Fabrication and characterization of integrated ceramic microreactors for high temperature hydrogen production

The area of microreactors has undergone rapid growth over the past few years. The advantages of using microreactors over macroscale reactors make them useful for various applications, including on-site synthesis of hazardous chemicals, catalyst development and optimization, and the reforming of fuels such as methanol and hydrocarbons for hydrogen production for fuel cells. For the reforming of hydrocarbon fuels, the challenges are to avoid coking by operating at temperatures greater than 800 C, achieving high conversion in a small reactor volume, and minimizing the pressure drop across the reactor. A suitable microreactor, to meet these challenges, must be compatible with high temperature operations, have a high surface area per unit volume, and have a high porosity with open, interconnected pores. We have successfully synthesized inverted beaded porous monoliths as catalyst support structures made from SiC and SiCN ceramic materials in order to meet the specified requirements. Both SiC and SiCN porous structures are stable to temperatures greater than 900 C and have geometric surface areas between 105 and 108 m2/m3. We will show the fabrication of these structures, their impregnation with catalyst, and their integration into high-temperature-compatible alumina reactor housings. We will show the characterization of SiC and SiCN porous structures to confirm the thermal stability of these structures at temperatures greater than 900°C under oxidizing environments, to confirm their promise for high temperature reforming of hydrocarbon fuels. We will show preliminary conversion data for the decomposition of ammonia on Ru-impregnated inverted beaded structures inside a test fixture up to 500 C and we hope to show conversion data from an all ceramic microreactor at temperatures as high as 1000 C.