Synthesis of high surface area silicon carbide by fluidized bed chemical vapour deposition

Abstract

Activated carbon granulates loaded with small amounts of nickel have successfully been converted into high surface area silicon carbide granulates by reaction with hydrogen and silicon tetrachloride at 100 kPa and 1380 K (C+SiCl 4+2H 2→SiC+4HCl). A cone shaped Fluidized Bed Chemical Vapour Deposition reactor is demonstrated to achieve reproducible and homogeneous conversions of considerable amounts of activated carbon. High surface area silicon carbide has thus been synthesized with surface areas ranging between 25 and 80 m 2 g −1. The shape memory concept is applicable, because the shape of the activated carbon determines the morphology of the silicon carbide. The conversion process 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. Carbon conversions range from 10% to 45%. The high surface area SiC obtained after conversion and removal of the residual carbon has high potential as catalyst support for liquid-phase application at demanding pH conditions and processes operating at high temperatures.