Poly(amidoamine) Dendrimer Modified with Terminal Hydroxyl Functional Group as an Efficient Alternative for CO2 Capture

Abstract

Poly(amidoamine)-type dendrimers (PAMAM) were synthesized by divergent routes, and generations (G0.5, G1.0, G1.5, G2.0 and G2.5) along with hydroxylated half-generation polymers (G0.5-OH, G1.5-OH and G2.5-OH) were characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry. Carbon dioxide (CO2) capture tests were performed using thermogravimetric analysis. Among the absorption temperatures tested, 60 °C was the most promising: 0.77, 1.08, and 1.14 mol CO2 L-1 for G0.5-OH, G1.5-OH and G2.5-OH, respectively, of CO2 and partial pressure of 45 kPa. This showed that dendrimers with larger molecular structures have more hydroxyl groups and consequently capture more CO2. However, at low partial pressures (< 2 kPa), CO2 solubility in PAMAM increased with temperature reduction, confirmed by Henry’s solubility constant (398.4 mol m-3 kPa-1, in G2.5-OH at 40 °C). According to the thermodynamic properties of CO2 solubilization, the process was spontaneous (∆Gsol < 0) and exothermic (∆Hsol < 0).