The presence of SO2 gas out of standard value at the atmosphere causes damages to human health and environment. There are various methods to remove SO2 exhaust from the flue gas. One of the latest considered methods is the absorption in which diamines are used as solvent. In the current study, quantum density functional theory computation at gas phase was applied to study the absorption characteristics of SO2 and CO2. First, the optimum structure and energy of all three diamine compounds, SO2 and CO2 were explored by the computational level of theory B3LYP/6-31G(d,p) [1]. Then, the frequency analysis of the combinations was performed to guarantee the structures are at the ground state; notice that frequency must be positive. Studying the interaction of the diamines with SO2 and CO2 was carried out by introducing the gases to the diamines at the initial distance of 3 Å. Finally, the compounds at the same computational level were optimized and was obtained through the following relation; see Table 1 for the results.

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