Modified polyamines for CO2 absorption product preparation and characterization

Aliphatic polyamines easily absorb acidic gases but unfortunately are not s uitable for industrial application because their solutions are difficult; t o regenerate. Molecular modification is of primary importance to reduce the ir basicity and to allow their use in acid gas recovery processes. Various modified polyamines were prepared by reacting tetraethylenepentamine (TEPA) with formaldehyde and formaldehyde/phenol in various molar ratios. The phy sical and chemical characterization of the synthesized products showed a ge neral reduction of basicity; the modification of TEPA with formaldehyde and phenol gave products with high CO2 absorption capacity and easier regenera tion; moreover, the heat of reaction during CO2 absorption was reduced. The selected compound had a TEPA/CH2O/C6H5OH ratio equal to 1/0.5/0.4. This ne w product showed higher cyclic capacity, higher absorption rate, and lower degradation compared with diethanolamine under the same experimental condit ions. The product is stable, constant in composition, and suitable for indu strial scale-up.