Key properties promoting high activity and stability of supported PdSb/TiO2 catalysts in the acetoxylation of toluene to benzyl acetate

The influence of thermal pretreatment in air, helium and 10% H2/He on the catalytic performance of a supported 9% Pd, 12% Sb/TiO2 catalyst in the gas phase acetoxylation of toluene has been studied by integrated evaluation of catalytic tests and catalyst characterization using mainly XRD, TEM and XPS. A pretreatment temperature of 600 °C is beneficial for shortening the activation period, while the atmosphere during thermal pretreatment influences the long-term stability. Highest catalytic performance with a good long-term stability was reached with pretreatment in He, which creates Sb-containing Pd particles, on which a mixed Pd0/PdO surface is formed during time on stream. Sb stabilizes oxidized Pd species and leads to more stable catalysts in contrast to air-calcined samples. The catalyst pretreated in H2/He was completely inactive, due to the formation of a stable Pd8Sb3 alloy.

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► Performance of PdSb/TiO2 catalysts is governed by thermal pretreatment.
► The pretreatment gives best catalyst, Pd with PdO surface and highly dispersed Sb.
► Crystalline PdSb alloys formed in 10%H2/He flow are totally inactive.
► New preparation method makes use of deactivating additives dispensable.