Methyldiethanolamine (MDEA) aqueous solution is used to remove H2S from gas, which has the advantages of high selectivity, high acid gas load, low energy consumption and corrosiveness, and has been widely used in industry. However, MDEA, like other alkanolamines such as diethanolamine and monoethanolamine, degrades after being used for a period of time, resulting in a decrease in the performance of the solution and causing production problems such as solution foaming and corrosion.
There are many reasons for the degradation of MDEA solution, mainly due to the degradation of MDEA solution caused by CO2, and its products mainly include diethanolamine, methyl monoethanolamine, dimethyl monoethanolamine, ethylene oxide, triethanolamine, etc.; the degradation of MDEA solution caused by O2 , its products mainly include formate, acetate and glycolate, etc.; various acidic impurities cause the degradation of MDEA solution, and its products are thermally stable salts.
In order to prevent the degradation of MDEA solution, in addition to proper protection in the process, one of the main methods is to add antioxidants to the solution, such as adding certain thiols or quinones and oxime compounds to the MDEA solution.
