Luciene Santos Carvalho

n‐octane reforming over alumina‐supported Pt, Pt–Sn and Pt–W catalysts

Pt, Pt–Sn and Pt–W supported on γ‐Al2O3 were prepared and characterized by H2 chemisorption, TEM, TPR, test reactions of n‐C8 reforming (500°C), cyclohexane dehydrogenation (315°C) and n‐C5 isomerization (500°C), and TPO of the used catalysts. Pt is completely reduced to Pt0, but only a small fraction of Sn and of W oxides are reduced to metal. The second element decreases the metallic properties of Pt (H2 chemisorption and dehydrogenation activity) but increases dehydrocyclization and stability. In spite of the large decrease in dehydrogenation activity of Pt in the bimetallics, the metallic function is not the controlling function of the bifunctional mechanisms of dehydrocyclization. Pt–Sn/Al2O3 is the best catalyst with the highest acid to metallic functions ratio (due to its lower metallic activity) presenting a xylenes distribution different from the other catalysts. The acid function of Pt–Sn/Al2O3 is tuned in order to increase isomerization and cyclization and to decrease cracking, as compared to Pt and Pt–W.

Spectrophotometric determination of chromium in steel with 4-(2- thiazolylazo)-resorcinol (TAR) using microwave radiation

A spectrophometric method for the determination of Cr(III) with 4-(2- thiazolylazo)-resorcinol was developed. Cr(III) slowly forms a red complex with TAR at pH 5.7. Irradiating the reacting mixture with microwave energy can accelerate the complex formation. The absorbance reached its maximum with 5 min of irradiation and remained stable, at least, for 24 h. N-cetyl-N,N,N-trimethylammonium bromide (CTAB) was used for increasing the sensitivity and solubility of the system. The method allowed the determination of chromium ranging from 0.050 to 3.0 mg mL-1 (9.62 x 10-7 to 5.77 x 10-5 mol L-1) with a molar absorptivity of 2.73x104 L-1 mol-1 cm-1 and a detection limit of 17 ng mL-1 (3.3 x 10-7 mol L-1) at 545 nm. The selectivity was improved by using EDTA and citrate as masking agents. Fe(III) interferes and must be extracted previously, if present in the sample. The proposed method has been successfully applied to the determination of chromium in steel. The precision (R.S.D. < 2%) and accuracy were satisfactory.

A Simple Way to Produce γ-Alumina From Aluminum Cans by Precipitation Reactions

In this paper, a new way for γ-alumina synthesis was proposed, the raw material being aluminum powders obtained by high-energy milling of aluminum cans. This seems a good option for this metal recycling and energy saving, as well as hydrogen production. The materials were prepared by precipitation techniques, in which aluminum powders reacted with hydrochloric acid, giving aluminum chloride, which was subsequently transformed into aluminum hydroxide by reaction with ammonium hydroxide or sodium hydroxide as precipitant agents, and finally into γ-alumina by calcination. Results showed that the used preparation methods gave a γ-alumina structure, confirmed by XRD, with surface areas values (174 and 204 m2 g-1) close to those of a commercial γ-alumina Cyanamid Ketjen (180 m2 g-1) or an alumina prepared by a typical precipitation route (203 m2 g-1). Using sodium hydroxide as precipitant agent turned out to be more ecologically compatible since it did not release harmful environmental compounds.

Performance of Nickel Supported on γ-Alumina Obtained by Aluminum Recycling for Methane Dry Reforming

In this paper, Ni/Al2O3 catalysts were prepared by using alumina synthesized from aluminum can powders, with or without ink. The catalysts produced were tested for methane dry reforming and showed not only high methane conversion (68–80%), but carbon dioxide (75–90%), selectivity to hydrogen (80–83%) as well as and H2/CO molar ratio close to 1. Therefore, it is a promising idea for future industrial applications. The results also showed that contaminant metals present in aluminum cans could affect the catalysts properties.Graphical Abstract

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.