Resumo Os óxidos de molibdênio são materiais tecnológicos muito interessantes, que apresentam diversos usos industriais. A adição de um segundo metal pode melhorar suas propriedades catalíticas, bem como alterar o comportamento eletrônico. Várias metodologias para adicionar um segundo metal podem ser encontradas na literatura, porém a comparação entre elas é dificilmente encontrada. Aqui duas rotas de processamento foram aplicadas para a síntese de óxido de molibdênio com adição de cobalto: via sólida e via úmida. Molibdato de amônio e nitrato de cobalto foram usados como materiais de partida e a adição de cobalto foi realizada antes da calcinação. Os materiais iniciais foram caracterizados por MEV, FTIR, FRX e DRX. Os produtos de calcinação foram avaliados por MEV, FRX, DRX e espectroscopia UV-vis. Produto calcinado cuja dopagem foi realizada via estado sólido apresentou menor tamanho de cristal (~25 nm), maior retenção de cobalto (desvio, δ ~10%) e band gap levemente menor em comparação com aquele dopado por via úmida (~40 nm e δ>11%).

Abstract Molybdenum oxides are very interesting technologic materials, which present several industrial uses. The addition of a second metal may enhance its catalytic properties as well as change electronic behavior. Several methodologies for adding a second metal can be found in the literature, however, the comparison between them is hardly ever found. Here two processing routes were tested for the synthesis of molybdenum oxide with cobalt addition: solid-state and wet routes. Ammonium molybdate and cobalt nitrate were used as starting materials and cobalt addition was carried out before calcination. Starting materials were characterized by SEM, FTIR, XRF, and XRD. Calcination products were evaluated by SEM, XRF, XRD and UV-vis spectroscopy. Calcined products whose doping was performed via solid-state presented smaller crystal size (~25 nm), larger cobalt retention (deviation, δ ~10%) and slightly smaller band gap in comparison to those doped via the wet route (~40 nm and δ>11%).

Abstract Due to ever more severe environmental regulations regarding SOx, NOx and other pollutants' emissions, there has been an interest in developing new and improved catalysts for hydroprocessing reactions. Mo2C has been reported to display good selectivity and activity for those reactions, especially for HDS. Addition of another metal to the carbide structure may improve catalytic properties. Mo2C with low cobalt addition (2.5 and 5%) was obtained via gas-solid reaction in a fixed bed reactor with CH4 (5%)/H2 atmosphere. XRD and TG/DTA analysis of the precursors were carried out in order to understand its mass loss profile, doping metal presence and phase distributions. CoMoO4 as well as MoO3 were identified after calcining doped precursors at 600 °C/180min. SEM, XRD, XRF, TOC, BET and laser granulometric analysis of the reaction products were also performed. Compositions verified by XRF and theoretical values were compatible. At 700 °C both carbide (Mo2C) and oxide (MoO2) phases are present, as identified in XRD analysis and observed by SEM. At 750 °C only single phase Mo2C was verified by XRD, indicating Co dispersion on the carbide matrix. Morphology at this temperature is compatible with pure Mo2C, though XRF indicates Co presence on the material.