A. Naydenov

COMPLETE OXIDATION OF BENZENE ON MANGANESE DIOXIDE BY OZONE

The kinetics of complete catalytic oxidation of benzene by ozone on MnO2 in gradientless conditions has been investigated. It was established that the decomposition of ozone and the oxidation of benzene on MnO2 proceed within the same temperature range (10–80 °C ), and the apparent activation energies are 32 kJ/mol and 30 kJ/mol, respectively. The complete oxidation of benzene by molecular oxygen takes place at temperatures above 160°C with an apparent activation energy of 88 kJ/mol. It has been assumed that the rate-determining step of complete oxidation by ozone is the ozone decomposition.

Ozone decomposition, benzene and CO oxidation over NiMnO3-ilmenite and NiMn2O4-spinel catalysts

Abstract The catalytic activities of NiMnO 3 and NiMn 2 O 4 during heterogeneous catalytic decomposition of ozone and ozone-catalytic oxidation (OZCO) of benzene at low temperatures (20–80°C) have been investigated. The sensitivity of the two oxides towards strong catalytic poisons, such as nitrogen oxides, during the decomposition of ozone has also been estimated. On the basis of the experimental results obtained it is concluded that the NiMnO 3 and NiMn 2 O 4 obtained have a high activity with respect to the reactions of ozone decomposition and CO and CH oxidation in the presence of ozone at temperatures close to the room temperature. The sample with an ilmenite structure shows, in all cases, a higher catalytic activity. The surface oxygen of NiMnO 3 is more reactive at room temperature than is the case of NiMn 2 O 4 . The hypothesis according to which when the two metal cations are in octahedral coordination the catalyst activity is higher and the stability towards catalytic poisons is enhanced has proved to be correct. It should be noted that a catalyst has been synthesized which is able to decompose ozone at room temperature and to activate the organic molecule to a degree permitting catalytic oxidation by ozone at room temperature. In addition, this catalyst shows a relatively high stability with respect to poisoning by nitrogen oxides.

Complete oxidation of benzene over Au−V2O5/TiO2 and Au−V2O5/ZrO2 Catalysts

A gold promotional effect is reported for the complete oxidation of benzene using Au/V2O5 supported on titania or zirconia catalysts.

Catalytic oxidation of CO and C6H6 on alumina-supported Cu-Cr and Co-Cr oxide catalysts in the presence of ozone

The activity of alumina-supported Cu-Cr and Co-Cr oxide catalysts in CO and C6H6 oxidation with both molecular and ozone-enriched oxygen was studied. It was proved that the use of ozonized oxygen leads to a considerable decrease of the reaction temperatures.

On the Mechanism of Indeno(1,2,3-c,d)- pyrene Ozonation

Summary. Calculations on the strongly cancerogenic indeno[1,2,3-c,d]pyrene and all its possible primary and secondary ozonides by the MNDO method indicate the breaking of the C21–C22 bond of the pyrene fragment as the energetically most favourable first step of the oxidative degradation. Localization energies calculated within the simple Hückel model predict that the attack of the C21–C22 pair by ozone is most probably also kinetically the most preferred reaction path. The rather low localization energy of C20 in the pyrene fragment indicates the possibility of competitive reactions between ozonolysis and the formation of phenols and quinones. The theoretical results are supported by experimental findings on the ozonation of indeno[1,2,3-c,d]pyrene in aqueous medium.Zusammenfassung. MNDO-Berechnungen über das krebserregende Indeno[1,2,3-c,d]pyren und seine möglichen primären und sekundären Ozonide deuten auf die Brechung der C21–C22-Bindung des Pyrenresters als die energetisch günstigste erste Stufe des oxidativen Abbaus hin. Die nach dem einfachen Hückel-Modell berechneten Lokalisierungsenergien zeigen, daà der Ozonangriff an das C21–C22-Paar vielleicht auch der kinetisch bevorzugte Weg ist. Die zu kleine Lokalisierungsenergie beim C20-Atom im Pyrenrest indiziert mögliche Konkurrenz zwischen der Ozonolyse und der Bildung von Phenolen und Chinonen. Die theoretischen Ergebnisse werden durch experimentelle Resultate über die Ozonierung von Indeno[1,2,3-c,d]pyren in wäàrigem Medium bestätigt.