Tetsuya Nanba

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

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.

Oxidation of carbon black over various Pt/MOx/SiC catalysts

Abstract Catalytic activities of various Pt/MOx/SiC systems for carbon oxidation under simulated diesel exhaust gas were investigated in temperature-programmed reactions. When Pt/MOx (MOx=TiO2, ZrO2, Al2O3) was loaded onto silicon carbide (SiC), the oxidation activities became higher than those of Pt/MOx alone or other Pt/MOx/SiC systems (MOx=Ta2O5, WO3, Nb2O5, SnO2, SiO2, CeO2, MoO3, V2O5). Among them, Pt/TiO2/SiC exhibited the highest activity. We discuss the activity of MOx=TiO2, ZrO2, and Al2O3 in connection with NO oxidation activity, adsorption of sulfate onto the support, Pt dispersion, and specific surface area of the catalyst. Furthermore, we investigated the catalytic performance of Pt/TiO2/SiC in more detail under isothermal conditions and in a staged arrangement.

An exploratory study of diesel soot oxidation with NO2 and O2 on supported metal oxide catalysts

Abstract A number of supported metal oxide catalysts were screened for their catalytic performance for the oxidation of carbon black (CB; a model diesel soot) using NO 2 as the main oxidant. It was found that contact between the carbon and catalyst was a key factor in determining the rate of oxidation by NO 2 . Oxides with low melting points, such as Re 2 O 7 , MoO 3 and V 2 O 5 showed higher activities than did Fe 3 O 4 and Co 3 O 4 . The activities of MoO 3 and V 2 O 5 on various supporting materials were also examined. MoO 3 /SiO 2 was the most active catalyst among the supported MoO 3 examined, whereas, V 2 O 5 /MCM-41 showed the highest activity among the supported V 2 O 5 . Different performances of the supported MoO 3 catalysts were explained by the interaction of MoO 3 with the supports: a strong MoO 3 /support interaction may result in a poor mobility of MoO 3 and a poor activity for oxidation of carbon by NO 2 . The high activity of V 2 O 5 /MCM-41 was associated with its catalysis of the oxidation of SO 2 by NO 2 to form SO 3 , which substantially promotes oxidation of carbon by NO 2 . Addition of transition metal oxides or sulfates to supported MoO 3 and V 2 O 5 was also investigated. Combining MoO 3 or V 2 O 5 with CuO on SiO 2 , adding VOSO 4 to MoO 3 /SiO 2 or MoO 3 /Al 2 O 3 and adding TiOSO 4 or CuSO 4 to V 2 O 5 /Al 2 O 3 improved the catalytic performance.

Catalytic performance of Pt supported on various metal oxides in the oxidation of carbon black

Abstract The effect of support materials for Pt catalysts on the oxidation of carbon black, a model diesel-exhaust soot was examined. Among eight kinds of Pt-supported metal oxides (Ta2O5, Nb2O5, WO3, SnO2, SiO2, TiO2, Al2O3 and ZrO2), Pt/Ta2O5 showed the highest activity towards the oxidation of carbon black in a model diesel exhaust, containing O2, H2O, NO and SO2 in N2. Pt catalysts supported on other non-basic metal oxides such as Nb2O5, WO3, SnO2 and SiO2 showed similar high activities. The high activity for these catalysts was attributed to their non-basicity and negligible affinity toward SO3 (or H2SO4), which results in less poisoning of the supported Pt and also in a smooth supply of SO3 to the carbon surface, which is oxidized by NO2 with a catalysis of SO3.

Synergistic catalysis of carbon black oxidation by Pt with MoO3 or V2O5

Abstract A series of SiO2-supported MoO3, V2O5, and Pt catalysts were prepared for the study of model soot oxidation with simulated diesel exhaust gas. Composite samples of Pt with the metal oxides demonstrated higher oxidation activities than the single-component SiO2-supported MoO3, V2O5 or Pt catalysts in the absence of SO2 in the reactant gas. Based on the effects of NO2 on carbon oxidation, a synergistic reaction mechanism was suggested to explain the effects of combining Pt with the oxides: Pt catalyzes the oxidation of NO with gas phase O2 to NO2, while MoO3 and V2O5 catalyze the oxidation of carbon with NO2. Finally, the effects of SO2 on the carbon oxidation reaction were examined and discussed.

Plasma Catalysis for Environmental Treatment and Energy Applications

The current status of plasma-catalysis research and the associated possible applications are outlined. A basic explanation of plasma chemistry is given, which is then used as a foundation to indicate the research vector for the ongoing development of various applications. As an example of an environmental application, volatile organic compound decomposition using plasma-catalysis is discussed in depth, from the fundamental concept to the current industrial application status. As a potential application of plasma-catalysis towards the realization of a future “hydrogen society”, ammonia synthesis is discussed in terms of current social attitudes and regulations, along with historical developments. Additionally, up-to-date information on the fundamentals of the nonthermal plasma interaction with a catalyst is provided.

Screening of Catalysts for Acrylonitrile Decomposition

The catalytic decomposition of acrylonitrile over various metal components (Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, Ga, Pd, Ag, and Pt) supported on several metal oxides (Al2O3, SiO2, TiO2, ZrO2, and MgO) and ZSM-5 was studied. The most promising catalyst was Cu-ZSM-5, which exhibited 100% conversion and at least 80% N2 selectivity above 350 °C.

Morphology of active species of Ag/ZrO2 for low-temperature soot oxidation by oxygen

The catalytic oxidation of carbon black, a model soot, over Ag/ZrO2 was studied. Transmission electron microscopy observations revealed that Ag nanoparticles with sizes of 2–10 nm on the catalysts presented 3–10 wt% Ag loading. Temperature-programmed reaction and transient activity measurements of carbon black oxidation revealed that the oxidation rate also increased with an increasing number of Ag nanoparticles on the catalysts up to 5 wt% Ag loading. The catalytically active Ag species thus was concluded to be nanoparticles with sizes of 2–10 nm.

Use of Double Wash-Coatings of Platinum and Zeolite Catalysts to Improve Selective Reduction of NOx by Hydrocarbons

The selective catalytic reduction by hydrocarbons (HC-SCR) of NOx under lean conditions has been improved by the use of double-layered catalysts with a lower layer of Pt/SiO2 and an upper layer of a zeolite such as H-, Ce-, and Cu-ferrierite (-FER). H-FER wash-coated over Pt/SiO2 (H-FER//Pt/SiO2) performed best among the samples examined. The promotional effect was attributed to the synergy of the oxidation catalyst (Pt/SiO2) in converting NO into NO2, which is more reactive to C3H6, and the HC-SCR catalyst (H-FER). Cu-FER//Pt/SiO2 was also effective at widening the temperature window, but with this combination the performance was attributed to a simple summation of the activity of two HC-SCR catalysts that were active at different temperatures.

Effect of the support for Pt catalysts on soot oxidation

Abstract The effect of the support for Pt catalysts on the oxidation of carbon black, a model diesel-exhaust soot were examined. Among eight kinds of Pt-supported metal oxides, Pt/Ta2O5 showed the highest activity towards the oxidation of carbon black in a model diesel exhaust, containing O2, H2O, NO, and SO2 in N2. Pt catalysts supported on other non-basic metal oxides such as Nb2O5, WO3, SnO2, and SiO2 showed similar high activities. The cause of the high activity for these catalysts was investigated in relation to the roles of NO2 and SO3 (or H2SO4) in this catalytic process.