Catalytic octanal oxidation with oxygen was performed at 100 degrees C and the total pressure of 5 and 10 bar in a falling film microreactor with varying reaction plates bearing different in-channel mixing structures. The liquid flow rate was changed in the range of 3.3-17.5 mL/min. The liquid-sided mass transfer over grooved or finned structured plates was enhanced by factors of 1.12 and 1.20, respectively, compared to that on a standard plate with 16 microchannels with dimensions of 1200 mu m x 400 mu m. The liquid flow rate over the structured plates could be increased by 60%-80% without any loss of octanal conversion. A two-dimensional convection and diffusion model adopted from Al-Rawashdeh et al. [Chem. Eng. Sci. 2008, 63, 5149] was formulated to simulate the reactor behavior, and its predictions describe the experimental results in terms of octanal conversion with an accuracy of 4.3% when the actual temperature distribution in the reactor plate is taken into account.