BASIC NITRITE SODALITE - NA8(ALSIO4)6(OH.H2O)(NO2) - A SUITABLE MATERIAL FOR THE UPTAKE OF CARBON-DIOXIDE

The solid solution series basic sodalite-nitrite sodalite Na8[AlSiO4]6(OH · H2O)2-x(NO2)x has been synthesized under hydrothermal conditions at 470 K (autogeneous pressure). The observed composition range 0 ≤ x ≤ 2 could be varied by using different amounts of sodium nitrite in the starting reaction mixture. Besides the crystal data and the thermoanalytical properties of this new material its sorption capacity for carbon dioxide has been investigated. At elevated temperatures (970 K) an intracage reaction of the enclathrated sodium hydroxide with carbon dioxide could be estimated, yielding to an uptake of 25 mg CO2 per gram sodalite, whereas no CO2 absorption could be estimated at room temperature. The reaction mechanism involves the partial destruction of the NaOH · H2O complex followed by the formation of Na2CO3 within the sodalite cages, as demonstrated by X-ray powder diffraction, IR spectroscopy, and thermoanalytical results. © 1991.