Thermal transformations of graphite and anthracite in the presence of lithium carbonate

The method of differential scanning calorimetry was used to study mixtures of graphite and anthracite with lithium carbonate in an argon atmosphere and in air. It was found that in the temperature range of 100–500°C, a stronger mass loss occurs in argon than in air. This phenomenon is caused by the removal of oxygen compounds with carbon. Competing processes take place in the air – the formation of oxygen compounds with carbon, coal and desorption of oxygen-containing substances. A comparison of thermal effects on the curves of DSC and gravimetry for graphite–lithium carbonate systems in argon, in air is carried out. It was found that up to 700°C in the reaction products, the molar ratio of carbon oxides (IV; II) can be estimated at 10 : 1. Endothermic effects of lithium carbonate melting in an argon atmosphere for mixtures of graphite and anthracite with lithium carbonate were observed at 732°C and 727°C, respectively. In air, the peaks of endothermic effects do not correspond to the heat absorption curves in argon. The most probable explanations of the observed effects are given – the presence of phases of carbonate and lithium oxide; the manifestation of the stretched nature of the pre-transition region of lithium carbonate. By the method of powder X-ray diffractometry, it was found that the burnout of the carbon phase at 500°C in graphite, anthracite does not lead to a significant change in the interplane distances in lithium carbonate.