Satoshi Kushiyama

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.

Decomposition of benzene using a nonthermal plasma reactor packed with ferroelectric pellets

The decomposition of benzene in air was carried out using a nonthermal discharge plasma reactor packed with ferroelectric materials. It was found that ferroelectric materials having a diameter of 1-2 mm and a relative dielectric constant of /spl epsi//sub r/ /spl ges/1100 exhibited the most effective energy efficiency for the decomposition of benzene. Benzene of low concentration, below 50 ppm, was completely decomposed to CO and CO/sub 2/ without the formation of other hydrocarbons. The ratio of CO to CO/sub 2/ produced from benzene was minimized under the atmosphere containing more than 5% of O/sub 2/.

Effective combination of nonthermal plasma and catalysts for decomposition of benzene in air

Abstract The effective combination of plasma energy and solid surface properties, such as catalysis and adsorption, was investigated using packed-bed type catalyst–hybrid and adsorbent–hybrid reactors that were packed with a mixture of BaTiO 3 pellets and other ceramic pellets (catalyst or adsorbent). The plasma reactor that employed catalysts indicated improvement in CO 2 selectivity and suppression of N 2 O formation compared with the reactor that was packed with BaTiO 3 alone. It was also found that the catalysts and adsorbents in the plasma reactor were useful in enhancing energy efficiency. Furthermore, the catalyst and adsorbent positions in the plasma reactor were very important for induction of surface reactions on the packed materials.

Decomposition of benzene using alumina-hybrid and catalyst-hybrid plasma reactors

In order to investigate the effects of alumina and metal ions in plasma discharge, plasma reactors packed with a mixture of BaTiO/sub 3/ pellets and porous Al/sub 2/O/sub 3/ pellets (alumina-hybrid reactor), and with a-mixture of BaTiO/sub 3/ pellets and metal-supported Al/sub 2/O/sub 3/ pellets (catalyst-hybrid reactor) were examined for oxidation of dilute benzene in air. It was found that the oxidative decomposition of benzene was enhanced by concentrating benzene on the Al/sub 2/O/sub 3/ pellets and the catalyst pellets. Furthermore, the selectivities to CO/sub 2/ in the alumina-hybrid reactor and the catalyst-hybrid reactors were higher than those in the plasma reactor packed with BaTiO/sub 3/ pellets alone. In particular, the selectivities to CO/sub 2/ in the catalyst-hybrid reactors using Ag, Co, Cu and Ni/Al/sub 2/O/sub 3/ were higher than those from the alumina-hybrid reactor. In addition, the presence of the alumina and catalysts suppressed the formation of N/sub 2/O.

Decomposition of nitrous oxide over supported rhodium catalysts and dependency on feed gas composition

Abstract The catalytic decomposition of nitrous oxide to nitrogen and oxygen was studied overRh/ZnO, Rh/CeO 2 , Rh/ZSM-5, Cu ZSM-5 and Co Al CO 3 HT (hydrotalcite). The effects of metal loading and calcination conditions upon the catalytic performance were examined on Rh/ZnO. A 0.5 wt.% Rh/ZnO catalyst was found to be the most active catalyst, whose reaction rate was 4.0 × 10 4 μmol(N 2 O) · g −1 · h −1 under the conditions of 950 ppm N 2 O and 5% O 2 at 300°C. The oxidized Rh/ZnO showed a higher activity than that calcined in a reducing atmosphere. The TEM and EDX observations revealed the formation of particles of ca. 50Ain diameter. They consisted of rhodium and zinc oxides as major and minor components, respectively. The activities of all these catalysts decreased when NO 2 and H 2 O were added to the feed.

Removal of dilute benzene using a zeolite-hybrid plasma reactor

The decomposition of benzene was carried out using a plasma reactor packed with a mixture of BaTiO/sub 3/ and zeolite pellets, the zeolite-hybrid reactor. The reactor performance was characterized by measuring CO/sub x/ formed during plasma discharge and CO/sub x/ adsorbed on the solid surface. The decomposition efficiency of benzene in the hybrid reactor was 1.4 to 2.1 times higher than that in a conventional plasma reactor packed with BaTiO/sub 3/ alone. Benzene existing outside a zeolite crystalline pore was found to decompose more easily than that inside a zeolite pore. In addition, the presence of zeolites suppressed the formation of NO/sub x/.

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.

Effect of coexisting components on aromatic decomposition in a packed-bed plasma reactor

Abstract Decomposition of the aromatics benzene (C6H6), toluene (C6H5CH3), and o-xylene (C6H4(CH3)2) was carried out in a plasma reactor packed with BaTiO3 pellets in the presence of various background gases. The order of decomposition efficiency was C6H6 C6H5CH3>C6H4(CH3)2. When the reactant gas consisted of a mixture of C6H6, C6H5CH3, and C6H4(CH3)2, decomposition of C6H6 was suppressed, whereas the decompositions of C6H5CH3 and C6H4(CH3)2 were enhanced compared with the single-component decompositions of these aromatics. It seems that the migration of reactant molecules to the solid surface and the molecular sizes play important roles in these behaviors.

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.