Diffuse Reflectance IR Fourier-Transform (DRIFT) spectroscopy is an increasingly popular technique in catalysis research as it permits in situ observation of the reactor bed in powd. or granular form. However, DRIFTS in its conventional form suffers from temp.-gradient problems. One soln. is to couple the DRIFTS cell with a continuous recycle flow system. The value of such an arrangement is illustrated via studies of the kinetics and mechanism of CO2 methanation over Ru/TiO2 under transient and steady-state conditions. Metal-absorbed CO is identified as the main reaction intermediate through titrn. to CH4 in transient hydrogenation. The COad is probably supplied via rapid establishment of the reverse water gas shift equil.: H2 + CO2 -> COad + H2O involving adsorbed formate intermediate(s). [on SciFinder (R)]