Aqueous amine solutions for enhanced CO₂ capture and efficient desorption

Background

As the world grapples with the escalating issue of carbon emissions and their significant impact on climate change, the pursuit of innovative solutions for achieving carbon neutrality and a sustainable future has become paramount. Carbon capture, utilization, and storage (CCUS) technologies are crucial in this endeavor, with amine-based post-combustion capture (PCC) being the most established and widely implemented method for large-scale applications.

The development of an optimal CO₂ capture solvent is a critical challenge in CCUS, requiring characteristics such as high CO₂ cyclic capacity, efficient mass transfer, rapid CO₂ desorption, efficient regeneration, and stable long-term recyclability. These factors influence the size of equipment needed and the overall capital cost of CO₂ capture plants. Efficient desorption is particularly important, as it significantly impacts regeneration energy requirements, which constitute a major portion of the total energy consumption in PCC.

Current approaches to CO₂ capture using amine-based solvents face several challenges. The high thermal energy required for CO₂ desorption and solvent regeneration is a major drawback, accounting for 60% to 80% of the total energy consumption in PCC. Additionally, solvent degradation during the CO₂ capture process can lead to reduced absorption capacity and increased operational issues such as corrosion, foaming, fouling, and the generation of harmful by-products.

Extensive research has been conducted to develop stable solvents with superior CO₂ capture and regeneration efficiencies, focusing on the reaction pathways and kinetics of amine interactions with CO₂. However, despite these efforts, challenges persist in achieving efficient solvent regeneration and minimizing degradation.

The need for alternative pathways, such as capturing CO₂ as bicarbonate and using it in less energy-intensive processes, is being explored to address these issues and improve the overall efficiency and cost-effectiveness of amine-based CO₂ capture technologies.

Technology overview

The technology described is a surface-active amine-based solution designed for enhanced CO₂ capture and desorption. The solution, specifically DMAPA-6PO, features a tertiary amine with propylene oxide groups chemically introduced to its structure, which enhances its surface activity. This modification allows the amine to capture CO₂ more efficiently by forming bicarbonate rather than carbamate, which is typical in conventional amine-based CO₂ capture systems.

The process involves bubbling CO₂ through the amine solution at ambient temperature, where the solution rapidly captures CO₂, reaching a maximum loading capacity of 1.29 mol CO₂/mol amine. The captured CO₂ is then desorbed at a controlled temperature of 80°C, achieving significant regeneration efficiency and cyclic capacity, with the solution demonstrating stability over multiple cycles.

The differentiation of this technology lies in its built-in surface activity, which significantly enhances CO₂ solubilization in the aqueous media, leading to higher bicarbonate production and more efficient CO₂ desorption. Unlike traditional amine-based solvents like MEA, which primarily form stable carbamates requiring high energy for regeneration, the DMAPA-6PO solution captures CO₂ as bicarbonate. This results in a lower heat duty for CO₂ release, making the process more energy-efficient.

The surface-active amine also shows superior performance in terms of desorption rate and cyclic capacity, maintaining a higher CO₂ capture capacity regeneration over multiple cycles. These features make DMAPA-6PO a promising candidate for large-scale CO₂ capture and storage applications, offering a more sustainable and cost-effective solution compared to conventional methods.