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1995 (1)
1985 (1)
1Author    Naoki Toshima, Yumi Yamaji, Toshiharu Teranishi, Tetsu YonezawaRequires cookie*
 Abstract    h o to s e n s itiz e d R e d u c tio n o f C a r b o n D io x id e in S o lu tio n U s in g N o b le -M e ta l C lu s te rs f o r E le c tr o n T r a n s f e r Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday Carbon dioxide was reduced to methane by visible-light irradiation of a solution composed of tris(bipyridine)ruthenium(III) as photosensitizer, ethylenediaminetetraacetic acid disodium salt as sacrificial reagent, methyl viologen as electron relay, and a colloidal dispersion of polymer-protected noble-metal clusters, prepared by alcohol-reduction, as catalyst. Among the noble-metal clusters examined, Pt clusters showed the highest activity for the formation of methane as well as hydrogen. In order to improve the activity, oxidized clusters and bimetallic clusters were also applied. For example, the CH4 yield in 3-h irradiation increased from 51 x 10"3 |xmol with unoxidized Pt clusters to 72 x 10" 3 pmol with partially oxidized ones. In the case of Pt/Ru bimetalic systems, the improve­ ment of the catalytic activity by air treatment was much greater than in case of monometallic clusters. 
  Reference    Z. Naturforsch. 50a, 283—291 (1995); received October 4 1994 
  Published    1995 
  Keywords    Carbon dioxide, Photosensitized reduction, Electron transfer, Metal cluster, Colloidal catalyst 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0283.pdf 
 Identifier    ZNA-1995-50a-0283 
 Volume    50 
2Author    A. HengleinRequires cookie*
 Title    Sonolysis of Carbon Dioxide, Nitrous Oxide and Methane in Aqueous Solution  
 Abstract    Water was irradiated with ultrasonic waves under an argon atmosphere which contained small amounts of carbon dioxide, nitrous oxide or methane. The yield of the products was measured as a function of the composition of the gas atmosphere. Maximum yields were observed at a few per cent of the added polyatomic gas. No chemical effects occurred in the irradiation under an atmosphere of pure C0 2 , N 2 0 or CH 4 . It is concluded that the gas mixture in the tiny gas bubbles, in which the chemical effects are brought about, is not in Henry's equilibrium with the aqueous gas solution. The main product of the sonolysis of C0 2 is CO, a small amount of formic acid also being formed. The sonolysis is explained by both the attack of H atoms from the sonolysis of water and direct decomposition of C0 2 due to the high temperatures existing in compressed gas bubbles. The main products of the sonolysis of N 2 0 are nitrogen, nitrite and nitrate. N 2 0 enhances the rate of various oxidations such as that of iodide, nitrite and propanol-2. In the methane containing solution, a lot of hydrogen is produced, the main oxidation products being ethane, ethylene, C 3 -and C 4 -hydrocarbons and carbon monoxide. A mechanism is postulated which involves both the attack on methane by radicals from the decomposition of water and thermal decomposition of methane. The local radical concentrations are so high that a methane molecule may undergo multiple radical attack. The similarity between sonolytic reactions and reactions occurring in flames is emphasized. 
  Reference    (Z. Naturforsch. 40b, 100—107 [1985]; received August 14 1984.) 
  Published    1985 
  Keywords    Ultrasonic Waves, Carbon Dioxide, Nitrous Oxide, Methane, Free Radicals 
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 TEI-XML for    default:Reihe_B/40/ZNB-1985-40b-0100.pdf 
 Identifier    ZNB-1985-40b-0100 
 Volume    40