A Comparative Assessment of Emerging Solvents and Adsorbents for Mitigating CO2 Emissions From the Industrial Sector by Using Molecular Modeling Tools

Abstract

The possibilities offered by molecular modeling tools to obtain relevant data at process conditions, while also gaining molecular insights on the techniques used for CO 2 capture and separation, are presented here using selected case studies. Two different technologies, absorption with amine-based systems and adsorption on porous materials, were explored, using the molecular-based equation of state, soft-Statistical Associating Fluid Theory (SAFT), and Grand Canonical Monte Carlo simulations, respectively. The aqueous monoethanolamine (MEA) system was set as the benchmark for absorption and compared to the performance of 8 alternative amine-based systems, while 16 adsorbents belonging to different families (zeolites, metal-organic frameworks, amorphous silicas, and activated carbons), bare or functionalized with alkylamines, were investigated for the separation of CO 2 by adsorption. In addition to obtaining molecular information on the CO 2 capture process, the models were further used to examine the CO 2 capture performance in terms of cyclic working capacity and energy index as key performance indicators, allowing the identification of promising systems that can improve the current ones to be further evaluated for separation in non-power industries. Results show that for the same total amine mass concentration, non-aqueous amine solvents have a 5-10% reduction in cyclic working capacity, and a 10-30% decrease in the energy index compared to their aqueous counterparts due to their lower heat of vaporization and specific heat capacity. In addition, M-MOF-74, NaX, and NaY structures present the best results for adsorption in temperature swing adsorption (TSA) processes. Similar values of energy requirements to those of amine-based systems (2-2.5 MJ kg CO 2 −1 ) were obtained for some of the adsorbent; however, the disadvantage of the TSA process versus absorption should be considered. These results confirm the reliability of molecular modeling as an attractive and valuable screening tool for CO 2 capture and separation processes.

Toward Nonaqueous Alkanolamine-Based Carbon Capture Systems: Parameterizing Amines, Secondary Alcohols, and Carbon Dioxide-Containing Systems in s-SAFT-γ Mie

“…This agrees with similar work by Alkhatib et al 17 Wanderley et al 18 maintain that energy costs associated with vaporization (and energy duties overall) can certainly be reduced by using nonaqueous cosolvents. 18 However, there are certain drawbacks associated with the use of nonaqueous carbon capture fluids: Reduced heat transfer will likely necessitate more expensive heat exchangers, 18 and CO 2 removal is more inefficient for nonaqueous water alternatives, 16,17,19 although this may not always be the case. 16,18 Mathias et al 20 point out that process intensification and process integration may be able to compensate for the disadvantages of nonaqueous systems.…”

Assessment of Low Global Warming Potential Refrigerants for Drop-In Replacement by Connecting their Molecular Features to Their Performance

“…These models have rigorous physical basis from statistical mechanics, enabling them to accurately capture the effect of intermolecular interactions (i.e., dispersive, associating, polar) on macrolevel phenomena. This is an added edge over conventional EoSs, that are incapable of explicitly modeling polar interactions governing the behavior of third and fourth generation refrigerants and other green substances of polar nature. − The adoption of SAFT-based models as a central pillar for screening tools has been steadily growing, − holding the promise of similar success when applied to screening alternative eco-friendly refrigerants as drop-in replacements under the same operating conditions and technical criteria. This is fueled by the demonstrated success of our group in accurately modeling the holistic thermodynamic behavior of third and fourth generation refrigerants. − On another front, the physical basis of SAFT-based models can enable the extraction of microlevel tendencies linked with observable physicochemical properties and technical performance.…”

Effect of Amine Functionalization of MOF Adsorbents for Enhanced CO2 Capture and Separation: A Molecular Simulation Study

“…MOFs with high porosity, open metal uncoordinated sites and good thermal stability have demonstrated excellent qualities for CO 2 /N 2 separations (Yazaydin et al, 2009 ; Zhang et al, 2010 ; Sumida et al, 2011 ; Yu et al, 2017 ) and are emerging as promising candidates for CO 2 separation at industrial conditions. For instance, the M-MOF-74 family (with M being the divalent metal used), also known as M 2 (dobdc) or CPO27-M, presents one of the highest found CO 2 adsorption capacities at low to moderate CO 2 partial pressures, relevant at the required conditions for CO 2 capture from flue gas (Britt et al, 2008 ; Caskey et al, 2008 ; Dietzel et al, 2009 ; Yazaydin et al, 2009 ; Valenzano et al, 2010 ; Alonso et al, 2018 ; Bahamon et al, 2020 ). However, in some cases, because CO 2 typically adsorbs via weak physisorption interactions, most of these synthesized structures cannot satisfy industrial requirements.…”