Kinetics Of The Reactive Absorption And Desorption Of CO₂ In Organic Amines

Carbon dioxide contributes almost 60% of the total greenhouse gas emissions on a global warming potential basis. It is a crucial task we are facing nowadays to select affordable and environmentally acceptable absorbent for CO2. The mechanism and kinetics of CO2 absorption and desorption in organic amines are attracting interests both in academic and industrial fields.As a widely used absorbent for CO2, the absorption conditions for monoethanolamine (MEA) were optimized. The absorption capacity and rate decrease as the increasing of initial MEA concentration which causes greater mass transfer resistance, however, increase as increasing of CO2 pressure which raises concentration of reactant CO2. The absorption rate accelerates when the temperature increases. Meanwhile, the absorption capacity of MEA obtains maximum at 300.15K. Increasing n(N2):n(CO2) from 0 to 9 enhances the absorption capacity and rate, and futher increasing decreases both the the absorption capacity and rate. It is deduced that the standard molar heat of reaction between MEA and CO2 is -147.68kJ/mol by vant't Hoff Equation.In the selection of optimal absorbent among variuos amines, tetraethylene pentamine (TEPA) was appropriate for its superior absorption capacity, absorption rate, desorption effect and desorption rate.Kinetics equations of CO2 absorption in MEA, DEA are first-order with respect to MEA/DEA and CO2. Kinetics equations of CO2 absorption in TEA, DETA, TETA, and TEPA are second-order with respect to TEA/DETA/TETA/TEPA and first-order with respect to CO2.Desorption kinetics of alkanolamines and polyethylene polyamines could be expressed by the equation which is similar to Weibull Equation:x=n(1-e-tm/β).