A revision of the mechanism of o-xylene oxidation to phthalic anhydride with V/Ti/O catalysts, and the role of the promoter Cs
2008; Elsevier BV; Volume: 142; Issue: 3-4 Linguagem: Inglês
10.1016/j.cattod.2008.06.028
ISSN1873-4308
AutoresN. Ballarini, Alida Brentari, F. Cavani, Silvia Luciani, Carlotta Cortelli, F. Cruzzolin, R. Leanza,
Tópico(s)Polyoxometalates: Synthesis and Applications
ResumoThis paper describes the effect of Cs oxide, a promoter of an anatase-supported 7 wt.% V2O5 catalyst for the oxidation of o-xylene to phthalic anhydride. The effect of Cs was investigated in relation to the reaction network at 320 °C, i.e., under conditions of incomplete o-xylene conversion. It was found that at this temperature the catalytic performance was affected by a surface-saturation effect. However, Cs had the role of favoring the desorption of intermediates and keeping a cleaner and more oxidizing catalyst surface, so accelerating the conversion of the reactant and the consecutive oxidations occurring upon the reaction intermediates finally leading to phthalic anhydride. This de-saturation derived from the enhancement of the V re-oxidation rate, which is one main effect of Cs in V/Ti/O catalysts. Besides the route of o-xylene oxidation to the main reaction intermediate o-tolualdehyde, a parallel reaction pathway included the direct oxidation of o-xylene to phthalaldehyde; the latter was one intermediate in the formation of phthalide, via intramolecular condensation, and of phthalic acid.
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