Luiz Antônio Magalhães Pontes

Simultaneous determination of copper and iron in automotive gasoline by X-ray fluorescence after pre-concentration on cellulose paper.

This paper proposes an alternative analytical method using energy dispersive X-ray fluorescence (EDXRF) to determine Fe and Cu in gasoline samples. In the proposed procedure, samples were distilled and the distillation residues were spotted on cellulose paper disk to form a uniform thin film and to produce a homogeneous and reproducible interface to the XRF instrument. The disks were dried at 60 degrees C for 20min and copper and iron were determined directly in the solid phase at 6.40 and 8.04keV, respectively. The calibration curves showed linear response in the 20-800mugL(-1) concentration range of each metal. The precisions (repeatability) calculated from 15 consecutive measurements and defined as the coefficient of variation of solutions containing 100mugL(-1) of Fe and Cu were 7.8 and 8.1%, respectively. The limits of detection (LOD), defined as the analyte concentration that gives a response equivalent to three times the standard deviation of the blank (n=10), were found to be 10 and 15mugL(-1) for Fe and Cu, respectively. The proposed method was applied to copper and iron determination in gasoline samples collected from different gas stations.

Cracking and hydrocracking of triglycerides for renewable liquid fuels: alternative processes to transesterification

Os processos industriais mais utilizados na producao de combustiveis liquidos semelhantes ao diesel usam catalisadores homogeneos basicos atraves das metanolise e etanolise de oleos tais como os de soja, canola, palma entre outros. Desse modo, se obtem o biodiesel. Por sua vez, transformacoes termo-cataliticas usando as facilidades existentes nas refinarias de petroleo sao alternativas que merecem atencao devido a sua viabilidade economica. De fato, tres processos industriais ja estao em funcionamento e novos projetos estao em fase final para comercializacao. O presente trabalho analisa os experimentos ja realizados por pesquisadores brasileiros nas areas do craqueamento, do craqueamento catalitico e do hidrocraqueamento catalitico dos oleos vegetais puros ou modificados. A partir dos resultados descritos, sao sugeridas novas direcoes destas pesquisas para os proximos anos. The most used industrial processes for the production of liquid fuels like diesel type are based on the methanolysis and ethanolysis of various oil reactants, such as palm, soybean and rapeseed oils, in the presence of homogeneous base catalysts. However, thermal and catalytic transformations of vegetable oils using available reactors and industrial processes are possible alternatives and deserve attention. In fact, three industrial processes are operating and new projects are announced. The present work analyses the experimental studies performed up to now by Brazilian researchers in the field of cracking, catalytic cracking and hydrocracking of pure or modified vegetable oils. From the published results, some research areas for the near future are suggested.

Indirect determination of chloride and sulfate ions in ethanol fuel by X-ray fluorescence after a precipitation procedure

This paper proposes an alternative analytical method using energy dispersive X-ray fluorescence (EDXRF) to determine chloride and sulfate ions in ethanol fuel samples after precipitation procedure. The preconcentration methodology involved the precipitation of the analytes as silver chloride and barium sulfate followed by filtration through a paper filter, which demonstrated to be a convenient substrate for EDXRF measurements. The elements were determined directly on the filters using silver and barium lines for the indirect determination of chloride and sulfate ions, respectively. The precisions calculated from 20 consecutive measurements and defined as the coefficient of variation of standard solutions containing 1.0 microg mL(-1) of Cl(-) and SO(4)(2-) were 7.3% and 5.9%, respectively. The limits of detection (LOD), defined as the analyte concentration that gives a response equivalent to three times the standard deviation of the blank (n=10), were found to be 25 microg L(-1) and 30 microg L(-1) for Cl(-) and SO(4)(2-), respectively. The proposed method was applied to chloride and sulfate ions determination in hydrated ethanol fuel samples collected from different gas stations.

Mathematical Equations Evaluation for Prediction of Brazilian Diesel Specification Parameters

In Brazil, the monitoring of commercial diesel quality follows quite consolidated procedures, however require equipment with high costs of operation and maintenance. In this work, mathematical equations available in the literature, were used for obtaining physico-chemical properties of the diesel fuel density, kinematic viscosity at 40 ° C, average boiling points, aniline point, API gravity, diesel index, cetane index and flash point, using experimental data such as atmospheric distillation (ASTM D86) and density (ASTM D4052). Values calculated of cetane index were compared with those obtained by ASTM methods, through the Students t test (5% significance level), the mean absolute percentage error (MAPE), correlation coefficient, R, and boxplot graphical. For the three evaluated equations, the theoretical and experimental results of cetane index showed correlation coefficients near of unity. In relation to the Student t test, the IC_PA equation was more appropriate to the level of significance of 5%, with application of a mean absolute error of 0.425 and MAPE of 0.977%. This paper presents results that indicate the possibility of using of methodologies based on mathematical equations to predict cetane index of Brazilian diesel.