A novel flow apparatus is described which can be used for the conversion of lactic acid (LA) to acrylic acid in the gas phase. The design of the setup addresses two problematic issues, i.e. decomposition of LA by catalytically active centers in the containment material and formation of carbonaceous deposits on the catalyst bed due to experimental restrictions. By spatially separating the evaporator from the reactor and by using high-temperature stable plastics, the setup allows aqueous LA to be evaporated without its decomposition and simultaneously avoids formation of deposits on the catalyst bed. Thus, the apparatus design ensures to study the true catalyst deactivation behavior without falsification of the results due to experimental shortcomings. As a practical example, an aqueous solution with 20 wt% LA has been successfully converted on zeolite Na-Y with n (Si)/n (Al) = 2.4. A novel flow apparatus is described which can be used for the conversion of LA to acrylic acid in the gas phase. The design of the setup addresses especially the formation of carbonaceous deposits on the catalyst bed due to experimental restrictions. As an example, zeolite Na-Y is used as a catalyst. The obtained results are remarkable in terms of catalyst deactivation behavior.