The construction, operation and experimental evaluation of a laboratory scale fixed bed reactor for the decomposition of sulphur trioxide with a supported platinum and palladium based catalyst, were undertaken. The heating was accomplished with an electrical furnace and the objective was to operate at steady state with an acceptable conversion of sulphur trioxide involving an endothermic reaction. The catalyst consisted of 0.5 wt.% platinum and 0.5 wt.% palladium on rutile and the effect of the inlet temperature and weight hourly space velocity (WHSV) was investigated. It was found that the reactor attained a steady state of operation for experiments conducted over a temperature range of 903 K and 1103 K with a sintered pelletized catalyst at a high temperature prior to reduction and reaction. Sulphur trioxide conversions equivalent to 60%, within 80% of the equilibrium value, were obtained at 1103 K over a range of weight hourly space velocities (2.6-865 h(-1)) involving a low gas velocity (Re-P = 16) with a range of fixed bed configurations (2.5 mm diameter with 5-400 mm bed lengths). Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.