Biomedical subjects

Masayoshi Sadakata

Publications and source records attributed to Masayoshi Sadakata.

6 recordsLinked to original sources

PubMed2006

Reduction features of NO over a potassium-doped C12A7-O- catalyst.

The NO reduction features over a noble-metal-free NO(x) storage/reduction catalyst ([Ca24Al28O64](4+*)4O-/K, defined as C12A7-O-/K), including the NO conversion, the N2 selectivity, and sulfur tolerance, were investigated with hydrogen and C3H6 as the reducing agents in a fixed-bed continuous flow reactor. The NO conversion and the N2 selectivity on the C12A7-O-/K catalyst mainly depends on the sample temperature, the percentage of potassium, the reducing agents, and the composition of the mixture of gases. The C12A7-O-/10%K catalyst possessed the highest selective reduction ability (to N2) among the catalysts C12A7-O-/x%K. Over 50% of NO can be reduced to N2 with H2 as the reduction agent at 550-700 degrees C. The C12A7-O-/K catalyst also shows higher NO(x) storage capacity (183.9 micromol/g at about 550 degrees C) as well as sulfur tolerance for both the NO(x) storage and the reduction processes. The catalyst characteristics and the intermediate species formed in the NO storage and reduction processes were investigated by the X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and time-of-flight mass spectrometry. The mechanism of NO(x) reduction was addressed according to the above investigations.

Catalysis↗

PubMed2005

Mechanistic features for hydroxyl anion emission from the modified 12CaO.7Al2O3 surface.

OH(-), O(-), and H(-) emissions from the [Ca(24)Al(28)O(64)](4+).4(OH(-)) (defined as C12A7-OH(-)) surface were investigated by time-of-flight (TOF) spectrometry. The emission intensities were sensitive to surface temperature and extraction field. The apparent activation energies of anions decreased with the increase of applied extraction field. At an extraction field of 800 V/cm, the emission ratio of OH(-) to total anions is 0.98-0.65 in the temperature range of 870-1075 K. The OH(-) emission from C12A7-OH(-) was described by the following kinetic processes: the OH(-) anions in the cages migrated onto the sample surface by field enhanced thermal diffusion, and then desorbed to form the gas-phase anions of OH(-). The O(-) emission originated from the dissociation of O(2-) and OH(-). Similarly, H(-) emission was also attributed to the dissociation of OH(-) on the C12A7-OH(-) surface.

Aluminum Oxide↗

PubMed2005

Features and mechanism of H- anion emission from 12 CaO x 7 Al2O3 surface.

The hydrogen anion (H-) and other anionic species (O-, OH-, e-) in the gas phase, emitted from the synthesized crystal surface of 12 CaO x 7 Al2O3-H- (C12A7-H-), have been observed. The emission intensity of all the anionic species strongly depends on the sample surface temperature and the extraction field. H- has the highest emission branch ratio, and the extraction field can reduce its apparent activation energy. H- emission current at a microA/cm2-level has been achieved, which is about 4 orders of magnitude higher than that obtained from the thermal desorption process of CaH2. The observed anions of H- and OH- are attributed to their migration from the C12A7-H- cages onto the surface [i.e., Y-(cages) --> Y-(surface) --> Y-(gas phase) (Y = H, OH)]. The weak O- and electron emission would both arise from the dissociation of O2-: O2-(surface) --> O-(surface) + e-(surface) --> O-(gas phase) + e-(space).

Aluminum Oxide↗

PubMed2005

One-step synthesis of phenol by O- and OH- emission material.

A novel approach to the direct synthesis of phenol from benzene was obtained with high benzene conversion (30%) and phenol selectivity (approximately 90%) by using a microporous material [Ca24Al28O64]4+.4O-(C12A7-O-) as catalyst with oxygen and water; active O- and OH- anions are proposed to play important roles in the formation of phenol by hydroxylating the aromatic ring of benzene.

Journal Article↗

PubMed2004

Novel dry-desulfurization process using Ca(OH)2/fly ash sorbent in a circulating fluidized bed.

A dry-desulfurization process using Ca(OH)2/fly ash sorbent and a circulating fluidized bed (CFB) was developed. Its aim was to achieve high SO2 removal efficiency without humidification and production of CaSO4 as the main byproduct. The CaSO4 produced could be used to treat alkalized soil. An 83% SO2 removal rate was demonstrated, and a byproduct with a high CaSO4 content was produced through baghouse ash. These results indicated that this process could remove SO2 in flue gas with a high efficiency under dry conditions and simultaneously produce soil amendment. It was shown that NO and NO2 enhanced the SO2 removal rate markedly and that NO2 increased the amount of CaSO4 in the final product more than NO. These results confirmed that the significant effects of NO and NO2 on the SO2 removal rate were due to chain reactions that occurred under favorable conditions. The amount of baghouse ash produced increased as the reaction progressed, indicating that discharge of unreacted Ca(OH)2 from the reactor was suppressed. Hence, unreacted Ca(OH)2 had a long residence time in the CFB, resulting in a high SO2 removal rate. It was also found that 350 degrees C is the optimum reaction temperature for dry desulfurization in the range tested (320-380 degrees C).

Adsorption↗

PubMed2002

Binding and desulfurization characteristics of pulp black liquor in biocoalbriquettes.

To control pollutant emissions from coal combustion in some developing countries, biocoalbriquette, an artificially produced solid fuel, was developed. Both the breaking strength and production costs of the biocoalbriquette have become essentially the most important factors in popularizing it in these countries. To increase the breaking strength and decrease the production costs, it is proposed in this study to use pulp black liquor, a byproduct from the pulp production industry, as a binder. The influences of pulp black liquor on the briquetting and combustion characteristics were investigated. Furthermore, the desulfurization characteristics of pulp black liquor were also evaluated through combustion experiments. The study results show that the briquetting pressure has a limited effect on the breaking strength. An increase in the briquetting pressure yields greater breaking strength of up to the 50 MPa. Above 50 MPa, the breaking strength changes very little with the briquetting pressure. The use of pulp black liquor has had a greater effect on increasing the breaking strength than on changing the briquetting pressure and also on improving the combustion characteristics of the biocoalbriquette. On the other hand, pulp black liquor has some desulfurization capabilities. When used as a binder, it not only increases the breaking strength and decreases the necessary briquetting pressure, but it also improves some characteristics of the combustion and reduces the pollutants emission.

Air Pollution↗