The removal of trace amounts of acetylene in ethylene streams is a high-volume industrial process that must possess high selectivity of alkyne hydrogenation over hydrogenation of alkenes. Current technology uses metallic nanoparticles, typically palladium or platinum, for acetylene removal. However, problems arise due to the deactivation of the catalysts at high temperatures as well as low selectivities at high conversions. Pore expanded MCM-41 is synthesized via a two-step strategy in which MCM-41 was prepared via cetyltrimethylammonium bromide (CTMABr) followed by the hydrothermal treatment with N,N-dimethyldecylamine (DMDA). This material was washed with ethanol to remove DMDA, or calcined to remove both surfactants. PE-MCM-41 based materials were impregnated with palladium, gold, and palladium-gold nanoparticles. The removal of DMDA had an effect on both the conversion and selectivity, in which they were found to drop significantly. However, by using the bimetallic PdAu catalysts, higher selectivity could be achieved due to increased electron density.

The removal of trace amounts of acetylene in ethylene streams is a high-volume industrial process that must possess high selectivity of alkyne hydrogenation over hydrogenation of alkenes. Current technology uses metallic nanoparticles, typically palladium or platinum, for acetylene removal. However, problems arise due to the deactivation of the catalysts at high temperatures as well as low selectivities at high conversions. Pore expanded MCM-41 is synthesized via a two-step strategy in which MCM-41 was prepared via cetyltrimethylammonium bromide (CTMABr) followed by the hydrothermal treatment with N,N-dimethyldecylamine (DMDA). This material was washed with ethanol to remove DMDA, or calcined to remove both surfactants. PE-MCM-41 based materials were impregnated with palladium, gold, and palladium-gold nanoparticles. The removal of DMDA had an effect on both the conversion and selectivity, in which they were found to drop significantly. However, by using the bimetallic PdAu catalysts, higher selectivity could be achieved due to increased electron density.

Transition metal nanoclusters are more active and selective catalysts than their bulk counterparts as the fraction of surface atoms increases with the decreasing particle size. When stabilized in organic or aqueous solutions, they can catalyze many reactions. The catalytic activity of metal nanoclusters depends on the particle size and size distribution. Particle size can be controlled by encapsulating the nanoclusters in the cavities of highly ordered porous materials such as zeolites. In this project, osmium(0) nanoclusters were formed within the void spaces of zeolite. Thus, nanoclusters of certain size were prepared as supported catalyst. Osmium(III) cations were introduced into the cavities of zeolite by ion exchange and were reduced partially or completely to form intrazeolite osmium(0) nanoclusters. The intrazeolite osmium(0) nanocusters were characterized by HRTEM, TEM, EDX, XPS, XRD, ICP-OES spectroscopic methods and N2 adsorption-desorption technique. Intrazeolite osmium(0) nanoclusters were employed as catalyst in the aerobic oxidation of alcohols in organic solution.

Made available in DSpace on 2015-05-14T13:21:33Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1872624 bytes, checksum: 82d5c5729cedad38a0a2aa4e489a50cd (MD5) Previous issue date: 2009-11-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Biodiesel production is based on the is transesterification of vegetable oils or animal fat, using homogeneous or heterogeneous catalysts. Wheres, the heterogeneous-based processing presents slower conversions compared to homogenous ones, such processes lead to noncorrosive manufacturing and avoids the occurrence of saponification reactions. Thus, this work aims at evaluating the catalytic activity of the SnO2 supported on vermiculite clay [(Mg, Fe, Al)3(Al, Si)4O10(OH)2.4H2O] for the transesterification of soybean oil. The several catalysts were obtained by impregnation of vermiculite with tin resin, previously synthesized by the polymeric precursor method. All samples were characterized thermal analysis (TG/DTA), X-ray diffraction (XRD), grazing angle XRD, X-ray fluorescence (XRF), scanning electron microscopy (SEM), infrared (IR) and confocal Raman spectroscopy is Biodiesels were synthesized using a molar ratio of 1:10 (soybean oil: ethanol), 5,0 % (wt / wt) catalys treational temperature q 65 °C, besing characterized by dynamic and kinematic viscosities. In this work the vermiculite was treated with nitric acid (HNO3). The leaching process did not modifi, the thermal stability of inorganic solids. XRF date indicates satisfactory impregnation of the catalyst supports by the precursor resins. The XRD patterns identified the presence of cassiterite phase as well as the presence of characteristic phases of clay minerals which was confirmed by grazing incidence XRD. The spectroscopic data indicated the presence of peaks characteristic of the catalytic support as well as the active phase of catalyst (SnO2). The formation of active species (alkoxide) at low temperature, on the surface of catalysts, favored the soybean oil transesterification process. Rheological studies gave preliminary evidence that the catalytic reaction occurred with reduction of 40 % in the viscosity. / A produção de biodiesel é baseada na transesterificação de óleos vegetais ou gorduras animais, utilizando catalisadores homogêneos ou heterogêneos. O processo de transesterificação heterogênea apresenta conversões mais baixas em comparação com o homogêneo, porém, não apresenta problemas de corrosão e reduz à ocorrência de reações paralelas como saponificação. Neste sentido, este trabalho visa avaliar a atividade catalítica do SnO2 suportado em vermiculita [(Mg, Fe, Al)3(Al, Si)4O10(OH)2.4H2O] para a transesterificação do óleo de soja. Os diversos catalisadores foram obtidos pela impregnação da vermiculita com resina de estanho previamente sintetizada pelo método dos precursores poliméricos. Todas as amostras foram caracterizadas por análise térmica (TG/DTA), difração de raios-X (DRX), DRX de ângulo rasante, fluorescência de raios-X (FRX), microscopia eletrônica de varredura (MEV), espectroscopia vibracional na região do infravermelho (IV), espectroscopia Raman confocal. Os biodieseis foram sintetizados utilizando uma razão molar de 1:10 (óleo de soja: etanol) e 5,0 % (wt/catalisador) em peso, a 65 °C, e cujas caracterizações foram feitas por intermédio de medidas de viscosidade dinâmica e cinemática. Neste trabalho a vermiculita foi submetida a tratamento ácido utilizando ácido nítrico. O processo de lixiviação não causou mudanças na estabilidade térmica do sólido inorgânico. Dados da FRX apresentaram resultados satisfatórios de impregnação dos suportes catalíticos pelas resinas precursoras. Os DRX tanto identificaram a presença da fase cassiterita como também a presença das fases características dos argilominerais, confirmada pelas análises do DRX de ângulo rasante. Os dados espectroscópicos indicaram a presença dos picos típicos do suporte catalítico como também da fase ativa do catalisador (SnO2). A formação da espécie ativa (alcóxido) a baixa temperatura sobre a superfície dos catalisadores favoreceu o processo de transesterificação do óleo de soja comercial. Os estudos reológicos deram uma confirmação preliminar de que ocorreu o fenômeno da catálise, com redução de até 40 % da viscosidade.