The process of sulphur trioxide production could be conducted as a one-step process in microreactors with forced decreasing temperature profile due to their unique heat and mass transfer capabilities. The choice of a very active catalyst in such reactors is one of the key issues to avoid excessive microfabrication and consequently reactor costs. Comparing vanadium to platinum, we found that platinum is the preferred catalyst based on calculations of the ratio of catalyst to reactor volume combined with the specific activity of the catalysts. To demonstrate the feasibility of the one-step process experimentally, we prepared catalysts with 9 wt.% Pt on TiO2 on microstructured titanium foils by means of a sot-gel method followed by wet impregnation. The catalyst was investigated by SEM, EDX, adsorption measurements and microprobe analysis to study the Pt distribution. We found almost equal distribution of platinum in the TiO2 layer, both with respect to the axial position in the channels as well as regarding the concentration profile of Pt in depth of the support layer. Pores might at least partially be blocked with Pt. Furthermore, we investigated the influence of the start-up behaviour on the lifetime of the catalyst, finding that starting up with the SO2-O-2 mixture gives the most stable operation. Humidity, which cannot be avoided in the laboratory set-up and the graphite-sealed microreactor, is assumed to be the main reason for deactivation during shut-downs. (C) 2010 Elsevier B.V. All rights reserved.