Degradation kinetics of monoethanolamine during CO2 and H2 S absorption from biogas

Abstract

The rate of degradation of MEA during CO2 and H2 S absorption in the biogas upgrading process was examined in four degradation systems, i.e., MEA-CO2 , MEA-CO2 -O2 , MEA-CO2 -H2 S and MEA-CO2 -O2 -H2 S. Degradation experiments were performed in a 800-ml stainless steel autoclave reactor, using MEA concentrations of 3 and 5 mol/L, CO2 loadings of 0.4 and 0.5 mol CO2 /mol MEA, O2 pressure of 200 kPa, and H2 S concentrations of 84 and 87 mg/L at temperatures of 120 and 140C. The results showed that, for the MEA-CO2 system, an increase in temperature or MEA concentration resulted in a higher rate of MEA degradation. In contrast, an increase in CO2 loading in the MEA-CO2 -O2 system led to a reduction of MEA degradation. The degradation rate of the system with O2 was with 8.3 times as high as that of the system without O2 . The presence of H2 S did not appear to affect the rate of degradation in the MEA-CO2 -H2 S system. However, for the system in which both H2 S and O2 were present, the MEA degradation was additionally induced by H2 S, thus, resulting in higher degradation rates than those of the system with O2 only. The extent of degradation under the same period of time increased in the order MEA-CO2 , MEA-CO2 -H2 S < MEA-CO2 -O2 < MEA-CO2 -O2 -H2 S.

Keywords

• monoethanolamine
• degradation
• carbon dioxide
• absorption
• biogas