High-throughput synthesis and screening methods have been developed for the heterogeneously catalyzed gas phase hydrogenation of CO and CO2 ('methanation') over zirconia and ceria supported noble and base metal catalysts at 300-400 degrees C and ambient pressure. The discovery libraries, for primary screening, consisted of 11 x 11 arrays of 111 catalysts on 3 in. quartz wafers, and 16 x 16 arrays of 256 catalysts on 4 in. quartz wafers. Catalysts were prepared by liquid dispensing techniques and screened for catalytic activity in scanning mass spectrometers (SMS). This primary screening tool uses quadrupole mass spectrometry for rapid serial detection. More than 500 potential catalysts could be screened in a single day. A kinetic model based on fast equilibration by the reverse water-gas-shift reaction in parallel with about an order of magnitude slower CO hydrogenation is in good agreement with COx conversion data. CO2 is mainly reverse shifted to CO. Ru, Rh, and Ni were found to promote methanation whereas Pt tends to catalyze the reverse WGS reaction. Methanation activity can be enhanced by some acidic and redox dopants or suppressed by basic dopants. High conversions were achieved in SMS demonstrating the minimal scalability risk for short contact time reactions. (c) 2005 Elsevier B.V. All rights reserved.