Production of Hydrogen and their Use in Proton Exchange Membrane Fuel Cells

This work will show an overview of the hydrogen production from ethanol by steam reforming method, using distinct catalysts, resulting in low carbon monoxide content in H2 produced; a thermodynamic analysis of reforming employing entropy maximization, the ideal condition for ethanol, and other steam reforming reactions, the state of the art of steam reforming catalysts for H2 production with low CO content. Moreover, in the second part, there will be an overview of the use of hydrogen in a proton exchange membrane fuel cell (PEMFC), the fuel cell operational conditions, a thermodynamic analysis of PEMFC, the catalysts used in the electrodes of the fuel cell, consequences of the CO presence in the hydrogen fuel feed in PEMFC, and the operation conditions for maximum output power density

Development and evaluation of heterogeneous catalytic systems for Suzuki-Miyaura carbon-carbon coupling reactions

Submitted by Priscila Lima ([email protected]) on 2019-03-15T18:39:56Z No. of bitstreams: 2 Dissertação - Guilherme Botelho Meireles de Souza - 2019.pdf: 5510816 bytes, checksum: f6513aa17377c0da69eb5c65d1712796 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)Rejected by Liliane Ferreira ([email protected]), reason: 1) Por que você colocou título alternativo em português se o idioma principal já está em português? 2) Algumas palavras-chave apresentam pontuação NO FINAL (vírgula) 3) Assim como o título em português, você colocou resumo em outro idioma em português novamente. O principal já é em português. 4) Na citação, o nome do autor deve apresentar o último sobrenome em caixa alta. Veja: SOUZA, Guilherme Botelho Meireles de. OU SOUZA, G. B. M. Só na citação que é assim, pois é ABNT. Na caixa de metadados é normal, sem caixa alta. on 2019-03-18T15:39:47Z (GMT)Submitted by Priscila Lima ([email protected]) on 2019-03-18T15:46:38Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Guilherme Botelho Meireles de Souza - 2019.pdf: 5510816 bytes, checksum: f6513aa17377c0da69eb5c65d1712796 (MD5)Approved for entry into archive by Liliane Ferreira ([email protected]) on 2019-03-20T15:00:22Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Guilherme Botelho Meireles de Souza - 2019.pdf: 5510816 bytes, checksum: f6513aa17377c0da69eb5c65d1712796 (MD5)Made available in DSpace on 2019-03-20T15:00:22Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Guilherme Botelho Meireles de Souza - 2019.pdf: 5510816 bytes, checksum: f6513aa17377c0da69eb5c65d1712796 (MD5) Previous issue date: 2019-02-21Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESSuzuki-Miyaura cross-coupling reactions are one of the most efficient and powerful tools for the formation of new carbon-carbon bonds, which have been widely applied in modern organic synthesis and industrial processes. Generally, these reactions are carried out by homogeneous catalysis, employing expensive palladium complexes such as PdCl2 associated with harmful phosphine ligands. However, these synthetic route presents several drawbacks such as high associated toxicity, catalyst recovery difficulties and waste disposal problems. In this context, several heterogeneous catalysts were proposed to overcome the great challenge of separation and recovery of homogenous catalysts. Also, a low-cost catalyst was presented as an alternative for the usage of palladium as the main Suzuki-Miyaura cross-coupling catalyst. Palladium, Nickel, Copper and Cobalt catalysts supported on niobium pentoxide (Nb2O5) were synthesized via wet impregnation method and tested for the Suzuki-Miyaura coupling reaction between phenylboronic acid and 4- bromoanisole. The catalysts were well characterized by scanning electron microscopy, N2 physisorption, X-ray diffraction, X-ray fluorescence, Thermogravimetry/Differential Thermal Analysis. Both Copper and Cobalt catalyst did not show any activity towards Suzuki- Miyaura cross-coupling reaction. Palladium catalyst resulted in high isolated yields (up to 91%) under optimized conditions. Satisfactory yields (up to 48%) were achieved employing the Nickel catalyst. Recycling tests were performed and significant loss in activity was observed after the first catalytic cycle, which can be attributed to catalyst loss during its retrieval by filtration between cycles, leaching of the active phase, in particular for Pd/Nb2O5 catalyst, or the poisoning by inorganic species (mostly potassium) on the spent catalyst’s surface.As reações de acoplamento cruzado Suzuki-Miyaura são uma das ferramentas mais eficientes e poderosas na formação de novas ligações carbono-carbono e têm sido amplamente aplicadas em síntese orgânica moderna e em processos industriais. Geralmente, estas reações são realizadas via catálise homogênea, empregando complexos de paládio caros, tais como PdCl2, associados a ligantes de fosfina nocivos. No entanto, esta via sintética apresenta várias desvantagens como elevada toxicidade, dificuldades de recuperação dos catalisadores e problemas na eliminação dos resíduos. Neste contexto, vários catalisadores heterogêneos foram propostos para superar o grande desafio de separação e recuperação dos catalisadores homogêneos. Além disso, um catalisador de baixo custo foi apresentado como uma alternativa para o uso do paládio como principal catalisador na reações de acoplamento cruzado de Suzuki- Miyaura. Catalisadores de paládio, níquel, cobre e cobalto suportados em pentóxido de nióbio (Nb2O5) foram sintetizados via método de impregnação com excesso de solvente e testados frente as reação de acoplamento Suzuki-Miyaura entre o ácido fenilborônico e o 4-bromoanisol. Os catalisadores foram caracterizados por microscopia eletrônica de varredura, fisissorção de N2, difração de raios X, fluorescência de raios X e termogravimetria / análise térmica diferencial. Os catalisadores de cobre e cobalto não apresentaram qualquer atividade em relação à reação de acoplamento cruzado de Suzuki-Miyaura modelo. O catalisador de paládio proporcionou altos rendimentos isolados (até 91%) sob condições otimizadas. Rendimentos satisfatórios (até 48%) foram obtidos utilizando o catalisador de níquel. Testes de reciclagem foram realizados e significativa perda de atividade foi observada após o primeiro ciclo catalítico, o que pode ser atribuído à perda de catalisador durante a sua recuperação por filtração entre os ciclos, lixiviação da fase ativa, em particular para o catalisador Pd/Nb2O5, ou envenenamento pela deposição de espécies inorgânicas (principalmente potássio) na superfície do catalisador usado

Continuous Treatment of Refractory Wastewater from Research and Teaching Laboratories via Supercritical Water Oxidation–Experimental Results and Modeling

Teaching and research laboratories generate wastes of various compositions and volumes, ranging from diluted aqueous solutions to concentrated ones, which, due to milder self-regulation waste-management policies, are carelessly discarded, with little attention given to the consequences for the environment and human health. In this sense, the current study proposes the application of the supercritical water oxidation (SCWO) process for the treatment of complex refractory wastewater generated in research and teaching laboratories of universities. The SCWO, which uses water in conditions above its critical point (T > 647.1 K, p > 22.1 MPa), is regarded as an environmentally neutral process, uniquely adequate for the degradation of highly toxic and bio-refractory organic compounds. Initially, the wastewater samples were characterized via headspace gas chromatography coupled with mass spectrometry. Then, using a continuous tubular reactor, the selected operational parameters were optimized by a Taguchi L9 experimental design, aiming to maximize the total organic carbon reduction. Under optimized conditions—that is, temperature of 823.15 K, feed flow rate of 10 mL min−1, oxidizing ratio of 1.5 (50% excess over the oxygen stoichiometric ratio), and sample concentration of 30%—TOC, COD, and BOD reductions of 99.9%. 91.5% and 99.2% were achieved, respectively. During the treatment process, only CO2, methane, and hydrogen were identified in the gaseous phase. Furthermore, the developed methodology was applied for the treatment of wastewater samples generated in another research laboratory and a TOC reduction of 99.5% was achieved, reinforcing the process’s robustness. A thermodynamic analysis of SCWO treatment of laboratory wastewater under isothermal conditions was performed, using the Gibbs energy minimization methodology with the aid of the GAMS® 23.9.5. (General Algebraic Modeling System) software and the CONOPT 4 solver. Therefore, the results showed that SCWO could be efficiently applied for the treatment of wastewater generated by different teaching and research laboratories without the production of harmful gases and the addition of hazardous chemicals

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved