ISSN:
0941-1216
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The Decisive Cooperation of Metal and Oxygen Ions of Nickel Oxide During the Oxidation of o-XyleneAs can be concluded from the experimental results at 450°C in the reaction mixtures consisting of N2—O2-o-Xylene, both nickel oxide pure and doped with Li2O or In2O3 is unsuited as catalyst for the oxidation of o-xylene to phthalic anhydride. In contrast to NiO which ionosorbs both oxygen and o-xylene, NiO—Li2O, a strong ionosorbent for o-xylene, prevents the ionosorption of oxygen because of the large concentration of holes. Since gaseous oxygen does not react with ionosorbed o-xylene but a reduction of nickel oxide to metallic nickel has been observed in spite of the fact of enough oxygen in the gas phase it can be assumed that o-xylene is forced to remove oxygen ions from the NiO lattice under generation of oxygen-ion vacanxies and nickel atoms. The predominant portions of the reaction products are H2O and CO2. With undoped nickel oxide and NiO—In2O3 which were not reduced under the same experimental conditions, the reaction products had roughly the same composition.The reduction of NiO—Li2O however will be prevented in a gas mixture with a high oxygen pressure which oxidizes the formed nickel atoms on the surface of NiO—Li2O to nickel oxide making possible the entrance of oxygen from the gas phase and, therefore, the oxidation of o-xylene.A turbulent motion of a 2-component catalyst powder from NiO-1mole% Li2O covered with ionosorbed o-xylene and ZnO-1mole% In2O3 covered with ionosorbed oxygen in the same gas mixture resulted in the same reaction products as in the presence of sole NiO—Li2O under simultaneous reduction of nickel oxide. From that we can conclude that the oxidation of o-xylene by oxygen ions of NiO occurs more easily than the reaction with ionosorbed oxygen on ZnO—In2O3 which obviously seems to be bounded too strongly. This result is also confirmed by the prevention of the oxidation of gaseous o-xylene in the presence of only ZnO—In2O3.Finally, the operation of the carrier catalyst V2O5/TiO2 which is employed for the oxidation of o-xylene to phthalic anhydride will be prevented to a large extent in simultaneous presence of nickel oxide either pure or doped with Li2O and In2O3 in roughly the same amount. This result can be mentioned as a proof for the interaction of a 2-component catalyst the mechanism of which is at present not satisfactorily understood.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prac.19953370125
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