Catalytic decomposition of hydrazine on tungsten carbide: the influence of adsorbed oxygen

Passivated and nonpassivated tungsten carbide (WC) powders were prepared by a temperature-programmed reaction and used as catalysts in the hydrazine decomposition reaction. All catalysts were active at 313 K. The only products of reaction were nitrogen and ammonia, suggesting that the reaction route and the rate-determining step were not modified by adsorbed oxygen. Surface oxygen atoms reacted with hydrazine, resulting in a larger decrease in the rate of reaction for the passivated solids. Excess carbon on the surface of the carbide inhibited the decomposition of hydrazine and resulted in a decrease of ca. 48% in the specific surface area of the tungsten carbide. The excess carbon may be removed in flowing hydrogen at 1000 K. When compared to commercial Ir catalyst (Shell 405), WC is less active in the hydrazine decomposition reaction. (C) 2002 Elsevier Science (USA).21011

Catalytic partial oxidation and steam reforming of methane on La2O3-Al2O3 supported Pt catalysts as observed by X-ray absorption spectroscopy

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Structural transformations of Pt supported on Al2O3 or La2O3-Al2O3 were studied by X-ray absorption near edge structure (XANES) at the Pt L-3 edge during heating and cooling under partial oxidation of methane (POM) conditions, and by extended X-ray absorption fine structure (EXAFS) under steam reforming of methane (SRM) conditions. Ignition of the POM reaction occurred simultaneously with the reduction of PtO2 to metallic Pt, indicating that the ignition occurs on metallic Pt. When the temperature of the POM reaction was decreased, carbon accumulated on the metallic Pt surface, and the activation of CH4 was suppressed at about 370 degrees C. Nevertheless, the oxidation of carbon remaining on the metallic Pt surface continued until a temperature of around 270 degrees C was reached, when oxidation of Pt occurred and the oxidation reactions were extinguished. The EXAFS data obtained during SRM and under H-2 suggest that complex alterations in the structure of Pt particles occur with changes of temperature and reactant composition. The SRM activity of Pt catalysts depends on both the access of CH4 to active Pt sites, and the changes in the structure of Pt particles under reaction conditions. For both reactions, Pt supported on La2O3-Al2O3 was more stable than Pt supported on Al2O3, indicating a higher stability of Al2O3 modified with La2O3. (c) 2012 Elsevier B.V. All rights reserved.4317987Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Brazilian Synchrotron Light Laboratory (LNLS, Campinas, Brazil)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

High tannin sorghum in diets of japanese quails (Coturnix coturnix japonica)

This experiment was carried out to evaluate the effects of replacing corn by high tannin sorghum in diets of japanese quails (Coturnix coturnix japonica) on performance and egg quality. Two hundred and fifty-two quails with 50 weeks of age were evaluated during four periods of 21 days. The treatments consisted of diets containing 20, 40, 60, 80 and 100% of sorghum, and a control treatment (100% of corn). Diets were formulated so that the levels of energy, protein, amino acids (methionine+cystine and lysine), calcium and phosphorus were similar A completely randomized experimental design was used, with six treatments, six replicates and seven quails for experimental unit. Evaluated parameters were egg production (%), feed intake, feed: gain ratio (kg/kg and kg/dozen), egg mass (g), egg weight and egg quality (Haugh unit, eggshell percentage, shell thickness and yolk color). The increasing sorghum levels had a negative linear effect (p<0.05) on egg production (Y=82.9138 - 0.0966553X; R²=0.87), egg mass (Y= 8.0840626 - 0.009336932X; R²=0.80) and yolk color (Y=7.14340-0.0546875X; R²=0.98). On the other hand, the replacement had a positive linear effect on feed:gain ratio expressed as kg/kg (Y=0.372174 + 0.000536191X; R²=0.92) and as kg/dozen (Y=2.71516 + 0.00423485X; R²=0.94). Control treatment means were different by Dunnett's test (p<0.05) for egg mass (g) when compared to the treatment with 100% of replacement and for yolk color when compared to treatments containing 20, 40, 60, 80 and 100% of sorghum. There were no differences (p>0.05) in feed intake, egg weight, Haugh unit, eggshell percentage and shell thickness. In conclusion, up to 80% of high tannin sorghum may be used on diets if xanthophyll pigments are added in order to maintain the commercial quality of final products