Mixed Diethanolamine and Polyethyleneimine with Enhanced CO₂ Capture Capacity from Air

Abstract

Supported polyethyleneimine (PEI) adsorbent is one of the most promising commercial direct air capture (DAC) adsorbents with a long research history since 2002. Although great efforts have been input, there are still limited improvements for this material in its CO2 capacity and adsorption kinetics under ultradilute conditions. Supported PEI also suffers significantly reduced adsorption capacities when working at sub‐ambient temperatures. This study reports that mixing diethanolamine (DEA) into supported PEI can increase 46% and 176% of pseudoequilibrium CO2 capacities at DAC conditions compared to the supported PEI and DEA, respectively. The mixed DEA/PEI functionalized adsorbents maintain the adsorption capacity at sub‐ambient temperatures of −5 to 25 °C. In comparison, a 55% reduction of CO2 capacity is observed for supported PEI when the operating temperature decreases from 25 to −5 °C. In addition, the supported mixed DEA/PEI with a ratio of 1:1 also shows fast desorption kinetics at temperatures as low as 70 °C, resulting in maintaining high thermal and chemical stability over 50 DAC cycles with a high average CO2 working capacity of 1.29 mmol g−1. These findings suggest that the concept of “mixed amine”, widely studied in the solvent system, is also practical to supported amine for DAC applications.

Fundamental Insight into Humid CO2 Uptake in Direct Air Capture Nanocomposites Using Fluorescence and Portable NMR Relaxometry

“…The activation barrier for CO 2 adsorption and/or proton transfer may also play a more significant role at these lower temperatures. We contend that this technique will be particularly useful for studying an array of materials and additives for understanding and optimizing sub-ambient capture processes. , We turn now to studying changes in polymer mobility under a variety of simulated DAC conditions, namely, 100 sccm of 400 ppm CO 2 in N 2 at different RH.…”

“…7 Indeed, a diverse array of recent work studying nonvolatile aminopolymers loaded onto mesoporous oxide composites is driving extraordinary advances in the field. 8−14 However, certain fundamental knowledge gaps remain that will influence how these and similar materials are employed over long cycle times, 15−17 in different environments, 18,19 and within different operational design constraints in real-world DAC systems. 20 One such knowledge gap involves structure−property− performance relationships associated with polymer segmental mobility in confinement.…”

“…The deployment of negative emissions technology is also projected to play an increasingly important role in limiting the effects of anthropogenic climate change. − Among the direct air capture (DAC) technologies currently being investigated for pilot and commercial scale deployment, solid adsorbents based on supported amines are garnering much enthusiasm . Indeed, a diverse array of recent work studying nonvolatile aminopolymers loaded onto mesoporous oxide composites is driving extraordinary advances in the field. − However, certain fundamental knowledge gaps remain that will influence how these and similar materials are employed over long cycle times, − in different environments, , and within different operational design constraints in real-world DAC systems …”

Additives enhancing supported amines performance in CO2 capture from air

“…Most of the research focuses on the co-impregnation of additives with amines, 18,27,[35][36][37][38] by which the diffusion limitation of CO 2 can be alleviated due to the inter-actions between the amines and the additives. Jones's group conducted a study wherein various additives were impregnated with polyethyleneimine (PEI) into SBA-15.…”

Distribution and Mobility of Amines Confined in Porous Silica Supports Assessed via Neutron Scattering, NMR, and MD Simulations: Impacts on CO2 Sorption Kinetics and Capacities

“…Thus, from the earliest studies on these materials, the mobility of the supported amines within the mesopores of the support was recognized as an important factor. Further research on those materials aimed to improve their CO 2 uptake properties by varying pore sizes, − leaving behind surfactants (e.g., CTAB) − around pore walls, using additives (e.g., PEG) − or smaller, molecular amines (e.g., diethanolamine), , and using combinations of grafted amines together with physically impregnated amines. , Researchers observed varied gas capture performance under these different circumstances. In many cases, the authors suggested that a more favorable distribution and motions of amines were the main driving forces behind the improved performance.…”