Amino Acid Salts as Potential Solvents for CO2 Capture


March 2005-February 2010


MSc.Eng. M.E. Majchrowicz

Thesis advisor: W.P.M. Van Swaaij

Supervisor: D.W.F. Brilman


The problem of global warming has resulted in the environmental concern over a reduction of greenhouse gas emission from industrial sources. The major greenhouse gases contributing to problem are methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O) and halogens such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs). Among these, carbon dioxide is the primary contributor to the problem due to its high abundance, and thus a major target for reduction. To reduce its excessive emissions, several pre- and post-combustion technologies have been introduced in the gas sweetening industry. Among these, the gas absorption with a chemical reaction process using aqueous amines is at present the most often utilized. During this process, an industrial gas stream is flowing through an absorption column where an amine-based solvent is sprayed into the gas flow and carbon dioxide is captured in the liquid and bonded by chemical reactions. The amine solution is then regenerated in another column called desorber by heating up to about 120oC. A carbon dioxide stream with a purity of 95% up to 99% leaves the desorber and a lean amine solution is recycled to the absorber part.

The cost of absorption process using conventional solvents such as aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) and their mixtures, as well as of sterically hindered amines such as 2-amino-2-methyl-1-propanol (AMP) is still relatively high.

A major reason for the high cost is that conventional solvents introduce a variety of practical problems including:

(i) high energy consumption for the solvent regeneration

(ii) fast evaporation rate causing high absorbent losses

(iii) high rate of corrosion of the process equipment, and

(iv) high rate of degradation in the presence of oxygen.

All these problems translate into high capital as well as high operating (energy!) costs. One way to reduce the process costs is to use better solvents in the CO2 separation process.


Aqueous alkaline salts of amino acids could be an interesting alternative for the currently, commercially used (alkanol)amines. Generally, amino acid salt solutions can be characterized by a lower vapor pressures (due to ionic nature), higher stability towards oxidative degradation and a chemical reactivity with carbon dioxide comparable or even higher than those of (alkanol)amines. A further interesting feature is their ability to precipitate solids when absorbing carbon dioxide. Both the higher solvent loadings at lower gas partial pressures and the chemical composition of the solids formed make these novel absorption systems very interesting and a promising candidate for more economic CO2 capture.

The main goal of the research is to study the potential of a CO2 absorption process on basis of these (precipitating) amino acid salts. In this project, initially different amino acid (salts) will be screened for their precipitating behavior (i.e. varying operating conditions like pressure, temperature and concentration, identifying the composition of solids formed, etc.) and their ability to capture CO2. For the most promising absorption systems both, the absorption- and regeneration characteristics will be investigated in more detail.

Two D-Assignments are available to students as a part of this research project. For more information, please contact Magdalena Majchrowicz or Wim Brilman.


This research is carried out within the CATO programme. It is financially supported by the Dutch Ministry of Economic Affairs (EZ) and the consortium partners. More details can be found on the following website: