SYNTHESIS OF HIGH-SURFACE-AREA SILICON-CARBIDE BY FLUIDIZED-BED CHEMICAL-VAPOR-DEPOSITION

Activated carbon granulates loaded with small amounts of nickel have s uccessfully been converted into high surface area silicon carbide gran ulates by reaction with hydrogen and silicon tetrachloride at 100 kPa and 1380 K (C + SiCl4 + 2H(2) --> SiC + 4HCl). A cone shaped Fluidized Bed Chemical Vapour Deposition reactor is demonstrated to achieve rep roducible and homogeneous conversions of considerable amounts of activ ated carbon. High surface area silicon carbide has thus been synthesiz ed with surface areas ranging between 25 and 80 m(2) g(-1). The shape memory concept is applicable, because the shape of the activated carbo n determines the morphology of the silicon carbide. The conversion pro cess is shown to be Limited by the gasification of carbon into methane . The formed methane is then totally converted into SiC via the Vapour Liquid Solid mechanism and conventional Chemical Vapour Deposition. C arbon conversions range from 10% to 45%. The high surface area SIC obt ained after conversion and removal of the residual carbon has high pot ential as catalyst support for liquid-phase application at demanding p H conditions and processes operating at high temperatures. (C) 1997 El sevier Science B.V.