Comparing the reactivity of SO2-amine and CO2-amine compounds

Several solvents are applied in removal of harmful gases. In petroleum industry, to removegases such as SO2, amine solvents are used. As in flue gas both SO2 and CO2 gases are present inhigh concentration, it is important to study the reactivity and stability of each gas with diamines.As a result, in the present study, quantum density functional theory method at gas phase wasapplied to study the absorption characteristics of SO2 and CO2. First, the optimum structure andenergy of all three diamine compounds, SO2 and CO2 were explored by the computational levelof theory B3LYP/6-31G(d,p). Then, the frequency analysis of the combinations was performedto guarantee the structures are at the ground state; notice that frequency must be positive. Inorder to investigate the reactivity [1] of SO2 and CO2 in the amines, the natural charge and LUMOand HOMO energies were obtained. and Egap are given through the following relations: (...) where q is the natural charge and shows the atom type in each gas (C and two O atoms in CO2gas and S and two O atoms in SO2). The second term in Eq. (1) is zero. See Table 1 for results. Interestingly, from the table, CO2 with diamine is more stable than diamine+SO2 gassince the energy gap is higher. In addition, the charge variation in the case of CO2 gas is lowerthan SO2. However, N,N N -(trimethyl)-N-(2-hydroxyethyl)-ethylenediamine leads to the moststable solution in all cases.

Keywords:

Flue Gas , Natural Charge , Energy Gap , Diamine , DFT