A couple of processes for electrosynthetic production of expendable reagents, namely acids, bases, and oxidants, from the native salt content of raw waters and industrial wastes were investigated, and the composition of mixed acids and bases made of sodium sulfate or sodium chloride salts were predicted using a model predicated on conservation principles, mass action relations, and Pitzer equations. Electrodialysis with bipolar membranes (BMED) was used to produce acids and bases in a single pass. Product concentration was limited only by the salt content of the feed water. The current efficiency for acid production was slightly higher than that for base, but neither dropped below 75%. Acid and base current utilization showed the same trends with respect to feed salt content and flow velocity, with higher efficiency at higher feed salt concentrations and flow velocities. Operating the BMED stack near the limiting current density of the bipolar membrane (BLCD) or above the limiting current density of the diluate compartment (LCD) decreased current efficiency and increased electrical power dissipation. Electrodialytic acid and base production was approximately10 times cheaper than the chemicals' f.o.b. unit costs as quoted on Alibaba.com. The mechanism and cost of on site peroxodisulfuric acid production by electrolysis of sulfuric acid solutions with boron doped diamond film anodes was investigated experimentally and with molecular dynamics (MD) and density functional theory (DFT) simulations. The cost of on site peroxodisulfate production was approximately 4 times less expensive than purchasing a 25 lb bag. It was shown that direct discharge of sulfate species produces sulfate radicals, which subsequently combined to form peroxodisulfuric acid. The likely hood of these reactions was dependent on electrode surface condition. Sulfate radicals could also be produced in solution by reaction with hydroxyl radicals generated by water discharge.

L’électrosynthèse microbienne est une technologie innovante qui permet de convertir le dioxyde de carbone en molécules organiques en utilisant une cathode comme source d’électrons de la réduction microbienne du CO2. Le procédé «Biorare» propose de coupler l’électrosynthèse microbienne avec l’oxydation de déchets à l’anode afin d’augmenter le rendement énergétique du procédé. Il devient ainsi possible de traiter un effluent à l’anode et de valoriser du CO2 à la cathode. La thèse a eu pour objectif d’améliorer les performances de la bioanode et de la biocathode séparément, afin de réaliser in fine un prototype de procédé «Biorare» à l’échelle du laboratoire. Parmi plusieurs types de déchets testés, les boues biologiques se sont avérées bien adaptées pour une utilisation à l’anode en assurant des densités de courant jusqu’à 10 A/m2. Toutefois, ces performances étant peu reproductibles, nous avons choisi d’exploiter des biodéchets, dont le gisement représente plus de 22 millions de tonnes en France et la valorisation est aujourd’hui obligatoire. Leur utilisation brute n’a pas permis de dépasser 1 A/m2 mais une méthode innovante de formation des bioanodes a permis d’augmenter les densités de courant jusqu’à 7 A/m2, de façon reproductible et dans des conditions extrapolables. Les travaux sur les biocathodes ont révélé que l’hydrogène est un intermédiaire réactionnel clé pour le transfert d’électrons de la cathode vers les microorganismes qui réduisent le CO2. Cela a conduit à découpler le procédé initial en deux étapes : l’hydrogène est produit dans une cellule d’électrolyse microbienne qui oxyde les biodéchets et, en aval, un bioréacteur gaz-liquide utilise l’hydrogène pour convertir le CO2 en acétate, éthanol, formiate, ou butyrate, suivant les systèmes microbiens. Cette stratégie permet d’augmenter les performances d’un facteur 24 avec une vitesse de production d’acétate de 376 mg/L/j et des concentrations jusqu’à 11 g/L. / Microbial electrosynthesis is an innovative technology to produce organic molecules from CO2, using a cathode as electron source for the microbial reduction of CO2. The Biorare process intends to associate the microbial electrosynthesis with the oxidation of organic wastes at the anode, in order to increase the energetic yield of the process. The system allows thus both the treatment of polluted effluents at the anode and CO2 valorization to organic molecules at the cathode. The purpose of the PhD work was to improve the bioanode and biocathode performance separately, to finally design a Biorare prototype at laboratory scale. Among the various wastes tested, biological sludge was a good substrate, which led to current densities up to 10 A/m2. However, the performance was not reproducible and it was decided to use food wastes, which constitute an abundant resource of 22 million tons in France that must be valorized. The use of raw food waste did not allow exceeding 1 A/m2, but a new method for bioanode formation improved the current density up to 7 A/m2 in a reproducible and close-to-industrial way. The study on biocathodes revealed hydrogen as a key intermediate in electron transfer from the cathode to the microbial cells that reduce CO2. This led to dissociate the initial process into two steps: hydrogen is produced in a microbial electrolysis cell that oxidizes food wastes and, downstream, a gas-liquid bioreactor uses hydrogen to convert CO2 to acetate, ethanol, formate or butyrate, depending on the microbial system. This strategy allowed increasing the performance by a factor 24 with a maximal acetate production rate of 376 mg/L/j and concentrations up to 11 g/L.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-05-06T14:20:44Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE DIGITALIZADA JADSON LIRA.pdf: 4010526 bytes, checksum: 63a863c1b0d3601216c34c2e43933805 (MD5) / Made available in DSpace on 2016-05-06T14:20:44Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE DIGITALIZADA JADSON LIRA.pdf: 4010526 bytes, checksum: 63a863c1b0d3601216c34c2e43933805 (MD5) Previous issue date: 2015-10-07 / CNPq / PDSE / CAPES / No presente trabalho foi estudada uma nova metodologia eletroquímica para a síntese de 2,2’-bipiridinas e 3,3’-bipiridazinas através da reação de homoacoplamento catalisada por um complexo de Ni, em eletrodo constituído por uma mistura de materiais carbonáceos (grafite e nanotubos de carbono). Tal metodologia envolveu o uso de uma célula de cavidade e uma pequena quantidade de solvente. Foi constatado que a adição de nanotubos de carbono à composição da matriz catódica, aumentou a área efetiva do eletrodo e a condutividade, contribuindo para o aumento da intensidade da corrente e difusão de espécies iônicas. Foi possível trabalhar com uma solução aquosa de KCl 0,1 mol.L-1 no compartimento anódico com uma redução significativa do uso de solvente orgânico na cavidade catódica (dimetilformamida, 65 vezes menor que uma reação clássica). Também foi possível diminuir a quantidade de solvente necessário para extração e purificação dos produtos (diclorometano/hexano, 100 vezes menor), obtendo-se bons rendimentos para os produtos de acoplamento (83-89%), com exceção das eletrólises que envolveram reagentes di-halogenados (32-79%). Foi observado que a eficiência de corrente variou de acordo com o método de eletrólise (potencial ou corrente controlada), sendo mais efetivo a potencial controlado. Outros catalisadores (Pd e Co) foram testados proporcionando baixos rendimentos de homoacoplamento (<45%). O limite de reutilização do cátodo foi atestado através da análise por XPS de amostras do material coletadas ao longo de quatro eletrólises (sem uso de quantidades adicionais do catalisador e do eletrólito de suporte). E revelou uma redução na atividade do catalisador de níquel, possivelmente provocada pela mudança na sua composição após sucessivas eletrólises. / In the present work, it was investigated a new electrochemical method for the synthesis of 2,2'-bipyridines and 3,3’-bipyridazines through the homocoupling reaction catalyzed by a Ni complex, into an electrode comprising a mixture of carbonaceous materials (graphite and carbon nanotubes). This methodology involved the use of a cavity cell and a small amount of solvent (dimethylformamide 300L). The addition of carbon nanotubes to the cathode matrix composition increased the effective area of the electrode and conductivity, thus contributing increment of the current intensity and diffusion of ionic species. It was possible to work with a 0.1 mol.L-1 KCl aqueous solution in the anode compartment, with a significant reduction of organic solvent used in the cathodic cavity (dimethylformamide, 65 times lower than the classical reaction). It was also possible to reduce the amount of solvent needed for extraction and purification of the product (dichloromethane/hexane, 100 times lower), resulting in good yields of the coupling product (83-89%), except with electrolysis involving dihalogenated reagents (32-79%). It was also observed that the current efficiency varies with the electrolysis method (controlled potential or current), being more efficient at controlled potential. Other catalysts (Pd and Co) were tested providing low yields of the homocoupling product (<45%). The recycling limit of the cathode was attested by XPS analysis of the material collected over four electrolysis (without the use of additional amounts of the catalyst and supporting electrolyte), which revealed a reduction in the nickel catalyst activity; possibily caused by the change in its composition after successive electrolysis.

Orientador: Rodnei Bertazzoli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-08T23:20:02Z (GMT). No. of bitstreams: 1 Oliveira_Barbarade_M.pdf: 510349 bytes, checksum: 9d4dd8bbac953e65a290c93e04ed8aee (MD5) Previous issue date: 2007 / Resumo: Este trabalho apresenta o estudo do comportamento dos surfactantes catiônicos cloreto de tricaprilmetilamônio (Aliquat® 336) e cloreto de metiltributilamônio (Aliquat® 175) na eletrossíntese de peróxido de hidrogênio. Inicialmente, foram realizados experimentos de medida de tensão superficial pelo método do anel de du Noüy, com o objetivo de encontrar a concentração micelar crítica dos surfactantes. As medidas foram realizadas em solução de K2SO4 0,1 mol L-1, em pH 3,5, a 25 ± 1°C. Uma CMC de a 4,0 10-5 ± 1,0 10-5 mol L-1 para o tensoativo A336 e 3,2 10-2 ± 1,0 10-2 mol L-1 para A175 foram consideradas. Em seguida, foram feitas voltametrias de varreduras lineares em solução de K2SO4 0,1 mol L-1, em pH 3,5, a 25 ± 1°C em solução saturada de oxigênio para diferentes concentrações dos surfactantes com o uso de um eletrodo de carbono vítreo monolítico (CVM). A partir dos voltamogramas obtidos, foram comparadas as separações entre os patamares de redução do O2 observados para as diferentes concentrações dos tensoativos. Também foram obtidos os gráficos de Levich, observando que o processo de redução é controlado por transporte de massa. A partir de relação linear destacada pelo gráfico de Levich, obtiveram-se os valores do coeficiente de difusão do oxigênio, que foram comparados com valores já obtidos na literatura. Os dados foram explorados acerca dos valores de CMC encontrados para os surfactantes. Posteriormente, foi realizada a redução direta do O2 à H2O2 em solução ácida na presença dos surfactantes em um reator eletroquímico de batelada com recirculação com catodo de carbono vítreo reticulado (CVR), sob diferentes concentrações dos tensoativos. Os experimentos foram conduzidos em solução de K2SO4 0,1 mol L-1, em pH 3,5, a 17 ± 1 °C em potencial constante a -1,6 V vs. Pt. A vazão de oxigênio gasoso em solução foi mantida em 6 L min-1 durante todos os ensaios. A máxima concentração de peróxido de hidrogênio gerado foi de 521,5 mg L-1 para a concentração de 1,0 10-5 mol L-1 do surfactante A336 durante 2 horas de eletrólise, com um consumo energético de 3,5 kWh kg-1 e uma eficiência de corrente de 72 %. Já para o surfactante A175, sob as mesmas condições, o máximo de peróxido gerado foi de 471,0 mg L-1 para a concentração de 1,0 10-5 mol L-1 do surfactante / Abstract: As a first step of the investigation, experiments of surface strength measurement were performed by using the du Nouy method, to determine of the surfactants¿ Critical Micelle Concentration (CMC). Concentrations ranging 4.0 10-5 ± 1.0 10-5 mol L-1 and from 3.2 10-2 ± 1.0 10-2 mol L-1 for A336 and A175, respectively, were considered. Experiments were carried out in a K2SO4, 0.1 mol L-1 solution, pH 3.5 and temperature of 25 ± 1 oC. Then, linear sweep voltammetry technique was used to record i/E couples on vitreous carbon disc electrode in oxygen saturated 0.1 mol L-1 K2SO4 solution, pH 3.5, in a cell of three electrode. By the examination of the voltammograms for oxygen reduction were identified a dependence of the surfactant concentration. I/E values in the region of mass transfer control were organized in Levich plots, which through at the oxygen diffusion coefficients were calculated as a function of the surfactants concentration. In a sequence of the investigation, the electrosynthesis of hydrogen peroxide was carried out in a flow electrochemical reactor in which the O2 saturated solution was recirculated through a reticulated vitreous carbon cathode. Different concentrations of surfactants were used. Potential selected for the runs was ¿1.6V vs. Pt and oxygen flow rate was 6 L min-1. In two hours of electrolysis, 521.5 mg L-1 of H2O2 was generated using 1,0 10-5 mol L-1 of A336. Current efficiency was 72% and energy consumption was 3.5 kWh kg-1 of hydrogen peroxide. By using the same concentration of A175, hydrogen peroxide concentration was 471.0 mg L-1 / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Microbial electrosynthesis (MES) has recently emerged as a novel biotechnology platform for value-added product generation from waste CO2 stream. Integrating MES technology with renewable energy sources for both CO2 valorization and renewable energy storage is regarded as one type of artificial photosynthesis and a perfect example of circular bioeconomy. However, several challenges remain to be addressed to scale-up MES as a feasible process for chemical production, which include enhanced production rate, reduced energy consumption and excellent resistance to external fluctuations. To fill these knowledge gaps, different in-depth approaches were proposed in this dissertation by optimizing the cathode architecture, CO2 flow rates and utilizing efficient photoelectrode to improve MES performance and stability. A novel cathode design, made of conductive hollow fiber membrane, was developed in this dissertation to improve CO2 availability at MES cathode surface via direct CO2 delivery to chemolithoautotrophs through the pores in the hollow fibers. By modifying the hollow fiber surface with carbon nanotubes (CNTs), higher bioproduct formation was achieved with excellent faradaic efficiencies, which could be attributed to the improved surface area for bacterial adhesion and the reduction of cathodic electron transfer resistance. Since CO2 flow rate from industrial facilities typically varies over time, this hollow-fiber architecture was also applied to test the resistance of MES systems to CO2 flow rate fluctuation. Stepwise increase of CO2 flow rates from 0.3 ml/min to 10 ml/min was tested and the effect of CO2 flow rate fluctuations was evaluated in terms of biochemical generation and microbial community. MES was further integrated with renewable energy supply for both energy storage and CO2 transformation into biofuels and biochemicals. Stable MES photoanode, based on molybdenum-doped bismuth vanadate deposited on fluorine-doped tin oxide glass (FTO/BiVO4/Mo), was prepared for efficient solar energy harvesting and overpotential reduction for oxygen evolution reaction (OER), which contributed to one of the highest solar-to-biochemical conversion efficiencies ever reported for photo-assisted MES systems. The applied nature of this dissertation with fundamental insights is of great importance to bring MES one step closer to full-scale applications and enable MES technology to be economically more viable for renewable energy storage and CO2 valorization.

Les travaux s’articulent autour du développement de nouveaux agents de fluoration et sur l’étude de leurs réactivités au cours de différentes réactions.Dans une première partie, nous décrivons la synthèse de nouvelles sources réactives de fluorure à partir de liquides ioniques de type imidazolium possédant un fluor en partie anionique. Les deux liquides ioniques [bmim][F] et [bdmim][F] obtenus ont ensuite été testés dans différents processus de monofluoration et de fluorodésulfuration oxydative.Une deuxième partie concerne le développement de réactifs de trifluorométhoxylation.Dans un premier temps, nous nous sommes attachés à synthétiser des nouveaux précurseurs de carbène possédant un groupement OCF3. Nous avons ensuite évalué leur réactivité au cours de différents processus. Dans un second temps, nous nous sommes axés sur la réactivité d’un composé FAR (Fluoroalkyl Amino Reagent) dans des réactions d’acylation aromatique.Enfin, le dernier chapitre rapporte l’étude du comportement électrochimique en réduction du gaz SF6, le but étant d’obtenir une nouvelle source radicalaire de SF5. Après une première partie analytique, l’hexafluorure de soufre a été engagé dans des processus d’électrosynthèse pour tenter de piéger les intermédiaires réactionnels issus de sa réduction. / The manuscript deals the development of new fluorinating reagents and their reactivity in various reactions.In the first part, we were interested in developing new fluoride sources from ionic liquids with imidazolium as the cationic part, and associated to the fluoride as anion. Two ionic liquids, [bmim][F] and [bdmim][F], were obtained. They were then tested in monofluoration and fluorodesulfurization reactions.The second chapter concerns the development of new trifluoromethoxylation reagents.We began by synthetizing new carbene precursors with an OCF3 group. We then evaluated their reactivities in different processes. A second part was centered on a FAR compound and its reactivity in aromatic acylation reactions.Finally, the last chapter describes the behavior of SF6 in electrochemistry reduction with different conditions, the aim being to have a new source of SF5 radical. After a first part concerning analytical studies of the sulfur hexafluoride, the aforementioned compound was engaged an electrosynthetic process to trap intermediate species coming from its reduction.

No description available.

The efficiency of boron-doped diamond electrodes (BDD) has been investigated by electrolysis of an aqueous solution containing sodium sulfate. A Synthesis StarterKit from Condias was used, which contained the BDD anode with an active surface area of 3.14 cm2, and electrosynthesis was performed in a batch mode reactor. In this report, the electrooxidation of sodium sulfate to sodium persulfate is well reported. The production of persulfate was studied at different cell voltages and electrolyte concentrations. The amount of persulfate produced was determined by the iodometric titration and itwas found that its concentration in the electrolyte was directly proportional to the persulfate concentration, i.e, a larger amount of persulfate could be obtained when the electrolyte was highly concentrated, up to 1 M. For each of the samples the amount of persulfate that theoretically is possible to produce was calculated and subsequently compared to the actual amount of persulfate that was formed, ie. current efficiencies. These current efficiencies were unexpectedly low for all experiments except for one data point. Hydrogen gas was also produced as a by-product at the cathode, but it couldn ot be collected in the present setup. The results and some possible improvements are discussed in the report. / Effektiviteten av att använda bor-dopad diamant (BDD) för elektrosyntes med en vattenlösning innehållande natriumsulfat för att producera persulfat har undersökts. Den utrustningen som använde svar ett Syntes StarterKit från företaget Condias, denna innehöll en cell med BDD som anodmaterial vilken hade en aktiv area på 3,14 cm2. Produktionen av persulfat studerades vid olika cellspänningar och elektrolytkoncentrationer. Mängden av producerad persulfat bestämdes genom titrering. Detv isade sig att koncentrationen av elektrolyten var proportionell mot persulfatkoncentrationen, dvs. mer persulfat producerades vid högre elektrolytkoncentrationer. För varje prov beräknades även det teoretiska antalet mol persulfat som kan åstadkommas och jämfördes sedan med det faktiska antalet mol som producerades, detta gav strömeffektiviteten för den önskade reaktionen. Denna effektivitet var oväntat låg för alla prov förutom ett i experiment 4. Vätgas producerades som en biprodukt vid katoden, men på grund av begränsad tillgång till utrustning och tid kunde denna gas inte samlas uppför vidare analys. Resultaten och möjliga förbättringar diskuteras även i rapporten.

No description available.

Neste trabalho são descritas a síntese e a redução eletroquímica em DMF de alguns cinamatos de metila substituídos no anel aromático. O objetivo deste estudo foi verificar a influência de vários substituintes sobre o curso da reação de eletro-hidrodimerização (EHD). Os substratos utilizados foram os o-metil- (1), o-cloro- (2), o-nitro- (3), m,p-dicloro- (4), m-cloro- (5) e p-cloro- (6), m-nitro- (7), o-metoxicarbonil- (8) cinamatos de metila. As técnicas empregadas foram a voltametria cíclica (verificação dos potenciais de redução) e eletrólises preparativas a potencial controlado. Quando o substrato 1 foi eletrolisado, uma mistura de dois estereoisômeros do 4,5-bis-(o-metilfenil)-2-oxo-ciclopentanocarboxila-to de metila, ainda não descritos na literatura, foi obtida, um resultado diferente das EHD de cinamatos descritas que conduzem a um único estereoisômero com elevada diastereosseletividade. O o-clorocinamato de metila (2) investigado em dois potenciais diferentes, sofreu uma desalogenação e forneceu o cinamato de metila (-1,25 V vs. Ag/AgI) e este foi transformado em seu hidrodímero cíclico em –1,45 V vs. Ag/AgI. Nos substratos 4 e 6 ocorreu uma competição entre a desalogenação e a dimerização enquanto que no caso de 5 somente foi observada a EHD. Foi sugerido um mecanismo para a desalogenação. Após eletrólises em vários potenciais, os nitroderivados 3 e 7 conduziram a misturas dos reagentes de partida e os ácidos carboxílicos correspondentes, mas não foram observados produtos de EHD. As eletrólises do o-metoxicinamato de metila (8) não forneceram o dímero esperado na redução de cinamatos, mas compostos policíclicos inéditos cuja formação pode ser convenientemente explicada por meio de ciclizações de Dieckmann que envolvem o grupo metoxicarbonílico do anel aromático. / The synthesis and electrochemical reduction in DMF of some ring substituted cinnamic esters are described. The main objective if this work is to verify the influence of the substituents on the electrohydrodimerization (EHD). The substrates studied were the methyl esters of o-methyl- (1), o-chloro- (2), o-nitro- (3), m,p-dichloro- (4), m-chloro- (5), p-chloro- (6), m-nitro- (7) and o-methoxycarbonyl- (8) cinnamic acids. Their electrochemistry was investigated employing cyclic voltammetry (determination of the reduction potentials) and preparative electrolysis at controlled potential. When substrate 1 was electrolyzed, a mixture of two stereoisomers of methyl 4,5-bis-(o-methylphenyl)-2-oxo-cyclopentane-carboxylate, not yet described in literature, was obtained, a result which differs from the usual EHD of cinnamates, which lead to only one stereoisomer with high diastereoselectivity. Methyl o-chlorocinnamate (2) electrolysed at –1,25 V vs Ag/AgI was dehalogenated and afforded methyl cinnamate. When the electrolysis was performed at –1,45 V, the main product was the cyclic expected hydrodimer of methyl cinnamate. In the case of substrates 4 and 6 a competition of dehalogenation and cimerization was observed whereas for 5 only the EHD occurred. A mechanism for the dehalogenation is suggested. Several electrolysis at different potentials, of the nitro-derivatives 3 and 7 yielded mixtures of starting material and the corresponding carboxylic acids. In this no EHD products were observed. The electrochemical reduction of methyl o methoxycarbonyl-cinnamate (8) did not lead to the expected EHD dimer, but new polycyclic compounds were isolated. Their formation is conventiently explained by Dieckmann cyclization which involve the methoxycarbonyl group of the aromatic ring.