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The absorption performance of low-partial-pressure H 2 S in a monoethanolamine (MEA)-activated Nmethyldiethanolamine (MDEA) aqueous solution was investigated. The absorption amount (in mass, g H 2 S/g solutions) and H 2 S loadings (mol H 2 S/(mol MEA + mol MDEA)) were measured, and the apparent absorption rate was determined from the time-dependent absorption capacity. Experimentally, the temperature and partial pressure of H 2 S (P H 2 S ) ranged from 303.2 to 323.2 K and from 300 to 500 Pa, respectively. The mass fractions of MDEA (w MDEA ) and MEA (w MEA ) ranged from 0.30 to 0.50 and from 0 to 0.075, respectively. The temperature, w MDEA , w MEA , and P H 2 S dependencies of the absorption performance were analyzed. It is impressive that the addition of MEA significantly enhanced the absorption amount of H 2 S yet slightly influenced the apparent absorption rate. In addition, a tray column consisting of six plates was used to verify the removal efficiency of low-partial-pressure H 2 S (P H 2 S = 500 Pa) and the results showed that in the case of w MDEA = 0.5, w MEA = 0.075, and T = 313.2 K, the removal efficiency achieved 95% when the ratio of gas to liquid was 40, indicating that MEA-activated MDEA aqueous solutions are promising in the removal process of low-partial-pressure H 2 S.

The absorption performance including absorption capacity and loading values of low-partial-pressure H2S in tetramethylammonium glycinate ([N1111]­[Gly]) promoted N-methyldiethanolamine (MDEA) aqueous solution was measured. The apparent absorption rate was calculated from the time-dependent absorption capacity. The effects of absorbent composition, temperature, and H2S partial pressure on absorption capacity and apparent absorption rate were demonstrated. The H2S removal efficiency was verified in a tray tower using the [N1111]­[Gly]–MDEA aqueous solution as an absorbent, and the results show that the removal efficiency can reach 100%, which met the requirement of the first degree of Chinese cleaner production standard (coking industry, HJ/T 126-2003, I, H2S ≤ 0.2 g/m3). Compared with the traditional amine-based absorbents like MDEA–monoethanolamine aqueous solution, the [N1111]­[Gly]-promoted MDEA aqueous solution has a higher absorption capacity and a higher absorption rate for H2S. Moreover, when the mass fraction of MDEA reaches up to 50%, the removal efficiency in the tray tower can still reach 100%. The decrease of the water content in the absorbent can greatly reduce the energy cost of the regeneration of rich solution and the cooling of poor solution. Therefore, the new absorbent proposed in this work has good commercial application potential in the field of desulfurization of the coke oven gas.

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