Influence and role of added alkali metals on the gas-phase oxidation of benzyl alcohol catalyzed by Cu ion-exchanged NaX zeolites

The influence and the role of alkali metals added to Cu ion-exchanged NaX ( Cu-NaX) catalysts on the gas-phase catalytic oxidation of benzyl alcohol we re examined based on the oxidation results, O-2 uptakes and in situ IR meas urements. The addition of alkali metals to the Cu-NaX catalyst particularly promoted the catalytic activity for partial oxidation. The dependence of t he percentage of Cu ion exchange of the alkali metal-added Cu-NaX catalyst on the catalytic activity in the benzyl alcohol oxidation and the effect of the added alkali metal/Cu ratio on the oxidation activity confirmed that t he alkali metals added to the Cu-NaX catalyst contributed to an increase in the yield of benzaldehyde, while prohibiting an increase in the yield of c arbon dioxide. The added alkali metals present in the spatial vicinity of t he Cu ions functioned more effectively for the promotion of the partial oxi dation. The O-2 species sorbed on the catalyst during the benzyl alcohol ox idation was suggested to contribute to the production of benzaldehyde. The O-2 uptake of the alkali metal-added Cu-NaX catalyst, which was pre-treated at 773 K under a CO atmosphere, became greater than that of the Cu-NaX cou nterpart without the added alkali metal. The alkali metal-added Cu-NaX cata lyst was directly observed to produce a partial oxidation product under mil der conditions than the Cu-NaX catalyst based on in situ IR measurements. T he alkali metals added to the Cu-NaX catalyst will play an important role i n increasing the O-2 uptake, of which the sorbed O-2 species will participa te in the partial oxidation of benzyl alcohol.