A system containing nine catalytic microreactors for parallel preparation and testing of heterogeneous catalysts is described. The catalyst samples are prepared in the form of thin films coated on thin quartz rods by dip-coating in solutions of different composition. Catalyst-coated rods are placed within thin tubes housed inside a wider tube heated in an electrical furnace. A multiport valve serves to sequentially conduct the reaction products from each microreactor to a mass spectrometer for analysis. The system was tested with the reaction of methane reforming with carbon dioxide over Pt/Ce1-xGdxO2-0.5x and Pt/Ce1-xSmxO2-0.5x at 650 and 700degreesC. Individual catalysts were characterized by X-ray analysis, and induction-coupled plasma mass spectrometry for catalyst mass and elemental composition. The measurements showed that Pt/CeO2 had the highest activity among the series of catalysts tested and generally the activity increased with the cerium oxide content. After exposure to the feedstream for 2 - 3 h at 700degreesC, most catalysts suffered significant deactivation except the mixed oxides with 25 - 85% samarium oxide that maintained relatively stable activity.