Elmar Kessler

• A new class of amines that are promising solvents for reactive CO2-absorption processes was thoroughly investigated in a comprehensive experimental study. The amines are all derivatives of triacetoneamine and differ only in the substituent of the triacetoneamine ring structure. These amines are abbreviated by the acronym EvA with a consecutive number that designates the derivatives. About 50 EvAs were considered in the present study, from which 26 were actually synthesized and investigated as aqueous solvents. The investigated properties were: solubility of CO2, rate of absorption of CO2, liquidliquid and solid-liquid equilibrium, speciation (qualitative and quantitative), pK-values, pH-values, foaming behavior, density, dynamic viscosity, vapor pressure, and liquid heat capacity. All 26 EvAs were assessed in an experimental screening. The results were compared with the results of two standard solvents from industry: aqueous solvents of monoethanolamine (MEA) and a solvent blend of methyl-diethanolamine and piperazine (MDEA/PZ). Detailed studies were carried out for two EvAs that revealed significantly improved performance compared to MEA and MDEA/PZ: EvA34 combines favorable properties of MEA and MDEA/PZ in one molecule. EvA25 reveals a liquid-liquid phase split that reduces the solubility of CO2 in the solvent and shifts the CO2 into the aqueous phase. This allowed the design of a new CO2-absorption process, that takes advantage of the liquid-liquid phase split. Finally, the chemical speciation in 16 EvAs was investigated by NMR spectroscopy. From the results, relationships between the chemical structure of the EvAs and the observed speciation, basicity, and application properties were established. This enabled giving guidelines for the design of new amines and proposing new types of amines, which were called ADAMs.