The capture of carbon dioxide by ammonia in both aqueous and non-aqueous solutions was investigated at atmospheric pressure and 273 K under different operating conditions. The CO 2 capture is fast and efficient ranging between 78 and 99%, depending on both the NH 3 concentration and the solvent nature. The precipitation of solid mixtures of ammonium bicarbonate, ammonium carbonate and ammonium carbamate occurred in ethanol-water solution. Selective precipitation of ammonium carbamate was achieved by reacting gaseous CO 2 and NH 3 in anhydrous ethanol, 1-propanol or N,N-dimethylformamide (DMF) in a flow reactor that operates in continuous. In the second step of the process, the pure ammonium carbamate is used to produce urea with good yield (up to 54% on carbamate basis) at 393-413 K in the presence of inexpensive Cu(II) and Zn(II) catalysts. The yield of urea depends on several factors including the catalyst, the reaction temperature and the reaction time. Identification and quantification of urea in the reaction mixtures was obtained by analysis of its 13 C NMR spectrum. A preliminary mechanistic interpretation of the catalytic reaction is also briefly presented and commented.

No abstract

The CO2 uptake by single 2-amino-2-methyl-1-propanol (AMP) and its blends with 2-(ethylamino)­ethanol (EMEA) or N-methyl-2,2′-iminodiethanol (MDEA) has been investigated in both aqueous and nonaqueous solutions, and compared with aqueous 2-aminoethanol (MEA), the most used sorbent in carbon capture and storage (CCS) processes. The loading capacity, the rate of absorption, and the heat of CO2 absorption have been experimentally determined for all the amine solutions. 13C NMR analysis allowed the identification of the carbonated species formed in solution and evaluation of their relative amounts. The most promising sorbents have been further tested in continuous cycles of absorption and desorption carried out in packed columns, in order to verify their CO2 (15% in N2) capture efficiency. Thanks to their good CO2 loading, high rate of reaction with CO2, and low heat of absorption, the AMP–EMEA blend solutions, both in water and in organic diluents, are good candidates for CO2 capture as an alternative to the conventional aqueous MEA solution.

No abstract