By measurements of axial gas phase concentration profiles in a fluidized-bed methanation reactor for the production of synthetic natural gas, regeneration of the catalyst inside the fluidized-bed reaction system could be proven. Moreover, by varying space velocity, bed height, catalyst mass, flow rates, and dilution rites, it could tie shown that both hydrodynamic as well as chemical boundary conditions can influence the Surface coverage and therefore selectivity and deactivation processes.