Nesse estudo um planejamento experimental de misturas de biodieseis é utilizado para avaliar e otimizar a estabilidade oxidativa de amostras de biodiesel de soja contendo diferentes teores de biodiesel de sebo e de mamona. As misturas de biodieseis foram preparadas com teores que variaram entre 80-86% (v/v) para a soja, 5-15% (v/v) para o sebo e 1-10% (v/v) para a mamona. O período de indução da amostra de biodiesel de soja puro serviu de base para a comparação com a estabilidade das misturas. A estratégia de planejamento experimental de misturas mostrou-se adequada para a formulação de misturas de biodiesel com ótima estabilidade oxidativa. O modelo quadrático obtido na etapa de otimização ajustou-se adequadamente aos dados experimentais, sendo capaz de prever as proporções ótimas para misturas com maior estabilidade oxidativa. O melhor período de indução foi obtido com as seguintes proporções: 82,5% (v/v) de soja, 7,5% (v/v) de sebo e 10,0% (v/v) de mamona.

This study proposes an experimental design of biodiesel constrained mixtures to evaluate and optimize the oxidative stability of soybean biodiesel mixed with different amounts of tallow and castor bean biodiesels. To prepare the biodiesel blends, the proportions of each type of biodiesel were varied, producing mixtures that contained 80-86% (v/v) soybean, 5-15% (v/v) tallow, and 1-10% (v/v) castor bean biodiesel. The induction period of pure soybean biodiesel served as the baseline for comparing the stability of the mixtures. The experimental design strategy was capable of producing the best oxidative stability for biodiesel mixtures. The quadratic model obtained in the optimization stage fits the experimental data well. The higher induction period occurred at the following composition: 82.5% (v/v) soybean, 7.5% (v/v) tallow and 10.0% (v/v) castor bean.

Total spectrofluorimetry associated to Principal Components Analysis (PCA) were used to classify into different groups the samples of diesel oil, biodiesel, vegetal oil and residual oil, as well as, to identify addition of non-transesterified residual vegetable oil, instead of biodiesel, to the diesel oil. Using this method, the samples of diesel oil, mixtures of biodiesel in diesel and mixtures of residual oil in diesel were separated into well-defined groups.

Neste trabalho são analisadas algumas alternativas tecnológicas para o desenvolvimento de pequenas graxarias destinadas à pequena produção de carne. É considerado que a substituição do conceito de "resíduos animais" pelo conceito de "matéria-prima para graxaria" pode ser amplificada com algumas implementações no processo produtivo, agregando valor aos subprodutos animais, no sentido de uma produção mais limpa, o que reduz o impacto ambiental da atividade e os riscos das más condições higiênicas.

This paper analyses some alternative technologies for the development of small rendering plants to small meat producers. It is considered that the replacement of the concept of "animal waste" by the "by-product or raw material for grease and rendering plants" concept can be amplified with some implementations in the production process, adding value to animal by-products to produce a greater recovery of these by-products, or even total use, eliminating waste and reducing the environmental impact of the activity and the risk of poor hygienic conditions.

Conventional sample holder cells used to the electric characterization of ceramics at high temperature consists of an alumina tube and platinum wires and plates using a complex design. The high cost materials used in the conventional sampler holder cell were replaced by stainless steel and conventional ceramics. The sample holder was validated by characterizing yttria-stabilized-zirconia in a temperature range of 25 to 700 ºC. The results do not present variations, discontinuity or unusual noise in the electric signals. Several samples were characterized without maintenance, which demonstrates that the sample holder is electric and mechanic adequate to be used to electrical characterization of ceramics up to 700 ºC.

The nature of gold species in Au/CeX Zr1-X O2 catalysts was successfully investigated using the visible and near infrared photoacoustic spectroscopy and Fourier transform infrared spectroscopy of adsorbed carbon monoxide. It was found that the visible and near infrared photoacoustic spectroscopy is a powerful technique for investigating the changes of gold particle size due to addition of zirconium and the oxidation state of gold particles. It was also noted that the increase of zirconium in the solids makes gold incorporation more difficult due to the electronic shielding caused by zirconium, decreasing the probability of replacing cerium by gold. For the samples studied, the particle size ranged from 20-30 nm and the Au+, Au3+ and Auº species were found in the catalysts.

Thermal baths to decrease ambient temperature are an indispensable tool for most research and teaching laboratories, especially those in tropical or equatorial regions. A simple and inexpensive thermal bath has been developed based on a scratched compressor. It has three possible setups for cooling: sample immersed into the bath, sample flowing through the bath, and cooling liquid flowing in a jacket around the sample. It has been tested for 40 months. The temperature ranges from room temperature to 0 °C, when using water. The repeatability is better than 3% and the precision varies from 0.5% to 2%.

Este trabalho estuda o fluxo de etileno glicol (MEG) sobre duas superfícies sólidas com constituições químicas diferentes: borossilicato e dióxido de estanho (SnO2). O alinhamento intermolecular, determinado como polarização e anisotropia, mostrou dependência da natureza química do sólido. A razão entre as tensões interfaciais dinâmicas foi 1.09 ± 0.07, devendo ser maior para MEG/borossilicato do que para MEG/SnO2. A razão da capilaridade foi 0.92 ± 0.06, sendo menor para MEG/borossilicato. Medidas estáticas do ângulo de contato mostraram valores menores para borossilicato do que para SnO2. Os mapas de polarização e anisotropia apresentaram valores mais altos para MEG/SnO2, o que pode ser explicado pela alta tensão interfacial do MEG/borossilicato. Estes resultados são compatíveis com interações de volume mais fortes em MEG/SnO2 e com contribuições de superfície mais fortes em MEG/borossilicato. Isto pode ser atribuído ao borossilicato ser mais eletronegativo, favorecendo mais as pontes de hidrogênio com o MEG.

This work studied ethylene glycol (MEG) flowing on two different solid surfaces, borosilicate and thin dioxide (SnO2). Intermolecular alignment, determined as polarization and anisotropy, showed dependence on the solid chemical nature. The ratio between dynamic surface tensions was found 1.09 ± 0.07, being stronger for MEG/borosilicate than for MEG/SnO2. The capillary ratio found was 0.92 ± 0.06, being smaller for MEG/borosilicate. Static contact angle measurements gave lower values for borosilicate than for SnO2. Both polarization and anisotropy maps presented higher values for MEG/SnO2, which can be explained by MEG/borosilicate higher interfacial interaction. The results obtained are compatible with stronger bulk phenomena for MEG/SnO2 and with stronger interfacial phenomena for MEG/borosilicate. This may be due to borosilicate being more electronegative, yielding more efficiently hydrogen bonds with MEG.