A highly active Cu-based Deacon catalyst with an enhanced lifetime was developed by combining two corrosion-resistant high-throughput reactor setups in this combinatorial study. Catalyst activities were studied in a sequential 10-fold reactor equipped with online MS. For accelerated catalyst ageing studies, a parallel 10-fold reactor was used. The starting point was a CuTi mixed-metal oxide found in former discovery investigations. As development criteria, catalyst stability and HCl conversion were selected. The amount of Cu in the CuTi catalysts were analyzed before and after the ageing process by X-ray fluorescence spectroscopy. Dopant elements were selected that are reported to form oxides with a high corrosion resistance against gaseous HCl. Our study revealed that doping with 1 mol % Nb reduced the Cu leaching during the reaction. Furthermore, the activation energy was decreased by Nb, which enhanced the chlorine production.