In this paper, we present improvements to postcombustion capture (PCC) processes based on aqueous monoethanolamine (MEA). First, a rigorous, rate-based model of the carbon dioxide (CO 2 ) capture process from flue gas by aqueous MEA was developed using Aspen Plus, and validated against results from the PCC pilot plant trials located at the coal-fired Tarong power station in Queensland, Australia. The model satisfactorily predicted the comprehensive experimental results from CO 2 absorption and CO 2 stripping process. The model was then employed to guide the systematic study of the MEA-based CO 2 capture process for the reduction in regeneration energy penalty through parameter optimization and process modification. Important process parameters such as MEA concentration, lean CO 2 loading, lean temperature, and stripper pressure were optimized. The process modifications were investigated, which included the absorber intercooling, rich-split, and stripper interheating processes. The minimum regeneration energy obtained from the combined parameter optimization and process modification was 3.1 MJ/kg CO 2 . This study suggests that the combination of a validated rate-based model and process simulation can be used as an effective tool to guide sophisticated process plant, equipment design and process improvement. 24

Liquid−liquid equilibria (LLE) were measured at 298.15 K for six ternary systemsheptane + toluene + sulfolane, heptane + m-xylene + sulfolane, cyclohexane + benzene + sulfolane, cyclohexane + toluene + sulfolane, 1-heptene + benzene + sulfolane, and 1-heptene + toluene + sulfolaneand for two quaternary systemscyclohexane + 1-heptene + benzene + sulfolane and cyclohexane + 1-heptene + toluene + sulfolane. LLE data of two systems including heptane are compared with the results of Cassell et al. (J. Chem. Eng. Data 1989, 34, 434−438). The equilibrium data of four ternary systems including cyclohexane and 1-heptene were used to regress interaction parameters in a nonrandom two-liquid (NRTL) model. These parameters were used to predict equilibrium data of the quaternary systems. The predicted data are in good agreement with experimental ones.

The calcium looping (CaL) process is a promising CO 2 capture technology, which uses CaO-based sorbents by employing a reversible reaction between CaO and CO 2 , generally named carbonation and calcination for each direction of the reaction. Although CaO-based sorbents possess many advantages, including wide availability, relatively low cost, and high theoretical CO 2 uptake (∼0.786 g of CO 2 /g of CaO), it mainly suffers from a rapid decline in CO 2 capture performance during cyclic operation, which has remained an urgent issue required to be addressed for industrial applications of the CaL process. Extensive studies have been conducted thus far, attempting to prevent and/or alleviate the rapid performance decay of the sorbents. Thus, this paper reviews the recent development of the CaL process worldwide with an emphasis on its development in China, mainly focusing on the advancement in the design and reinforcement of CaO-based sorbents. These activation strategies mainly include doping, chemical pretreatment, incorporation of supports with high Tammann temperatures, and structural modification, which do enhance the cyclic performance of the sorbents. However, some challenges still exist in the development of the CaO-based sorbents, such as the cost of the synthesis route, the scale-up pathways of the sorbents, the assessment of cyclic performance under mild conditions, and the ignorance of mechanical strength and attrition resistance of the sorbents. Therefore, life cycle assessment together with techno-economic analysis is essential when synthesizing CaO-based sorbents. In addition, more work should be conducted under industrially relevant conditions in fluidized bed reactors and even pilot-scale reactors, which are much closer to industrial situations. In this case, mechanical strength and attrition resistance are also assessed during cyclic operation.

Amino acids are potential solvents for carbon dioxide separation processes, but the kinetics and mechanism of amino acid−CO 2 reactions are not well-described. In this paper, we present a study of the reaction of glycine with CO 2 in aqueous media using stopped-flow ultraviolet/visible spectrophotometry as well as gas/liquid absorption into a wetted-wall column. With the combination of these two techniques, we have observed the direct reaction of dissolved CO 2 with glycine under dilute, idealized conditions, as well as the reactive absorption of gaseous CO 2 into alkaline glycinate solvents under industrially relevant temperatures and concentrations. From stopped-flow experiments between 25 and 40 °C, we find that the glycine anion NH 2 CH 2 CO 2 − reacts with CO 2(aq) with k (M −1 s −1 ) = 1.24 × 10 12 exp[−5459/T (K)], with an activation energy of 45.4 ± 2.2 kJ mol −1 . Rate constants derived from wetted-wall column measurements between 50 and 60 °C are in good agreement with an extrapolation of this Arrhenius expression. Stopped-flow studies at low pH also identify a much slower reaction between neutral glycine and CO 2 , with k (M −1 s −1 ) = 8.18 × 10 12 exp[−8624/T (K)] and activation energy of 71.7 ± 9.6 kJ mol −1 . Similar results are observed for the related amino acid alanine, where rate constants for the respective neutral and base forms are 1.02 ± 0.40 and 6250 ± 540 M −1 s −1 at 25 °C (versus 2.08 ± 0.18 and 13 900 ± 750 M −1 s −1 for glycine). This work has implications for the operation of carbon capture systems with amino acid solvents and also provides insight into how functional groups affect amine reactivity toward CO 2 .

The hydration of CO(2) plays a critical role in carbon capture and geoengineering technologies currently under development to mitigate anthropogenic global warming and in environmental processes such as ocean acidification. Here we reveal that borate catalyzes the conversion of CO(2) to HCO(3)(-) via the same fundamental mechanism as the enzyme carbonic anhydrase, which is responsible for CO(2) hydration in the human body. In this mechanism the tetrahydroxyborate ion, B(OH)(4)(-), is the active form of boron that undergoes direct reaction with CO(2). In addition to being able to accelerate CO(2) hydration in alkaline solvents used for carbon capture, we hypothesize that this mechanism controls CO(2) uptake by certain saline bodies of water, such as Mono Lake (California), where previously inexplicable influx rates of inorganic carbon have created unique chemistry. The new understanding of CO(2) hydration provided here should lead to improved models for the carbon cycle in highly saline bodies of water and to advances in carbon capture and geoengineering technology.