This paper describes the synthesis and characterization of ceramic microreactors composed of inverted beaded silicon carbide (SiC) monoliths with interconnected 0.75-, 2.2-, or 7.2-μm pores as catalyst supports, integrated within high-density alumina reactor housings obtained via an optimized gel-casting procedure. Structural characterization revealed that these tailored macroporous SiC porous monoliths are stable at temperatures up to at least 1200 °C, and have surface areas and porosities as high as 7.4 × 10 7 m 2 / m 3 and 74%, respectively. Further characterization of the ceramic microreactors using the decomposition of ammonia with Ru as the catalyst at temperatures between 450 and 1000 °C showed that as much as 54 sccm of hydrogen, or 9.8 × 10 4 sccm H2 per cm3 of monolith volume, could be obtained from a 36-sccm entering stream of NH3 at >99.9% conversion at temperatures above 700 °C. Moreover, using SiC as a catalyst support appears to increase the catalytic activity of the Ru catalyst, as evidenced by high turnover frequencies.