Hydrogen is a vital component in several different chemical reactions as well as a potential fuel source for the future. The water gas shift (WGS) reaction converts CO and water to hydrogen and CO2. The objective of this work is to first, characterize the potential benefits of the addition of lanthanum oxide (lanthana) to the iron-chromium-copper (Fe-Cr-Cu) oxide catalysts industrially used in high temperature water gas shift processes, and second, analyze these catalysts using in-situ UV-Visible spectroscopy. The benefits of each component in the catalyst are discussed as well as potential benefits from the addition of lanthana. Lanthana is a rare earth oxide that dramatically increases the surface area of the iron based WGS catalysts, and small concentrations of other rare earth oxides (i.e. cerium) have been shown to increase the rate of desorption of CO2 from iron surfaces (Hu Yanping 2002). Lanthana has similar chemical properties to other rare earth oxides tested and has not been previously tested as an additive to the WGS catalyst. Therefore catalysts with 0, 1, 2, 5, 10, and 20 wt% lanthana were made via a co-precipitation method in order to measure changes in activity, physical stability, and thermal stability. Catalyst characterization techniques utilized include electron dispersive X-ray spectroscopy (EDX), temperature programmed reduction (TPR) with hydrogen, and nitrogen physisorption (BET). The kinetic analysis was performed utilizing both mass spectroscopy (MS) and gas chromatography (GC). The addition of 1 wt% lanthana to the Fe-Cr-Cu catalysts increases WGS reaction rates of the catalyst at 425°C and 350°C, however the 0% La catalyst has the highest rates at 375°C and 400°C. The 0% La catalyst shows significant drop off in rate at 425°C, suggesting that the lanthana provides a small thermal stabilizing, i.e. the addition of lanthana prevents catalyst sintering at higher temperatures. Traditionally, chromia acts as the sole thermal stabilizer in these catalysts. The addition of large amounts of lanthana inhibits the chromia stabilizing effect, however small additions of lanthana appear to have an additional catalyst promotional effect without interfering with the chromia thermal stabilization. The increased WGS reaction rates at higher temperatures could allow for greater throughput of reactants in industrial settings. Higher concentrations of lanthana decrease the activity due to what is believed to be disruption of the chromia stabilizing effect as well as reduced amount of the active phase of catalyst. In-situ UV-Visible analysis shows that the oxidation state of the iron in the catalyst has a direct correlation to the UV-Visible light absorbance of the surface of the iron catalyst. Extent of reduction is traditionally measured with a synchrotron which is significantly more expensive than UV-Vis spectroscopy. This study uses the more economical UV-Vis spectrometer to determine similar information. The lanthana doped catalysts show an over-reduction of iron during WGS conditions (i.e. rapid reduction of Fe2O3 to Fe3O4 and FeO).

Orientador: Lauro Tatsuo Kubota / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T13:04:11Z (GMT). No. of bitstreams: 1 Camargo_MaiuiNagaoLindqquerde_M.pdf: 3614340 bytes, checksum: 6d1263c93417d379a0c3010830acb5e6 (MD5) Previous issue date: 2015 / Resumo: Este trabalho visa demonstrar como o grau de redução do óxido de grafeno eletroquimicamente reduzido (ERGO) pode ser modulado dependendo das condições experimentais utilizadas para se fazer a redução eletroquímica, e como ele influencia nas propriedades eletroquímicas do material final. Esta influência pôde ser constatada por medidas eletroquímicas, de espectroscopia Raman e de fotoelétrons excitados por raios-X (XPS). Através de experimentos eletroquímicos feitos na presença da sonda de ferri/ferrocianeto de potássio, foi possível demonstrar que os eletrodos de ouro modificados com os ERGOs com maiores graus de redução se comportam eletroquimicamente de maneira similar ao não modificado, e portanto, a redução dos grupos oxigenados da superfície do material é importante para que essa similaridade seja atingida. No entanto, essa sonda não permite monitorar o balanço entre grupos oxidados e reduzidos e para fazer isso, foi escolhida uma sonda eletroativa sensível aos grupos oxigenados. Análises feitas na presença de ?-nicotinamida adenina dinucleotídeo (NADH) demonstraram que grupos funcionais oxigenados essenciais para a oxidação dessa espécie estavam diminuindo na superfície do material com o aumento do grau de redução deste. Os espectros de Raman e de XPS também confirmaram essa informação. Além disso, a capacidade adsortiva do ERGO foi testada utilizando o corante Azul de Meldola. Novamente, o grau de redução do ERGO teve papel fundamental, uma vez que interações ?-? ou eletrostáticas podem ser favorecidas entre o ERGO e o corante, dependendo do grau de redução do primeiro, implicando em propriedades distintas dos materiais frente a oxidação de NADH / Abstract: This work aims to demonstrate how the extent of reduction of the electrochemically reduced graphene oxide (ERGO) can be modulated depending on the experimental conditions used for performing the electrochemical reduction, and how it influences on the electrochemical properties of the final material. This influence can be verified by electrochemical, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. By means of electrochemical experiments carried out in the presence of the ferro/ferricyanide probe, it was possible to demonstrate that the gold electrodes modified with the ERGOs with higher extents of reduction behave electrochemically in a similar manner to the non-modified, and therefore, the reduction of the oxygenated groups on the surface of the material is important for this similarity to be reached. However, this probe does not permit the monitoring of the balance between oxidized and reduced groups and to do so, an electroactive probe sensitive to the oxygenated groups was chosen. Analyses done in the presence of ?-nicotinamide adenine dinucleotide (NADH) enabled the conclusion that the oxygenated functional groups essential for the oxidation of this species decreased on the surface of the material with the increase of the extent of reduction. The Raman and XPS spectra also confirmed this information. Apart from this, the adsorptive capacity of the ERGO was tested using the dye Meldola's Blue. Once again, the extent of reduction of the ERGO had a fundamental role, since ?-? or electrostatic interactions can be favoured to occur between the ERGO and the dye, depending on the extent of reduction of the former, leading to distinct properties of the materials regarding NADH oxidation / Mestrado / Quimica Analitica / Mestra em Química