The direct gas-phase epoxidation of propene in a catalytic membrane reactor has been investigated. Powdered Au/Ti-SiO2 catalyst pressed into a disc was used as a membrane contactor, allowing different feeding of the reactants and providing resistance to their direct contact. The optimization of this reactor concept was performed by screening different propene, oxygen and hydrogen feeding strategies on the catalyst in order to maximize the hydrogen efficiency (propene oxide/water formation ratio). Several membrane configurations were tested and it was found that the optimal configuration was obtained by feeding propene and oxygen separately from hydrogen. The system was operated as a membrane contactor where propene and oxygen flows were forced through the catalytic membrane and the hydrogen had to reach the catalyst by counter diffusion, thereby being the limiting reactant. This creates a favorable concentration profile of the reactants that enhances the performance of the membrane reactor. The membrane thickness and resistance (porosity-tortuosity) were experimentally found to be influential on the hydrogen efficiency. The experimental results were evaluated using a comprehensive reactor model. A membrane thickness of 0.2 mm was determined to be the minimum value needed to ensure a positive effect of the membrane reactor on the hydrogen efficiency. This value can be influenced by changing the resistance of the reactants through the catalytic membrane. The combination of experimental and theoretical information leads to the optimized membrane reactor design where an excess of propene is coupled with a controlled hydrogen supply by diffusion along the catalytic membrane.