Heloysa Martins Carvalho Andrade

Brazil nut shells as a new biosorbent to remove methylene blue and indigo carmine from aqueous solutions.

The adsorption of methylene blue and indigo carmine, respectively a basic and an acid dye, was studied on raw Brazil nut shells. The dye removal from solution by BNS was governed by: (i) polarization effects between the colored ions and the surface sites, leading to physisorbed species due to weak electrostatic forces and (ii) diffusion limitations affecting the kinetic parameters. Thermodynamic studies showed that the adsorption of methylene blue and of indigo carmine was spontaneous and exothermic occurring with entropy decrease. H(0) values confirmed the physical nature of the adsorption processes. The adsorption followed the Langmuir model and pseudo-second order kinetics over the entire range of tested concentrations but the process was controlled by intraparticle diffusion. The maximal uptakes were 7.81 mg g(-1), for methylene blue, and 1.09 mg g(-1) for indigo carmine, at room temperature. These results indicate that Brazil nut shells may be useful as adsorbent either for basic or acid dyes.

Zeolite catalysts for the water gas shift reaction

Abstract Cu- and Cu,Zn-ZSM-5 zeolite catalysts were prepared using different cation exchange procedures. The samples were characterized by TPR; CO-FTIR; O 2 -TPD, XRD; BET and XPS. These catalysts showed appreciable activity and selectivity for the water gas shift reaction at 300–400°C and vapor/gas ratio=3. The Cu,Zn-ZSM-5 catalysts deactivated after a long exposure to steam, at high temperature. The catalytic activity of co-exchanged zeolite catalysts depended on the preparation method. The introduction of zinc ions enhanced the activity of the Cu-ZSM-5 catalysts but Zn-ZSM-5 catalyst was found to be inactive for the water gas shift reaction. The role of zinc was to change the distribution of the copper species in the zeolite catalyst.

Composition effects on the activity of Cu±ZnO±Al2O3 based catalysts for the water gas shift reaction: A statistical approach

Abstract An experimental mixture plan was used in order to assess the composition effects on the catalytic activity of a ternary Cu–ZnO–Al2O3 catalyst for the water gas shift reaction (WGSR) in a constrained region of the mixture space centered in a defined catalyst composition (Cu/Zn/Al=40/45/15). The obtained interaction coefficients indicated that an important role is played by the Al component on the Zn containing, Cu rich catalyst. XRD, FTIR, XPS, TG/DTA and activity test data gave support to the statistical assumptions. The catalytic activity for the WGSR was ascribed to metallic copper sites obtained from calcined and further reduced, well interdispersed mixtures of hydroxycarbonates.

Synthesis and characterization of magnetic mesoporous particles.

Magnetic mesoporous particles were synthesized and their magnetic and structural properties are reported. The synthesis procedure consists of four steps: (i) preparation of magnetite colloidal nanoparticles; (ii) growth of a silica layer; (iii) development of the mesoporous structure and (iv) template removal. Two different methods for the template removal were studied and their effectiveness was discussed. Magnetization and Mössbauer spectroscopy measurements showed superparamagnetic behavior for the particles at room temperature. X-ray diffraction and nitrogen adsorption measurements showed a mesoporous MCM-41 structure with 2.48nm pore diameter and 1023m(2)/g total area.

Effects of additional gases on the catalytic decomposition of N2O over Cu-ZSM-5

N2O decomposition into N2 and O2 was investigated in the presence of O2, NO, CO2, CO, CH4, SO2 and water vapor. Activity inhibition was observed in the presence of water vapor, and oxidant gases, whilst the reductant gases, enhanced the catalytic activity, in the temperature range of 350–550°C.

Evaluation of the Cu Doping Effects in CeO2 Catalytic Supports Obtained by Combustion Reaction

This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reaction method. Thus were obtained catalytic supports with the composition Ce1-xCuxO2 and the effect caused by doped element in the structure of the CeO2 was evaluated. The concentration value (x) of the Cu doped took over the values of 0.0; 0.3 and 0.5 mol. The catalytic supports developed were submitted to the structural characterization by X-ray diffraction, morphologic analysis by SEM and textural analysis by means of adsorption-dessorption of N2 by BET method. The results showed that the doped element (Cu) was not completely incorporated in the CeO2 structure and was evidenced that how much larger the quantity of Cu larger maid the disorder of the atomic structure of the obtained material. The analyzed supports present mesoporous nature structure.

The Role of the Coprecipitation Sequence of Salt Precursors on the Genesis of Cu-ZnO-Al2O3 Catalysts: Synthesis, Characterization and Activity for Low Temperature Shift Reaction

Cu-ZnO-Al2O3 catalysts for the low-temperature water-gas shift reaction were prepared using methods of direct and reverse coprecipitation. The catalysts obtained were characterized by DRX, TPR, XPS, N2O chemisorption, Hg-Porosimetry and BET surface area. It was observed that the precipitation sequence of the precursors led to significant differences in values of copper dispersion and consequently in the activity of the catalyst for the water-gas shift reaction.

Evaluation of NiFe2O4 Spinel, Synthesized by Combustion Reaction, as a Catalyst for Selective CO Oxidation

The selective reaction of CO oxidation (PROX) was named as the most attractive way to reduce the CO concentration, thereby purifying the hydrogen. The aim of this work is to make the structural and morphologic characterization of the NiFe2O4 spinel synthesized by combustion reaction, using glycine as fuel, and to evaluate as catalyst in the reaction of selective oxidation of carbon monoxide in the presence of hydrogen, oxygen and carbon monoxide. The powder was prepared by using a vitreous silica crucible on a hot plate at 480°C and according to stoichiometry established by theory of propellants and explosive. The powder was characterized by X-ray diffraction (XRD), FTIR, textural analyses, transmission electron microscopy (TEM) and catalytic measurements. The results from XRD show characteristic peaks of spinel phase without presence of secondary phases. The morphologic results show surface area of 3.1 m2/g and particle size calculated by TEM of 21.72 nm. The catalyst was active and selective for O2, reaching 100% of conversion.

Spectroscopic and catalytic studies on Cu-MCM-22: Effect of copper loading

Copper exchanged MCM-22 zeolites with varying copper contents were prepared, characterized and tested in the nitrous oxide decomposition. Over-exchanged samples showed high activity, comparable to very active Cu-ZSM-5 catalysts. The nature of the copper species was investigated by TPR-H 2 , FTIR-CO and FTIR-NO, evidencing at least three different species: exchanged Cu 2+ ions, cationic oligomeric species and oxidic phases. Upon NO adsorption, mononitrosilic complexes Cu I -(NO) were formed, and completely oxidized to Cu II -(NO) with increasing NO pressure. Nitrate complexes were extensively formed by reaction with the oxidic phases in the sample with 183% cation exchange level.

30-P-13-Transition metal exchanged-MCM-22 catalysts for N2O decomposition

Publisher Summary This chapter presents transition metal-exchanged-MCM-22 catalysts for nitrous oxide (N 2 O) decomposition. Transition metal-exchanged-MCM-22 catalysts have shown high activity on the decomposition of N 2 O, comparable to the well-known ZSM-5 catalysts. Copper (Cu)-MCM-22 is highly active, but suffers inhibition by excess oxygen. Cobalt (Co)-MCM-22 is not as active as Co-ZSM-5 because of the formation of cobalt monoxide (CoO) but is nearly insensitive to oxygen (O 2 ). Fe-MCM-22 presents an intermediate behavior and shows low tolerance to oxygen. Activities and oxygen tolerance are explained based on the nature of the active species formed in each case.