membranes in the SO2 electrolyser was evaluated by using chemical stability tests and electrochemical MEA characterisation. F6PBI was used as the PBI-containing base excess polymer which was blended with either partially fluorinated aromatic polyether (sFS001), poly(2,6-dimethylbromide-1,4-phenylene oxide (PPOBr) or poly(tetrafluorostyrene-4-phosphonic acid) (PWN) in various ratios. Some of the blend membranes also contained a cross-linking agent which was specifically added in an attempt to reduce swelling and promote cross-linking within the polymer matrix. The chemical stability of the blended membranes was confirmed by using weight and swelling changes, TGA-FTIR and TGA-MS. All membranes tested showed low to no chemical degradation when exposed to 80 wt% H2SO4 at 80°C for 120 h. Once the MEA doping procedure had been optimised, electrochemical characterisation of the PBI MEAs, including polarisation curves, voltage stepping and long term operation (> 24 h) was used to evaluate the MEAs. Although performance degradation was observed for the PBI membranes during voltage stepping, it was shown that this characterisation technique could be applied with relative ease, producing valuable insights into MEA stability. Since it is expected that the SO2 electrolyser will be operated under static conditions (cell temperature, pressure and current density) in an industrial setting (HyS cycle or for SO2 removal), a long term study was included. Operating the SO2 electrolyser under constant current density of 0.1 A cm-2 confirmed that PBI-based polyaromatic membranes were suitable, if not preferred, for the SO2 environment, showing stable performance for 170 hours. This work evaluated the performance of commercial materials while further adding insights into both characterisation techniques for chemical stability of polymer materials and electrochemical methods for MEA evaluation to current published literature. In addition to the characterisation techniques this study also provides ample support for the use of PBI-based materials in the SO2 electrolyser. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2015

Les processus photocatalytiques à la surface d’oxydes métalliques semi-conducteurs font l’objet d’intensesrecherches au niveau mondial car ils constituent des alternatives efficaces, respectueuses de l’environnement etpeu coûteuses aux méthodes conventionnelles dans les domaines de la purification de l’eau et de l’air, et de laproduction « verte » d’hydrogène. Cependant, certaines limitations pour atteindre des efficacitésphotocatalytiques élevées ont été mises en évidence avec les matériaux semiconducteurs classiques du fait de larecombinaison rapide des porteurs de charge générés par illumination. Le développement de photocatalyseurs àbase d’héterostuctures obtenues par dépôt de métaux à la surface de matériaux semiconducteurs ou parassociation de deux semiconducteurs possédant des bandes d’énergie bien positionnées devrait permettre delimiter ces phénomènes de recombinaison via un transfert de charge vectoriel. Dans ce contexte, trois typesd’hétérostructures telles que des nanomatériaux à base d’hétérojonction semiconducteur n/semiconducteur n(SnO2/ZnO), metal/semiconducteur n (RuO2/TiO2 and RuO2/ZnO) et semiconducteur p/semiconducteur n(NiO/TiO2) ont été synthétisées avec succès par différentes voies liquides. Leur composition, leur texture, leurstructure et leur morphologie ont été caractérisées par spectroscopies FTIR et Raman, par diffraction des rayonsX, microscopie électronique en transmission (MET) et porosimétrie de sorption d’azote. Par ailleurs, unecombinaison judicieuse des données issues de mesures effectuées par spectroscopie UV-visible en réflexiondiffuse (DRS) et par spectroscopies de photoélectrons X (XPS) et UV (UPS) a permis de déterminer lediagramme d’énergie des bandes pour chaque système étudié. Les catalyseurs ainsi obtenus ont conduit à desefficacités photocatalytiques plus élevées qu’avec le dioxyde de titane P25 pour la dégradation de colorantsorganiques (bleu de méthylène, l’orangé de méthyle) et la production d’hydrogène. En particulier, lesnanocomposites RuO2/TiO2 et NiO/TiO2 contenant une quantité optimale de RuO2 (5 % en masse) et de NiO(1% en masse), respectivement, ont conduit aux efficacités photocatalytiques les plus importantes pour laproduction d’hydrogène. Ces excellentes performances photocatalytiques ont été interprétées en termesd’alignement adéquat des bandes d’énergies des matériaux associé à des propriétés texturales et structuralesfavorables. Ce concept de photocatalyseurs à base d’hétérojonctions semiconductrices d’activité élevée devrait àl’avenir trouver des débouchés industriels dans les domaines de l’élimination de l’environnement de composésorganiques indésirables et de la production « verte » d’hydrogène. / Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention aspotentially efficient, environmentally friendly and low cost methods for water/air purification as well as forrenewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies havebeen found due to the fast recombination of the charge carriers. Development of heterostucture photocatalystsby depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable bandedge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw newprospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor(SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor(NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition,texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Ramanspectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, asuitable combination of UV–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy(XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for eachsystem. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen.Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %)and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen.These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPSmeasurements along with their good textural and structural properties. This concept of semiconductingheterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future toremove undesirable organics from the environment and to produce renewable hydrogen.

Thesis (M. Tech. - (Engineering: Electrical, Department: Electronic Engineering, Faculty of Engineering and Technology))--Vaal University of Technology. / Industrial countries, such as South Africa, rely heavily on energy sources to function profitably in today’s economy. Based on the 2008 fossil fuel CO2 emissions South Africa was rated the 13th largest emitting country and also the largest emitting country on the continent of Africa, and is still increasing. It was found that fuel cells can be used to generate electricity and that hydrogen is a promising fuel source. A fuel cell is an energy generation device that uses pure hydrogen (99.999%) and oxygen as a fuel to produce electric power. A regenerative fuel cell is a fuel cell that runs in reverse mode, which consumes electricity and water to produce hydrogen. This research was aimed at designing and constructing an optimised control system to control the hydrogen pressure in a proton exchange membrane regenerative fuel cell. The hydrogen generated by the fuel cell must be stored in order to be used at a later stage to produce electricity. A control system has been designed and constructed to optimise the hydrogen pressure control in a regenerative proton exchange membrane fuel cell. An experiment that was done to optimise the hydrogen system included the effects that the cathode chamber pressure has on the production of hydrogen and the most effective method of supplying hydrogen to a storage tank. The experiment also included the effects of a hydrogen buffer tank on the output hydrogen pressure and if the system can accommodate different output pressures. It was found that the cathode chamber pressure doesn’t need to be controlled because it has no effect on the rate of hydrogen produced. The results also showed that the flow of hydrogen need not to be controlled to be stored in a hydrogen storage tank, the best method is to let the produced hydrogen flow freely into the tank. The hydrogen produced was also confirmed to be 99.999% pure. The system was also tested at different output pressures; the control system successfully regulated these different output pressures.

Hydrogen (H2) represents an energy carrier endowed with the potential to contribute to the design of a robust and reliable global energy system by complementing electricity as well as liquid fuels use in an environmentally responsible manner provided that the pertinent H2 production technologies (conventional and new ones) can reach techno-economically attractive performance levels in the presence of irreducible (macroeconomic, fuel market, regulatory) uncertainty. Indeed, the role of H2 in the global energy economy is widely recognized as significant in light also of fast-growing demand in the petrochemical and chemical processing sector as well as future regulatory action on greenhouse gas emissions. Pd and Pd/Alloy-based catalytic membrane reactor (CMR) modules potentially integrated into H2 production (HP-CMR) process systems offer a promising technical pathway towards H2 production with enhanced environmental performance in a carbon-constrained world. However, the lack of accumulated operating experience for HP-CMR plants on the commercial scale poses significant challenges. Therefore, any preliminary attempt to assess their economic viability is certainly justified. A comprehensive techno-economic performance assessment framework has been developed for HP-CMRs with CO2 capture capabilities. A functional Net Present Value (NPV) model has been developed first to evaluate the economic viability of HP-CMRs. The plant/project value of HP-CMR is compared to other competing technology options such as traditional coal-gasification and methane steam reforming-based hydrogen production plants with and without CO2 capture. Sources of irreducible uncertainty (market and regulatory) as well as technology risks are explicitly recognized and the effect of these uncertainty drivers on the plant’s/project’s value is taken into account using Monte-Carlo techniques. Therefore, more realistic distribution profiles of the plant’s economic performance outcomes are generated rather than single-point value estimates. It is shown that future regulatory action on CO2 emissions could induce appealing NPV-distribution profiles for HP-CMRs in the presence of uncertainty and technology risks. Finally, the valuation assessment is complemented with a sensitivity analysis for different representative values of the discount rate that span a reasonable range associated with business and financing risks. It apparently indicates that creatively structured financing mechanisms leading to a reduction of the cost of capital/discount rate could induce more appealing economic performance outcomes and valuation profiles. Furthermore, the proposed research work aims at the development of a methodological framework to assess the economic value of flexible alternatives in the design and operation of HP-CMR plants with carbon capture capabilities under the aforementioned sources of uncertainty. The main objective is to demonstrate the potential value enhancement associated with the long-term economic performance of flexible HP-CMR project investments by managing the uncertainty associated with future environmental regulations. Within the proposed context, promising design flexibility concepts for HP-CMR plants are introduced and operational as well as constructional flexibility options are identified and assessed. In particular, operational flexibility will be realized through periodic and temporary shutdowns of the carbon capture unit in response to regulatory uncertainties. Constructional flexibility will be realized by considering the installation of a carbon capture unit at three strategic periods: 1) installation in the initial design phase, 2) retrofitting at a later stage and 3) retrofitting with preinvestment. Monte Carlo simulations and financial analysis will be conducted in order to demonstrate that, in the presence of irreducible uncertainty, design flexibility options could lead to economic performance enhancement of HP-CMR plants by actively responding to the above sources of uncertainty as they get resolved over the plant’s lifetime.

A digestão anaeróbia tem se apresentado como um processo de grande interesse sob a ótica da potencial produção de energia renovável (H2 e CH4), considerando-se a ampla variedade de compostos orgânicos que podem ser utilizados. Neste estudo desejou-se avançar na compreensão do sistema de reatores anaeróbios de duas fases (acidogênico seguido de metanogênico) operados em condições termofílicas (55°C), alimentados com melaço da cana-de-açúcar, subproduto da indústria sucroalcooleira. Os experimentos foram conduzidos em reatores anaeróbios de leito fixo estruturado com fluxo ascendente e o melaço foi diluído com água de abastecimento, para adequação da concentração aos processos de tratamento de águas residuárias. Na 1ª Etapa dois reatores acidogênicos foram operados em paralelo para avaliar diferentes formas de inoculação e meios suportes, a fim de manter a produção continua e estável de hidrogênio. Para isso foram aplicadas diferentes cargas orgânicas (2,5, 5 e 10 gDQO.L-1) que resultam em COV de 30, 60 e 120 g.DQO.Lreator1.dia-1, com TDH fixo de 2 horas. A expressão do gene hidrogenase foi detectado em ambos os reatores, mas em maior proporção no reator inoculado com lodo de reator UASB e usando como material suporte a espuma de poliuretano. Sequencialmente a este reator, foi acoplado um reator metanogênico, alimentado com efluente do reator acidogênico, estabilizado nas condições apresentadas, e operado com COV crescentes de 1, 2, 5, 7, 14, 17 e 26,5 gDQO.Lreator-1.dia-1 e consequente diminuição do TDH de 240, 96, 48, 32, 24, 16 e 12 horas. O reator acidogênico na 2ª etapa foi operado por 417 dias consecutivos e COV de 120 g.DQO.Lreator1.dia-1, produzindo hidrogênio continuamente, alcançado valores de produção bruta de H2 de 7,60 LH2.dia-1. O reator metanogênico foi operado por 251 dias consecutivos, produzindo metano e alcançado valores de produção bruta de CH4 de 5,90 LCH4.dia-1. A eficiência de remoção de DQO do sistema de reatores foi de aproximadamente 90%, com contribuição aproximadamente de 10% para o reator acidogênico e contribuição aproximadamente de 80% para o reator metanogênico. O reator acidogênico alcançou rendimento de produção de hidrogênio por kg de melaço aplicado de 392 LH2.kgmelaço-1 e o reator metanogênico de 387 LCH4.kgmelaço-1. Para finalidade de comparações e aplicabilidade, o ganho energético global do sistema de reatores de duas fases foi de aproximadamente 5,7 kWh.kgmelaço-1 (1,4 kWh.kgmelaço-1 para o reator acidogênico e 4,3 kWh.kgmelaço-1 para o reator metanogênico). A produção continua de H2 obtida neste estudo está relacionada à associação das vias dos ácidos produtores de hidrogênio já consolidados pela literatura pertinente (acético e butírico) e pela produção de hidrogênio pela rota do ácido lático, devido a associação entre as comunidades de microrganismos estabelecidas no reator. O sequenciamento massivo MiSeq mostrou a seleção de diversos gêneros de microrganismos com redundância funcional e pertencentes principalmente aos Filos Firmicutes, Proteobacteria e Thermotogae, tais como Clostridium sensu stricto, Thermohydrogenium, Thermoanaerobacterium e Cellulosibacter (Firmicutes); Pseudomonas, Enterobacter, Shewanella e Petrobacter (Proteobacteria) e Fervidobacterium (Thermotogae). Microrganismos produtores de ácido lático também foram selecionados tais como: Lactobacillus, Leuconostoc, Sporolactobacillus e Trichococcus. Dos pontos de vista científico e tecnológico este estudo deu mais um passo para a compreensão dos bioprocessos envolvidos nos sistemas anaeróbios em dois estágios produzindo H2 e CH4 continuamente por longo período de tempo. / Anaerobic digestion has shown as an interesting process for renewable energy production (H2 and CH4), for a wide variety of organic compounds (carbon source). This study aimed to advance the understanding of a two-stage process anaerobic system (acidogenic bioreactor followed by methanogenic bioreactor) under thermophilic condition (55°C) fed with molasses, a sugarcane industry by-product. The experiments were conducted at up-flow structured bed reactors and sugarcane molasses was diluted with tap water, to adjust the concentration to the wastewater treatment. At first stage two acidogenic reactors were operated in parallel to evaluate different source of inocula and support bed, to obtain continuous and stable hydrogen production. It was applied 2.5, 5 and 10 gCOD.L-1 resulting in OLR of 30, 60 and 120 g.COD.Lreactor-1.day-1, with HRT fixed at 2 hours of hydrogenase gene was detected in both reactors but with higher number of copies of the gene in the reactor that showed higher hydrogen production: the reactor sed with sludge of UASB reactor and using polyurethane foam as support material. To this reactor was coupled a methanogenic reactor fed with effluent from acidogenic reactor and operated with increasing OLR (1, 2, 5, 7, 14, 17 e 26,5 gCOD.Lreactor-1.day-1) decreasing the HRT (240, 96, 48, 32, 24, 16 and 12 hours). The acidogenic reactor was operated during 471 days with OLR of 120 g.COD.Lreactor-1.day-1, with HRT fixed at 2 hours, with continuous hydrogen production with a gross production of 7.60 LH2.day-1. The methanogenic reactor was operated for 251 days, with continuous methane production of up to 5.90LCH4.day-1. The COD removal efficiency using the two-stage system was approximately 90% , with 10% contribution by the acidogenic reactor and 80% contribution by the methanogenic reactor. The acidogenic reactor achieved hydrogen yield per kg of applied molasses equal to 392 LH2.kgmolases-1. The methanogenic reactor achieved methane yield per kg of applied molasses equal to 387 LCH4.kgmolasses-1. For comparison and applicability purposes, the overall energy yield using the two stage reactor system was approximately 5.7 kWh.kgmolasses-1 (Acidogenic reactor 1.4 kWh.kgmolasses-1 and Methanogenic reactor 4.3 kWh.kgmolasses-1). The continuous production of H2 obtained in this study is related to the association of the hydrogen producer acids pathway established by the relevant literature (acetic and butyric) and the hydrogen production by the lactic acid pathway due to the microorganisms association established in the reactor. Metagenomic analysis by MiSeq Plataform revealed that hydrogen production was due the selection of microorganisms with functional redundancy mainly of Phyla Firmicutes, Proteobacteria and Thermotogae, such as Clostridium sensu stricto, Thermohydrogenium, Thermoanaerobacterium, Cellulosibacter (Firmicutes); Pseudomonas, Enterobacter, Shewanella and Petrobacter (Proteobacteria) and Fervidobacterium (Thermotogae). Genera of acid latic producers, such as Lactobacillus, Leuconostoc, Sporolactobacillus and Trichococcus, were also selected. From the scientific and technological point of view this study has taken another step towards the understanding of bioprocesses involving two stage anaerobic systems for a long term continuous production of H2 and CH4.

Ces dernières années, les matériaux fonctionnels hybrides ont commencé à être employés pour des applications de la haute technologie, allant des senseurs bio/médicaux, à la production d’énergie renouvelable. Pour cette raison, ils sont devenus le centre de plusieurs études dans le domaine des sciences des matériaux. Simultanément, des molécules conjuguées ont été examinée intensément à cause de leurs propriétés venant de leurs longs systèmes π, allant de la possibilité de conduire l’électricité, à leur capacité d’absorber la lumière dans une grande fenêtre spectrale. Le travail de cette thèse se concentre sur l’introduction de tels systèmes dans deux sortes de matériaux hybrides, les dispositifs photovoltaïques pour la production d’électricité (en particuliers les cellules solaires à pigment photosensible) et de carburants alternatifs (hydrogène), et pour les hydrogels biocompatibles sensibles aux stimuli (capables de conduire l’électricité et de réagir sous irradiation), et sur l’étude de leur influence sur les caractéristiques du matériau final. / In recent years hybrid functional materials began to be employed in a series of technologically advanced applications spanning from bio/medical sensors, to renewable energy generation. For this reason, they became the focus of several studies in the field of materials science. At the same time, conjugated molecules have also been intensively investigated, due to the properties arising by the presence of long π-conjugated systems, from the possibility to conduct electricity to the ability to absorb light in a wide range of wavelengths. This PhD work focused on the introduction of such systems in two different kinds of hybrid materials, namely photovoltaic devices for the production of electricity (in particular Dye Sensitzed Solar Cells) and alternative fuels (hydrogen), and biocompatible stimuli-responsive hydrogels (capable to conduct electricity and to react upon irradiation), and on the study of their influence on the characteristics of the final material.

Impulsionados pela busca de fontes limpas de energia, surgem os processos de combustao com recirculacao quimica (CLC), e reforma com recirculacao quimica (CLR). CLC e CLR sao processos quimicos para oxidacao de hidrocarbonetos gasosos. E utilizada a acao de transportadores de oxigenio (TO), para transferir oxigenio do ar para o combustivel (neste caso o metano), evitando-se o contato direto entre ar atmosferico e metano por diversos motivos. Os TOs, compostos por oxidos metalicos na forma de po fino, circulam continuamente entre dois reatores de leito fluidizado (reator de ar e de combustivel), sofrendo sucessivos ciclos de reducao e oxidacao. Os processos se diferenciam com relacao aos produtos, em CLC objetiva-se a geracao de energia, atraves da oxidacao completa do combustivel, resultando em uma mistura de CO2 e H2O, podendo ser facilmente separada por condensacao. No caso do CLR a oxidacao ocorre de maneira parcial, dando origem a uma mistura de gas de sintese (H2 + CO). O CLC apresenta vantagens com relacao aos processos tradicionais de captura de CO2, pois nao se faz necessaria a utilizacao de processos secundarios para separacao gasosa, economizando assim energia, alem do fato de nao gerar gases do tipo NOx. O presente trabalho apresenta a preparacao de duas series de materiais, via impregnacao seca, uma com composicao 2, 4 e 8% m/m de oxido de niquel e outra com os mesmo teores de oxido de niobio, suportados sobre alumina comercial de alta area superficial especifica. Os materiais foram caracterizados pelas tecnicas de picnometria a helio, volumetria de nitrogenio, porosimetria por intrusao de mercurio, DRX, MEV, TPR 5%H2/N2 analisado com TCD em ChemBet, TPR 5%CH4/Ar e TPO 5%O2/Ar sendo a variacao de massa analisada em termobalanca (TGA/DSC), alem de se utilizar de espectrometria de massas para analise dos gases gerados. Os diferentes transportadores de oxigenio foram testados em reator de leito fixo, sendo avaliados em diferentes condicoes experimentais tais como: temperaturas de operacao, vazoes de reagentes gasosos, concentracoes de metano, adicao de CO2 e H2O ao combustivel. Os produtos da reacao no reator de leito fixo foram analisados por cromatografia gasosa e espectrometria de massa. Os resultados mostraram que; o deposito de carbono sobre o catalisador pode ser drasticamente reduzido com a adicao de mistura oxidante junto ao combustivel e que estes oxidos estudados tem potencial aplicacao industrial, mostrando-se seletivos para reforma do metano com consecutiva producao de gas de sintese. / Driven by the demand for clean energy sources, arise chemical-looping combustion - CLC, and chemical-looping reforming - CLR. CLC and CLR are chemical processes for oxidation of gaseous hydrocarbons. Both of them use the action of catalysts, here called oxygen carriers (OC), which transfers oxygen from the air to the fuel (in this case methane), avoiding the direct contact between the two gases for various reasons. The OC\'s are composed of metal oxides in the form of fine power, circle continuously between two fluidized bed reactors (fuel reactor and air reactor), suffering successive cycles of reduction and oxidation. The two processes differ in relation to the products; the aim of CLC is generation of energy (heat), through the complete oxidation of the fuel, resulting in a mixture of CO2 and H2O, which can be easily separated by condensation. In the case of CLR, the oxidation occurs partially, resulting in synthesis gas, a mixture of H2 and CO. The CLC processes shows advantages when compared to other traditional processes for capture of CO2, because it is not necessary to use secondary processes for gas separation, saving energy, besides the fact of no NOx is generated. This work describes the preparation of two series of materials via dry impregnation, which are composed of 2, 4 and 8% w/w niobium oxide or nickel oxide, supported on commercial alumina, with high specific surface area. The materials were characterized by the techniques of helium pycnometry, nitrogen volumetry, mercury intrusion porosimetry, DRX, MEV, TPR 5% H2/N2 analyzed with TCD in ChemBet, TPR 5% CH4/Ar and TPO 5% O2/Ar, being the changes in mass and heat analyzed in a thermogravimetric balance (TGA/DSC) coupled to a mass spectrometer permitting the analysis of the generated gases. The different oxygen carriers were tested in a fixed bed reactor, evaluated in different experimental conditions, such as operation temperature, flow rate of gaseous reactants, methane concentrations, addition of CO2 and H2O to the fuel. The products of the reaction in the fixed bed reactor were analyzed by gas chromatography and mass spectrometry. The results show that: the carbon deposits over the catalysts can be drastically reduced by addition of oxidizing mixture together to the fuel and these studied oxides have a potential industrial application, showing selectivity to reforming of methane with consecutive synthesis gas production.

Impulsionados pela busca de fontes limpas de energia, surgem os processos de combustao com recirculacao quimica (CLC), e reforma com recirculacao quimica (CLR). CLC e CLR sao processos quimicos para oxidacao de hidrocarbonetos gasosos. E utilizada a acao de transportadores de oxigenio (TO), para transferir oxigenio do ar para o combustivel (neste caso o metano), evitando-se o contato direto entre ar atmosferico e metano por diversos motivos. Os TOs, compostos por oxidos metalicos na forma de po fino, circulam continuamente entre dois reatores de leito fluidizado (reator de ar e de combustivel), sofrendo sucessivos ciclos de reducao e oxidacao. Os processos se diferenciam com relacao aos produtos, em CLC objetiva-se a geracao de energia, atraves da oxidacao completa do combustivel, resultando em uma mistura de CO2 e H2O, podendo ser facilmente separada por condensacao. No caso do CLR a oxidacao ocorre de maneira parcial, dando origem a uma mistura de gas de sintese (H2 + CO). O CLC apresenta vantagens com relacao aos processos tradicionais de captura de CO2, pois nao se faz necessaria a utilizacao de processos secundarios para separacao gasosa, economizando assim energia, alem do fato de nao gerar gases do tipo NOx. O presente trabalho apresenta a preparacao de duas series de materiais, via impregnacao seca, uma com composicao 2, 4 e 8% m/m de oxido de niquel e outra com os mesmo teores de oxido de niobio, suportados sobre alumina comercial de alta area superficial especifica. Os materiais foram caracterizados pelas tecnicas de picnometria a helio, volumetria de nitrogenio, porosimetria por intrusao de mercurio, DRX, MEV, TPR 5%H2/N2 analisado com TCD em ChemBet, TPR 5%CH4/Ar e TPO 5%O2/Ar sendo a variacao de massa analisada em termobalanca (TGA/DSC), alem de se utilizar de espectrometria de massas para analise dos gases gerados. Os diferentes transportadores de oxigenio foram testados em reator de leito fixo, sendo avaliados em diferentes condicoes experimentais tais como: temperaturas de operacao, vazoes de reagentes gasosos, concentracoes de metano, adicao de CO2 e H2O ao combustivel. Os produtos da reacao no reator de leito fixo foram analisados por cromatografia gasosa e espectrometria de massa. Os resultados mostraram que; o deposito de carbono sobre o catalisador pode ser drasticamente reduzido com a adicao de mistura oxidante junto ao combustivel e que estes oxidos estudados tem potencial aplicacao industrial, mostrando-se seletivos para reforma do metano com consecutiva producao de gas de sintese. / Driven by the demand for clean energy sources, arise chemical-looping combustion - CLC, and chemical-looping reforming - CLR. CLC and CLR are chemical processes for oxidation of gaseous hydrocarbons. Both of them use the action of catalysts, here called oxygen carriers (OC), which transfers oxygen from the air to the fuel (in this case methane), avoiding the direct contact between the two gases for various reasons. The OC\'s are composed of metal oxides in the form of fine power, circle continuously between two fluidized bed reactors (fuel reactor and air reactor), suffering successive cycles of reduction and oxidation. The two processes differ in relation to the products; the aim of CLC is generation of energy (heat), through the complete oxidation of the fuel, resulting in a mixture of CO2 and H2O, which can be easily separated by condensation. In the case of CLR, the oxidation occurs partially, resulting in synthesis gas, a mixture of H2 and CO. The CLC processes shows advantages when compared to other traditional processes for capture of CO2, because it is not necessary to use secondary processes for gas separation, saving energy, besides the fact of no NOx is generated. This work describes the preparation of two series of materials via dry impregnation, which are composed of 2, 4 and 8% w/w niobium oxide or nickel oxide, supported on commercial alumina, with high specific surface area. The materials were characterized by the techniques of helium pycnometry, nitrogen volumetry, mercury intrusion porosimetry, DRX, MEV, TPR 5% H2/N2 analyzed with TCD in ChemBet, TPR 5% CH4/Ar and TPO 5% O2/Ar, being the changes in mass and heat analyzed in a thermogravimetric balance (TGA/DSC) coupled to a mass spectrometer permitting the analysis of the generated gases. The different oxygen carriers were tested in a fixed bed reactor, evaluated in different experimental conditions, such as operation temperature, flow rate of gaseous reactants, methane concentrations, addition of CO2 and H2O to the fuel. The products of the reaction in the fixed bed reactor were analyzed by gas chromatography and mass spectrometry. The results show that: the carbon deposits over the catalysts can be drastically reduced by addition of oxidizing mixture together to the fuel and these studied oxides have a potential industrial application, showing selectivity to reforming of methane with consecutive synthesis gas production.