The thermal reduction methods in general utilize carbon or a carbide as the reducing agent. [22]
6NaOH + 2C ---> 2Na2CO3 + 2Na + 3H2
A mixture of rubidium chloride or cesium chloride with calcium carbide heated to 700-900C in vacuo gives a 75% yield of the alkali metals. [23] With
sodium chloride a temperature of 950C is used. [24] The production of potassium is reported using silicon or calcium carbide as the reducing agent at
a temperature of 100-1150C.
2KF + CaC2 ---> 2K + CaF2 + 2C
Part of the KF may be substitued by K2CO3 or K2SiO3 without any loss in yield.
2K2CO3 + 3Si + 6CaO ---> 4K + 2C + 3(2CaO*SiO2)
These methods usually require good vacuums at high temperatures.
[22] G.L. Putnam, Ind. Eng. Chem. 30, 1138 (1938).
[23] V.D. Polyakov and A. A. Fedorov, J. Applied Chem. (USSR) 13, 1833-8 (1940) [C. A. 35, 5049 (1941)]
[24] P. V. Gel'd et al., J. Applied Chem. (USSR) 20, 800-8 (1947) [C. A. 42, 4478 (1948)] |