Liquid-like H2O adsorption layers to catalyze the Ca(OH)2/CO2 solid–gas reaction and to form a non-protective solid product layer at 20°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°C. Then the particles were used in the reaction with gaseous carbon dioxide at 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 distributed inside the initial porous particles. The same reaction with dry-calcium hydroxide powders converts up to 10% at a temperature of 100°C. The observed catalytic effect is dependent upon the initial amount of water adsorbed. A minimum number of four layers of water adsorbed onto the calcium hydroxide surfaces is required to promote the catalytic effect.