Solid sorbents for the reversible capture of carbon dioxide

We have produced a large number of solid sorbents by impregnation of high surface area, high pore volume solid supports with suitable amines. Silica, silica-zirconia, alumina and clay supports have been tested with some alkanolamines and polyamines. The new sorbents were characterised by TGA, XRD, BET and SAXS, showing an amine content in the range 24-54 % by weight. Absorption/desorption experiments were performed both on a micro-scale, using Pore CO2 in a thermogravimetric apparatus, and in a lab-scale reactor (10-18 g of sorbent) using a synthetic flue gas with 3.7 % CO2. The absorption step was performed at room temperature and the sorbent saturation was monitored by gas chromatographic analysis. The desorption step was performed by heating to 60-100degreesC, alternatively with a moderate flow of nitrogen or under reduced pressure (20 mmHg). The uptake capacity of the sorbents was measured both by gravimetric determination after the absorption and desorption steps, and by titration of the desorbed carbon dioxide. The best performances were exhibited by the alumina based sorbents impregnated with alkanolamines, which reversibly trap CO2, by 6.5-9.6 % of the sorbent weight. A preliminary technical economic evaluation for an industrial application is proposed.