Abstract
The mechanism was proposed of heterogeneous catalytic CO2 absorptions with primary/secondary amines involving ‘catalytic carbamate formation’. Compared with the non-catalytic ‘Zwitterion mechanism’, this Eley–Rideal model was proposed for CO2 + RR′NH with MCO3 (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 CO2–MEA absorptions with the existence of 0–25 g CaCO3, MgCO3 and BaCO3. 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 CO2 + primary/secondary amines over alkaline earth metal carbonate (MCO3).
Highlights
The CO2 absorption with alkanolamine solution is an important industrial operation for post-combustion carbon capture (PCCC), and the kinetics of the reactions of CO2–amine solutions are of& 2019 The Authors
(5) Compare the rate equations with the non-catalytic one and estimate the enhancement of solid chemicals. This Eley–Rideal 3 model was suitable for describing catalytic CO2 absorption with primary/secondary amines, which was quite useful for the kinetic studies of heterogeneous catalysis in the field
The Eley–Rideal model was proposed for catalytic carbamate formation of CO2 þ RR0NH with MCO3, based on the similar reactions of CO2 þ MeOH over ZrO2–MgO catalyst [25]
Summary
The CO2 absorption with alkanolamine solution is an important industrial operation for post-combustion carbon capture (PCCC), and the kinetics of the reactions of CO2–amine solutions are of. Apart from experimental results, the kinetic models of heterogeneous catalytic CO2 absorption with primary and secondary amines awaited kinetic investigations, such as studies on reaction mechanism, elementary steps, rate-determining steps, reaction orders and rate constant, etc. We completed several tasks in this work: (1) propose a mechanism of heterogeneous catalytic carbamate formation on the solid surface of MCO3 with Eley –Rideal model; (2) characterize catalyst surface with SEM and BET methods; (3) develop four elementary steps with rate-determining steps (RDS) of each sub-case. (5) Compare the rate equations with the non-catalytic one and estimate the enhancement of solid chemicals This Eley–Rideal 3 model was suitable for describing catalytic CO2 absorption with primary/secondary amines, which was quite useful for the kinetic studies of heterogeneous catalysis in the field
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