Daisuke Hirabayashi

Steam reforming of biomass tar producing H2-rich gases over Ni/MgOx/CaO1-x catalyst.

Series nickel catalysts Ni/MgO(x)/CaO(1-)(x) (x=0.3, 0.5, 0.7, Ni: 5 wt%) were prepared and tested in fixed-bed reactor for biomass tar steam reforming, toluene as tar destruction model compound. Different ratios of MgO and CaO were mixed to simulate dolomite as Ni support. Two preparation methods: solid mixing with (SMW) and without water (SM) were used, the preparation methods and concentration of MgO had an important influence on toluene conversion and products. Catalysts prepared by SM method exhibited higher performance on toluene conversion, resulted in higher H(2) yield, and also, higher CO(2) and lower CO selectivity with higher temperature. For the same preparation method, higher concentration of MgO resulted in higher toluene conversion, and also influence on CO, CO(2) selectivity, but no obvious influence on the H(2) yield. Catalysts were characterized by BET, X-ray diffraction (XRD), SEM.

Design of a Reduction-Resistant Ce0.8Sm0.2 O 1.9 Electrolyte Through Growth of a Thin BaCe1−xSmxO3−α Layer over Electrolyte Surface

A method that can block off electronic current through a samaria-doped ceria (SDC, Ce 0 . 8 Sm 0 . 2 O 1 . 9 ) electrolyte is proposed. A thin BaCeO 3 -based layer 12 μm thick was grown by a solid-state reaction of the electrolyte substrate and a BaO film deposited previously over the substrate surface at 1500°C. A homogeneous junction between the layer and the electrolyte was formed, thus allowing no delamination and cracking of the layer. Tolerance of this layer to CO 2 was high enough to suppress decomposition into BaCO 3 and CeO 2 . Open-circuit voltages of a hydrogen-air fuel cell with the coated SDC electrolyte were near 1 V or more in the range of 600-950°C. The resulting peak power density was higher than that of a fuel cell with an uncoated SDC electrolyte.

Single-Chamber SOFCs with a Ce0.9Gd0.1 O 1.95 Electrolyte Film for Low-Temperature Operation

Single-chamber solid oxide fuel cells (SOFCs) with an anode-supported Ce 0 . 9 Gd 0 . 1 O 1 . 9 5 electrolyte were operated in a mixture of butane and air at furnace temperatures of 200-300°C. The electromotive force (emf) of the cell and the voltage drop were strongly influenced by the catalytic activity of the anode for the partial oxidation of butane. The promotion of hydrogen formation by the addition of Ru to the anode caused an increase in the emf and a reduction in the voltage drop. As a result, stable power densities of 44 and 176 mW cm - 2 were obtained at 200 and 300°C, respectively.

Bi-Based Oxide Anodes for Direct Hydrocarbon SOFCs at Intermediate Temperatures

Doped Bi-based oxides were investigated as potential anode materials for direct hydrocarbon solid oxide fuel cells (SOFCs) at intermediate temperatures. (Bi 2 O 3 ) 0 . 8 5 (Ta 2 O 5 ) 0 . 1 5 met this criterion most successfully. A fraction of Bi 2 O 3 in this material was reduced to BiO and Bi metal under fuel conditions, which yielded high conductivities (<1 S cm - 1 ) based on oxide ions and electrons above 500°C. Carbon deposition was successfully prevented when butane was used as the fuel below 800°C. The catalytic activities for hydrocarbon oxidation were high enough to promote the complete oxidation of butane during cell operation. These abilities provided an enhanced anode performance with increasing temperature from 600 to 750°C, and the resulting polarization resistance reached 1.4 Ω cm 2 at 750°C.

Characterization and Applications of Calcium Ferrites Based Materials Containing Active Oxygen Species

Characterization and application of calcium ferrites based solid solutions containing active oxygen species for catalysts in propylene total and methane partial oxidation has been studied. The calcium ferrite based solutions containing brownmillerite phases showed a structural transition based on the migration of oxide ions at high temperature. The calcium ferrite solution provided two types of active oxygen species due to the existence of the brownmillerite phase. These oxygen species individually played important roles in the propylene and methane oxidation mechanisms.

Oxygen Radicals Occlusion/Release Behavior of Nanoporous Aluminosilicate, Ca12Al14-XSiXO33+0.5X (0≦X≦4)

Oxygen radicals occlusion / release behavior of nanoporous aluminosilicate, Ca12Al14-XSiXO33+0.5X (0≦X≦4), synthesized under different condition was examined by the temperature programmed reduction (TPR) in an atmosphere of hydrogen in the temperature range of 200-1000°C and temperature programmed oxidation (TPO) measurement at 800°C. From the TPR results of Ca12Al14O33 (X=0) and Ca12Al10Si4O35 (X=4), it was found that there were three oxygen release peaks, denoted as α, β and γ, on each sample and the peaks appeared in the temperature range 300-420°C, 420-600°C, and 600-750°C, respectively. The oxygen contents of α and γ of samples were almost the same. However, the oxygen content of β in the sample with x = 4 was much larger, almost double, compared to that in x = 0. From the TPR, TPO results and catalytic performance, it was concluded that the oxygen content of β peak strongly influenced the catalytic activity of the nanoporous aluminosilicate in the propylene combustion.

Intermediate-Temperature SOFCs with Ru-Catalyzed Ni-Cermet Anodes

The promotion of the direct electrochemical oxidation of hydrocarbons in a solid oxide fuel cell was investigated using a ceria-based electrolyte with different noble metals-containing anode at 600 °C. The attempted approach toward this objective was to avoid interference from a large amount of steam and CO2 products, because they degrade the anode performance. Ru was an effective catalyst for removing these gases from the anode surface due to its high catalytic activity for the steam and CO2 reforming of hydrocarbons. This permitted a smooth access of the unreacted hydrocarbons to the three-phase boundary, thus resulting in a noticeably high anode performance. The resulting peak power density reached 750 mW cm -2 with dry methane, which was comparable to the peak power density of 769 mW cm -2 with wet hydrogen.

Separation and Enrichment of Calcium Component by Extraction of Coal Burnt Ash with Organic Acid.

A recovery of calcium resource from such solid waste as coal burnt ash, which involves a large amount of calcium-derived compounds, was investigated by extraction with organic acids. The effect of organic acid on the quality of extracted solid product was studied, in terms of the amount of recovered calcium component and impurities, by employing 6 organic acids: formic acid, acetic acid, propionic acid, oxalic acid, malonic acid and succinic acid. Extraction was performed by dissolving the coal ash samples with organic acid and by filtrating the solid residue to separate the calcium-rich solution. Calcium in the coal ash sample was dissolved with the organic acid, and CaO was recovered from the resulting solution by the evaporation followed by the calcination at 900 °C.As the results, it was found that CaO content in the extract was concentrated up to 75.7-92.7 % from coal burnt ash containing 33.9 % of CaO. The enrichment of CaO was related with pKa value of organic acid. Increasing in pKa value resulted in higher yield of CaO with lower amount of such impurities as SiO2, Al2O3 and Fe2O3.A highly porous structure of CaO extracted with organic acid was obtained. The pore diameter and the pore volume of extracted CaO were 0.31-1.35 μm and 2.02-2.74 l / kg, respectively, compared to those of calcined limestone: 0.075 μm and 1.18 l / kg. Owing to highly porous structure of extracted CaO with organic acid, the capacity of extracted CaO for dry sorption of SO2 was found to be about 2 times larger than that of CaO obtained by calcination of limestone.