Investigation of low concentration $SO_2$ adsorption performance on different amine-modified Merrifield resins

Özet

Three amine-modified Merrifield resins (AMMRs) were synthesized with ethane diamine, methylamine anddimethylamine to assess the impact of amine group on $SO_2$ adsorption under low $SO_2$ concentration. The dimethylamine-modified Merrifield resin (DMAMR) grafting with tertiary amine groups showed the greatest $SO_2$adsorption compared with ethane diamine-modified Merrifield resin (EDAMR) and methylamine-modifiedMerrifield resin (MAMR). Different amine groups had different reaction mechanisms with $SO_2$. It was mucheasier for $SO_2$ to form noncovalent charge transfer complex with tertiary amine group than the zwitterion andion/counterion products with primary and secondary amine groups under dry condition. The noncovalentcharge transfer complex had a relatively weaker thermostability than the zwitterion and ion/counterion products. As the temperature increased from 25 °C to 75 °C, the $SO_2$ adsorption capacity on DMAMR decreased by78.92%, which was much higher than that of EDAMR and MAMR (63.77% and 63.41% respectively). As $SO_2$concentration increased from 40 ppm to 100 ppm, significant increase (∼100%) in $SO_2$ adsorption capacity wasobserved. Lower $SO_2$ flow rate led to a more sufficient reaction between$SO_2$ and amine groups, resulting theincrease in $SO_2$ adsorption capacities. Water vapor enhanced the $SO_2$ adsorption performance of AMMRs significantly due to the formation of salt. However, it was more difficult for tertiary amine group to react with $SO_2$in the presence of water due to its relatively weaker basicity. DMAMR showed a greater regeneration performance than EDAMR and MAMR under dry and humid condition.