MPa Of Oxygen Pressure Research Articles

Neutron Diffraction Analysis and Electromagnetic Properties of Ultrasonic Wet-Magnetic Separated NixZn1−xFe2O4 Nano-powders

Nano-sized ferrite powders less than 50 nm were prepared through combustion reaction followed by pulverizing and separating through ultrasonic-wet magnetic classification processes to study the electromagnetic properties of the nano-sized ferrites for developing an high performance electromagnetic interference filter. Neutron diffraction analysis of the ferrites prepared at 10 MPa of oxygen pressure shows that the final phase is Ni0.33Zn0.67Fe2O4 (χ2 = 1.48), which lattice parameter is 0.8412(2) nm. The residual magnetization, maximum magnetization, coercive force, susceptibility and Curie temperature of Ni0.33Zn0.67Fe2O4 particles are 0.88 Wb/m2 kg, 7.749 Wb/m2 kg, 1292 A/m, 0.068 m3/kg, and 413.93 K, respectively. Finally, the nano-sized ferrite particle less than 50 nm with more than 99% purity were obtained. The increasing frequency reduced complex permeability which real value (μr0) shows the maximum value at the less than 0.5 GHz. The dielectric constants of the powders are er′ = 5.7 and er″ = 2.5. The nano-sized Ni0.33Zn0.67Fe2O4 ferrite absorber works effectively in the range of 3–5 GHz. Typical FESEM image of Ni0.33Zn0.67Fe2O4 nano-powders.

Production, characterization and evaluation of the energetic capability of bioethanol from Salicornia Bigelovii as a renewable energy source

Abstract Bioethanol production from biomass must be sustainable for providing a real solution to the use of bioethanol as an alternative transportation fuel. In this work, we succeed in using Salicornia Bigelovii (halophyte plant) as a raw material for bioethanol production. The characterization studies indicate a biomass composition comparable to traditional lignocellulosic biomasses: about 46.22 ± 1.20 of cellulose, 14.93 ± 0.37 of hemicellulose and, a low lignin content (1.96 ± 0.21). The highest cellulose content (75.4%) without the presence of furfural aldehyde is obtained employing the wet oxidation pretreatment method, it is performed at 200 °C with test cycles of 10 min applying 1.0 MPa of oxygen pressure. The enzymatic hydrolysis of cellulose is improved employing a dilute-acid hydrolysis after the pretreatment cycle, reaching an overall glucose yield of 91%. Moreover, inhibition of cellulose enzymatic conversion by filtrates is not observed during this process. The simultaneous saccharification and fermentation (employing Saccharomyces cerevisiae yeast for 120 h) of the pretreated material (using wet oxidation followed by dilute-acid hydrolysis), shows a higher ethanol production yield of 98%. These results demonstrate that there is no need of additional nutrients for the fermentation of Salicornia Bigelovii hydrolysates. Additionally, the electrochemical evaluation demonstrate that bioethanol has a similar energetic capability than analytical ethanol, presenting a current density of ∼0.23 mA cm−2.

Efficient catalytic wet oxidation of phenol using iron acetylacetonate complexes anchored on carbon nanofibres

Iron acetylacetonate complexes anchored on oxidized carbon nanofibres (CNFs) were prepared by a three steps procedure: (i) oxidation of commercial CNFs by treatment with HNO 3, (ii) synthesis of acetylacetonate (acac) functional groups on the oxidized CNFs surfaces (acac/CNFs) and (iii) iron ions complexation on the acac sites of the CNFs (Fe-acac/CNFs). The surface groups exposed on the functionalized CNFs were characterized by using attenuated total reflectance Fourier transform infrared spectroscopy, temperature programmed desorption, thermogravimetric analysis and X-ray photoelectron spectroscopy. The functionalized CNFs and the iron complexes anchored on the CNFs were tested as heterogeneous catalysts for the wet oxidation of phenol with pure oxygen. Complete phenol conversion and high mineralization values were achieved with fresh and reused Fe-acac/CNFs catalysts, which demonstrate the improved stability of the catalysts under the phenol degradation reaction conditions. Furthermore these conditions are comparatively mild, typically 413 K of reaction temperature and 2.0 MPa of oxygen pressure.

Ruthenium catalysts supported on high-surface-area zirconia for the catalytic wet oxidation of N, N-dimethyl formamide

Three weight percent ruthenium catalysts were prepared by incipient-wet impregnation of two different zirconium oxides, and characterized by BET, XRD and TPR. Their activity was evaluated in the catalytic wet oxidation (CWO) of N, N-dimethyl formamide (DMF) in an autoclave reactor. Due to a better dispersion, Ru catalyst supported on a high-surface-area zirconia (Ru/ZrO 2-A) possessed higher catalytic properties. Due to over-oxidation of Ru particles, the catalytic activity of the both catalysts decreased during successive tests. The effect of oxygen partial pressure and reaction temperature on the DMF reactivity in the CWO on Ru/ZrO 2-A was also investigated. 98.6% of DMF conversion was obtained through hydrothermal decomposition within 300 min at conditions of 200 °C and 2.0 MPa of nitrogen pressure. At 240 °C and 2.0 MPa of oxygen pressure 98.3% of DMF conversion was obtained within 150 min.

Partial oxidation kinetics of m-hydroxybenzyl alcohol with noble metal catalysts in supercritical carbon dioxide

Partial oxidation of m-hydroxybenzyl alcohol was studied over several supported noble metal catalysts in a temperature range from 373 to 413 K, up to 2 MPa of oxygen pressure and 20 MPa of carbon dioxide pressure. The major product detected was m-hydroxybenzaldehyde. A charcoal supported palladium catalyst gave the highest yield of the aldehyde. For high temperature above 393 K and high oxygen pressure above 0.5 MPa, total oxidation was observed, which caused the selectivity of m-hydroxybenzaldehyde to decrease. Supercritical carbon dioxide medium seemed to improve heat dissipation of the reaction to allow the partial oxidation of m-hydroxybenzyl alcohol to occur under mild conditions. The partial oxidation of benzyl alcohol over a charcoal supported palladium catalyst was also examined for comparison and the major product formed was benzaldehyde. The conversion of benzyl alcohol and the selectivity to benzaldehyde was higher than those for the case of partial oxidation of m-hydroxybenzyl alcohol.

Activity and leaching features of zinc–aluminum ferrites in catalytic wet oxidation of phenol

A series of ZnFe 2− x Al x O 4 spinel type catalysts prepared by sol–gel method have been characterized and tested for catalytic wet oxidation (CWO) of phenol with pure oxygen. The iron species existed in these materials as aggregated iron oxide clusters and Fe 3+ species in octahedral sites. With a decrease in iron content the concentration of the first iron species decreased and the latter increased. Complete phenol conversions and high chemical oxygen demand (COD) removals were obtained for all catalysts during phenol degradation at mild reaction conditions (160 °C and 1.0 MPa of oxygen pressure). Increasing with the concentration of Fe 3+ species in octahedral sites, induction period became significantly shortened. After phenol was completely degraded, the concomitant recycling of the leaching Fe 3+ ions back to the catalyst surface was observed, and in this case it is possible to perform successful CWO reactions with some cycles. It is also suggested that during the reaction the Fe 3+ cations coordinated in octahedral sites in the ZnFe 2− x Al x O 4 catalysts are resistant to acid leaching, but the reduced Fe 2+ cations become much more labile, leading to increased Fe leaching.

Synthesis and Crystal Structure Analysis of KAg11(VO4)4.

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Neutron-diffraction study of zinc-nickel ferrite powders prepared by combustion synthesis

The NixZn1-xFe2O4 ferrites were prepared with different powder sizes of Fe, NiO, ZnO and Fe2O3 by self-propagating high-temperature synthesis at the O2 partial pressures of 2.6 and 5.0 MPa. The analysis of neutron-diffraction patterns revealed that the final stoichiometries of the ferrites were Ni0.40Zn0.60Fe2O4 and Ni0.38Zn0.62Fe2O4, respectively. The lattice parameter of the Ni0.40Zn0.60Fe2O4 phase formed at 2.6 MPa of oxygen pressure was a=0.84097 nm, whereas the lattice parameter of the Ni0.38Zn0.62Fe2O4 phase formed at 5.0 MPa of oxygen pressure was a=0.84123 nm. The lattice parameter of the ferrite significantly depended on the initial ratio of ZnO/NiO powder sizes, which supports the assumption that the reaction mechanism involves the comparative reduction reactions of ZnO and NiO with Fe on the powder surface.