Determination of Cd and Pb in fuel ethanol by filter furnace electrothermal atomic absorption spectrometry

A method was developed for quantification of Cd and Pb in ethanol fuel by filter furnace atomic absorption spectrometry. Filter furnace was used to eliminate the need for chemical modification, to stabilize volatile analytes and to allow the application of short pyrolysis step. The determinations in samples were carried out against calibration solutions prepared in ethanol. Recovery tests were made in seven commercial ethanol fuel samples with values between 90 and 120%. Limits of detection were 0.1 µg L-1 for Cd and 0.3 µg L-1 for Pb. Certified water samples (APS 1071, APS 1033, NIST 1643d, NIST 1640) were also used to evaluate accuracy and recoveries from 86.8% to115% were obtained.

Electrocatalysis and electrocatalysts for low temperature fuel cells: fundamentals, state of the art, research and development

This article deals with electrocatalysis and electrocatalysts for low temperature fuel cells and also with established means and methods in electrocatalyst research, development and characterization. The intention is to inform about the fundamentals, state of the art, research and development of noble metal electrocatalysts for fuel cells operating at low temperatures.

Effect of temperature on the electro-oxidation of ethanol on platinum

We present in this work an experimental investigation of the effect of temperature (from 25 to 180 ºC) in the electro-oxidation of ethanol on platinum in two different phosphoric acid concentrations. We observed that the onset potential for ethanol electro-oxidation shifts to lower values and the reaction rates increase as temperature is increased for both electrolytes. The results were rationalized in terms of the effect of temperature on the adsorption of reaction intermediates, poisons, and anions. The formation of oxygenated species at high potentials, mainly in the more diluted electrolyte, also contributes to increase the electro-oxidation reaction rate.

A utilização de etanol em célula a combustível de óxido sólido

This work reports a review on the status and technical feasibility of the application of ethanol as fuel for Solid Oxide Fuel Cells (SOFC), presenting both external reform and cell with direct utilization of ethanol. Based on this survey, both experimental results and mathematical modeling indicated the technical feasibility of power generation by ethanol SOFC, with cell units producing 450 mW/cm², sufficient for scale up to large stationary plants. The quantitative assessments in the literature show this field to be promising for researchers and private sector investment as well being a strategic technology for government policy in the short and long term.

Tecnologia de células a combustível

The fuel cell principle was discovered by Sir Grove 150 years ago. However material problems prohibited its commercialization for a long time. A change has been occurring during the last 30 years, so two types of fuel cell technologies can be distinguished: low and high temperature operation cells. Nowadays, only phosphoric acid cells are commercially offered as 200 kWel power plants. Membrane cells are more suitable for automobile electrotraction with a very low (or no) environmental impact. The fuel continues, however, to play a very particular role, since hydrogen is not easy to store and to transport. The more promising target is the utilization of liquid methanol. The Brazilian scenario concerning this kind of technology is discussed.

Células a combustível de baixa potência para aplicações estacionárias

A paradigmatic shift in developing fuel cell for stationary applications has been occurring in the last ten years. Previously, 100 kW class to a few MW class power plants were preferred but recently, the development has drifted towards units of only a few kW. The motivation is the present market situation, which favors disperse residential electric power generation from natural or liquefied gas. Membrane-type fuel cells are very promising for this application, due to their present state of development in the automobile industry. More recently, small ceramic fuel cells (SOFC) has also been found to be adequate for this application. Considering a family of 4 members, 1 kW (electric) units seem to be optimal for individual residences. This presentation discusses briefly the Brazilian scenario with respect to these units.

A escolha da faixa espectral no uso combinado de métodos espectroscópicos e quimiométricos

A method is presented for the choice of spectral regions when absorption measurements are coupled to chemometric tools to perform quantitative analyses. The method is based on the spectral distribution of the relative standard deviation of concentration (s c/c). It has been applied to the development of PLS-FTNIR calibration models for the determination of density and MON of gasoline, and ethanol content and density of ethanol fuel. The new method was also compared with the correlation (R²) method and has proved to generate PLS calibration models that present better accuracy and precision than those based on R².

Eletrocatálise das reações de oxidação de hidrogênio e de redução de oxigênio

This work discusses the electrocatalytic processes taking place in the polymer electrolyte fuel cell electrodes, specifically the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR), because these are clear examples of electrochemical reactions favored by the use of electrocatalysts. Since the gaseous reactants are very little soluble in the electrolyte, the use of special electrodes, named gas diffusion electrodes, is required to promote easy and continuous access of reactant gases to the electrocatalytic sites. Besides this, other important aspects such as the use of spectroscopic techniques and of theoretical models to improve the knowledge of the electrocatalytic systems are shortly discussed.

Determinação espectrofotométrica simultânea de cobre e ferro em álcool etílico combustível com reagentes derivados da ferroína

In the present work three ferroin reagents were studied for the simultaneous spectrophotometric determination of iron and copper: 1,10-phenanthroline, 2,2'-bipyridine and 2,4,6-tri(2-pyridyl)-1,3,5-triazine. Effect of pH, conditions, order reagent addition, interferences, amount of reagents, lineal range, sensitivity and stability of each system were compared. The 2,4,6-tri(2-pyridyl)-1,3,5-triazine can be used for determination of iron in the presence of copper with a detection limit of 5 µg L-1 and coefficient of variation of 2.0%; However it was not possible to determine directly copper in the presence of iron with this reagent. 1,10-phenanthroline can be used for simultaneous determination of the metallic ions with detection limits of 7 and 8 mg L-1 and coefficients of variation of 1.8 and 2.3% in the determination of iron and copper, respectively. The results showed also that 2,2'-bipyridine can be used for simultaneous determination of the metallic ions with detection limits of 11 and 32 µg L-1 and coefficients of variation of 1.9 and 2.5% in the determination of iron and copper, respectively. The reagents were used for spectrophotometric determination of iron and copper in ethanol fuel.

Pilhas a combustível de óxido sólido: materiais, componentes e configurações

In this paper the current status of fuel cells is described with particular emphasis on high (T > 800 ºC) and intermediate (T < 800 ºC) temperature solid oxide fuel cells. Also the importance of the fuel cell technology is shown. Reviewed are the fundamental features, the basic principles, types of fuel cell, fabrication methods, cell configurations and the development of components (cathodes, anodes, electrolytes, interconnect) and materials.

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.

Avaliação da eficiência de uma célula a combustível estacionária de ácido fosfórico

Operation and performance of a commercial PAFC power plant were analyzed. Processes influencing energy conversion efficiency were studied in each module of the fuel cell power plant. The main processes were simulated using mass and energy balance equations, and the results were validated by means of experimental data. It was concluded that the electrical efficiency is higher in comparison with microturbines. The main result achieved is a better understanding of balance of plant processes, knowledge necessary for fuel cell power plant development.

Cério: propriedades catalíticas, aplicações tecnológicas e ambientais

Cerium based-compounds have great importance in a wide range of technological applications, such as: fuel cell devices development; metallurgic processes, petroleum refining; glass and ceramic production. Recently, its catalytic properties have been also explored for environmental applications, especially those to prevent or to control atmospheric and water pollution. Subjects covered in this work include a brief description of the fundaments of cerium catalytic properties and some relevant technological applications. Special attention is given to its photocatalytic activity and its ability to degrade pollutants. Recent results and future prospect about these applications are also evaluated.

Montagem e caracterização elétrica de pilhas a combustível de óxido sólido (PaCOS)

This paper is focused on a review of the design features and the electrochemistry characterization of anode-supported planar SOFC. Studies and results of metallic alloy interconnectors and recovery for protection against corrosion and for contact layer are showed. Moreover a discussion of examples of measurements of impedance spectrometry, according to the literature and our experimental results are made. For the anode supported fuel cells the power density varies from 0.1 to 0.5 Wcm², according to results in the literature (showed in this paper). For electrolyte supported fuel cell the power density can be 10 Wcm-2 for high temperatures. An English-Portuguese glossary of most used terms in SOFC stack is given for greater clarity and to introduce new terms to the reader.