Water-Lean Solvents for Post-Combustion CO₂Capture: Fundamentals, Uncertainties, Opportunities, and Outlook

Abstract

This review is designed to foster the discussion regarding the viability of postcombustion CO capture by water-lean solvents, by separating fact from fiction for both skeptics and advocates. We highlight the unique physical and thermodynamic properties of notable water-lean solvents, with a discussion of how such properties could translate to efficiency gains compared to aqueous amines. The scope of this review ranges from the purely fundamental molecular-level processes that govern solvent behavior to bench-scale testing, through process engineering and projections of process performance and cost. Key discussions of higher than expected CO mass transfer, water tolerance, and compatibility with current infrastructure are presented along with current limitations and suggested areas where further solvent development is needed. We conclude with an outlook of the status of the field and assess the viability of water-lean solvents for postcombustion CO capture.

Introduction: Carbon Capture and Separation

“…It is intuitive that substituting water with low heat capacity organic solvents can allow a significant gain in efficiency. Heldebrant and co-workers 9 focus on the use of concentrated organic "water-lean" solvents, or even nonaqueous solvents, bearing or solvating N-based species. Solvents technologies are surveyed, covering aspects from the atomistic description of the capture phenomenon to bench-scale testing, with the aim to assess the viability of water-lean solvents for postcombustion CO 2 capture.…”

Molecular Insights into Benzimidazole‐Linked Polymer Interactions with Carbon Dioxide and Nitrogen

“…Hence, there have been many different alternative materials have been studied such as ionic liquids, deep eutectic solvents, membranes, metal organic frameworks, covalent organic frameworks, porous polymers or other porous materials . Among those, covalent porous adsorbents have received remarkable attention both from industry and academia over the past couple of decades since they can be custom designed and engineered to have high CO 2 sorption performance and gas separation selectivity with regeneration properties that can be achieved with low energy input in comparison to corrosive and toxic amine solutions, Covalent porous organic polymers have structures that include attractive interaction sites that has high affinity for CO 2 with low‐to‐moderate binding energies that allows modest regeneration energy costs. In contrast with metal organic frameworks, amorphous covalent porous organic polymers mostly work with well‐known physisorption mechanism …”

Structural Elucidation of Covalent Organic Polymers (COP) and Their Linker Effect on Gas Adsorption Performance via Density Functional Theory Approach

“…Therefore, solid adsorbents have been considered for this purpose, despite most of the current capture infrastructure is based on liquid state amine based absorbents. Regardless of either adsorbents or absorbents, capture materials must include the characteristics of null (or minimum) toxicity, low corrosivity, low regeneration cost and low degradation properties . There is an increasing interest on some new alternative materials that are considered as alternative CO 2 capture solvents such as ionic liquids and deep eutectic solvents …”

“…According to above‐mentioned constraints, covalent porous adsorbents have received remarkable attention in recent years due to their structures that allows multiple alternatives for custom design and engineering in order to achieve high CO 2 adsorption performance that can support high gas selectivity with low energy cost regeneration properties in comparison to toxic and corrosive amine solutions, Powerful and ever‐expanding methods could be provided by molecular and polymer synthesis methods that can result in outstanding chemical selectivity, stereospecifity, control of polymer composition, size and architecture for the targeted intended utilization of these materials . Having said that, covalent porous organic polymers (CPOP) have structures that include attractive high‐affinity CO 2 (and other gases depending on the structure) interaction sites with low‐to‐moderate binding energies.…”