Carbothermal reduction of quartz in methane-hydrogen-argon gas mixture

Synthesis of silicon carbide (SiC) by carbothermal reduction of quartz in a CH4-H2-Ar gas mixture was investigated in a laboratory fixed-bed reactor in the temperature range of 1573 K to 1823 K (1300 °C to 1550 °C). The reduction process was monitored by an infrared gas analyser, and the reduction products were characterized by LECO, XRD, and SEM. A mixture of quartz-graphite powders with C/SiO2 molar ratio of 2 was pressed into pellets and used for reduction experiments. The reduction was completed within 2 hours under the conditions of temperature at or above 1773 K (1500 °C), methane content of 0.5 to 2 vol pct, and hydrogen content ≥70 vol pct. Methane partially substituted carbon as a reductant in the SiC synthesis and enhanced the reduction kinetics significantly. An increase in the methane content above 2 vol pct caused excessive carbon deposition which had a detrimental effect on the reaction rate. Hydrogen content in the gas mixture above 70 vol pct effectively suppressed the cracking of methane.