The power-to-gas technology - particularly power-to-methane - enables the use of the existing gas infrastructure in Austria and binds CO2 in the form of synthetic natural gas. Since existing methanation concepts with fixed-bed reactors exhibit challenging thermal management with temperature hotspots, a validation of a thin double-wall tube reactor with active cooling is the main target of this master's thesis. The experimental results are reproduced in a simulation model for a future upscale of the reactor. Based on the simulation, the CO2 throughput of the reactor increased to a large industrial scale. The tubular reactor (Di=14 mm) cooled by thermal oil has been installed in the existing pilot plant at the Chair of Process Engineering for Industrial Environmental Protection at the University of Leoben. The operating behavior is investigated with several test series under pressure and input flow rate variations. The obtained results from the experimental tests are mapped in different simulation models in Aspen Plus®. After selecting suitable operating points, the upscaling calculation is executed for a throughput of 800 to 20 000 kg CO2 per day. By calculating the dimensions of the bundle and casing, the number of reactor tubes is shown in a schematic drawing. The laboratory tests show that CO2 conversion rates between 90 ¿ 99 % in one reactor stage can be obtained with commercially available bulk catalysts in a pressure range of 4 to 10 bar. A second reactor stage guarantees that Austrian feed-in criteria are met for grid injection. Simulated results approach experimentally generated data with a deviation of ±1 %, which makes a realistic upscaling for an industrial reactor feasible. At a daily throughput of 20 000 kg CO2 (operating point: 12000 h-1, 8 bar), the tube bundle reactor requires 2021 tubes with Di=14 mm. The outer shell of the shell-and-tube reactor has a diameter of 1.104 m for this set-up. Due to the optimized thermal management in the actively cooled double tube, high CO2 conversion rates can be achieved despite increased flow rates. In combination with the simulated upscaling, an estimation of operating resources for future developments of further prototypes is possible.