Carbothermal reduction of alkali hydroxides using concentrated solar energy

The reduction of hydroxides of various alkali metals (i.e., Na, K and Li wi th carbon) using concentrated solar radiation at high temperatures in the r ange of 900-1600 degreesC results in the production of CO, H-2 and the alka li metal. These reactions are highly endothermic; for instance, C+LiOH --> Li+0.5H(2)+ 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 d egreesC, the carbonate of the alkali metal is formed as an intermediate com pound. In the second stage, at slightly higher temperatures in the range of 1200-1600 degreesC, 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 recycl ed. The metal can also be used as a chemical, fuel or as an intermediate ma terial for production of other energy-intensive metals, such as magnesium. Thermodynamic calculations and experimental results, which verify this hypo thesis, are presented. Potential applications and advantages of the process are discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.