Akira Obuchi

Bio: Akira Obuchi is an academic researcher from National Institute of Advanced Industrial Science and Technology. The author has contributed to research in topics: Catalysis & Selective catalytic reduction. The author has an hindex of 28, co-authored 111 publications receiving 2430 citations. Previous affiliations of Akira Obuchi include Hong Kong Environmental Protection Department.

Performance of platinum-group metal catalysts for the selective reduction of nitrogen oxides by hydrocarbons

Abstract: The performances of platinum-group metals, platinum, iridium, palladium, rhodium and ruthenium supported on γ-alumina, as catalysts for the selective reduction of nitrogen oxides by hydrocarbons were investigated. Platinum and rhodium had high nitric oxide conversion activities both in model mixtures and in real diesel exhaust gases, especially at relatively low temperatures between 200 and 350°C. It was confirmed that the platinum-rhodium and platinum catalysts have higher activity and durability than a catalyst composed of copper supported on ZSM-5 under real diesel exhaust conditions. The platinum-containing catalysts, however, produced more nitrous oxide than nitrogen. It is expected that platinum-group metal catalysts will be able to be used for practical purposes if once their selectivity toward nitrogen is improved.

Detection of Anammox Activity and Diversity of Anammox Bacteria-Related 16S rRNA Genes in Coastal Marine Sediment in Japan

Abstract: A first assessment of anammox activity, which is a unique N2 emission process, was conducted in samples of coastal marine sediment from Japan with a 15N tracer. The occurrence and diversity of bacteria possibly responsible for the anammox process were also evaluated by selective PCR-amplification of the 16S rRNA gene for known anammox bacteria. Anammox activity, detected by measuring 14N15N gas production, was only found in samples collected at the intertidal sand bank located at the Yodo River estuary. In the Yodo River samples, 16S rRNA gene fragments affiliated with the known anammox bacterial lineage were also recovered, and the two major phylotypes were both "Candidatus Scalindua wagneri" relatives with 95% and 98% sequence similarity. Even from the other samples in which no recognizable anammox activity was detected, 16S rRNA gene fragments related to known anammox bacteria, but not to "Ca. S. wagneri", were detected. This is the first report of anammox-mediated N2 emission in coastal marine environments in Japan. Notably, the PCR-based analysis allowed us to discover unexpected phylogenetic diversity of anammox bacteria-related 16S rRNA gene sequences. The selective PCR primer set developed in this study could be a powerful tool to unveil the ecology of anammox bacteria in natural environments.

Improvement of Pt catalyst for soot oxidation using mixed oxide as a support

Abstract: Catalytic activity of pt catalysts for soot oxidation was studied using temperature programmed reactions. the activity of pt loaded over tio2-sio2 (pt/tio2-sio2) showed higher activity than other pt/mox systems (mox = tio2, zro2, sio2, al2o3. tio2-zro2. tio2-al2o3, zro2-sio2, zro2-al2o3, sio2-al2o3). the activity was highest when the molar ratio of tio2/(tio2 + sio2) ranged from 0.4 to 0.7. the effect of pretreatment with a gas containing low so2 concentrations on the activity was compared for pt/sio2, pt/tio2 and pt/tio2-sio2. in the case of pt/tio2-sio2, the activity was markedly promoted by the pretreatment whereas no variation in the activity was observed for pt/sio2. the difference in the behavior towards the so, pretreatment was attributed to property difference in the supports for sulfate accumulation. the high activity of pt/tio2-sio2 was also confirmed under practical conditions with a diesel engine exhaust using a catalyst-supported diesel particulate filter (dpf). (c) 2003 elsevier science b.v. all rights reserved.

Selective reduction of nitric oxide with propene over platinum-group based catalysts: Studies of surface species and catalytic activity

Abstract: The reduction of nitric oxide by propene in the presence of oxygen over platinum-group metals supported on TiO2, ZnO, ZrO2, and Al2O3 has been investigated by combined diffuse reflectance FT-IR spectroscopy and catalytic activity studies under flow reaction conditions at 523–673 K and atmospheric pressure. The catalytic activity for the selective reduction of nitric oxide and the intensity of the IR bands due to reaction species depended strongly on the nature of the support, type of supported metal, reaction time and temperature. The main surface species detectable by IR were adsorbed hydrocarbons (2900–3080 cm−1), isocyanate (2180, and 2232–2254 cm−1), cyanide (2125 cm−1), nitrosonium (1901 cm−1), CO2 (2343–2357 cm−1), CO (2058 cm−1) and carbonate (1300–1650 cm−1) species. In the case of rhodium containing catalysts, when supported on Al2O3, they exhibited both the highest concentration of surface species and the highest activity for nitric oxide reduction and selectivity to nitrogen. The catalytic activity and the IR intensities of the nitrosonium and isocyanate bands increased with reaction temperature, reached their maximum between 570 and 620 K, and then decreased at higher temperatures. The IR band intensities due to nitrogen containing surface species were found to be strongly correlated to the activity for nitric oxide conversion and only slightly related to the selectivity to dinitrogen.

Carbon oxidation with platinum supported catalysts

Abstract: The effect of the support oxide, Pt precursor and reactant gas composition on the catalysis of soot oxidation was investigated using carbon black as a model soot and simulated exhaust gases. The Pt precursors used were Pt(NH3)4(OH)2, H2PtCl6·6H2O, Pt(NH3)4(NO3)2, and Pt(NH3)4Cl2. The support metal oxides used were SiO2, Al2O3, and ZrO2. Pt/SiO2 prepared from Pt(NH3)4(OH)2 showed the highest carbon oxidation activity. It had much higher activity in the condition of N2+O2+H2O+NO+SO2 than without NO and SO2.

Identification of Neutral and Charged N x O y Surface Species by IR Spectroscopy

Abstract: The infrared spectral performance of the N x O y species observed on oxide surfaces [N2O, NO−, NO, (NO)2, N2O3, NO+, NO2 − (different nitro and nitrito anions), NO2, N2O4, N2O5, NO2, and NO3 − (bridged, bidentate, and monodentate nitrates)] is considered. The spectra of related compounds (N2, H-, and C-containing nitrogen oxo species, C─N species, NH x species) are also briefly discussed. Some guidelines for spectral identification of N x O y adspecies are proposed and the transformation of the nitrogen oxo species on catalyst surfaces are regarded.

Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources.

Abstract: It is well known that urbanization and industrialization have resulted in the rapidly increasing emissions of volatile organic compounds (VOCs), which are a major contributor to the formation of secondary pollutants (e.g., tropospheric ozone, PAN (peroxyacetyl nitrate), and secondary organic aerosols) and photochemical smog. The emission of these pollutants has led to a large decline in air quality in numerous regions around the world, which has ultimately led to concerns regarding their impact on human health and general well-being. Catalytic oxidation is regarded as one of the most promising strategies for VOC removal from industrial waste streams. This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades. It addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions. It also highlights the primary routes for catalyst deactivation and discusses protocols for their subsequent reactivation. Kinetic models and proposed oxidation mechanisms for representative VOCs are also provided. Typical catalytic reactors and oxidizers for industrial VOC destruction are further discussed. We believe that this Review will provide a great foundation and reference point for future design and development in this field.