Influence of alkali promotion on phenol hydrogenation activity of palladium/alumina catalysts Original Research Article

A series of alkali metals (Li, Na, K and Cs) promoted alumina-supported palladium catalysts prepared by wet impregnation method were characterised by XRD and CO chemisorption measurements. The samples were evaluated for the gas phase hydrogenation of phenol to cyclohexanone in a fixed-bed micro reactor at 503 K under normal atmospheric pressure. The promoted palladium catalysts show a higher rate of phenol conversion and yield of cyclohexanone than unpromoted catalyst. Despite similar activity and selectivity for cyclohexanone between lithium- and sodium-promoted catalysts, the Na-promoted ones show a higher resistance for coke formation. The increase in the intrinsic activity of the palladium site on alkali promotion has been attributed to the increase in phenol activity of the promoted catalysts.