Liquid-like H2O adsorption layers to catalyze the Ca(OH)(2)iCO(2) solid-gas reaction and to form a non-protective solid product layer at 20 degrees C

Porous calcium hydroxide particles have been equilibrated with water vapor in the relative pressure range 0.4-0.85 at the temperature of 20 degrees C. Then the particles were used in the reaction with gaseous carbon dioxide a t the same temperature and at pressure of 0.65 kPa. The system is converted up to 85% into a non-protective layer of calcium carbonate which is all di stributed inside the initial porous particles. The same reaction with dry-c alcium hydroxide powders converts up to 10% at a temperature of 100 degrees C. The observed catalytic effect is dependent upon the initial amount of w ater adsorbed. A minimum number of four layers of water adsorbed onto the c alcium hydroxide surfaces is required to promote the catalytic effect. (C) 2000 Elsevier Science Ltd. All rights reserved.