Gas phase hydrogenation of phenol over supported palladium catalysts

A series of palladium supported on alumina, with Pd variation from 0.5 to 7.0 wt%, was prepared by wet impregnation method and characterised by XRD and CO chemisorption measurements. The catalysts were evaluated for a gas phase hydrogenation of phenol in a fixed-bed reactor at 503 K under normal atmospheric pressure. Palladium content beyond 3 wt% has no significant effect on the turnover number of phenol hydrogenation. The order of the reaction with respect to phenol partial pressure was found to be negative and increased from -0.13 to 0.46 with increasing temperature (473-533 K). The apparent activation energy (E-a) of the process was found to be 30 kJ/mol. On the basis of our results an electronic effect is envisaged for the higher catalytic behaviour of calcium-promoted Pd/Al2O3. (C) 1999 Elsevier Science B.V. All rights reserved.