Eley–Rideal model of heterogeneous catalytic carbamate formation based on CO(2)–MEA absorptions with CaCO(3), MgCO(3) and BaCO(3)

The mechanism was proposed of heterogeneous catalytic CO(2) absorptions with primary/secondary amines involving ‘catalytic carbamate formation’. Compared with the non-catalytic ‘Zwitterion mechanism’, this Eley–Rideal model was proposed for CO(2) + RR′NH with MCO(3) (M = Ca, Mg, and Ba) with four elementary reaction steps: (B1) amine adsorption, (B2) Zwitterion formation, (B3) carbamate formation, and (B4) carbamate desorption. The rate law if determining step of each elementary step was generated based on ‘steady-state approximation’. Furthermore, the solid chemicals were characterized by SEM and BET, and this rate model was verified with 39 sets of experimental datasets of catalytic CO(2)–MEA absorptions with the existence of 0–25 g CaCO(3), MgCO(3) and BaCO(3). The results indicated that the rate-determining step was B1 as amine adsorption onto solid surface, which was pseudo-first-order for MEA. This was the first time that the Eley–Rideal model had been adopted onto the reactions of CO(2) + primary/secondary amines over alkaline earth metal carbonate (MCO(3)).