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-mu m 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 degrees C, and have surface areas and porosities as high as 7.4 x 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 degrees C showed that as much as 54 sccm of hydrogen, or 9.8 x 10(4) seem H-2 per cm(3) of monolith volume, could be obtained from a 36-seem entering stream of NH3 at > 99.9% conversion at temperatures above 700 degrees C. Moreover, using SiC as a catalyst support appears to increase the catalytic activity of the Ru catalyst, as evidenced by high turnover frequencies. (c) 2006 Elsevier Inc. All rights reserved.