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Theoretical and experimental investigations have been performed to obtain carbonic anhydrase (CA) mimic catalysts that are effective for CO2 absorbents containing highly concentrated amines. One of...

Tetraethylenepentamine (TEPA) and its derivatives were used to functionalize mesocellular silica foam (MSU-F) supports by wet impregnation for utilization as solid sorbents for CO2 capture. TEPA de...

Ab initio quantum chemical calculations, combined with the SMD solvation model, have been conducted to reveal CO2 absorption mechanisms and the origin of the reduced stability of carbamate in aqueous solution of 2-amino-2-methyl-1-propanol (AMP). The calculated Gibbs free energy change for all the elementary steps in the conversion of carbamate to bicarbonate reveals that the reduced thermodynamic stability of AMP carbamate is largely ascribable to the shift of the equilibrium from the carbamate to the zwitterion intermediate, from which CO2 can be released and successively converted to bicarbonate. This feature of AMP is an attribute of the electronic effects of the substitution by methyl groups specifically at the α-carbon. Furthermore, the steric effects of the methyl groups are investigated from a dynamical point of view that suggests a new scenario in which the methyl groups promote the release of CO2 from the zwitterion intermediate.

Chemical modification of the amino functional groups of amine-impregnated solid sorbents is an effective strategy for drastically improving the regeneration performance for CO2 capture. In this study, isopropyl groups were introduced into tetraethylenepentamine (TEPA) to obtain N-(isopropyl)-TEPA (IP-TEPA), which was impregnated in mesocellular silica foam (MSU-F). The obtained solid sorbent enabled low-temperature regeneration with a low regeneration energy. To clarify the role of the IP groups, experimental and computational methods were used to compare the IP-TEPA/MSU-F sorbent with TEPA/MSU-F in terms of CO2 working capacity, reaction product stability, self-diffusion coefficient, 13C spin–lattice relaxation time, and CO2 capture performance in steam-aided vacuum swing adsorption.

In the present paper, we investigated CO 2 capture with six amine based absorbents, including three formulated solvents. Aqueous solutions of the amines (mass fraction; 30% for single amine and >30% for blended solvents) were used to evaluate the performance for CO 2 capture. Gas scrubbing, vapor-liquid equilibrium (VLE), and reaction calorimetry experiments were conducted in the laboratory to obtain the absorption rate, the amount of CO 2 absorbed, cyclic CO 2 capacity, and heat of reaction for each absorbent. The results of these absorbents were compared with the conventional amine absorbents (MEA, AMP, DEA, and MDEA). Three high performing formulated absorbents (RN-1, RN-2, and RN-3) were developed, and these had lower heats of reaction, higher cyclic capacities, and comparable absorption rates compared with MEA. Some blended solvents were already demonstrated with real blast furnace gas at pilot test plants with capacities of 1 ton-CO 2 /day and 30 ton-CO 2 /day and showed promising results in terms of reducing absorbent regeneration energy.

Tetraethylenepentamine (TEPA) components are separated by fractional distillation, and the structure of each fraction is established using spectroscopic methods. Then, solid sorbents incorporating these components are prepared, and the capacities and rates of CO2 absorption of the sorbents are evaluated to elucidate how the molecular structure affects the absorption performance.

A novel amine-based solid sorbent was prepared for CO 2 capture, and the CO 2 adsorption characteristics were evaluated for simulated flue gas. Furthermore, CO 2 capture tests using a lab-scale three-column fixed-bed system were performed. A novel amine compound was synthesized by attaching hindered functional groups to the terminal primary amino groups of a polyamine, followed by impregnation into pelletized mesoporous MSU-F silica. This novel amine-impregnated solid sorbent overcame the problem of limited CO 2 diffusion and exhibited extremely high regenerability even at low temperatures. Lab-scale CO 2 capture tests suggested that operation conditions such as temperature, cycle time, rinsing time, flow rate, and regeneration method directly affected CO 2 capture performance. In particular, direct low-temperature steam stripping desorption drastically enhanced CO 2 capture performance. Steam-aided vacuum swing adsorption (SA-VSA) process was feasible for our amine-based solid sorbent and enabled the recovery of CO 2 with high purity (>98%) and recovery rate (>93%). The regeneration heat calculated from the amount of recovered CO 2 and the amount of supplied steam was considerably lower (1.47 GJ/t-CO 2 ) than that of liquid amine solvents and other amine-based solid sorbents.

COURSE50 (ultimate reduction of CO2 in the steelmaking process through innovative technology for Cool Earth 50) aims to capture, separate, and recover CO2 from blast furnace gas. From a practical realization viewpoint, three points are important. The first is energy consumption to regenerate the absorbent, second is the energy cost of the heat for regeneration, and third is the facility cost. The advantage afforded by the COURSE50 approach in relation to the CO2 capture process is the utilization of unused waste heat from the steel mills. Energy consumption to regenerate the absorbent is determined mainly by three factors: the regeneration reaction determined primarily by the structure of the chemical absorbent, the energy required to heat that volume of absorption liquid, which is affected by the absorption rate of the agent, and the heat loss from the processes. The most influential factor is the energy required for the regeneration reaction. We discovered high-performance absorbents with the advantages of high absorption rates, high cyclic capacities, and low heats of reaction, and we then compared these with monoethanolamine (MEA) and N-methyldiethanolamine (MDEA). The newly discovered absorbents performed well in terms of absorption rates and cyclic capacities. Among these absorbents, some showed lower heats of reaction than MDEA. These results provide a basic guideline for the discovery of potential amine-based absorbents that may lead to the development of new absorbent systems for CO2 capture.

The present study was aimed at developing a non-aqueous absorbent system that does not form any precipitate/solid upon exposure to CO2. More specifically, the non-aqueous absorbent system must be a homogeneous mixture (single phase) within the whole range of CO2 loading. At the same time, sufficient amine regeneration must occur at a low temperature of 80–90 °C compared to reference non-aqueous monoethanolamine (MEA)-based absorbents. To achieve this target, 18 alcohols were investigated as solvents and 4 alkyl-linked alkanolamines were evaluated as absorbents. Several experiments mixing alkanolamines with alcohols were performed to evaluate their CO2 capture performance. High-performance non-aqueous liquid absorbents (without solid/precipitate formation) with the advantages of higher absorption rates, higher cyclic capacities, higher regeneration efficiencies, lower specific heats, and lower heats of reaction compared to reference MEA-based non-aqueous absorbents were successfully developed herein. The favorable features of these absorbents will provide the basis for the discovery of potential non-aqueous amine-based absorbents.