The application of the modulation concept to study the reaction pathway and the reaction rate constants of the methanol synthesis starting from CO and CO2 over a CuZr based catalyst is described. Kinetic data of different reaction steps can be calculated by performing modulation experiments using different feed gas compositions. The dynamic variations in the concentrations of products, intermediates and reactants are monitored in situ in a DRIFT cell. The observed retardation (phase shift Delta phi) is examined depending on the modulation frequency omega. This method is used to derive equilibrium and overall rate constants characterising the investigated reaction steps. By repeating the experiments at different reaction temperatures, constants such as Arrhenius activation energies can be assessed.