CATALYTIC ACTIVITY OF NAZSM-5 SUPPORTED CU CATALYSTS WITH OR WITHOUT ADDED ALKALI-METAL IN BENZYL ALCOHOL OXIDATION

The vapour-phase catalytic oxidation of benzyl alcohol has been carrie d out over NaZSM-5 supported copper and alkali-metal-added NaZSM-5 sup ported Cu catalysts. The NaZSM-5 zeolite supported copper catalyst has been prepared by three different methods, impregnation (Cu-imp1/NaZSM -5), modified impregnation (Cu-imp2/NaZSM-5) and also ion-exchange (Cu -ex-NaZSM-5) methods. The preparation method of the NaZSM-5 supported Cu catalyst influenced the oxidation activity of the catalysts, regard less of the alkali-metal addition. The NaZSM-5 supported copper cataly st (Cu-imp1/NaZSm-5) prepared by the impregnation method was found to show the highest oxidation activity among the prepared catalysts. Addi tion of alkali-metal to the NaZSM-5 supported Cu catalysts prepared by the different methods enhanced the oxidation activity, particularly t he partial oxidation activity of the Cu-NaZSM-5 catalysts. The Na ions originally present in the NaZSM-5 support which maintain the charge n eutrality were found not to affect substantially the catalytic activit y. The redox behaviour and the structure of the Cu species anchored in the NaZSM-5 support were investigated using O-2 uptake, CO adsorption and XRD measurements. The interaction of the Cu species impregnated i n the NaZSM-5 zeolite with O-2 was promoted by adding alkali metals. T he alkali metals added to the Cu-imp/NaZSM-5 zeolites were suggested t o enhance the formation of the oxidic Cu species, which are considered to be responsible for the oxidation activity.