Noriyasu Okazaki

Marked difference in activity of alumina catalysts for selective catalytic reduction of nitrogen monoxide by ethene in excess oxygen

Alumina is well-known as an effective catalyst for the title reaction. The present study revealed that the activity of an alumina catalyst for the reaction largely depended on its type. A critical factor affecting the activity of an alumina was neither the surface area nor pore structure, but the purity; the higher the purity, the higher the activity. Active alumina catalysts showed high activity for both the oxidation of NO to NO2 and the reduction of NO2 by ethene.

Nickel-catalyzed carbonization of wood for coproduction of functional carbon and fluid fuels I: production of crystallized mesoporous carbon

Japanese larch wood loaded with nickel (1%–4%) alone or with nickel and calcium (0.25%–1.5%) was carbonized at 800°–900°C for 0–120min with a heating rate of 5°–20°C min−1 in a helium flow of 5.8−46.4 ml STP cm−2 min−1 to examine the influence of these variables on the crystallization of carbon (the formation of T component) and the development of mesoporosity. From the obtained results, reaction conditions suitable for effective production of carbon with the dual functions of adequate electroconductivity and adsorption capacity in liquid phase were established, thereby explaining the factors that govern the process. It was also confirmed that mesopore having a diameter of about 4 nm was selectively produced at the cost of specific (BET) surface area in parallel with the formation of T component. This result provided good insight into how the simultaneous dual function could be realized.

Influence of calcium on the catalytic behavior of nickel in low temperature hydrogasification of wood char

Abstract Demineralized birch char co-loaded with nickel and calcium was hydrogasified to examine the catalytic behavior of the binary system at temperatures below 700°C. The activity of nickel was determined by the amount of co-existing calcium, and it became a maximum at a given ratio of calcium to nickel. This can be explained by the two roles of calcium: (1) retardation of nickel sintering and (2) inhibition of the formation of catalytically active nickel species. Calcium was considered to interact with nickel to form a certain double oxide of calcium and nickel, whereby both actions occur. On the basis of this assumption, the function of calcium for nickel- and iron-catalyzed hydrogasifications of wood char is discussed.

Deactivation by sulfur dioxide of alumina-based catalysts for selective catalytic reduction of nitrogen monoxide by ethene

Abstract The title reaction over alumina and 5.0 wt% Me (Me: Co, Fe or Cu) added alumina catalysts ( Me Al 2 O 3 ) was investigated in the presence of SO2. Their NO reduction activities were decreased by SO2 poisoning, depending on the kinds of the catalysts. A most strongly poisoned catalyst was Fe Al 2 O 3 , followed by Al2O3, Co Al 2 O 3 , and Cu Al 2 O 3 . The XPS studies of deactivated Me Al 2 O 3 catalysts revealed that sulfate-ion like species were formed on all the catalysts, and moreover, on Fe or Co Al 2 O 3 , corresponding metal-sulfate like species were also formed. The selective catalytic reduction of NO2 by ethene in the presence of SO2 was also investigated, and some mechanistic discussion was given.

Effect of pretreatment of oak bark to develop porosity in the cell tissue on subsequent iron-catalysed hydrogasification

Abstract Oak bark was immersed in boiling water or extracted with supercritical carbon dioxide in the presence of water to develop porosity in the cell tissue before iron catalyst was loaded by wet impregnation. The iron-loaded bark was carbonized at 500°C, and the resulting char was hydrogasified in a thermobalance to measure the reactivity by the temperature-programmed method. The reactivity up to 700°C was higher than that of raw bark char at 5 wt% iron loading because of improved dispersion of the metal particles. Supercritical extraction was superior to boiling in its effect. These pretreatments following demineralization with HCl enhanced the activity of iron to a greater degree, so that demineralized and extracted char with 5 wt% iron gave a conversion of 90% at 700°C. Demineralized and boiled char also exceeded demineralized char in reactivity at the same iron loading. These results showed the significance of development of porosity for higher catalytic activity of iron in subsequent gasification. The X-ray diffraction intensity of metallic iron was found to be useful for judging its dispersion on bark char containing a large amount of mineral matter.

Nickel-catalyzed carbonization of wood for coproduction of functional carbon and fluid fuels II: improved fuel quality of oil fraction and increased heating value of gas fraction

The yields and properties of oil and gas fractions coproduced during carbonization of larch wood loaded with Ni 2%, Ni 2%+Ca 1%, and Ni 4% and without catalyst (None) at 700°–900°C were examined to clarify the catalytic effect in terms of conversion into fluid fuels. The net calorific value of oil occurred mainly below 500°C and increased in the order None < Ni 2% < Ni 4% < Ni 2%+Ca 1%, while the yield decreased in this order. The same order held for the production of gases enriched with hydrogen at 500°–700°C. Even above 800°C, markedly promoted evolution of hydrogen took place for all catalyst systems. These observations confirmed the effectiveness of nickel-catalyzed carbonization at 900°C, particularly Ni 2%+Ca 1%, for both upgrading of oil and gaseous fractions, although the quality of oil was not satisfactory. The catalysis of nickel with and without calcium is discussed on the basis of the modified Broid-Shafizadeh scheme, and the scheme was altered to adapt to the high temperature region where oil was no longer produced.

Non-Fermi Liquids as Highly Active Oxygen Evolution Reaction Catalysts

Abstract The oxygen evolution reaction (OER) plays a key role in emerging energy conversion technologies such as rechargeable metal‐air batteries, and direct solar water splitting. Herein, a remarkably low overpotential of ≈150 mV at 10 mA cm−2 disk in alkaline solutions using one of the non‐Fermi liquids, Hg2Ru2O7, is reported. Hg2Ru2O7 displays a rapid increase in current density and excellent durability as an OER catalyst. This outstanding catalytic performance is realized through the coexistence of localized d‐bands with the metallic state that is unique to non‐Fermi liquids. The findings indicate that non‐Fermi liquids could greatly improve the design of highly active OER catalysts.

3.17 Preparation of Silica-Deposited Alumina Catalyst by Utilizing Organosilicon Complexes as Building Blocks for the Synthesis of Acidic Sites

Abstract To elucidate the structural details of the interface and its catalytic properties of silica-alumina, we prepared three types of silica-alumina catalysts employing trimethylsiloxyaluminumdichloride ((CH 3 ) 3 SiOALCL 2 ) 1 , polyhedral oligosilsesquioxane ((c-C 5 H 9 ) 7 Si 7 O 9 (OH) 3 ) 2 and CH 3 Si(OCH 3 ) 3 . The simultaneous silica and alumina-deposited catalysts derived from 1 exhibited high activity for cyclopropane isomerization but not for 1-butene isomerization. The results of the variation of activity for ethanol dehydration on silica and alumina-deposited catalysts suggested that the deposited ALOx is also active for ethanol dehydration. The silica cluster-deposited alumina catalysts derived from 2 exhibited high activity for 1-butene isomerization upon deposition of a small amount of silica, indicating that the active sites for the 1-butene isomerization were formed more efficiently than those formed on the silica-deposited alumina derived from CH 3 Si(OCH 3 ) 3 . The nature of active sites on the several types of silica-alumina for these reaction are discussed in terms of the structure of deposited silica.

A relationship between electrical conductivity and photodegradation in styrene-butadiene copolymer/multi-wall carbon nanotube composite

An effect of photodegradation on electrical conductivity of a styrene-butadiene copolymer (SBR)/multiwall carbon nanotube (MWNT) composite was studied with a TiO2/polyethylene oxide/methyl linoleate paint photocatalyst under UV and/or visible light irradiation. An oxidative etching of impurities on the MWNT surface was caused by the UV or visible light irradiation, leading to an increase of quality of MWNT. On the other hand, the photocatalyst addition caused the degradation of MWNT structure. A relationship between the electrical conductivity and MWNT content showed that the MWNT dispersity in a SBR was superior to that in a polystyrene (PS). In addition, the PS addition to SBR matrix caused MWNT aggregation. The electrical conductivity decrease of the MWNT composite was due to electrical percolation structure loss caused by the photocatalyst under the visible light irradiation, and its rate depended on the MWNT dispersity. The PS molecular weight change behavior with the photocatalyst was consistent with the electrical conductivity one of the SBR/MWNT. The photocatalyst ability was estimated from the electrical conductivity of the SBR/MWNT.

Catalytic behavior of Zn2+ or Cd2+ supported Y-zeolite for acetonitrile formation from ethene and ammonia

Abstract Zn/Y- and Cd/Y-zeolites were found to be much more active for the formation of acetonitrile from ethene and ammonia than Al 2 O 3 and H/Y-zeolite. Although Zn or Cd/Al 2 O 3 showed the higher activity than Al 2 O 3 itself, Y-zeolite was superior as a support to Al 2 O 3 . The partial pressure dependence of NH 3 on Zn/Y-zeolite was different from that on Cd/Y-zeolite. The reaction of ethylamine over Zn/Y and Cd/Y-zeolites was performed, since formation of a very small amount of ethylamine was observed during the reaction between ethene and ammonia. However, the amount of acetonitrile formed from ethylamine was very small on Zn/Y-zeolite. The amount of ethylamine rapidly decreased with reaction time. On the other hand, an induction period was observed on the formation of acetonitrile over Zn/Y-zeolite. The Cd/Y-zeolites were found to be almost inactive for the formation of acetonitrile from ethylamine. On the basis of the results obtained, the main reaction route for the acetonitrile formation is thought to be different from the route through the formation of ethylamine.