Thermodynamic modeling of silicon carbide formation during the Acheson process in non-stoichiometric mixtures

A brief review and critical evaluation of the literature related to the mechanism of carbothermic reduction of silicon oxide is presented. To resolve the contradictions in the literature data about the number of chemical reactions and key intermediate substances during the Acheson process, thermodynamic modeling of products of carbothermic reduction of silicon (IV) oxide at 1 bar total pressure was carried out. It was determined that CO2 and Si were absent among the intermediates at temperatures close to the silicon carbide formation temperature (from 1520 to ~2500 °С). Out of several dozen possible reactions, the two dominant reactions that result in the formation of silicon carbide in the Acheson process were identified. The effect of reagents temperature from 1000 to 3000 °С, bulk and local deviation from stoichiometry of the initial mixture on the composition of the reaction products was discovered. Obtained new data explains some empirical observations and greatly simplifies the physicochemical modeling of the Acheson process.