Role of potassium added to Ce/NaZSM-5 catalyst in partial oxidation activity of benzyl alcohol

Abstract

The vapor-phase catalytic oxidation of benzyl alcohol was carried out over cerium-impregnated NaZSM-5 (Ce/NaZSM-5) and K-added Ce/NaZSM-5 catalysts. The main products were benzaldehyde and carbon dioxide, together with trace amounts of benzene and toluene. The effect of the added K on the catalytic activity in the benzyl alcohol oxidation was different by the amount of supported Ce (Ce: 1.4 × 10⁻²–7.1 × 10⁻¹ mmol g(NaZSM-5)⁻¹, low Ce (Ce_L): ≃10⁻² mmol g(NaZSM-5)⁻¹, high Ce (Ce_H): ≃10⁻¹ mmol g(NaZSM-5)⁻¹). The BET surface area and the temperature-programmed oxidation (TPO) of the fresh and the used K-added Ce/NaZSM-5 catalysts was measured to obtain information on the role of the added K in the catalytic activity of the benzyl alcohol oxidation. The amount of O₂ uptake of the pre-reduced K-added Ce_H/NaZSM-5 catalysts was also measured to estimate the ability to store the oxygen species on the cerium. The main role of potassium added to the high Ce-loaded NaZSM-5 (Ce_H/NaZSM-5) catalyst was to prevent the build-up of coke-like materials on the catalyst surface during the oxidation and so prolong the catalytic life.