Carbon di:oxide removal from waste gas - by chemical reaction with porous solid basic nitrite-sodalite

摘要

A process and substance for CO2 removal from off-gases at elevated temp. are claimed, the novelty being that (i) the CO2 is fixed as Na2CO3 by chemical reaction on passage through a porous solid at 700-750 deg.C with evolution of only H2O; (ii) the solid is an aluminosilicate with a framework structure of space-filling packed cells of sodalite type with statistical 50% occupation of the cells by NaNO2 as temp.-stabilising guest molecule and 50% occupation by NaOH.H2O as reactive guest molecule, the solid having the compsn. Na8(AlSiO4)6(NO2)(OH.H2O) (i.e. basic nitrite-sodalite); and (iii) after satn. with CO2, the solid can be regenerated by heating at 850 deg.C in air to release the CO2 while retaining the framework structure and can be simultaneously modified by oxidn. of the temp. stabilising guest molecule to nitrate. USE/ADVANTAGE - The process is useful for CO2 removal from fossil fuel combustion waste gases. The CO2 is immobilised as a stable cpd. (Na2CO3) in a temp. range in which zeolites have very low sorption rates and the solid can be easily regenerated and simultaneously modified.