| abstract |
Methods for the electrolysis of aqueous solutions of alkali metal carbonates and bicarbonates for the production of alkali metal hydroxides at current efficiencies of > 85 percent without the simultaneous co-production of halogen or acid can be performed at very low, commercially attractive cell voltages and at high current densities in single or two solution compartment cells with carbon dioxide as the only substantive co-product by maintaining cell pH at > 7. The methods are also especially suitable for retrofitting existing chlor-alkali facilities for shifting the balance of production in favor of caustic soda at peak demands. The methods may also be performed with fuel cell configurations for even more attractive operating economics. The electrochemical cell (10) has a cell divider (22); a hydrogen consuming anode (14); a caustic producing multi-dimensional cathode (16); and appropriate inlets (28, 30, 38) and outlets (41, 40, 32, 34). |