Research On Absorption And Desorption Of SO₂ In Composite Organic Amine System

In this paper,N, N’-bis (2-hydroxypropyl) piperazine (HPP) was the main absorbent,and N-hydroxyethyl piperazine (HEP), triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AMP), diethylenetriamine (DETA) were used as secondary adsorbents to form a composite amine. The densities of the composite amine solutions were measured in a range of temperatures from 293.15 to 323.15K by using a pycnometer. The viscosities were measured in a range of temperatures from 293.15 to 323.15K by using an ubbelohde capillary viscometer. The performance of absorption and desorption properties were studied by static method. The results showed that the density and viscosity of the four kinds of compound amine solutions were lower than that of pure HPP and decreased with the increasing of the ratio of added amine. The absorption property of the compound amine with HEP and DETA was improved, the desorption rate declined. While the absorption/desorption propertiy of the composite amines with TEA and AMP were both decreased. The HPP-HEP compound amine system was chosen for further study.The pKa values of HPP-HEP compound amine, the crystallization temperature of the solution and the thermal stability of the system were also investigated. With the increasing of the proportion of HEP, pKa1 and pKa2 both increased compared with HPP.The crystallization temperature of HPP-HEP compound amine solution was lower than that of pure HPP solution in the condition of the same mass fraction. The thermal stability of HPP-HEP composite amine was similar to that of pure HPP. The thermodynamic parameters of HPP and HEP were estimated in the standard state. The optimum conditions of the absorption were: n (HPP): n (HEP) =9: 1, the concentration of the absorbent was 0.3mol/L, the absorption temperature was 50 ℃, desorption at 102 ℃ for 3 h. The absorption capacity was 0.5151 mol·mol-1 and the desorption rate was 92.49%. The absorption capacity was still higher after four cycles.The composite amine of HPP-(1-piperazinepropanol) was synthesized by chemical synthesis method,and the synthesis product was confirmed by liquid chromatography.The contents of HPP and 1-piperazinepropanol in the product were determined by acid-base titration. The crystallization temperature of aqueous solution of different products was determined and the crystallization temperature was found lower than that of pure HPP solution. The absorption/desorption of SO2 using different products were studied,which indicated that 1-piperazinepropanol had no significant effect on the desorption and desorption performance of HPP.