Carbothermal reduction of alkali hydroxides using concentrated solar energy

The reduction of hydroxides of various alkali metals (i.e., Na, K and Li with carbon) using concentrated solar radiation at high temperatures in the range of 900–1600°C results in the production of CO, H2 and the alkali metal. These reactions are highly endothermic; for instance, C+LiOH→Li+0.5H2+CO requires 523 kJ/mol (at 298 K). The reaction is performed in two basic stages. In the first stage, at a temperature range of 900–1300°C, the carbonate of the alkali metal is formed as an intermediate compound. In the second stage, at slightly higher temperatures in the range of 1200–1600°C, the carbonates are decomposed and reduced to the metal element and additional CO. The metal element can be reoxidized with water and then produce additional hydrogen. The hydroxide is recovered and recycled. The metal can also be used as a chemical, fuel or as an intermediate material for production of other energy-intensive metals, such as magnesium. Thermodynamic calculations and experimental results, which verify this hypothesis, are presented. Potential applications and advantages of the process are discussed.