https://doi.org/10.1021/acs.iecr.2c02344
“At first sight, the themical stability of various solvents looks complicated since many variables influence the formation of unwanted degradation compounds. These include factors like temperature, flue gas composition (O2, NOx, SOx, CO2, particle impurities), plant construction material, hold-up time, and circulation rate. Over the years, simplified lab-scale experiments have focused on specific aspects or factors of degradation chemistry. Combining the understanding from these simplified experiments has resulted in the design of more complex setups that have been capable of capturing the behavior of degradation products in large pilot and demonstration plants such as the SINTEF Tiller CO2 plant and the plant at Technology Centre Mongstad (TCM). (11)
Amine solvents without CO
2 are relatively stable even under accelerated conditions in lab-scale experiments.
(12,13) But when CO
2 is present, the oxidative and thermal stability is reduced. So, ironically, the component we are removing reduces the solvent stability.
In terms of chemical stability, simplified lab-scale systems either focus on oxidative or thermal degradation. Although this division between thermal and oxidative degradation is commonly used, it is not precise as thermal degradation compounds are also formed during oxidative degradation studies. Further, some thermal degradation compounds influence oxidative degradation and vice versa. In reality, in the CO2 capture plant, it is the combination of oxidative and thermal conditions that induce the degradation pathways that take place. Thus, separating oxidative and thermal degradation studies will not reproduce all the pathways taking place in a process.
In the laboratory, the degradation studies typically focus on either amine loss and the effect of structural changes in a molecule
(12−18) or investigation of one single amine or amine blend to better understand the solvent degradation pathways.
(19−29) Examples of solvent systems investigated in more detail are MEA, Pz, and AMP/Pz.
The motivation in the laboratory scale is, often, identifying stable amines and amine blends, identifying degradation compounds to be followed during piloting and demonstration, and understanding the degradation mechanisms helping to choose operation conditions during piloting and/or demonstration.
An overview of amines that have been part of degradation studies is given in Table S1 in the
Supporting Information. “
