C. M. B. M. Barbosa

Flash Pyrolysis of Oleic Acid as a Model Compound Adsorbed on Supported Nickel Catalysts for Biofuel Production

Flash pyrolysis of oleic acid was studied over 10 wt.% nickel catalysts supported on silica and alumina. The catalysts were impregnated with 10 wt.% oleic acid. The dried precursors and the catalysts containing oleic acid were characterized by thermogravimetric analysis. The calcined catalysts were analyzed by X-ray diffraction (XRD) and temperature programmed reduction (TPR). Samples containing adsorbed oleic acid were submitted to flash pyrolysis up to 650 °C. Whereas pyrolysis of oleic acid without catalyst converted only about 10%, the pyrolysis of oleic acid adsorbed on catalysts allowed practically a complete conversion. NiO/alumina yielded a higher amount of liquid hydrocarbons than NiO/silica. The main products obtained with NiO/silica were 1-alkenes, whereas the main products obtained with NiO/alumina were alkene isomers and aromatics. Small amounts of oxygenated compounds were also observed, principally alcohols. The flash pyrolysis of oleic acid adsorbed on different catalyst surfaces appears as a useful way to distinguish activity trends of different catalyst samples.

Adsorption of the reactive gray BF-2R dye on orange peel: kinetics and equilibrium studies

AbstractAdsorption of the reactive gray BF-2R dye from an aqueous solution using orange peel as the adsorbent was investigated by the batch method. Experiments characterizing the chemical and physical properties of the adsorbent found that orange peel is a microporous material with a pHzpc 3.9 and containing carboxylic and sulfonic groups. The greatest adsorption capacity was obtained using a 23 factorial design for 0.25 g of adsorbent, particle size <0.419 mm and at 300 rpm. The pseudo-second-order model provided the best fit of the experimental data. The Weber–Morris model indicated that two or more mechanisms control the process. Statistical analysis of the equilibrium studies indicated that there was not a significant difference between the Langmuir and the Fritz–Schlunder models according to an F-test. The results showed that orange peel can remove the reactive gray BF-2R dye.

Adsorption of anionic dyes from an aqueous solution by banana peel and green coconut mesocarp

AbstractBanana peel (BP) and green coconut mesocarp (GCM) were evaluated as adsorbents for the removal of the dyes reactive gray BF-2R (RG), reactive turquoise Q-G125 and remazol golden yellow RNL-150% (RGY). Adsorbents were classified as mesoporous materials, with the pHzpc of 5 for BP and 7 for GCM. The initial pH of the best-adsorbing solution of the dyes was 2.0. There was no significant difference between the kinetic models evaluated by the F test at a 95% level of confidence, except for the RGY/GCM system. The adsorption process is not merely a function of an intraparticle diffusion step. The Freundlich model was the best fit for RGY/GCM, and no significant difference was evident between the two models evaluated for the other systems by the F test. For RG/BP, the models did not fit the experimental data. The adsorbents evaluated may be useful for the treatment of effluents that contain dyes.

Mechanism-based kinetics of the water–gas shift reaction at low temperature with a ruthenium catalysts

The kinetics of the water–gas change reaction was evaluated with formulated ruthenium catalysts (Ru 2 wt%/TiO2, Ru 2 wt%/Al2O3) in a fixed bed reactor with a gas mixture containing 15% CO + Ar at temperatures ranging from 453 to 573 K under atmospheric pressure. Component mass balances were developed to represent the experimental data of the operations, including reaction rates expressed by the surface redox and Langmuir–Hinshelwood (LH) models. Parametric estimation was performed using nonlinear programming with MATLAB software, and an algorithm developed to fit the model to the data. The LH model provided the best adjustment, indicating orders of apparent activation energies of 12 and 12.9 kJ/mol for the reactions with Ru/TiO2 and Ru/Al2O3 catalysts, respectively. For comparison purposes, an empirical model of power law for the reaction rate was adjusted, involving unit reaction orders for CO, H2O and CO2, and zero order for the hydrogen, providing an apparent activation energy of 53.8 kJ/mol. The evolutions of component concentration were simulated allowing the model validation by comparing calculated versus experimental values.

Kinetic and Equilibrium Adsorption Studies for Removal of Naphthenic Acids Present in Model Mixture of Aviation Kerosene

In this work, the adsorbent Sr-MCM-41 was evaluated for its ability to remove naphthenic acids present in model mixture of aviation kerosene (jet fuel) by conducting kinetic and adsorption equilibrium studies in finite bath systems. The adsorption isotherm model of Brunauer, Emmett, and Teller (BET) was used for the equilibrium modeling. Additionally, the linear driving force model was used for the kinetic modeling. The analysis of variance was incorporated to judge the compatibility of the models. The kinetic study found that the system reached equilibrium after 480 min. The equilibrium study showed a maximum adsorption capacity of 2.0 g g−1. The models represented the experimental data satisfactorily, and this was confirmed by the variance analysis. Under the conditions studied, the presented results show the technical potential of using the adsorbent for the removal of naphthenic acids from jet fuel.