Mechanism and Kinetics of Carbon Dioxide Capture Using Activated 2-Amino-2-methyl-1,3-propanediol

Abstract

The continued use of fossil fuels as primary sources of energy in industry and other applications stands the test of time, due to their availability and relatively lower cost than alternative sources of energy. In view of this perspective, obtaining an advanced bulk carbon dioxide (CO2) capture medium becomes an urgent necessity so as to mitigate their effect, especially in global warming, as the use of fossil fuels produces a high rate of CO2. In this work, the mechanism and kinetics of CO2 capture using aqueous piperazine (PZ) as an activator to 2-amino-2-methyl-1,3-propanediol (AMPD) were investigated. The termolecular mechanism was used to model the kinetics of the system. Reaction kinetics of the single pure amines was first obtained. The reaction rate constant, the k value of AMPD, was 77.2 m3/kmol·s, with a reaction order, n, of 1.25 at 298 K. while that of PZ was equal to 11,059 m3/kmol·s and n as 1.49 at 298 K. Blending of 0.05 kmol/m3 of PZ with 0.5 kmol/m3 of AMPD gave a rate constant, k, value of 23,319 m3/kmol·s and n equal to 1.23 at 298 K. The result obtained for the blended system is more than twice the value of the summation of the corresponding pure amines; in addition, it is comparably higher than the rate constant of monoethanolamine (MEA) in use as a commercial solvent for CO2 capture. Therefore, an aqueous blend of PZ with AMPD deserves more comprehensive study as a solvent for commercial CO2 capture. AMPD like other sterically hindered amines absorbs CO2 in an equimolar ratio that is significantly higher than that of MEA. PZ serves as a promoter in the amine mixture and is required in a very small proportion.