Synthesis of NiO-MgO-ZrO(2) catalysts and their performance in reforming of model biogas

Catalysts containing NiO/MgO/ZrO(2) mixtures were synthesized by the polymerization method in a single step. They were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) and physisorption of N(2) (BET) and then tested in the reforming of a model biogas (1.5CH4:1CO(2)) in the presence of air (1.5CH(4) + 1CO(2) + 0.25O(2)) at 750 degrees C for 6h. It was observed that the catalyst Ni20MZ performed better in catalytic processes than the well known catalysts, Ni/ZrO(2) and Ni/MgO, synthesized under the same conditions. The formation of solid solutions, MgO-ZrO(2) and NiO-MgO, increased the rate of conversion of reactants (CH(4) and CO(2)) into synthesis gas (H(2) + CO). The formation of oxygen vacancies (in samples containing ZrO(2) and MgO) seems to promote removal of the coke deposited on the nickel surface. The values of the H(2)/CO ratio were generally found to be slightly lower than stoichiometric, owing to the reverse water gas shift reaction occurring in parallel. (C) 2011 Elsevier B.V. All rights reserved.

Cobalt catalysts derived from hydrotalcite-type precursors applied to steam reforming of ethanol

Catalysts derived from Co/Mg/Al hydrotalcite-type precursors modified with La and Ce were characterized by XANES and tested in ethanol steam reforming. The reaction data showed that, with a molar ratio of water: ethanol = 3:1 in the feed, addition of Ce and La favored acetaldehyde production. Increasing the water content (water:ethanol = 5:1) decreased the acetaldehyde formation by favoring the adsorption of water molecules on these samples, enhancing the acetaldehyde conversion. (C) 2011 Elsevier B.V. All rights reserved.

Carbon dioxide reforming of ethanol over Ni/Y(2)O(3)-ZrO(2) catalysts

Supported nickel catalysts of composition Ni/Y(2)O(3)-ZrO(2) were synthesized in one step by the polymerization method and compared with a nickel catalyst prepared by wet impregnation. Stronger interactions were observed in the formed catalysts between NiO species and the oxygen vacancies of the Y(2)O(3)-ZrO(2) in the catalysts made by polymerization, and these were attributed to less agglomeration of the NiO during the synthesis of the catalysts in one step. The dry reforming of ethanol was catalyzed with a maximum CO(2) conversion of 61% on the 5NiYZ catalyst at 800 degrees C, representing a better response than for the catalyst of the same composition prepared by wet impregnation. (C) 2009 Published by Elsevier B.V.

Ethanol steam reforming for production of hydrogen on magnesium aluminate-supported cobalt catalysts promoted by noble metals

The performance of noble metal (Pt, Ru, Ir)-promoted Co/MgAl(2)O(4) catalysts for the steam reforming of ethanol was investigated. The catalysts were characterized by energy-dispersive X-ray spectroscopy, Xray diffraction, UV-vis diffuse reflectance spectroscopy, temperature-programmed reduction, temperature-programmed oxidation and X-ray absorption near edge structure (XANES). The results showed that the formation of inactive cobalt aluminate was suppressed by the presence of a MgAl(2)O(4) spinel phase. The effects of the noble metals included a marked lowering of the reduction temperatures of the cobalt surface species interacting with the support. It was seen that the addition of noble metal stabilized the Co sites in the reduced state throughout the reaction. Catalytic performance was enhanced in the promoted catalysts, particularly CoRu/MgAl(2)O(4), which showed the highest selectivity for H(2) production. (C) 2009 Elsevier B.V. All rights reserved.

Co catalysts supported on SiO(2) and gamma-Al(2)O(3) applied to ethanol steam reforming: Effect of the solvent used in the catalyst preparation method

Cobalt catalysts were prepared on supports of SiO(2) and gamma-Al(2)O(3) by the impregnation method, using a solution of Co precursor in methanol. The samples were characterized by XRD, TPR, and Raman spectroscopy and tested in ethanol steam reforming. According to the XRD results, impregnation with the methanolic solution led to smaller metal crystallites than with aqueous solution, on the SiO(2) support. On gamma-Al(2)O(3), all the samples exhibited small crystallites, with either solvent, due to a higher Co-support interaction that inhibits the reduction of Co species. The TPR results were consistent with XRD results and the samples supported on gamma-Al(2)O(3) showed a lower degree of reduction. In the steam reforming of ethanol, catalysts supported on SiO(2) and prepared with the methanolic solution showed the best H(2), CO(2) and CO selectivity. Those supported on gamma-Al(2)O(3) showed lower H(2) selectivity. (C) 2011 Elsevier Ltd. All rights reserved.

MODELLING OF HIGH-PRESSURE PHASE EQUILIBRIUM IN SYSTEMS OF INTEREST IN THE FOOD ENGINEERING FIELD USING THE PENG-ROBINSON EQUATION OF STATE WITH TWO DIFFERENT MIXING RULES

In this work, thermodynamic models for fitting the phase equilibrium of binary systems were applied, aiming to predict the high pressure phase equilibrium of multicomponent systems of interest in the food engineering field, comparing the results generated by the models with new experimental data and with those from the literature. Two mixing rules were used with the Peng-Robinson equation of state, one with the mixing rule of van der Waals and the other with the composition-dependent mixing rule of Mathias et al. The systems chosen are of fundamental importance in food industries, such as the binary systems CO(2)-limonene, CO(2)-citral and CO(2)-linalool, and the ternary systems CO(2)-Limonene-Citral and CO(2)-Limonene-Linalool, where high pressure phase equilibrium knowledge is important to extract and fractionate citrus fruit essential oils. For the CO(2)-limonene system, some experimental data were also measured in this work. The results showed the high capability of the model using the composition-dependent mixing rule to model the phase equilibrium behavior of these systems.

Serological response of guinea pigs to oily and aqueous inactivated vaccines containing a Brazilian isolate of the Bovine Viral Diarrhea Virus (BVDV)

Bovine Viral Diarrhea Virus (BVDV) is widespread in cattle in Brazil and research shows its large antigenic variability. Available vaccines are produced with virus strains isolated in other countries and may not be effective. In this study, inactivated vaccines containing the Brazilian BVDV-Ib IBSP11 isolate were developed and tested on 6 groups of 10 guinea pigs (Cavia porcellus). Animals in groups A and C received an aqueous vaccine (aluminum hydroxide); B and D groups received an oily vaccine (Montanide ISA50); Group E positive-control animals were given an imported commercial vaccine with BVDV-la Singer; Group F animals were sham vaccinated (negative control). Groups A, B and E received two doses, and Groups C and D, three, every 21 days. Twelve blood samples were taken, at 21-day intervals over 231 days, and evaluated for antibody titer through virus-neutralization (VN), using a homologous strain (IBSP11), and a heterologous strain (BVDV-la NADL). Most animals, 42 days following the first dose, seroconverted to both strains and, after the second dose, there was a significant increase of titers in all groups. The oily formulation induced greater response after the third administration. This increase was not observed with the aqueous vaccines, regardless of the virus used in the VN. Antibody decline was more rapid in animals that received aqueous vaccines. The results showed the importance of studying the influence of endemic strains of commercial vaccines, to improve the efficacy of BVD vaccination. Use of the endemic strain in vaccine formulation presented promising results, as well as the use of guinea pigs as a laboratory model. (C) 2011 Elsevier Ltd. All rights reserved.

Ab initio calculation of the BCC Fe-Al-Mo (Iron-Aluminum-Molybdenum) phase diagram: Implications for the nature of the tau(2) phase

The metastable phase diagram of the BCC-based ordering equilibria in the Fe-Al-Mo system has been calculated via a truncated cluster expansion, through the combination of Full-Potential-Linear augmented Plane Wave (FP-LAPW) electronic structure calculations and of Cluster Variation Method (CVM) thermodynamic calculations in the irregular tetrahedron approximation. Four isothermal sections at 1750 K, 2000 K, 2250 K and 2500 K are calculated and correlated with recently published experimental data on the system. The results confirm that the critical temperature for the order-disorder equilibrium between Fe(3)Al-D0(3) and FeAl-B2 is increased by Mo additions, while the critical temperature for the FeAl-B2/A2 equilibrium is kept approximately invariant with increasing Mo contents. The stabilization of the Al-rich A2 phase in equilibrium with overstoichiometric B2-(Fe,Mo)Al is also consistent with the attribution of the A2 structure to the tau(2) phase, stable at high temperatures in overstoichiometric B2-FeAl. (C) 2009 Elsevier Ltd. All rights reserved.

Dendrimer-assisted immobilization of alcohol dehydrogenase in nanostructured films for biosensing: Ethanol detection using electrical capacitance measurements

The selective determination of alcohol molecules either in aqueous solutions or in vapor phase is of great importance for several technological areas. In the last years, a number of researchers have reported the fabrication of highly sensitive sensors for ethanol detection, based upon specific enzymatic reactions occurring at the surface of enzyme-containing electrodes. In this study, the enzyme alcohol dehydrogenase (ADH) was immobilized in a layer-by-layer fashion onto Au-interdigitated electrodes (IDEs), in conjunction with layers of PAMAM dendrimers. The immobilization process was followed in Teal time using quartz crystal microbalance (QCM), indicating that an average mass of 52.1 ng of ADH was adsorbed at each deposition step. Detection was carried out using a novel strategy entirely based upon electrical capacitance measurements, through which ethanol could be detected at concentrations of 1 part per million by volume (ppmv). (C) 2007 Elsevier B.V. All rights reserved.

Phase-transition studies of Ba(0.90)Ca(0.10)(Ti(1-x)Zr(x))O(3) ferroelectric ceramic compounds

Perovskite-structured Ba(0.90)Ca(0.10)(Ti(1-x)Zr(x))O(3) ceramics were prepared in this work and subsequently studied in terms of composition-dependent dielectric and high-resolution long-range order structural properties from 30 to 450 K. The dielectric response of these materials was measured at several frequencies in the range from 1 kHz to 1 MHz. Combining both techniques, including Rietveld refinement of the X-ray diffraction data, allowed observing that, when increasing Zr(4+) content, the materials change from conventional to diffuse and relaxor ferroelectric compounds, the transition occurring spontaneously at the x = 0.18 composition. Interestingly, this spontaneous transition turned out to be prevented for a further increase of Zr(4+). On the basis of all the dielectric and structural results processed, a phase diagram of this system is presented. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Phase diagram and spectral properties of a new exactly integrable spin-1 quantum chain

The spectral properties and phase diagram of the exactly integrable spin-1 quantum chain introduced by Alcaraz and Bariev are presented. The model has a U(1) symmetry and its integrability is associated with an unknown R-matrix whose dependence on the spectral parameters is not of a different form. The associated Bethe ansatz equations that fix the eigenspectra are distinct from those associated with other known integrable spin models. The model has a free parameter t(p). We show that at the special point t(p) = 1, the model acquires an extra U(1) symmetry and reduces to the deformed SU(3) Perk-Schultz model at a special value of its anisotropy q = exp(i2 pi/3) and in the presence of an external magnetic field. Our analysis is carried out either by solving the associated Bethe ansatz equations or by direct diagonalization of the quantum Hamiltonian for small lattice sizes. The phase diagram is calculated by exploring the consequences of conformal invariance on the finite-size corrections of the Hamiltonian eigenspectrum. The model exhibits a critical phase ruled by the c = 1 conformal field theory separated from a massive phase by first-order phase transitions.

Aerobic oxidation of monoterpenic alcohols catalyzed by ruthenium hydroxide supported on silica-coated magnetic nanoparticles

Ruthenium hydroxide supported on silica-coated magnetic nanoparticles was shown to be an efficient heterogeneous catalyst for the liquid-phase oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant in the absence of co-catalysts or additives. The material was prepared through the loading of the amino modified support with ruthenium(III) ions from an aqueous solution of ruthenium(III) chloride followed by treatment with sodium hydroxide to form ruthenium hydroxide species. Characterizations suggest that ruthenium hydroxide is highly dispersed on the support surface, with no ruthenium containing crystalline phases being detected. Various carbonylic monoterpenoids important for fragrance and pharmaceutical industries can be obtained in good to excellent yields starting from biomass-based monoterpenic alcohols, such as isobomeol, perillyl alcohol, carveol, and citronellol. The catalyst undergoes no metal leaching and can be easily recovered by the application of an external magnet and re-used. (C) 2011 Elsevier Inc. All rights reserved.

Picosecond Dynamics of the Prototropic Reactions of 7-Hydroxyflavylium Photoacids Anchored at an Anionic Micellar Surface

Three water-insoluble, micelle-anchored flavylium salts, 7-hydroxy-3-octyl-flavylium chloride, 4`-hexyl-7-hydroxyflavylium chloride, and 6-hexyl-7-hydroxy-4-methyl-flavylium chloride, have been employed to probe excited-state prototropic reactions in micellar sodium dodecyl sulfate (SDS). In SDS micelles, the fluorescence decays of these three flavylium salts are tetraexponential functions in the pH range from 1.0 to 4.6 at temperatures from 293 to 318 K. The four components of the decays are assigned to Four kinetically coupled excited species in the micelle: specifically, promptly deprotonable (AH(+)*) and nonpromptly deprotonable (AH(h)(+)*) orientations of the acid in the micelle. the base-proton geminate pair (A*center dot center dot center dot H(+)), and the free conjugate base (A*). The initial prompt deprotonation to form the germinate pair occurs at essentially the same rate (k(d) similar to 6-7 x 10(10) s(-1)) for all three photoacids. Recombination of the germinate pair is similar to 3-fold faster than the rate of proton escape from the pair (k(rec) similar to 3 x 10(10) s(-1) and k(diss) similar to 1 x 10(10) s(-1)), corresponding to an intrinsic recombination efficiency of the pair of similar to 75%. Finally, the reprotonation of the short-lived free A* (200-350 ps, depending oil the photoacid) has two components, only one of which depends oil the proton concentration in the intermicellar aqueous phase. Ultrafast transfer of the proton to water and substantial compartmentalization of the photogenerated proton at the micelle surface Oil the picosecond time scale strongly suggest preferential transfer of the proton to preformed hydrogen-bonded water bridges between the photoacid and the anionic headgroups. This localizes the proton in the vicinity of the excited base much more efficiently than ill bulk water, resulting ill the predominance of geminate re reprotonation at the micelle surface.

Co/Al2O3 catalysts promoted with noble metals for production of hydrogen by methane steam reforming

The effect of noble metal addition on the catalytic properties of Co/Al2O3 was evaluated for the steam reforming of methane. Co/Al2O3 catalysts were prepared with addition of different noble metals (Pt, Pd, Ru and Ir 0.3 wt.%) by a wetness impregnation method and characterized by UV-vis spectroscopy, temperature programmed reduction (TPR) and temperature programmed oxidation (TPO) of the reduced catalysts. The UV-vis spectra of the samples indicate that, most likely, large amounts of the supported cobalt form Co species in which cobalt is in octahedral and tetrahedral symmetries. No peaks assigned to cobalt species from aluminate were found for the promoted and unpromoted cobalt catalysts. TPO analyses showed that the addition of the noble metals on the Co/Al2O3 catalyst leads to a more stable metallic state and less susceptible to the deactivation process during the reforming reaction. The Co/Al2O3 promoted with Pt showed higher stability and selectivity for H(2)production during the methane steam reforming. (C) 2007 Elsevier Ltd. All rights reserved.

Production of hydrogen by ethanol steam reforming on Co/Al2O3 catalysts: Effect of addition of small quantities of noble metals

The catalytic performance of Co/Al2O3 catalysts promoted with small amounts noble metals (Pt, Pd, Ru, Ir) for steam reforming of ethanol (SRE) has been investigated. The catalysts were characterized by the energy dispersive X-ray, X-ray diffraction, BET surface area, X-ray absorption fine structure and temperature reduction programmed techniques. The results showed that the promoting effect of noble metals included a marked decrease of the reduction temperatures of both Co3O4 and cobalt surface species interacting with the support due to the hydrogen spillover effect, leading to a significant increase of the reducibilities of the promoted catalysts. The better catalytic performance for the ethanol steam reforming at 400 degrees C was obtained for the CoRu/Al2O3 catalyst, which presented an effluent gaseous mixture with the highest H, selectivity and the reasonable low CO formation. (C) 2007 Published by Elsevier B.V.