Experiments have been conducted on Cu/ZnO and Cu/ZnO/Al2O3 catalysts at 225 degrees C and 2.86 MPa in an isothermal, differential packed bed reactor to identify promising periodic operations strategies and find cycling variables which give the largest improvement in the synthesis rate relative to steady state. Modulating the H-2 and CO2 concentrations appears to be the best strategy. However, the increased rate under composition modulation was insensitive to cycle period, amplitude and split in the cycle period range from 2 to 30 min. Higher methanol yield resulted from the suppression of the reverse water gas shift reaction. Higher rates under cycling arise from structural or compositional changes to the catalyst surface.