Estudo do efeito de tratamentos térmicos em catalisadores de PtRu/C frente à reação de oxidação de hidrogênio na presença de CO

In this work the effects of time and temperature of thermal treatments under reducing atmosphere (H2) on PtRu/C catalysts for the hydrogen oxidation reaction (HOR) in the presence of CO on a proton exchange membrane fuel cell (PEMFC) single cells have been studied. It can be seen that the increase of the treatment temperature leads to an increasing sintering of the catalyst particles with reduction of the active area, although the catalyst treated at 550 ºC presents more CO tolerance for the HOR.

Direcionamentos da tecnologia industrial de células a combustível de óxidos sólidos

This manuscript shows an overview of the solid oxide fuel cell (SOFC) technology based on industrial developments. The information presented has been collected mostly at conferences that the authors attended. It is observed that several companies have been pursuing the development of the SOFC technology. Significant advances in stability and power density have raised the economic interest in this technology recently. It is revealed that the SOFC materials are essentially the same ones that have been used in the past decades, and that the two most important designs of pre-commercial SOFC prototypes are the tubular and planar ones.

Influência de M/C (M = Mo, Cu, Fe e W) incorporado à camada difusora do eletrodo de difusão de gás frente à reação de oxidação de hidrogênio na presença de CO

The performance of proton exchange membrane fuel cells (PEMFC) with Pt-based anodes is drastically lowered when CO-containing hydrogen is used to feed the system, because of the strong adsorption of CO on platinum. In the present work the effects of the presence of a conversion layer of CO to CO2 composed by several M/C materials (where M = Mo, Cu, Fe and W) in gas diffusion anodes formed by Pt catalysts were investigated. The diffusion layers formed by Mo/C e W/C show good CO-tolerance, and this was attributed to the CO removal by parallel occurrence of the water-gas shift reaction and the so-called bifunctional mechanism.

Reatividade de ciclopropenonas frente a nucleófilos e sua correlação com potenciais de redução em meio aprótico

In this work we studied the reactivity of isopropylphenylcyclopropenone towards some nitrogen nucleophiles whose reactions with methylphenylcyclopropenone and diphenylcyclopropenone were previously studied. The electrochemical behavior of these cyclopropenones was evaluated for the first time, and a correlation between electrochemical parameters and reactivity of this class of compounds was done.

Feromônios de insetos: tecnologia e desafios para uma agricultura competitiva no Brasil

Pheromones are chemical compounds used by species to communicate intra and inter specifically. As strategy of integrated pest management (IPM), the use of these compounds allows the monitoring of target insects that results in more reliable interventions and consequently avoiding unnecessary use of pesticides. In certain crops these compounds are used as a control measure, not only monitoring. The Brazilian agriculture has a portfolio of 49 major crops that are attacked by 447 species of insects. Of this total, 103 species have already been the subject of study in the research with pheromones. Currently, in the Brazilian market, 28 pheromone products are indicated for the control of 19 insect pests. However, these products are not used regularly in major crops of the country. This stems from the lack of implementation of IPM of these crops. While the research focused on the main species of agribusiness pests, marked of pheromones products is serving to more marginal crops like apples and peaches at the expense of major crops like soybean and corn.

Estudo da reatividade do estado excitado triplete de 1,4-diaza-9-fluorenonas frente a doadores de hidrogênio e de elétron

The effect of the introduction of nitrogen atoms upon the triplet excited state reactivity of 1,4-diaza-9-fluorenone (1) and 1,4-diaza-9-benz[b]fluorenone (2), in acetonitrile, was investigated employing the nanosecond laser flash photolysis technique. The intersystem crossing quantum yield (Φces) for 1 and 2 was determined using 9-fluorenone as a secondary standard (Φces= 0.48, in acetonitrile) and for both diazafluorenones a value of Φces= 0.28 was found. Quenching rate constants ranged from 8.17x10(4) L mol-1 s-1 (2-propanol) to 1.02x10(10) L mol-1 s-1 (DABCO) for 1,4-diaza-9-fluorenone and from 6.95x10(5) L mol-1 s-1 (2-propanol) to 5.94x10(9) L mol-1 s-1 (DABCO) for 1,4-diaza-9-benz[b]fluorenone, depending if the quenching process involves energy, hydrogen or electron transfer. A comparison between quenching rate constants for both diazaflurenones and the parent compound, i.e. 9-fluorenone, a ketone with lowest triple state of ππ* configuration, lead to the conclusion that the reactive triplet excited state for 1,4-diaza-9-fluorenone and 1,4-diaza-9-benz[b]fluorenone has ππ* configuration.

Constituintes químicos do caule de Spathelia excelsa (rutaceae) e atividade frente a Aedes aegypti

Phytochemical investigation from the stems of Spathelia excelsa (Rutaceae) collected in Amazonas yielded deacetylspathelin (1), 7,8-dimethoxyflindersine (2), new glabretal-type triterpenoid 3β-angeloyl-21,24-epoxy-7α, 21α, 23α, 25-tetrahydroxy-4α, 4β, 8β, 10β-tetramethyl-25-dimethyl-14, 18-cyclo-5α, 13α, 14α, 17α-cholestane (3), in addition to the known steroids β-sitosterol and stigmasterol. Their structures were established on the basis of spectral data. The compounds 1 and 3 were assayed on Aedes aegypti (larvicidal and adulticidal activities and compound 3 exhibited larvicidal properties with LC50 of 4,8 µg/mL.

Tecnologia de nanocristais em fármacos

The use of poorly water soluble molecules in pharmaceutical area has grown. Since these molecules exhibit low oral bioavailability, they are not used in intravenous administrations. Therefore, it is necessary to develop their new formulations with the aim to increase their oral bioavailabilities as to enable intravenous applications. One of the few possibilities in achieving this is a nanonization process that can produce crystals smaller than 1 μm by high pressure homogenization and without use of organic solvents. This mini-review describes technical aspects of the nanocrystal production, morphological aspects (polymorphisms), the market relevance of the nanocrystals products that are already in clinical phase or at the market, as well as, perspectives for the near future.

Atual estágio de desenvolvimento da tecnologia GTL e perspectivas para o Brasil

Although the production of liquid fuels from coal, natural gas (CTL and GTL processes) and other carbon sources has been discovered 90 years ago, the interest was renewed in the last years motivated by stranded gas reserves and by petroleum market instability. This review intends to show the scenario of these technologies nowadays, discussing the applied technologies, the steps in an industrial plant, the ways to produce syngas and liquid fuels, the catalysts used, the type of reactors and the operating plants with their respective capacities, besides the technical, economical and environmental viability, challenges and perspectives for Brazil.

Processo de transferência de tecnologia da universidade para a indústria: estudo de caso envolvendo a conversão de glicerol

Currently, public policy has encouraged innovation in universities and also transference of technology to the industry. Another important stage to be considered would be the registration or filing of a patent and the economical viability study. Government programs, such as the innovation incentive program, among others, should facilitate popularization and promote interest by industry. In this work we described the steps, from the conception of the idea to the scale up going through its interest by the industry. The case study is about the glycerol conversion utilizing modified niobia as catalysts.

Desenvolvimento de tecnologia para confecção de eletrodos e conjuntos eletrodo-membrana-eletrodo (MEA) por impressão à tela para aplicação em módulos de potência de células PEMFC

Significant functions in the Proton Exchange Membrane Fuel Cells (PEMFCs) rely on Gas Diffusion Layers (GDLs), such as control the water balance in the membrane electrode assembly (MEA), allow suitable gas permeability and porosity, etc. Aware of the GDL importance in the cell performance and its great demand in scale-up projects, the fuel cell research group at Instituto de Pesquisas Energéticas e Nucleares (IPEN) has developed a Sieve Printing method (innovative in Brazil) as a strategic solution for producing GDL and electrodes used in high power PEMFC stacks. The method has shown to be adequate to fabricate low cost electrodes, GDLs of different dimensions and to produce any amount of MEAs for power stacks.

Estudo em raiz e ráquis foliar de spathelia excelsa: fitoquímica e atividade frente ao fungo Moniliophthora perniciosa associado ao cupuaçuzeiro (Theobroma grandiflorum)

The chemical composition of Spathelia excelsa (Krause) R. S. Cowan & Brizicky was investigated and the limonoids harrisonin (1) and deacetylspathelin (2), alkaloids folinin and casimiroin mixture (3a, b), plus a further casimiroin (3b) were identified in methanol extract from root. The CH2Cl2 extract from the rachis yielded protolimonoid 3β-angeloyl-21,24-epoxy-7α,21α,23α,25-tetrahydroxy-4α,4β,8β,10β-tetramethyl-25-dimethyl-14,18-cyclo-5α,13α,14α,17α-cholestane (4), and methanol extract, the limonoids limonin diosphenol (5) and perforatin (6), as well as the chromone biflorin (7). Harrisonin and biflorin were isolated for the first time in this genus. On the antifungal assay against witches' broom (Moniliophthoraperniciosa) compound 3b was found to be active.

Influência do método de preparação de eletrocatalisadores PtRu/C sobre a atividade catalítica frente à reação de oxidação de etanol em meio ácido

In this work the influence of variations in the borohydrate reduction method on the properties of PtRu/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH4 to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that PtRu nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The PtRu/C electrocatalyst (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation.