Experimental studies on the CO₂ absorption in enamine/ethanol solution

Biogas after purification can be used as a substitute for nature gas. The major drawback of aqueous alkanolamine based biogas purification processes is the high energy penalty during regeneration. The absorption of CO₂ in a TETA/ethanol solution can lead to a phase change, suggesting an energy-saving approach for CO₂ capture. The absorption of CO₂ in ethanol solutions of TETA with various temperatures and concentrations, and in ethanol solutions of different enamines were investigated. It was observed that the TETA/ethanol solution with high concentration has larger absorption rate and absorption capacity but lower absorption load. As the concentration of TETA is raised from 0.1 kmol·m^-3 to 0.3 kmol·m^-3, the absorption load is decreased from 1.88 mol CO₂·mol amine^-1 to 1.59 mol CO₂·mol amine^-1. The absorption load of CO₂ increases in the following order: DETA, TETA, TEPA. TEPA has the largest per enamine molecule absorption load of 2.11 mol CO₂ while DETA has the largest per amine group absorption load of 0.48 mol CO₂. TETA/ethanol absorbs CO₂ with solid products appears, this solid product decomposed temperature is 363 K.